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Boatowner's Illustrated Electrical Handbook Second Edition Charlie Wing International Marine / McGraw-Hill Camden, Maine • New York • Chicago • San Francisco Lisbon • London • Madrid • Mexico City • Milan New Delhi • San Juan • Seoul • Singapore • Sydney • Toronto
Copyright © 1993, 2006 by Charlie Wing. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, with- out the prior written permission of the publisher. 0-07-148693-3 The material in this eBook also appears in the print version of this title: 0-07-144644-3. All trademarks are trademarks of their respective owners. Rather than put a trademark symbol after every occurrence of a trademarked name, we use names in an editorial fashion only, and to the benefit of the trademark owner, with no intention of infringement of the trademark. Where such designations appear in this book, they have been printed with initial caps. McGraw-Hill eBooks are available at special quantity discounts to use as premiums and sales promotions, or for use in corporate training programs. For more information, please contact George Hoare, Special Sales, at [email protected] or (212) 904-4069. TERMS OF USE This is a copyrighted work and The McGraw-Hill Companies, Inc. ("McGraw-Hill") and its licensors reserve all rights in and to the work. Use of this work is sub- ject to these terms. Except as permitted under the Copyright Act of 1976 and the right to store and retrieve one copy of the work, you may not decompile, disas- semble, reverse engineer, reproduce, modify, create derivative works based upon, transmit, distribute, disseminate, sell, publish or sublicense the work or any part of it without McGraw-Hill's prior consent. You may use the work for your own noncommercial and personal use; any other use of the work is strictly prohibited. Your right to use the work may be terminated if you fail to comply with these terms. THE WORK IS PROVIDED "AS IS." McGRAW-HILL AND ITS LICENSORS MAKE NO GUARANTEES OR WARRANTIES AS TO THE ACCURACY, ADEQUACY OR COMPLETENESS OF OR RESULTS TO BE OBTAINED FROM USING THE WORK, INCLUDING ANY INFORMTION THAT CAN BE ACCESSED THROUGH THE WORK VIA HYPERLINK OR OTHERWISE, AND EXPRESSLY DISCLAIM ANY WARRANTY, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. McGraw-Hill and its licensors do not warrant or guarantee that the functions contained in the work will meet your requirements or that its operation will be uninterrupted or error free. Neither McGraw-Hill nor its licensors shall be liable to you or anyone else for any inaccuracy, error or omission, regardless of cause, in the work or for any damages resulting therefrom. McGraw-Hill has no responsibility for the content of any information accessed through the work. Under no circumstances shall McGraw-Hill and/or its licensors be liable for any indirect, incidental, special, punitive, consequential or similar damages that result from the use of or inability to use the work, even if any of them has been advised of the possibility of such damages. This limitation of liability shall apply to any claim or cause whatsoever whether such claim or cause arises in contract, tort or otherwise. DOI: 10.1036/0071446443
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For more information about this title, click here Contents Foreword by Ed Sherman v Introduction 1 1. Basic DC Circuits 2 What Electricity Is • Ohm's Law • Loads • Sources • Practice Problems 2. DC Measurements 14 Analog Test Instruments • Digital Test Instruments • Digital vs. Analog Test Instruments • Homemade Testers • Troubleshooting 3. Batteries 26 What Is a Battery? • A Few Messy Details • Electrical Model of Batteries • Monitoring Battery Health • Discharge Characteristics • Charging Characteristics • Charging Recommendations • Estimating Your Daily Load • Choosing a Battery Type • Optimum Depth of Discharge • Sizing the Alternator • Series vs. Parallel • Battery Boxes • ABYC Standards for Batteries 4. Alternators 48 A Galley Alternator • A Rotary Current Machine • Rectification • Controlling the Alternator • Type-P and Type-N Alternators • Powering the Voltage Regulator • Regulator Bypass Controls • Link 2000-R Charge Controller • Charging Setups • Alternator Installation • Troubleshooting 5. Bonding 70 What Is Bonding? • Lightning Protection • Corrosion Protection • Stray-Current Protection • To Bond or Not to Bond • Sizing the Anode(s) • Testing Your Protection • Noncathodic Corrosion • The ABYC on Cathodic Protection 6. DC Standards and Practices 92 Wiring Diagrams • Marine Wire • ABYC DC Load Calculation • Allowable Conductor Amperage • Allowable Voltage Drop • Identification and Installation • Overcurrent Protection • Conductor Connections • Ignition Protection 7. AC Basics 114 Alternating Current • Power Factor • AC Safety • Grounding • Conductor Identification • Transformers • AC Measurements • Troubleshooting AC Circuits • Checking Polarity 8. Inverters and Generators 128 Why Have AC Power? • Figuring Your AC Budget • Inverters • Transfer Switching • Generators • Toubleshooting Generators
9. AC Standards and Practices 144 Shore Power • Generator and Inverter Sources • Main Panelboard • AC Load Calculations • Overcurrent Protection • Approved Wire and Cable • Ampacity Tables • Conductor Installation • The Green Wire • Approved Shore-Power Circuits 10. Conservation for Liveaboards 182 Costs per Kilowatt-Hour • Lighting Savings • Refrigeration Savings • Other Savings 11. Solar Power 194 Is Solar for You? • How Photovoltaics Work • Photovoltaic Panels • Interpreting Specifications • Panel Orientation • Estimating Output • Mechanical Installation • Electrical Installation • Rules for Solar Success 12. Wind Power 208 Is Wind Power for You? • Getting Power from the Wind • How Much Wind Is There? • Estimating Daily Output • Specifications • Electrical Installation • Mechanical Installation • Water Generators 13. Installing Electronics 222 Antennas • Antenna Cable and Connectors • Moisture Protection • VHF Radio • GPS and SSB • Radar • Receiver/Transmitter Installation • Harnessing Electrical Noise • Electrical Filters 14. Do-It-Yourself Projects 238 Passive Circuit Components • Active Circuit Components • Projects Appendices 258 Other Wiring Standards • English/Metric Conversions • Temperature Conversions • Power Conversions • Resistance of Copper Wire • Losses in Coaxial Cables • Wiring Color Codes • Useful Electrical Formulas • Identifying Resistors • Identifying Capacitors • Trigonometric Tables Glossary 270 Index 276
Foreword Since I have used Charlie Wing's first edition of the the American Boat and Yacht Council (ABYC). As the Boatowner's Illustrated Electrical Handbook as a text for senior technical instructor for the ABYC and its cur- some of my electrical courses over the years, I am quite riculum designer I really appreciate the effort through- familiar with its contents. I've just finished reviewing out the book to advise the reader on how to make the second edition and can say without reservation that repairs and modifications to his or her boat and remain it is more than just an update. The diagrams are dra- compliant with the most recognized design and repair matically improved and the topics covered are really standards for recreational boats in the world. We at the comprehensive, just what's needed in today's world of ABYC know full well that adherence to these standards ever increasing complexity on newer boats. make a better, safer boat. This second edition is perfect for learning how your I have already begun recommending this second boat's electrical system and much of its equipment edition to my students and seminar participants, and works, and it will be an invaluable guide when adding will continue to do so. This book needs to be in every equipment as well. Further, Charlie Wing has remained boater's library as a ready reference on how to make faithful to the recommendation and application of the effective repairs and modifications that comply with standards for installation and equipment as set forth by ABYC standards. Ed Sherman ABYC Senior Instructor and Curriculum Designer v Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
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Introduction Many of us have, at the least, a passing familiarity with This book is my attempt at interpretation and illu- electrical wiring. When a switch or receptacle in our mination of the several wiring-related ABYC standards home fails, we replace it. Some of us feel secure in and much more. extending a circuit, adding a new circuit, even wiring My joy in life derives from explaining and illustrat- an entire house. We are able to do so because of the ing how things work—first as a physics teacher at Bow- National Electric Code (NEC) and because many excel- doin College, then as founder of the first two owner- lent books, based on the NEC, have been written for builder schools in the country, and later as author of both the novice and the professional. thirteen books on home building and repair and six Unfortunately, a boat is not a house—a fact that still books on marine topics. escapes all too many boatyards. I have always felt that knowledge is of limited utility I'll never forget the time I was working in a boat- unless based upon an understanding of the basic prin- yard rigging masts. I had spent an hour trying to deter- ciples—simply put, how things work. In this book you mine why a mast-top anchor light was not working. will find that each subject begins with a simple explo- The blue anchor-light supply conductor disappeared ration and explanation of the hows and whys. into the base of the 60-foot mast, yet no blue conductor I also feel that books—even those of a technical appeared at the other end. I commented on the mystery nature—should be fun. We boatowners have no need to a co-worker who I knew had worked as an electrician for Miss Grundy to rap our knuckles to command our at one the country's premier boatbuilders. attention. Discovery of how your boat works should "Sure," he said."We'd grab a spool of #14 whatever, be fun and exciting. To this end you will find dozens of and when that ran out, we just spliced in another. The simple experiments and projects designed to make the color of the wire doesn't matter." light in your mind come on, perhaps even add to the Or ask a random sampling of boatbuilders whether comfort and convenience of your boat. bronze through-hulls should be bonded. Chances are I hope you will come away from this book with the good you will get an even split of opinions. No won- feeling that (to paraphrase Ratty in Wind in the Wil- der boatowners are confused! lows) "There is nothing half so much worth doing as In fact, there is a voluntary standard for the con- messing about in your boat's electrical system." struction and repair of boats, including the topics of I have invented nothing. You will find here no new AC and DC wiring, lightning protection, and bonding law of physics, nor any previously unreported electrical for corrosion control. It is the American Boat and Yacht or magnetic phenomena. I have simply attempted to Council (ABYC) Standards for Small Craft. The stan- bring to you, the reader, a lucid and clearly illustrated dards are the marine equivalent of the residential account of how the best minds in the business think a National Building Code and National Electric Code. small boat should be wired. Twelve years ago, when the first edition of this book To this end, in this second edition I have redrawn was written, few boat manufacturers and fewer boat- many of the original illustrations, added illustrations, yards paid much attention to the fledgling ABYC. and added color to the ABYC-recommended wiring for Today, nearly all manufacturers and many boatyards AC shore-power systems. Also new is the ABYC proce- have joined the organization and have sent employees dure for testing and sizing protective zinc anodes, to the excellent technical courses offered by the ABYC's material on absorbed-glass mat (AGM) batteries, spe- Westlawn Institute of Marine Technology. In the words cific recommendations for charging most marine bat- of the ABYC, the standards are: " ...believed to rep- teries, descriptions of "smart"alternator regulators, and resent, as of the date of publication, the consensus of troubleshooting charts for engine-starting and battery- knowledgeable persons, currently active in the field of charging circuits. small craft, on performance objectives that contribute May your boat never corrode, your engine never fail to small boat safety." to start, and your batteries last forever! 1 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
1 CHAPTER Basic DC Circuits Current, I + Load R Voltage source V _ 2 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
B asic to the ability to work with electrical wiring—be it residential or marine—is an understanding of what electricity is. You'll find that the discovery of electricity, as we now understand it, was fairly recent. The key that unlocks the wiring puzzle is the con- cept of the electrical circuit. With this simple concept and a single formula—Ohm's Law—you can under- stand and predict the behavior of 99% of the wiring on your boat. You will be able to deal with circuits con- taining loads in series, loads in parallel, even loads in series/parallel combinations. Similarly, you will be able to predict the behavior of voltage sources in series and voltage sources in parallel. You will also discover the dif- ferences between voltage, current, energy, and power. Finally I have provided a set of 18 practice problems on which you can cut your electrical teeth. 3
What Electricity Is We live in the age of electricity. Without electricity we couldn't watch television, drive automobiles, make The Discovery of Electricity frozen margaritas, microwave popcorn, read at night, Democritus (460?–370? BC) proposes an "atomic the- or talk to our friends on the phone. ory" wherein all matter is made up of indivisible parti- Many people think electricity is difficult to under- cles, or atoms. stand. They are wrong. Because you are surrounded by Charles de Coulomb (1736–1806) discovers that the and unconsciously use electrical devices every day, little force of attraction between electric charges is propor- lights will go on in your head as you discover the con- tional to the product of the two charges and inversely cepts. You'll probably say, "Oooh—so that's why my proportional to the distance between them. boat battery is dead every morning!" Luigi Galvani (1737–1798) discovers that two unlike I believe you will find electricity to be fun. I am metals immersed in blood cause the muscles of a frog's absolutely sure that, having grasped the very simple legs to twitch. concepts behind boat wiring, you will feel more confi- Alessandro Volta (1745–1827) discovers that a current dent both in your boat and in yourself. flows between two connected unlike metals in a salt solution and, thus, invents the battery. Electricity consists of electrons. An electron is the smallest quantity of electricity that exists. It is such a John Dalton (1766–1844) proposes the first table of small quantity, however, that we use the unit coulomb atomic weights of elements. 18 (1 coulomb = 6.24 10 electrons) in calculations. André Ampere (1775–1836) develops the theory of mag- × The flow of electrons is often compared to the flow netic lines of force and quantifies electric current for of water, so it is natural that we call electron flow "elec- the first time. tric current." The basic unit of electric current is the Hans Oersted (1777–1851) discovers a connection ampere (1 ampere = 1 coulomb per second of electrons between electric current and magnetism and a way to moving past a point). measure electric current by the deflection of a magnet. What we usually refer to as electricity is the control Georg Ohm (1787–1854) discovers the relationship of electrons for useful purposes. Our understanding of (Ohm's Law) between voltage, current, and resistance in electron behavior allows us to predict the flow of elec- a circuit. trons through electrical circuits. The instruments on Michael Faraday (1791–1867) analyzes the chemical your boat contain circuits. Indeed, a boat's wiring is reactions in batteries and defines the terms "electrode," no more than a collection of circuits. When we under- "anode,""cathode," and "electrolyte." stand circuits, we will understand the behavior of elec- James Clerk Maxwell (1831–1879) develops the mathe- tricity on a boat. matical equations relating electricity and magnetism. Joseph Thomson (1856–1940) proves that electricity A Circuit consists of electrons. Electrons can be neither created nor destroyed, but can move through conductive materials.An electric current requires a continuous path of electrically conductive rials are termed conductors and others insulators. material, through which the electrons can return to The best conductors are gold, silver, mercury, cop- their source. per, and aluminum. Copper is most often the best com- If this were not so, electrons would dribble from the promise between cost and conductivity. The best insu- end of a wire like water from a leaky faucet, and bat- lators are glass, ceramics, mica, and plastics. Plastic is teries would soon sit like empty water glasses with all the material most often used due to its low cost, dura- their electrons lying around them in a pool. bility, and ease of manufacture. We call a continuous electrical path a circuit. If a cir- Unfortunately for boaters, salt solutions, such as cuit is unbroken, we call it a closed circuit. If it is inter- seawater, are also good conductors. rupted, preventing the flow of electricity, we say the cir- Electrical current is expressed as a rate of electron cuit is open. flow. In a circuit, two factors control the current (I): the All materials present a degree of resistance to elec- electrical driving force, or voltage (V), and the resis- tron flow, but the variation is so great that some mate- tance (R) to flow of the circuit materials. 4 Basic DC Circuits
Ohm's Law To see just how simple electricity is, we are going to Let's see how Ohm's Law is used. Ohm's Law applies consider the basic equation of current flow in an elec- to all situations, but it is useful only in circuits where trical circuit. With this equation you will be able to electricity is flowing. understand, predict, and troubleshoot more than 90% of all the electrical problems on a boat. Fig. 1.1 Simple Electric Circuit Current, I Question 1. Does current, I, increase or decrease as we increase the driving force (voltage, V)? Answer 1. Current most likely increases with increasing voltage. + Load R Question 2. Does current, I, increase or decrease as we increase the resistance to electron flow (resistance, R)? Voltage source Answer 2. Current most likely decreases with V increasing resistance. _ Question 3. Considering the answers to questions 1 and 2, what would be the simplest and, therefore, most likely, relationship between current (I), voltage (V), and resistance (R)? Answer 3. There are four possible "simplest" equa- tions: I = V + R, I = V – R, I = V R, and I = V/R The voltage source in Figure 1.1 is a device that pro- × duces a voltage difference. Examples are batteries and If you play with the values for a minute, you'll agree power supplies. Unless otherwise noted, assume voltage that the first three equations are unlikely. For example, sources are batteries. The load is any device or compo- if we make resistance, R, infinite, current, I, becomes ', nent that consumes electrical energy and, in so doing, –', ', and 0. Only the last value is reasonable, so the results in a voltage drop. Examples are resistors, lamps, relationship is most likely and motors. Unless otherwise stated, assume loads are resistances (the zigzag symbol). For a table of electri- I = V/R cal symbols used in this book, see Figure 6-1. Congratulations! You have just discovered Ohm's Example: If the load is a resistance of 2 ohms, and Law. If Georg Ohm hadn't beaten you to it in 1827, you the voltage source is a 12-volt battery, then by Ohm's might be up for a Nobel Prize. Law I = V/R = 12 V/2 = 6 A Ω Using Ohm's Law We can also rearrange Ohm's Law so that we can This is such an important relationship, we must be pre- calculate either V or I, given the other two values. The cise in its definition and the ways in which it can be alternate forms of Ohm's Law are: used. First, if we wish to calculate electrical quantities, V = I R × we must define the units in which these quantities are R = V/I measured. There is more good news. Ohm's Law applies to I = V/R more complex circuits as well. We can combine loads where: and sources in series (end-to-end), parallel (side-by- I = amperes, abbreviated as A side), and series/parallel, and the equations remain the V = volts, abbreviated as V simplest possible, as you will see in the figures and R = ohms, abbreviated as Ω examples that follow. Ohm's Law 5
Loads Loads in Series Example: R = 20 ,R = 30 ,R = 50 ,V = 3 1 2 Ω Ω Ω Resistive loads in series act like one continuous load of 12 V. a total resistance equal to the sum of the individual 1/R = 1/R + 1/R + 1/R 3 2 1 resistances: = 1/20 + 1/30 + 1/50 = 0.050 + 0.033 + 0.020 R = R + R + R ,etc. = 0.103 2 1 3 I = V/(R + R + R , etc.) 1 2 3 R = 1/0.103 = 9.68 Ω Fig. 1.2 Series Loads I I = V/R = 12 V/9.68 Ω = 1.24 A + R 1 Loads in Series/Parallel Voltage V Total load, R R 2 Observe that the parallel group of loads can be con- source sidered a single resistor in series with other series loads. We first calculate the equivalent value of the parallel _ loads, as in the previous example, and then add the R 3 result of the other series loads: Fig. 1.4 Series/Parallel Loads Example: R = 2 ,R = 3 ,R = 5 , V = 12 V I 3 2 1 Ω Ω Ω R = 2 + 3 + 5 = 10 Ω + R S1 Loads in Parallel The same voltage, V, exists across each of the loads. Voltage R S2 source Ohm's Law predicts the currents through the loads: V I = V/R ,I = V/R ,I = V/R ,etc. 3 1 2 1 2 3 Total current, I, is the sum of currents: _ I = I + I + I ,etc. R P1 R P2 3 2 1 = V(1/R + 1/R + 1/R , etc.) 3 2 1 In other words, 1/R = 1/R + 1/R + 1/R ,etc. 3 2 1 Example: R = 2 ,R = 3 ,R P1 = 5 ,R P2 = S2 S1 Ω Ω Ω Fig. 1.3 Parallel Loads 10 , V = 12 V Ω 1/R = 1/R + 1/R Total load, R P P1 P2 I = 1/5 + 1/10 = 0.20 + 0.10 = 0.30 + I 1 I 2 I 3 R = 3.33 Ω P Voltage R = R + R + R P S2 S1 source R 1 R 2 R 3 = 2 + 3 +3.33 Ω Ω Ω V = 8.33 Ω _ I = 12 V/8.33 Ω = 1.44 A 6 Basic DC Circuits
Sources Sources in Series Sources in Parallel Your boat probably has a battery selector switch. On Fig. 1.5 Series Sources its face it says: I OFF—1—2—BOTH + In the BOTH position, both of your batteries are V 1 connected in parallel; i.e., + terminal to + terminal, and _ – terminal to – terminal. Provided the batteries are of + the same voltage, the net result is simply a single battery V 2 V R of capacity equal to the sum of the individual capaci- ties. If they are not of the same voltage, the higher volt- _ + age battery will discharge into the lower voltage battery, possibly overcharging and destroying it. V 3 There is much controversy over charging and dis- _ charging marine batteries in parallel. Some experts are dead set against it, saying that the batteries will even- tually destroy each other. Other experts claim it is the One example of a voltage source is a battery. If you've only way to go when charging. Both arguments and the ever replaced the batteries in a flashlight, you know that reasoning behind them will be presented in Chapter 4. batteries can be stacked end to end. When you do that the total voltage equals the sum of the individual volt- Energy and Power ages. In general, voltages in series add. Energy is defined as the ability to do work. Power is V = V + V + V ,etc. defined as the rate of doing work. Power is, therefore, the 3 I 2 Therefore, I = (V + V + V )/R rate at which energy is used in doing work. I 2 3 Two Olympic runners exemplify the difference between energy and power. The first runner holds the Example: V = 1.5 V, V = 1.5 V, V = 3 V, R = 4 Ω record in the marathon. He is a lean, efficient running I 3 2 I = (1.5 + 1.5 + 3.0)V/4 Ω machine. He burns nearly all of his stored energy = 1.5 A resources steadily over a 2-hour period. The second A caution is in order, however. If batteries are added runner holds the record in the 100-meter dash. He uses in series, they must have the same ampere-hour capac- less total energy, but consumes it in an intense 10- ities and start with the same states of charge. If not, second burst. The first runner uses more energy, but the battery with the greatest capacity for supplying cur- the second uses energy at a higher rate, or power. rent may drive the voltage of the weakest battery nega- Except in nuclear reactions, energy can be neither tive, which usually destroys the weaker battery. created nor destroyed. What it can do, however, is change between its many forms. As an example, the water at the top of a hydroelec- tric dam possesses potential energy due to its height. Fig. 1.6 Parallel Sources As it falls and gains speed, its potential energy is con- I verted into kinetic (motion) energy.When the water hits the blades of a turbine, the kinetic energy of the water is transferred to the spinning turbine. The turbine + + turns a generator where the kinetic energy is converted to electrical energy. The electricity flows into your V 1 V 2 R home, where a lightbulb changes the electrical energy _ _ into light energy and heat energy. Ultimately, the heat escapes from your home into the atmosphere, where it causes water to evaporate into water vapor, which then turns into clouds, which then drop rain into the reser- voir. And so it goes. Sources 7
Practice Problems For the moment, we will concern ourselves only with The problems below are designed to sharpen your the energy transformations occurring between your skills in the application of Ohm's Law. They range boat's batteries and its loads. The battery, as we will see from the simplest possible to the most complex you'll in detail later, is just a box full of chemicals. When it is ever encounter on your boat. All you need to solve connected to a closed electrical circuit, the chemicals them is a simple four-function calculator, scratch react, sending a stream of electrons (amps) around the paper, and a pencil. circuit under electrical pressure (volts). In flowing You can make solving them a parlor game. Get your through the load (resistance), the electrons lose their mate to play with you. Take turns making up more pressure (the voltage drops), and the load produces problems and trying to stump the other person. Once heat, light, or some form of mechanical work. Chemi- you have mastered these examples, you are ready for cal energy changes to electrical energy, which then real components and real circuits. The answers to the changes to heat, light, or mechanical energy. You'll see problems are listed at the end of this chapter. later that recharging the battery involves the same steps, but in reverse order. Power is calculated as easily as volts, amps, and (A) I? ohms: P = V I + × where: P = power consumption in watts V = volts across the load I = amps through the load 6V 3 Ω Example: What is the power of a lightbulb that draws 1.25 amps at 12 volts? _ P = V I × = 12 volts 1.25 amps × = 15 watts Example: How many amps would a 20-watt lamp draw in a 12-volt circuit? P = V I (B) 1.5A × I = P/V = 20 watts/12 volts = 1.67 amps + Electrical equipment is usually labeled with its power consumption. If you look at the back or bottom 9V of equipment, or at the base of a bulb, you will gener- R? ally find either (X) volts and (Y) amps, or (X) watts at (Y) volts. _ Using Ohm's Law and the power equation, you should have no problem deducing either amps or watts, given two of the three variables in the equations. 8 Basic DC Circuits
(C) 0.25A (E) 2A + + V 1? 3 Ω I 1 V? 480 Ω V _ _ V 2 R 2 I 2 (D) I? (F) 2A + V 1 3 Ω I 1? + V 1 3 Ω I 1 12V V? _ _ 5 V 2 5 Ω I? V 2 Ω I 2 Practice Problems 9
Practice Problems (G) I? (I) 0.5A + I 1 I 2 I 3 + 6V 100 100 100 6V R? W? Ω Ω Ω _ _ (H) (J) I? + 0.4A 0.2A I 3 + V R 1? 100 R 3 9V 10W Ω _ _ 10 Basic DC Circuits
(K) 0.25A (M) I? + + V? 30W 12V 10 Ω 20W _ _ (L) I? (N) I? + + 10 Ω 12V 5W 20W 12V _ _ 20W @12V Practice Problems 11
Practice Problems (O) I? 4 Ω (Q) I 5 Ω 10 Ω + + I 2 I 3 I 4 I 5? 12V 9V 12V 6 Ω 100 150 R 2 R 3 _ _ Ω Ω (P) R 1 2A (R) 2A 5 Ω 10 Ω + + I 2? I 3 Voltage V 2? I 4 I 5 source V? 6 50 Ω 100 Ω Ω _ 100 150 _ Ω Ω Answers to Problems: e. V1 = 6 V j. I = 1.11 A o. I = 0.75 A a. I = 2 A f. V = 16 V k. V = 120 V p. V2 = 66.7 V, I2 = 1.33 A b. R = 6 Ω g. I = 0.18 A l. I = 2.08 A q. I5 = 0.036 A c. V = 120 V h. R1 = 50 Ω m. I = 2.87 A r. V = 21.05 V d. I1 = I2 = I = 1.5 A i. R = 12 , W = 3 W n. I = 0.7 A Ω 12 Basic DC Circuits
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2 CHAPTER DC Measurements 4 5 6 7 3 8 4 Volts + + 2 + – – 9 12 Volts + 1 – + 10 8 Volts DIM – 14 – 11 13 12 14 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
T heory is fine, but we need a way to monitor elec- trical systems in order to see if they are working as expected. Analog test instruments, displaying current and voltage, allow us to see, at a glance, what is happening. For the precision required to monitor batteries, however, it is better to use digital test instru- ments. Very often we need to know only whether there is voltage present. For these go, no-go tests, a simple homemade tester is described. Troubleshooting with testers leads you through the deductive process of isolating electrical problems. The practice problems at the end of the chapter will allow you to sharpen your troubleshooting skills. 15
Analog Test Instruments In Chapter 1, I asserted," ...with Ohm's Law, you will rotate about its bearing. The needle attached to the coil be able to understand, predict, and troubleshoot 90% displays the rotation against the scale in the back- of the electrical problems on a boat." Let me amend ground. that figure to 99%. In order that the ammeter be able to measure small You will recall that Ohm's Law allows us to calculate currents, the meter movement is very delicate. The the theoretical relationships between the voltages, cur- moving coil consists of many turns of fine wire, the rents, and resistances in a circuit. What if there were springs are "hair springs" similar to those in a wind- instruments we could plug into a circuit that would up watch, and the coil pivots on jewel bearings. Typi- –6 show us the actual values of voltage, current, and resis- cally, 50 µA (50 10 A or 0.000050 amp) deflects the × tance? By comparing the theoretical and actual values, needle full scale. we would find that either: (1) reality agreed with theory But the currents we are interested in typically range and all was well in the circuit, or (2) reality disagreed from 0.1 to 100 amps—about one million times 50 µA. with theory and there was something wrong in the cir- You can imagine what would happen if we tried to cuit. measure the 50-amp charging current in our battery There are instruments that measure volts, amps, leads with the 50 µA meter of Figure 2.1. and ohms, and using them to compare reality with the- How can we modify our 50 µA ammeter to measure ory is what we call troubleshooting. This chapter 50 amps? Ohm's Law to the rescue! Although a perfect describes the instruments and their use. ammeter would offer zero resistance to the current flowing through it, real ammeters are made of real wire and so have a finite resistance. Analog Ammeter (Current Meter) Figure 2.2 shows the resistance, R , of our amme- C The ammeter hasn't changed much since it was devel- ter coil with full-scale current of 50 µA flowing through oped by Jacques d'Arsonval in 1811. In Figure 2.1, cur- it. In parallel with the meter we place a shunt whose rent flows into terminal 1, through the spring, around resistance, R , is 10 –6 (one-millionth) of R . Since the S C the moving coil, through a second spring on the back- voltage across both R and R is the same, Ohm's Law C S 6 side, and out through terminal 2. The current in the predicts that I = 10 (one million) I , or 50 amps. C S × coil produces a magnetic field that interacts with the field of the permanent magnet, forcing the coil to Fig. 2.2 Ammeter Symbol and Internal Resistances Fig. 2.1 D'Arsonval Ammeter 1 20 30 10 40 Ammeter 0 50 symbol Shunt Meter coil A DC AMPS = RS RC IS IC Permanent 50A 50 µ A magnet Needle Spring Moving coil 2 Using this principle, the same 50 µA ammeter can be made to measure 100 µA, 500 µA, 30 mA, 10 A, 100 Shunt 2 1 A, or any other current merely by inserting the appro- priate shunt across the terminals, as shown. 16 DC Measurements
Analog Voltmeter Analog Ohmmeter (Resistance Meter) Might we use our little 50 µA d'Arsonval meter to mea- By now you are probably expecting me to tell you that sure voltage as well? Ideally, a voltmeter should mea- our 50 µA ammeter can be modified to measure resis- sure the voltage across a circuit without disturbing the tance as well. You are correct. circuit. That means it should look like a very high resis- To measure the resistance of a resistor or other cir- tance—much higher than any of the other resistances cuit load, we must isolate that component from the rest in the circuit. of the circuit. (Review the practice problems in Chap- ter 1 if you don't remember why.) Fig. 2.3 Using the Ammeter to Measure Voltage Sometimes we can open a switch; sometimes we can disconnect a terminal; sometimes we have to unsolder one end of the component. Regardless of how we iso- IA IL late the item, we measure its resistance indirectly by 50 µ A 0.5A applying a test voltage and measuring the resulting cur- Voltmeter rent. Because zero resistance (a possibility in case of a + short circuit inside the component) would draw a pos- sibly destructive high current, we place a known cur- 15V RV RL rent-limiting resistor in series with the meter. – 30 Ω Figure 2.4 shows our ohmmeter. Inside its case are our same 50 µA ammeter, a 1.5-volt battery, and a A series resistor, R . Maximum current will flow, and the R meter will deflect full scale, when the resistance being tested, R , is zero. From Ohm's Law: L Figure 2.3 shows a circuit consisting of a 15-volt I = V/R R battery and 30-ohm load, resulting in a current of: R = V/I R = 1.5 volts/0.00005 amp I = V/R L = 30,000 ohms = 15 volts/30 ohms = 0.5 amp Fig. 2.4 Using the Ammeter to Measure Resistance We have placed a series resistor, R , inside the case + V of our 50 µA ammeter. If we want the ammeter to deflect full scale when the voltage is 15 volts, then + 50 µ A Ohm's Law says that the series resistor that limits the – 1.5V current to 50 µA must be: I = V/R V RR Ohmmeter RL V R = V/I V V = 15 volts/0.00005 amp = 300,000 ohms A The load imposed on the circuit by our voltmeter— one ten-thousandth of the 30-ohm circuit load—is – clearly negligible. If the circuit load, R ,had been L 30,000 ohms instead of 30 ohms, then our voltmeter At the other end of the scale, the current approaches would have siphoned off 10% of the current, giving a zero, and the needle shows essentially no deflection. result 10% in error, as well as altering the performance Thus, we have a meter representing 0 ohms on the of the circuit. right, ' ohms on the left, and all other values on a log- Voltmeters are simply ammeters with internal series arithmic scale in between. Near 0 ohms the meter will resistors of 5,000 to 100,000 ohms per volt of full scale. be very sensitive and, as R approaches ', the meter L will be less sensitive. Analog Test Instruments 17
Digital Test Instruments Analog Volt-Ohm Meter (VOM) Fig. 2.5. Volt-Ohm Meter (VOM) To troubleshoot a circuit, you may need an ammeter, a voltmeter, an ohmmeter, or all three.You may also need a variety of ranges. Conveniently, it is a simple matter 500 200 100 50 20 OHMS to combine all of these functions into a single meter 1K 100 150 10 called a volt-ohm meter (VOM), as in Figure 2.5. ∞ 5K 50 20 30 40 0 200 To the 50 µA ammeter, we add a 1.5- or 9-volt bat- 0 0 10 2 4 6 8 50 250 tery, assorted precision resistors and shunts, and a mul- DCV 0 10 ma tipole, multiposition switch. More expensive VOMs incorporate input amplifiers that increase the input OHMS resistance and decrease the current drawn by the VOM. Rx1 Rx10 Rx100 In this way, the VOM intrudes less on the tested cir- cuit. 500 500 250 250 DCV ACV 50 50 10 250 10 DC mA – + Digital Volt-Ohm Meter (DVM) One of the very first clocks was a "water clock": Water dripped into a cup. When the cup was full, it tipped Fig. 2.6. Digital Volt-Ohm Meter (DVM) over, spilled its contents, and started over. In tipping, it advanced a counter mechanism that indicated the number of times it had tripped and thus the passage of time. A digital ammeter is exactly the same, except that it counts electrons instead of water drops. The cup is an electrical capacitor. As the capacitor collects electrons, DIGITAL MULTIMETER the voltage across its terminals increases. When the voltage of the capacitor reaches a predetermined level, DC AC CHECK K DC mA V V the capacitor is discharged, and the charging begins Ω again. The greater the current (flow of electrons), the more rapidly the capacitor charges and discharges. The charge/discharge cycles are electronically counted, and the number of cycles per second are directly propor- tional to current. The analogy between analog and digital ammeters, – voltmeters, ohmmeters, and multimeters is similar. 200 MA MAX COMMON AC 750V MAX DC 1000V DC MA/K Ω Given a digital ammeter, we just add shunts, resistors, + + batteries, and rotary switches. Figure 2.6 shows a typi- cal digital volt-ohm meter. 18 DC Measurements
Digital vs. Analog Test Instruments Digital vs. Analog Multimeters Digital vs. Analog Panel Meters So which is better—the analog or digital multimeter? Ammeters and voltmeters (Figures 2.7 and 2.8) are Both are available in a range of sizes, from shirt pocket used in distribution and circuit breaker panels to mon- to benchtop, and both can be had for as little as $10 to itor battery voltage and rate of charge/discharge. An as much as $400. To help you decide which is better analog "battery charge indicator" is simply a voltmeter for you, Table 2.1 lists the specifications of two typical with its needle pegged at the left until the voltage midpriced units. reaches approximately 8 to 10 volts, thus expanding the The specifications use several prefixes: scale over the useful voltage of a 12-volt battery. Digital panel meters are slowly replacing analog µ (micro) = 10 –6 —multiply by 0.000001 meters. They cost no more to produce than the analog m (milli) = 10 –3 —multiply by 0.001 variety and are far more accurate, so one hopes their 3 k (kilo) = 10 —multiply by 1,000 prices will soon drop. 6 M (mega) = 10 —multiply by 1,000,000 Fig. 2.7 Analog Panel Meters Table 2.1 Typical Analog and Digital Multimeter Specifications 5 10 0 15 Analog Digital DC Voltmeter Specification Multimeter Multimeter DC VOLTS DC volts lowest range 250 mV 300 mV highest range 1,000 V 1,000 V 10 20 30 accuracy 1 ±4% ±0.2% 0 40 DC Ammeter 50 AC volts lowest range 5 V 3 V DC AMPS highest range 1,000 V 750 V accuracy 1 ±4% ±0.5% 10 12 14 DC amps lowest range 50 µA 300 mA 8 DISCHARGED 0 50 100 CHARGING 16 highest range 10 A 10 A Battery Charge accuracy 1 ±3% ±0.5% DC VOLTS Indicator Resistance lowest range 2 k1 300 1 highest range 20 M1 30 M1 accuracy 1 ±3% ±0.2% DISCHARGED 0 50 100 CHARGING Battery Charge 1 Accuracy as percent of full scale Indicator 9 10 11 12 13 14 15 BATTERY CONDITION A glance at an old-fashioned watch gives you a sense of the approximate time very quickly. A digital watch, however, first requires recognition of the numbers dis- played, then an interpretation of the significance of the Fig. 2.8 Digital Panel Meters numbers. The same is true of analog and digital multi- meter displays. If you wish to know simply whether your battery is charging or discharging (roughly 14 versus 12 volts), Digital Ammeter the analog meter with ±4% accuracy (±0.6 volt on a 15-volt scale) will do the job. But if you want to know DC AMPS the percentage of charge remaining in your battery, where the same ±0.6 volt represents ±50% of battery capacity, you'd better use a digital meter with its ±0.2% Digital Voltmeter (±0.03 volt on a 15-volt scale) accuracy. DC VOLTS Digital vs. Analog Test Instruments 19
Homemade Testers Most of the wiring problems on a boat are of the go, Fig. 2.10 Homemade Test Buzzer no-go variety. All DC circuits start at the boat's 12-volt battery. As you check a suspect circuit farther and far- ther from the battery, there either is or isn't voltage present. At the first point you find no voltage present, you can be sure the problem lies between this point and the last point where voltage was present. The most common marine wiring problems are due to corrosion of connections and contacts.When copper corrodes, it forms green copper oxide—an excellent electrical insulator. As corrosion progresses, more and more of the contact surface through which current the buzzer in a small box with a switch that allows you flows is eliminated. Eventually, there is so much resis- to use either the light, the buzzer, or both simultane- tance and voltage drop across the contact that the ously. reduced voltage affects the load. If the load is a lamp, When connected to 12 volts, the bulb will glow for example, the lamp will dim. If the load is a motor, brightly. If the voltage is low, the bulb will glow, but the motor will slow down or not start at all. dimly. If there is no voltage, the bulb will not glow. There are two simple, do-it-yourself, troubleshoot- Similarly, at 12 to 16 volts, the buzzer will screech; at 3 ing devices you may end up using more than your to 12 volts, the buzzer will sound fainter; at less than 3 fancy multimeter. The first is nothing more than an volts, the buzzer will not sound at all. In a noisy envi- automotive bulb with attached test leads; the second is ronment, the light works best. In bright sunlight, the a Piezo electric alarm buzzer with test leads. buzzer is best. Next pick your tips. I find a set of interchangeable Fig. 2.9 Homemade Test Light tips, as shown in Figure 2.11, very useful. Permanently attached to the test leads are banana plugs. These can be plugged into banana-to-alligator adapters, banana-to-minipin adapters, and banana-to-miniprobe adapters. I choose the adapters based on wire size and whether I'm using one hand or two.Also handy is a sin- gle 50-foot extension lead with male and female banana plugs, so that I can extend one of the test leads the length of a boat or a mast. Figure 2.9 shows a typical 12-volt DC automotive Fig. 2.11 Interchangeable Test-Lead Tips bulb you can purchase at any Wal-Mart or auto parts store. Get a pair of high-quality "test leads" at Radio- Shack. These will be rubber-insulated, very fine- Banana plug Test lead stranded #14 to #18 wire with alligator clips, banana plugs, or minitest tips attached. Solder the test leads to the side and base of the bulb, as shown, or to a lamp Banana-to-alligator adapter Banana plug Test lead socket. Don't worry about ever having to replace the bulb. It is rated 5,000 hours at 13.5 V, so the only way it should fail is if you step on it or try to test a 110-volt circuit with it. Banana-to-minipin adapter Banana plug Test lead The second tool is similar but produces a noise instead of a light. As in Figure 2.10, solder test leads to a 3 V–16 V Piezo electric buzzer, which can be found at an electronics store for under $5. If you want to get fancy, assemble both the light and Banana-to-miniprobe adapter Banana plug Test lead 20 DC Measurements
Troubleshooting Multimeters, test lights, and test buzzers are all useful in the battery-select switch by a wire. The common termi- troubleshooting circuits. Only where a precise voltage nal of the battery switch feeds the positive bus bar in or a precise resistance is needed will the multimeter be the distribution panel. The cabin light circuit originates more useful than the simpler light or buzzer, however. at the "cabin lights" circuit breaker (or fuse) connected For simplicity, the examples and illustrations that fol- to the positive bus and then runs out of the panel to the low will show only the simple test light. Just remember cabin lights, which are connected as parallel loads. that where the test light is on, the buzzer would sound, At the light fixture, the positive wire feeds the on/off and the multimeter would show a voltage, but where switch, which then controls the bulb. The other termi- the test light is off, the buzzer would be silent, and the nal of the bulb connects to the negative wire, which multimeter would show no or low voltage. runs back to the negative bus in the distribution panel Figure 2.12 shows a simple cabin light circuit. The and the negative terminal of the battery, completing the positive side of battery 1 is connected to terminal 1 of circuit. Fig. 2.12 Typical Cabin Light Circuit Battery Positive bus bar Cabin switch lights 4 circuit BOTH 3 5 breaker Cabin light 1 2 6 7 8 switch 2 OFF + 1 9 Cabin light Battery 1 10 11 − 14 12 13 Negative bus bar Figure 2.13 shows the same cabin light circuit in the ous examples. In both Figures 2.12 and 2.13, fourteen form of a wiring diagram, using the standard compo- points to which we could connect test leads are num- nent symbols listed in Figure 6-1. Note that the circuit bered. As we troubleshoot the circuit, we will connect load consists of lamps, which are nothing more than our test light to pairs of these points to see whether resistances that glow white hot. We could equally well voltage is present. have shown the load as parallel resistances, as in previ- Fig. 2.13 Typical Cabin Light Wiring Diagram Positive bus bar Cabin 3 4 5 6 7 lights Battery circuit 8 switch breaker Cabin light switch 2 9 + 1 10 Battery 1 Cabin light – 14 11 13 12 Negative bus bar Troubleshooting 21
Troubleshooting Turn all circuit switches to their on positions (Fig- and 10. There should also be no voltage change from ure 2.14). The cabin lamps light up, meaning there is points 11 to 14. With one test lead on any of points 1 nothing wrong with the circuit. Since the wire and to 10 and the other lead on points 11 to 14, the test light switches are designed to have near-zero resistance, we should light, but with both leads on either the positive expect there to be no voltage drop between points 1 or negative side, the test light should not light. Fig. 2.14 Properly Working Cabin Light Circuit 4 5 6 7 3 8 2 9 + 1 10 – 14 11 13 12 In Figure 2.15 we investigate a cabin lamp that will applying the test leads to points 10 and 11 immedi- not light.All of the switches in the circuit are on, yet the ately and discover that the circuit is OK all the way to light remains off. Furthermore, all of the other cabin the bulb holder. lights in the same circuit do work. At this point I'd simply replace the bulb. If you want We could start testing at points 1 and 14 and work to be sure it's the bulb and not the bulb holder, how- our way toward the light. If we do, we'll find that the ever, get out your multimeter and measure the resis- test lamp lights at every point, just as it did with the tance between the bulb contacts. If the multimeter previous example of a normal circuit. If we suspect a reads infinite ohms, you know you have the culprit—a burned-out bulb, however, we can save a lot of time by burned-out filament. Fig. 2.15 Defective Cabin Light Circuit 4 5 6 7 3 8 2 9 + 1 10 – 14 11 13 12 22 DC Measurements
In Figure 2.16, we uncover a broken switch in the lights up. The problem must be either in the switch or cabin light. We start as in the previous example with a the short wire between the switch and the bulb holder. cabin light that will not light up with all switches in We place the test leads across 8 and 9. Now both the on position. the test lamp and the cabin light glow dimly. What's We suspect that the bulb filament has burned out, going on? Our test lamp has bridged the broken switch, so we place our test lamp leads between points 10 and but acts like a load in series with the cabin light. This 11. The test lamp does not light. We therefore know reduces the current and brightness of both bulbs. The that 12 volts is not reaching point 10. Next we place bulb is OK, but the light switch must be replaced. the test leads between 8 and 11. Now the test lamp Fig. 2.16 Uncovering a Defective Switch 4 5 6 7 3 8 DIMLY 2 LIT 9 + 1 10 DIMLY – 14 11 LIT 13 12 In the previous two examples, a component in the when we shake or hit the case the light becomes bright circuit had failed, resulting in an open circuit and zero again. current. The problem is due to poor contact. In a boat, poor In Figure 2.17, we know the circuit is closed because contact is usually caused by corrosion of switch con- the lamp is lit. But the lamp is dim. This is a very famil- tacts or connectors. We will use this example to iar phenomenon with flashlights—the light dims, but demonstrate the use of the multimeter. Fig. 2.17 Troubleshooting with the Multimeter 4 5 6 7 3 8 4 Volts + + 2 + – – 9 12 Volts + 1 – + 10 8 Volts DIM – 14 – 11 13 12 Troubleshooting 23
Troubleshooting Just to be sure our battery isn't low, we measure A common mistake is to think you are measuring a between points 7 and 12, accessed behind the distribu- voltage when, in fact, the multimeter is in the Amps tion panel. The meter reads 12 volts, so we know the position. The result is the same—something will blow. battery is charged, and the circuit is OK up to the point where it leaves the panel for its run to the cabin lights. Next, we try the other cabin lights in the circuit. Practice Problems They light normally, so we know our problem lies Table 2.2 below is intended to give you practice in trou- inside the dimmed light fixture. We remove the fixture bleshooting a circuit. First, cover up column 3, then, base, exposing the internal switch and bulb holder referring to Figure 2.12, see if you can guess the cause wiring. We measure the voltage across the lamp itself, of the problem, given the symptoms listed in columns points 10 and 11, and the meter reads only 8 volts. 1 and 2. Column 3 lists the most likely causes. Next, we measure the voltage across the switch, points 8 and 9. The meter reads 4 volts. We have found the missing volts! Bad switch con- Table 2.2 Symptoms and Causes tacts are providing a resistance in series with the lamp, resulting in a voltage drop. In fact, one-third of the Test Light Test Light ON OFF power in the circuit is being consumed within the Between Between Most Likely Cause switch, which we note is hot to the touch. — 1 and 14 Dead battery If we suspected internal resistance in the switch, 1 and 14 2 and 14 Positive battery cable why didn't we simply place the multimeter in the ohms mode and measure the resistance of the switch directly 2 and 14 3 and 14 Battery switch off or defective between points 8 and 9? 3 and 14 4 and 14 Bad connection or broken We could have, provided (and this is an extremely cable between battery switch important "provided") we first opened the circuit by and positive bus turning off either the battery switch or the circuit 6 and 14 7 and 14 Breaker off, defective breaker, breaker. or blown fuse If we tried measuring the resistance without open- 7 and 14 8 and 14 Broken wire from breaker to ing the circuit, the 12-volt battery would still be in the light switch circuit. Figure 2.4 showed that an ohmmeter consisted 8 and 14 9 and 14 Switch off or defective of a delicate 50 µA ammeter in series with an internal resistor and 1.5-volt battery. By placing the ohmmeter 9 and 14 10 and 14 Broken wire between light switch and bulb holder circuit in series with the cabin light circuit, we have effectively added or subtracted (depending on polarity) 10 and 14 11 and 14 Burned-out lamp or poor contact between bulb the 12-volt battery from the 1.5-volt battery. In the best and holder case, the resistance reading will be grossly in error. At 10 and 14 10 and 13 Negative battery cable worst, we will burn out the 50 µA ammeter. In general, to measure the resistance of a circuit 10 and 13 10 and 11 Bad connection at negative bus or broken wire from bus component, you must first remove the component to bulb holder from the circuit by disconnecting one of its leads. Never try to measure resistance within a circuit with a live voltage. A similar caution applies to measuring current in a circuit directly with a multimeter. Many inexpensive multimeters are designed to measure currents of up to 250 mA (0.25 amp). Others contain an internal shunt that allows measurements up to 10 amps. Make sure the current in a circuit is less than the maximum your meter can handle. Otherwise, you may blow the fuse or, worse, the meter itself. 24 DC Measurements
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3 CHAPTER Batteries Lead dioxide – Sponge lead + Lead sulfate Lead/Antimony grid Porous separator Unreacted region Sulfated region Sulfuric acid electrolyte 26 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
E xcept for the diesel engine, the greatest mystery to most boaters is the black box called the ship's battery. What is a battery? Exactly what is going on inside that black box? In this chapter, you will find the simple answers and a few messy details as well. Although it is more complex than simple conduc- tors and resistors, it is useful to have an electrical model of the battery. Monitoring batteries is the key to their perfor- mance. Monitoring the discharge/charge cycle requires an understanding of discharge characteris- tics, battery discharge ratings, and charging character- istics. You'll discover that charging recommendations vary between battery types. In selecting batteries for your boat, you have several choices. In addition, you have to size the batteries to your load and decide whether to install multiple batter- ies in series or in parallel. Safe installation involves electrical and mechanical considerations, both of which are covered by ABYC standards. 27
What Is a Battery? Probably no aspect of a boat is less well understood by is in your boat's batteries. The only difference is that its owner than its batteries. Our "knowledge" of bat- your boat's batteries consist of either three of these cells teries often consists of a few remembered facts from a in series (6-volt battery) or six cells (12-volt battery). high school chemistry course, experience with our own boats and automobiles, and, unfortunately, a barrage of advertising hype. Fig. 3.1 A Galley Battery, Step 1 As with most of today's mass-marketed products, Two C- or D-cells engineering takes a backseat to marketing. Meaningful in battery holder specifications and instructions have been replaced by technical-sounding words such as "heavy-duty," "marine-grade,""deep-cycle," and "Die-Hard." Some – + – + manufacturers have gone so far as to promise boating nirvana—a battery you can stick anywhere in your boat and never give it another thought. This is most unfortunate because: (1) it is not true, and (2) nothing is more important to the cruising boat than an adequate and reliable 12-volt system. Without a reliable source of 12 volts, most of us would have no lighting, refrigeration, navigation, or communication. In fact, we couldn't even start our engines. This chapter explains what you need to know in order to select and then maintain the batteries that are Battery acid the heart of your boat's electrical system. (sulfuric acid) Lead solder To read battery manufacturers' literature, you would think that today's batteries represent recent technolog- ical breakthroughs. The truth is that the chemistry of Thomas Edison's batteries of 100 years ago is identical to the chemistry of today's batteries. But what about Fig. 3.2 A Galley Battery, Step 2 the new, sealed, gel-cell batteries you can store under your bunk? You are right—they are newer. They were patented in 1933. Most of what you need to know about lead-acid batteries can be observed in a galley experiment using a Volt-Ohmmeter glass containing a cup of battery acid (siphon some set on DC Volts from your battery, or buy a quart at the auto parts store), two lengths of lead solder, two D-cells, a battery holder, and a voltmeter. Warning: battery acid is strong – + so wear rubber gloves and be very careful. Place the D-cells in the battery holder as in Figure 3.1. Connect one length of solder to the negative end, the other length to the positive end of the battery holder, and dip their ends into the acid. Bubbles will form and rise in the acid. Soon you'll notice one of the lengths of solder turning brown. Remove the batteries and connect the voltmeter to the Battery acid solder, as shown in Figure 3.2. The voltmeter will read (sulfuric acid) about 2 volts. Lead solder You have just manufactured and witnessed the operation of a lead-acid cell—the very same thing that 28 Batteries
What Is Going On? Fig. 3.3 The Charge/Discharge Cycle What you have just witnessed is the reversible chemi- - + cal reaction found in all lead-acid batteries: charging <= PbO + Pb + 2H SO = 2PbSO + 2H O 1 H2SO4 max 4 2 2 2 4 H2O min => Fully SG max discharging Charged Figure 3.3 shows the four phases of a lead-acid cell Pb PbO2 charge/discharge cycle. (See page 32 for more on spe- cific gravity, SG.) I Fully charged. In the equation, application of an exter- - + nal charging voltage has driven the reaction all the way Load to the left. The negative electrode has become pure lead (Pb), the positive electrode is now pure lead peroxide (PbO ), and the sulfuric acid electrolyte (H SO + 2 4 2 H O) is at its maximum concentration. 2 H2SO4 ↓ 2 Discharging H2O ↑ SG ↓ Discharging. By connecting a load (shown as a resistor in Figure 3.3), we complete the electrical circuit, allow- PbO2 ↓ Pb ↓ ing electrons to flow from one electrode to the other PbSO4 ↑ PbSO4 ↑ and the chemical reaction to proceed. The H SO 4 2 breaks into H and SO ions (molecules with either 4 extra or missing electrons). The H is attracted to the - + positive electrode where it steals the O from the PbO 2 2 and forms water, H O. The now free Pb combines with 2 the SO ions to form PbSO in place of the PbO .At the 4 4 2 negative electrode, SO ions also combine with the pure H2SO4 min 4 Pb to form more PbSO . Thus, both electrode materials 3 H2O max 4 Fully are converted to lead sulfate, PbSO , while the elec- Discharged SG min 4 trolyte loses sulfuric acid, H SO , gains water, H O, and 4 2 2 becomes more dilute. Pb min PbO2 min PbSO4max PbSO4max Fully discharged. The cell is fully discharged when it runs out of one of the necessary ingredients. Either the I PbO has been totally converted to PbSO , or all of the - Charger + 2 4 SO ions in the electrolyte have been used up, reduc- 4 ing it to pure water. In either case, PbO and electrolyte 2 strength have been minimized and PbSO maximized. 4 Charging. By connecting a charging voltage to the cell 4 H2SO4 ↑ we drive the electrons and the reaction in the reverse Charging H2O ↓ SG ↑ direction. Ideally, the negative electrode is restored to pure PbO , the positive terminal to pure Pb, and the 2 Pb ↑ PbO2 ↑ acid electrolyte to its maximum strength. PbSO4 ↓ PbSO4 ↓ What Is a Battery? 29
A Few Messy Details The good news is that the chemistry of the lead-acid gas and lose electrolyte.Water can be replaced in a con- battery is simple. The bad news is that the way in which ventional wet-acid battery. In a sealed or gel-cell bat- it actually happens is a bit more complex. tery, it cannot. Figure 3.4 shows a cross section of a cell. Both pos- • As we have seen, charging regenerates the H SO 4 2 itive and negative electrodes are immersed in elec- electrolyte. Pure H SO is 1.83 times as dense as water. 2 4 trolyte. The reactive materials, lead and lead peroxide, As the H SO is generated, it tends to sink. Since it is the 4 2 are suspended on lead grids that serve to both support H SO that makes the electrolyte conductive, its 4 2 the materials and conduct electric current. So far, so absence at the top of the cell limits the acceptance of simple. Now for the complications: charging current. In a conventional wet-acid battery, • Boat batteries are bounced around. In order that acceptance is slow until gassing begins. Rising gas bub- the plates not touch each other and short-circuit the bles then mix the electrolyte, and acceptance increases. cell, the many closely spaced plates (electrodes) are • Gelled-electrolyte batteries capture the electrolyte interleaved with porous fiberglass separators. in a gel, preventing stratification and increasing initial • The lead grid is chemically and electrically com- charge acceptance. "Starved electrolyte batteries" patible with the active materials that it supports, but it accomplish the same goal by limiting the electrolyte to is not very strong. To increase strength, it is alloyed with just enough to saturate the porous separators. either antimony (conventional wet, deep-cycle batter- • Most serious is the phenomenon of sulfation. If a ies) or calcium (sealed, maintenance-free batteries). battery is left in a discharged state (i.e., with much of its • When the discharge reaction starts, lead sulfate electrodes in the form of PbSO ), the initially fine, soft 4 first forms at the electrode surfaces. As discharge con- deposits grow into larger, harder crystals that clog the tinues, the already formed sulfate forms a barrier holes of the sponged electrodes. The battery becomes between the electrolyte and the unreacted material difficult to charge and displays reduced capacity.Vigor- beneath, slowing the reaction and limiting the current. ous overcharging and bubbling (equalization) can The greater the surface area and thinner the plates, the break up and dislodge the crystals, resulting in recovery greater the possible current flow. Engine-starting bat- of much of the original capacity. However, each time it teries have many thin plates in order to provide large is done, the plates shed more material and get closer to currents for short periods. The electrodes are also the end of their useful lives. "sponged" (made full of minute holes) in order to fur- So you see that, although the basic chemistry of all ther increase surface area. lead-acid batteries is the same, there are enough varia- • Lead, lead peroxide, and lead sulfate are not of the tions in construction to allow battery company mar- same density. When one replaces the other, expansion keting departments a field day. and contraction tend to dislodge the materials from the grids. Each time a cell is cycled, a small amount of lead Fig. 3.4 Cross Section of a Lead-Acid Battery Cell sulfate is shed and falls to the bottom of the cell. Even- Lead dioxide Sponge lead tually the accumulation at the bottom may short out – + the plates. The more complete the reaction (the deeper Lead sulfate the discharge), the greater the loss. Batteries designed Lead/Antimony grid for deep-cycling have fewer but thicker plates. • When a battery is fully charged, all of the lead sul- Porous fate of the positive plate has oxidized to lead peroxide. separator Further charging (overcharging) oxidizes the lead of the grid as well, turning it into lead peroxide. Lead per- Unreacted oxide has little mechanical strength, and the grid will region ultimately fall to the bottom of the cell. Sulfated • The rest of the overcharging energy goes into region hydrolysis—separation of the water of the electrolyte into H and O —which we saw as bubbles in our Sulfuric acid 2 2 electrolyte kitchen battery. Various tricks are employed in sealed batteries to recombine the gases into water, but, if over- charging and gassing are too vigorous, all batteries vent 30 Batteries
Electrical Model of Batteries An ideal voltage source would supply unlimited cur- Example: We monitor the current drawn by a starter rent, with no drop in voltage. Considering the con- motor as 200 amps.As soon as we switch on the starter, struction of the battery shown in Figure 3.4 and the we observe a drop in battery voltage from 12.5 to 9.5 messy complications described above, it is obvious that volts. The battery's internal resistance, R , is then: i the lead-acid battery is not an ideal source. For current to flow, the SO and H ions have to find R = V/I 4 i their way through the electrolyte. Resistance to this = (12.5 – 9.5) volts/200 amps movement is evidenced as an internal electrical resis- = 0.015 ohm tance, R . i When we disconnect a battery from an external cir- The voltage must be measured at the battery ter- cuit, no current should flow—at least theoretically. minals to eliminate the drop in the battery cables. However, there is still voltage inside the cell ready and R is typically quite large—on the order of 1,000 to p willing to supply current to anything that might bridge 10,000 ohms. It can be deduced by observing the drop the gap between the battery's electrodes. Impurities in battery stored capacity over time. in the electrolyte, as well as dirt and spilled electrolyte Figure 3.6 shows the self-discharge of a typical new on the surface of the battery, provide such paths. They battery at different temperatures. result in a parallel resistance, R , acting to self- p discharge the battery. This is why you should never add Fig. 3.6 Battery Self-Discharge vs. Time anything but distilled or demineralized water to your battery and why it is a good idea to keep its surfaces 100 clean. Figure 3.5 shows the electrical model of the battery 90 41 ° F consisting of an ideal voltage source with a series inter- nal resistance, R , and a parallel self-discharge resis- 80 i tance, R . Since chemical reactions always speed up Retained Capacity, % 68 ° F p with temperature, both resistances decrease with 70 increasing temperature. 86 ° F 60 Fig. 3.5 Electrical Model of the Battery + 104 ° F 50 0 3 6 9 12 15 18 Storage Time, Months R i Example: At 68°F, the battery loses the first 10% of charge in three months. If this is a 100 Ah battery, it R p loses 10% of 100 Ah, or 10 Ah over a period of 90 days. + Since there are 24 hours in a day, the discharge period 12V is 90 24, or 2,160 hours. The average discharge cur- × rent was thus 10 Ah/2,160 hours = 0.0046 amp. Using – Ohm's Law, – R = V/I p = 12 volts/0.0046 amp = 2,600 ohms R in a new lead-acid battery is very small—of the i order 0.01 ohm. It can be measured by drawing a The effect of temperature on R is evident from the p known current and observing the drop in voltage at the discharge curves. Performing the same calculations as terminals. above, we find that R at 40°F is 7,900 ohms, while at p 104°F it has dropped to just 930 ohms. Electrical Model of Batteries 31
Monitoring Battery Health Determining State of Charge Fig. 3.7 Correcting Measured Specific Gravity for Temperature Short of taking a battery apart and weighing the Add to At these amounts of chemicals present, how can we determine temperatures specific gravity the state of charge? Later we will describe battery- 120 ° F +0.016 charge regulators/monitors that regulate and keep 110 ° F +0.012 track of the amperes flowing into and out of a battery. 100 ° F +0.008 For now, we will consider the more basic methods that 90 ° F +0.004 have been used since batteries were invented. 80 ° F 0.000 First, in what sorts of units do we measure the 70 ° F − 0.004 amount of energy stored in a battery? As stated in 60 ° F − 0.008 Chapter 1, electrical energy is measured in watt- 50 ° F − 0.012 hours—the watts of power dissipated by the current 40 ° F − 0.016 flowing through a load times the duration of the flow 30 ° F − 0.020 in hours. Again, watts equals current times voltage: 20 ° F − 0.024 W = I V 10 ° F − 0.028 × where I = amps through the load 0 ° F − 0.032 V = volts across the load However, since the voltage of a battery is always nominally 12 volts until nearly discharged, it is custom- ary to drop the term "volts" and refer to the amount of Example: A battery is located in the engine com- energy drawn from or stored in a battery simply as partment. The temperature of the electrolyte is 95°F. ampere-hours (Ah). The hydrometer reads 1.250. What is its SG, corrected As an example, suppose we charge a battery at the to 80°F? Answer: 1.250 + 0.006 = 1.256. constant rate of 50 amps for 2 hours. At the end of 2 Figure 3.8 shows the relationship between state of hours we will have put 50 amps 2 hours, or 100 Ah, charge and electrolyte SG for a typical new lead-acid × into the battery. Then let's draw a constant 5 amps from battery. The form of the relationship is always correct, the battery for 10 hours. At the end of the 10 hours we but: will have drawn 5 10, or 50 Ah, out of the battery. 1. The high and low SG end points are particular to × Theoretically there should be 100 Ah – 50 Ah, or 50 Ah, still in the battery. the individual battery, depending on age, condi- Battery electrolyte is a mixture of water (density tion, and the preferences of the manufacturer. High SG is more often between 1.265 and 1.280. 1.000 gram/cubic centimeter) and sulfuric acid (den- 2. The SG has been measured only after the bat- sity 1.830 grams/cubic centimeter). Since flow of elec- tricity into and out of a battery results in either the gen- tery has rested for a time sufficient for the elec- eration of sulfuric acid or the loss of sulfuric acid, the trolyte to become homogeneous through diffu- sion, usually considered to be 24 hours. amount of stored energy in a battery is, therefore, a lin- 3. The SG has been corrected to the standard tem- ear function of the density of the electrolyte. Electrolyte density is usually expressed as its specific perature of 80°F. gravity—the ratio of its density to the density of water. Battery manufacturers can make the SG any value Specific gravity (SG) is measured with a battery they wish.A more concentrated electrolyte (higher SG) hydrometer calibrated for the range of electrolyte den- produces higher voltage and increased capacity, but it sities normally found in a battery, 1.000 to 1.300. Do also leads to shorter battery life. SGs are made higher in not confuse a battery hydrometer with an antifreeze colder climates. Most new battery high SGs fall in the coolant hydrometer, which is designed to measure SGs range 1.265 to 1.280. of less than 1.000. When a sample of electrolyte is Figure 3.9 shows a second electrochemical relation- drawn into the hydrometer, a float indicates the SG. ship—this time between SG and voltage. The open cir- However, the indicated SG must be corrected to what it cuit (no current being withdrawn) voltage of a single would be at a standard temperature, 80°F. Figure 3.7 lead-acid cell is determined by the homogeneous, tem- shows the corrections to make. perature-corrected electrolyte SG as: 32 Batteries
V = 0.84 + SG Fig. 3.8 Battery Remaining Capacity vs. Specific Gravity For a 12-volt (six-cell) battery the relationship 100 becomes that in Figure 3.9: V = 6 (0.84 + SG) 80 × Using either Figure 3.8 or Figure 3.9 requires that we actually measure the SG of the electrolyte. This 50% discharge operation is messy, destructive of clothing, awkward 60 in the spaces where batteries are usually stowed, and Remaining Capacity, % impossible with a sealed battery. 40 Fortunately, Figures 3.8 and 3.9 can be combined, resulting in the more convenient relationship between 20 state of charge and open-circuit voltage shown in Fig- ure 3.10. The figure shows that, after 24 hours of rest, 0 1.050 1.100 1.150 1.200 1.250 1.300 this battery would read 11.6 volts when fully dis- Specific Gravity after 24 Hours charged, 12.7 volts when fully charged, and 12.2 volts when 50% discharged. If we can wait 24 hours, determining the remain- ing capacity of a battery is simple using an accurate Fig. 3.9 Battery Open-Circuit Voltage vs. Specific Gravity voltmeter. The 24-hour rest period is provided by switching between two battery banks daily. 1.300 Why do we say the battery is fully discharged at 11.6 1.250 volts when the battery obviously has some amount of charge remaining? It is destructive to discharge a mul- 1.200 ticelled, lead-acid battery to 0 volts. With even small Specific Gravity after 24 Hours differences between cells, as 0 volts is approached, the 1.150 stronger cells can drive the weaker cells into reversed polarity. Their grids will be damaged by being con- 1.100 verted to PbSO . To avoid damage, "fully discharged" 4 is defined as 10.5 volts at the 20-hour discharge rate. 1.050 For example, for a 100 Ah battery, fully discharged is 1.000 the point where the voltage reads 10.5 V, at a discharge 11.6 11.8 12.0 12.2 12.4 12.6 12.8 current of 100 Ah/20 hours = 5 amps. Open-Circuit Battery Voltage after 24 Hours Self-Discharge and Winter Storage House batteries are very heavy, so it would be nice if Fig. 3.10 Battery Remaining Capacity vs. Voltage we could leave the really big ones on the boat over the 100 winter. Pure water (fully discharged electrolyte) would freeze and crack the battery case. However, fully 80 charged electrolyte (SG = 1.265) freezes at –72°F, while half-charged electrolyte (SG = 1.190) freezes at –12°F. 60 50% discharge The question for northern boatowners thus Remaining Capacity, % becomes how quickly a battery that has been washed with a baking-soda solution, rinsed with fresh water, 40 fully charged, and disconnected from its leads will self- discharge. According to Rolls Battery, at an average 20 temperature of 50°F, such a battery would discharge at about 0.0003 SG per day. To drop from SG 1.265 to SG 0 11.6 11.8 12.0 12.2 12.4 12.6 12.8 1.190 (freezing point –12°F) would take 250 days. Open-Circuit Voltage after 24 Hours Monitoring Battery Health 33
Discharge Characteristics Earlier we noted the custom of measuring battery Fig. 3.11 Battery Discharge Characteristics capacity in Ah. At small charge and discharge rates, the 13 losses due to internal resistance are small, and the num- bers of Ah we can withdraw very closely approximate 12 the numbers of Ah we have put in. When discharging at high currents, however, there 11 10.5V is an apparent loss of battery capacity.As discharge cur- 10 .25C .05C rent increases, the internal voltage drop through the Battery Voltage Under Load battery's internal resistance increases, so the 10.5-volt 9 cutoff point is reached sooner. Thus cutoff voltage for starter-motor applications is reduced to 7.2 volts. 8 Figure 3.11 shows discharge voltage vs. time at frac- 7 7.2V 2C 1C tions of the 20-hour Ah capacity, C. When a battery's 1 2 3 5 10 30 1 2 3 5 10 20 capacity, C, is stated as 200 Ah at the 20-hour discharge Minutes Hours Discharge Time at 68 ° F rate, it means that, when discharged at a constant rate of 0.05C (0.05 200 = 10 amps), the output voltage will × fall to the zero-capacity cutoff of 10.5 volts in 20 hours. If the discharge rate is increased to 0.25C (50 amps), however, it will fall to 10.5 volts in about 3 hours. In the Fig. 3.12 Capacity as a Function of Discharge Time first case, 10 amps 20 hours = 200 Ah. In the second × case, 50 amps 3 hours = 150 Ah. Discharged at 0.25C, 110 × the battery seems to have only 75% of its rated capacity. 100 This apparent loss of capacity vs. discharge rate is 90 clearly shown in the more general curve of Figure 3.12. Note, that if we discharge at less than the 20-hour rate, % of 20 Hr Capacity Available 80 the apparent capacity is greater than 100%. If this does 70 not surprise you, it shows that you understand the effect of battery internal resistance. 60 Since internal resistance is strongly affected by elec- 50 trolyte temperature, we would expect a family of such discharge curves for different temperatures. 40 0 5 10 15 20 25 Figure 3.13 shows capacity vs. both discharge rate Discharge Time, Hours and temperature. As in Figure 3.12, at 80°F, a battery discharged at five times the 20-hour rate (5 0.05C = × 0.25C) gives us 75% of its rated capacity. At 0°F and 0.25C, only 45% of the rated capacity is available. You may be wondering how this loss of Ah squares Fig. 3.13 Capacity as a Function of Temperature with the principle that electrons are neither created nor destroyed. Where did all those electrons go? 120 They are still there in the battery—they just got left 100 20 hr rate x1 behind. Due to the heavy current, the electrolyte in the plates was temporarily depleted. If we allow the bat- 80 x5 tery to rest awhile, electrolyte ions will diffuse into the % of 20 Hr Capacity x20 plates, and, when we start drawing current again, we'll 60 x40 find the voltage has recovered to more than 10.5 volts. 40 This recovery is a familiar phenomenon to those who have had to start balky automobiles in subzero weather. 20 If we are, in fact, willing to withdraw the current at a much lower rate, we will succeed in retrieving nearly 0 0 20 40 60 80 100 120 100% of our invested Ah. Temperature, ° F 34 Batteries
Battery Discharge Ratings The first two ratings are of most interest to boat- Because batteries are used in widely varying applica- owners. When running on battery power, the "house" tions, several standard capacity ratings have evolved: batteries are usually required to run from the time the engine is turned off until it is turned on again. For a 1. Ah at 20-hour rate—amps a battery will supply for cruising boat, the period is likely to last from 16 to 24 20 hours at 80°F, before dropping to 10.5 volts, hours, so the 20-hour Ah rating is an appropriate spec- times 20 hours. ification. 2. Cold cranking amps (CCA)—minimum number of Extremely large currents are drawn by engine start- amps a battery can supply for 30 seconds, at a tem- ing motors. You can obtain the CCA required by any perature of 0°F, before dropping to 7.2 volts. engine from its manufacturer. Small diesels, in the 10 to 3. Reserve capacity—number of minutes a battery will 50 hp range, require from 200 to 500 CCAs. supply a specified constant current (usually 25 Table 3.1 lists the three ratings, as well as other spec- amps) at 80°F, before dropping to 10.5 volts. ifications, for the most popular marine batteries. Table 3.1 Specifications of Popular Marine Deep-Cycle Batteries Capacities Dimensions, in. Brand Model Type 1 Ah, 20 hr CCA Reserve L W H Weight, lb. SIZE 24 Surrette/Rolls 24HT80M WA 80 324 163 11.0 6.8 9.5 50 Trojan 24-AGM WA 80 440 130 10.8 6.6 8.2 52 Exide Stowaway ST24DC140 AGM 80 400 140 10.3 6.6 9.4 – Lifeline 24 AGM 80 550 149 10.9 6.6 9.3 53 Deka Gel-Tech 8G24 GE 74 410 140 10.9 6.8 9.9 53 SIZE 27 Surrette/Rolls 24HT90M WA 90 405 183 12.5 6.8 9.5 62 Trojan 27-AGM WA 99 560 175 12.0 6.6 8.2 66 Exide Stowaway ST27DC180 AGM 105 500 180 12.8 6.8 9.5 – Lifeline 27 AGM 95 575 176 12.6 6.6 9.3 63 Deka Gel-Tech 8G27 GE 86 505 170 12.8 6.8 9.9 63 SIZE 4D Surrette/Rolls 12HHG185M WA 185 800 344 20.8 8.8 10.0 122 Trojan 4D-AGM WA 165 1110 325 20.9 8.3 8.5 115 Exide Stowaway ST4DDC250 AGM 160 600 250 20.8 8.8 10.9 – Lifeline 4D AGM 210 1100 380 20.7 8.7 10.3 130 Deka Gel-Tech 8G4D GE 183 1050 395 20.8 8.5 10.0 129 SIZE 8D Surrette/Rolls 12HHG8DM WA 275 1155 557 20.8 11.0 10.0 172 Trojan 8D-AGM WA 230 1450 460 20.5 10.6 8.0 155 Exide Stowaway ST8DDC400 AGM 200 800 400 20.8 11.0 10.9 – Lifeline 8D AGM 255 1350 461 20.6 11.0 10.2 158 Deka Gel-Tech 8G8D GE 225 1265 500 20.8 11.0 10.0 161 6-VOLT GOLF CART Trojan T-105 WA 225 — 447 10.4 7.1 10.9 62 Exide E3600 AGM 220 800 400 10.5 7.2 11.5 62 Lifeline GC4 AGM 220 760 452 10.4 7.1 11.6 66 Deka Gel-Tech 8G6V200 GE 180 585 375 10.3 7.1 10.9 72 1 WA = wet-acid, AGM = absorbed glass mat, GE = gelled electrolyte Discharge Characteristics 35
Charging Characteristics Charging a battery is the process of driving the lead- Optimally Fast Charging acid chemical reaction backward through application Optimally fast charging (charging as rapidly as possible of an external voltage. To fully charge a battery, we without damage) involves four phases (Figure 3.14). must convert 100% of the PbSO back to Pb and PbO . 4 2 On a boat, because charging requires running an engine, the usual goal is to recharge the battery as Fig. 3.14 Optimally Fast Charging quickly as possible without damaging it. Damage can Float occur through excessive gassing, overcharging, and Bulk Absorption cycle cycle cycle overheating. 15.0 I=4%C till V=17.5 Gassing. When the conversion of PbSO to Pb and V=14.4 till I=5%C Equalize once/mo. 4 PbO cannot keep pace with charging current, excess Charging Voltage 75% 85% 2 current results in hydrolysis, splitting the electrolyte's 14.0 V=14.4V Constant 13.5V water molecules into gaseous hydrogen and oxygen. till Wet-acid batteries vent the gases and thereby lose 13.0 I=25%C water. Through various tricks, including internal pres- sure, sealed batteries can recombine small amounts of 50% gas and prevent water loss. However, even the best 12.0 Time sealed batteries, including those with gelled electrolyte, Bulk cycle. If a healthy wet-acid battery is discharged can be overcharged to the point where they vent gas. No battery is totally immune to loss of electrolyte and more than 25% of its capacity, C, it will readily accept subsequent loss of capacity. For this reason most gel- charge rates of 0.25C or more, up to the point where it cell battery manufacturers specify a maximum charg- is about 75% charged. Gelled-electrolyte batteries, ing voltage of 13.8 volts, as opposed to the 14.2 to 14.6 because they do not suffer from electrolyte stratifica- specified for wet-acid batteries. tion, will typically accept charge rates of up to 0.5C. Absorption cycle. When a battery reaches its 75% Overcharging. A battery is fully charged when all of its charged state, the charging voltage has increased to PbSO has been converted to Pb. As current continues around 14.4 volts, and gassing begins. At this point, in 4 to flow, gassing continues, as above, with the same order to limit gassing, the charging voltage must be destructive effect. Even more damaging, however, is held constant at 14.4 volts or less, while the battery oxidation of the positive grids into PbO , a relative absorbs current at its own decreasing rate. At the point 2 nonconductor. The resulting increase in internal resis- where the constant-voltage current has dropped to a tance decreases both the battery's charge acceptance rate of 0.05C, the battery is approximately 85% rate and its ability to supply large discharge currents. charged; at 0.02C about 90% charged; and at 0.01C Overheating. A battery should never be charged when nearly 100% charged. How far the absorption cycle is its temperature is over 120°F. Internal heat is gener- carried depends on whether the engine is being run ated by the internal resistance of the battery.At a charg- only for charging (0.05C cutoff recommended), or ing current, I, of 100 amps and an internal resistance, whether the boat is under power or using shore power R , of 0.01 ohm, the heat generated would be: (0.01 to 0.02C cutoff recommended). i Watts = I 2 × R i Float cycle. The final stage, provided the battery is still = 100 amps 100 amps 0.01 ohm in the charge mode, is designed to just maintain the × × = 100 watts battery in its fully charged condition. If a battery is Note that the heat generated is proportional to the removed from all loads, as in the case of winter storage, square of the charging current, so a 100-amp charge the ideal float voltage is about 0.1 volt above the rested, rate would generate four times as much heat as a 50- open-circuit voltage, or approximately 13 volts. If the amp rate. The internal temperature rise is in addition battery is in a float cycle, but still online so that cur- to the ambient temperature of the space where the bat- rent is occasionally withdrawn, either the charger tery is located.A good way to kill batteries is fast charg- should be capable of supplying the entire draw, or the ing in a hot engine compartment while underway in float voltage should be increased to between 13.2 and the tropics. 13.5 volts. 36 Batteries
Charging Recommendations Equalization. As we saw on page 29, a fully charged bat- Table 3.2 Charging Parameters for Marine Batteries tery consists of pure lead plates immersed in a sulfuric (from PROsine 2.0 Inverter/Charger User's Manual) acid electrolyte; a fully discharged battery consists of Bulk/Absorption Float Equal. lead sulfate plates in pure water. If a battery is cycled Battery Vmax Imax Vmax Vmax short of full charge its plates will retain the last 10% of Canadian Tire Nautilus 5 14.1 25 13.0 17.5 lead sulfate. Over time this lead sulfate hardens and Canadian Tire Gel (Exide) 6 14.2 25 13.5 NR* resists both breaking down and current flow.As a result Concord AGM Valve Regulated 3 14.3 30 13.4 NR of the electrical resistance the battery shows a falsely Delco 1150, 1200, 2000, 16.0 20 13.5 17.5 Voyager (Delphi) high voltage, appearing to be fully charged when it Douglas Marine Deep Cycle 21 14.6 20 13.5 17.5 isn't. Over time the effective capacity of the battery Duralast Flooded Deep Cycle/ shrinks. Starting 14.8 25 13.6 15.5 The cure is equalization—a controlled overcharge, Duralast Flooded Starting/ during which the cells are brought back to their fully Deep Cycle 15.5 25 13.7 16.0 charged states. A constant current of 0.04C is applied Energizer Flooded Deep Cycle/ 14.8 25 13.6 15.5 Starting for 4 hours, or until battery voltage rises to the manu- Energizer Flooded Starting/ facturer-specified equalization voltage for the particu- Deep Cycle 15.5 25 13.7 16.0 lar battery. Overcharging forces all of the PbSO in each Eveready Flooded Deep Cycle/ 14.8 25 13.6 15.5 4 Starting cell to be converted, so that, except for material previ- Eveready Flooded Starting/ ously lost by shedding, each cell is restored to its origi- Deep Cycle 15.5 25 13.7 16.0 nal condition. Overcharging also causes gassing and, Exide Flooded 5 14.1 25 13.0 17.5 in wet-acid batteries, loss of electrolyte. After equaliza- Exide Gel Master 6 14.2 25 13.5 NR tion, wet-acid cells should be topped off with distilled GNB Action Pac 7 14.5 25 13.5 17.5 water. Because of the gassing, equalization should be GNB Evolyte 9 14.4 30 13.5 17.5 applied with care to sealed batteries and not at all to GNB Stowaway 8 15.3 25 14.3 17.5 gelled-electrolyte batteries (see pages 40–41 for bat- GNB Sunlyte 10 14.1 30 13.5 14.2 tery types). Hawker Energy Genesis 14 15 200 13.7 NR Interstate Flooded Deep Cycle/ Equalization should not be performed too often, Starting 14.8 25 13.6 15.5 however, since overcharging also oxidizes the positive Interstate Flooded Starting/ plates. It should be performed whenever cell specific Deep Cycle 15.5 25 13.7 16.0 gravities differ by 0.030 or more, indicating a difference Interstate Optima, Normal 19 14.7 200 13.5 17.5 in capacities of 15% to 20%. Alternatively, for batteries Johnson Contr Flooded Deep 14.8 25 13.6 15.5 Cycle/Start cycled daily, a routine equalization schedule of once per Johnson Contr Flooded Start/ month is recommended. Deep Cycle 15.5 25 13.7 16.0 Keystone Solid Energy Flooded 16 14 10 13.5 16.5 Each manufacturer publishes a recommended method Keystone Solid Energy Gel 15 14.2 12 13.7 16.5 for recharging its products. Sealed batteries are less Metra Electronic—Tsunami 19 14.7 200 13.5 17.5 likely than wet-acid batteries to require equalization Optima Blue, Red, Yellow Top 19 14.7 200 13.5 17.5 because they ordinarily neither lose nor gain elec- Rolls Deep Cycle (Surrette) 18 14.2 20 13.2 15.5 Sears Canada Marine (Delco)17 13.5 17.5 16.0 20 trolyte. Furthermore, they might gas excessively and Sears Canada Marine Flooded lose electrolyte if subjected to a high voltage. Constant- (Exide) 5 14.1 25 13.0 17.5 current charging is a possibility with wet-acid batter- Sears USA Flooded Deep Cycle/ ies because limited accidental overcharging results only Starting 14.8 25 13.6 15.5 in loss of replaceable water. Sealed-battery manufactur- Sears USA Flooded Starting/ 15.5 25 13.7 16.0 Deep Cycle ers, however, fear such an accident and so recommend Sears USA Gel 11 14.4 30 13.8 NR constant voltage with limited-current charging. Sonnenshein (all) 2 14.2 25 13.8 NR Automotive-type regulators can be set only to a sin- Surrette Deep Cycle 18 14.2 20 13.2 15.5 gle voltage. Regulators that can be programmed for Trojan (all) 1 14.4 30 13.5 17.5 optimally fast charging will be covered in Chapter 4. West Marine Sea Volt (Trojan) 1 14.4 30 13.5 17.5 Table 3.2 compares optimally fast charging voltages West Marine Sea Gel (Sonnenshein) 14.2 25 13.8 NR and currents for most "marine" batteries. *NR = Not Recommended Charging Recommendations 37
Estimating Your Daily Load The first step in selecting storage batteries is to deter- For many of the devices, two ratings have been mine the daily consumption of electricity in Ah. Table listed: (1) the typical consumption, and (2) the con- 3.3 lists equipment commonly found on boats. Power sumption of the most efficient models. The table shows ratings can usually be found on a nameplate, either in the total Ah/day for two cruisers: (1) with typical appli- watts or in amps. Make your own table using the form ances, and (2) with the most efficient appliances. shown in Table 3.4. To calculate the daily Ah require- The boat with typical appliances consumes 99 ment, first convert all nameplate ratings to amps by Ah/day, while the more efficient boat consumes only dividing watts by 12. Next multiply by the average half as much. The more efficient boat will thus require hours used per day to get Ah. Finally, add the Ah for only half as large a battery system, or, alternatively, will all the devices for the total Ah/day. go twice as long before requiring recharging. Table 3.3 Power Consumption for Cruising Boats at Anchor ÷12 = Average Hours Typical Efficient Area Appliance or Fixture Watts Amps per Day Ah Ah Galley Microwave (9 minutes/day) 550 45.8 0.15 6.9 6.9 Toaster (5 minutes/day) 800 66.7 0.04 Blender (30 seconds/day) 175 14.6 0.01 0.15 0.15 Coffee grinder (15 seconds/day) 160 13.3 0.005 2\" Refrigerator insulation 60 5.0 10 50.0 4\" insulation 60 5.0 5.0 21.9 Head Hair dryer (2 minutes/day) 1200 100 0.033 Lighting Reading lamp 2 incandescent 15-watt 30 2.5 2 5.0 2 halogen spots 5-watt 10 0.8 2 1.6 Galley fixture 2 incandescent 25-watt 50 4.2 2 8.4 2 fluorescent 8-watt 16 1.4 2 2.8 Anchor light manual 10-watt 10 0.8 14 11.2 automatic 10-watt 10 0.8 11 8.8 Fans Typical 6\", 100 cfm 12 1.0 5.0 5.0 Most efficient, 100 cfm 4 0.3 5.0 1.5 Entertainment Stereo 20-watt/channel 60 5.0 1.0 5.0 7-watt/channel 3.01.0 3.0 35 Television 19-inch CRT 80 6.7 4.0 15-inch LCD 36 3.0 2.0 6.0 6-inch color 15 1.7 4.0 3.4 VCR or DVD typical 110-volt AC 17 1.4 1.0 1.4 12-volt DC play only 10 0.8 1.0 0.8 Totals 99.150.9 38 Batteries
Table 3.4 Form for Estimating Power Consumption at Anchor ÷12 = Average Hours Estimated Area Appliance or Fixture Watts Amps per Day Ah Galley Microwave (9 minutes/day) 550 45.8 0.15 __________ Toaster (5 minutes/day) 800 66.7 0.04 __________ Blender (30 seconds/day) 175 14.6 0.01 __________ Coffee grinder (15 seconds/day) 160 13.3 0.005 __________ Refrigerator insulation 60 5.0 10 __________ 2\" 4\" insulation 60 5.0 5.0 __________ Head Hair dryer (2 minutes/day) 1200 100 0.033 __________ Lighting Reading lamp 2 incandescent 15-watt 30 2.5 2 __________ 2 halogen spots 5-watt 10 0.8 2 __________ Galley fixture 2 incandescent 25-watt 50 4.2 2 __________ 2 fluorescent 8-watt 16 1.4 2 __________ Anchor light manual 10-watt 10 0.8 14 __________ automatic 10-watt 10 0.8 11 __________ Fans Typical 6\", 100 cfm 12 1.0 5.0 __________ Most efficient, 100 cfm 4 0.3 5.0 __________ Entertainment Stereo 20-watt/channel 60 5.0 1.0 __________ 7-watt/channel 3.01.0__________ 35 Television 19-inch CRT 80 6.7 4.0 __________ 15-inch LCD 36 3.0 2.0 __________ 6-inch color 15 1.7 4.0 __________ VCR or DVD typical 110-volt AC 17 1.4 1.0 __________ 12-volt DC play only 10 0.8 1.0 __________ Other __________ __________ __________ Total Estimating Your Daily Load 39
Choosing a Battery Type Forget the marketing terminology you have seen in Some boaters still carry a small automotive engine- battery advertisements. Batteries can be divided into starting battery as a safety backup, however. four general categories: Absorbed-glass mat batteries were developed as superior 1. Conventional, wet-acid automotive starting engine-starting batteries, but are being used more and 2. Deep-cycle, wet-acid more as marine house batteries. They retain all of their 3. Absorbed glass mat electrolyte in spongy fiberglass mats and are "sealed" 4. Gelled electrolyte with valve-regulated caps, which recombine charging gases under most conditions. The thin, porous plates Conventional, wet-acid automotive starting batteries are that yield high starting-motor currents do not stand up engineered to supply extremely high currents (200 to as well as those of deep-cycle, wet-acid types. How- 1,000 amps) for periods of just a few seconds. In spite ever, they can both discharge and recharge at much of the high current, the duration is so short that the higher rates than wet-acid batteries. Because so many amount of energy drawn (amps hours, or Ah) is of these batteries are sold, competitive pricing makes × small. Used in this way, automotive starting batteries them attractive. Provided discharge is limited to are typically discharged only a few percent of their around 50%, they are suitable for the seasonal boater capacity before returning to the float state. who expects to replace the batteries every 3 or 4 years. The rate at which current can be drawn is propor- tional to plate area, so starting batteries are constructed with a large number of thin lead plates sandwiched between paper or plastic separator plates. When cycled Fig. 3.15 Nominal Battery Dimensions deeply, battery plate material is shed. Since starting bat- tery plates are so thin to start with, deep cycling will 10.5\" 12.5\" result in short life. Size 24 Size 27 Don't be fooled by warranties of 60 or more 12V 6.6\" 12V 6.6\" months or names such as "Die-Hard." While fine for starting the engine, if used to power your cabin lights 9\" 9\" and other house loads, you will be replacing this type of 21\" battery every season or two. Used only to start the engine, provided they are recharged immediately after Size 4D use, they make a good combination with a large, deep- 12V 9\" cycle house battery. 10\" Deep-cycle, wet-acid batteries have fewer but thicker plates designed for regular discharge to 50% or less of 21\" capacity. The largest users of such batteries are not boats but golf carts and forklifts, which require large currents and capacities, in addition to the ability to Size 8D 11\" cycle thousands of times. Such batteries have the max- 12V imum cycling potential and are ideally suited to cruis- ing boats with heavy house loads and long seasons, 10\" provided their owners are willing to spend the time monitoring and maintaining them. 2 x 10.5\"= 21\" In a well-equipped cruising boat, a deep-cycle house bank will also have sufficient cold-cranking Golf cart Golf cart 7\" 6V 6V capacity to start the engine. If, as recommended, the house batteries are separated into two banks, there is little need for a dedicated engine-starting battery. 11\" 40 Batteries
Gelled-electrolyte batteries were developed for applica- long seasons, and owners who are totally unwilling to tions where acid spills and gas venting were prohibited, monitor and maintain their batteries. Before purchas- such as military tanks and wheelchairs. Freedom of ing, however, you should seriously consider the AGM location and from maintenance have made them pop- battery, which shares many of the gel's advantages, yet ular on boats. They cannot be deep cycled as many may be occasionally and moderately overcharged. times as wet-acid, deep-cycle batteries, but they are less Figure 3.15 shows the nominal sizes of the most subject to damage if left in a discharged state, and popular batteries. Actual sizes vary, so assume an extra accept somewhat higher recharge rates.With the caveat 1 ⁄2 inch all around, or get actual specifications. that their lower charging voltages must never be Table 3.5 compares the advantages and disadvan- exceeded, gel-cells are suited to boats with large loads, tages of the four battery types. Table 3.5 Comparing Battery Types Battery Type Advantages Disadvantages Wet-acid automotive Lowest cost Can't stand many deep discharges High cranking amps Will be destroyed if left discharged Good for engine start battery Will spill electrolyte if tipped over Small, lightweight Relatively short life Relatively fragile Wet-acid deep-cycle Less expensive than gels and AGMs Electrolyte level must be monitored Maximum deep-cycle life (>1,000) Will be destroyed if left discharged too long Individual cells accessible Will spill electrolyte if tipped over Can be equalized Must be installed upright Water can be added to electrolyte Battery box should be vented overboard Extremely heavy Gelled electrolyte (gel-cell) Very rugged Most expensive Requires least attention, May be destroyed by overcharging provided not overcharged Moderate deep-cycle life (500 likely) Can be installed in any position Doesn't require venting Won't leak even if cracked Accepts high charge rate Absorbed glass mat (AGM) Most rugged of all High initial cost Can be installed in any position Moderate deep-cycle life (250 likely) Doesn't require venting Won't leak unless cracked Accepts highest charge rate Tolerates moderate equalization Choosing a Battery Type 41
Optimum Depth of Discharge Figure 3.16 shows expected lifetime cycles versus depth size 8D (220 Ah) and were bought for list price, less of discharge under laboratory conditions. The shape 15%. The costs (2005) assumed were: wet-acid $544, of the curves was established with one set of data each AGM $444, and gelled $308. The equivalent pair of 6- for wet-acid,AGM, and gelled-electrolyte batteries. The volt golf cart batteries cost $180. golf cart curve was assumed to be of the same shape Figure 3.17 leads to two conclusions: and fitted to the single published 100% discharge point. 1. Considering the cost of the batteries alone, the Fig. 3.16 Expected Charge/Discharge Cycles optimum depth of discharge is approximately 8K 50%. 2. Due to a lower purchase cost, the golf cart battery Battery Life Cycles (K=1,000) 4K Golf cart (6V) Charging Cutoff is the most economical battery. Best wet cells 6K Typical AGM Typical gelled Figure 3.14 showed that charging current should be reduced once a battery has been recharged to 75% of capacity. Stopping at 75%, however, results in sulfation. 2K If the engine is run only for charging, run time becomes uneconomical beyond 85 to 90%. When 0K 0 20 40 60 80 100 charging underway or with wind or solar, run time is Depth of Discharge, % not an issue, and recharge to above 90% is desirable. A boat is not an ideal environment, so you should We will assume a boat at anchor, a discharge limit of count on getting about half of the cycles shown. Thus, 30 to 50%, and a recharge cutoff of 85 to 90%. Since a instead of 3,000 discharges to 50% for the best wet-acid battery is usually considered "dead"when it has perma- battery, you might assume 1,500 cycles. Alternating nently lost 40% of its rated capacity, we will also de- banks daily, and recharging the banks in parallel, you rate our batteries by 20%. can project 1,500 recharges × 2 days = 3,000 days, or 8 Example: Our daily load is 75 Ah. We decide to dis- years. charge to 30% of capacity and charge to 85%. The With the same 50% discharge and 2-day cycle, golf required (derated to 80%) battery size is then cart batteries should last about 5 years, AGMs 4 years, and gelled electrolyte batteries 2 to 3 years. 75 Ah/0.80(0.85 – 0.30) = 170 Ah Figure 3.17 plots cost per kilowatt-hour versus Once you have estimated your daily load and cho- depth of discharge assuming half of the life cycles sen your charge-discharge range, Figure 3.18 allows shown in Figure 3.16. It was assumed the batteries were easy determination of the required battery size. Fig. 3.17 Lifetime Costs per kWh of Battery Types Fig. 3.18 Battery Size Selector 1.00 500 Gelled 0.80 AGM 400 (60 – 85)% (50 – 85)% Cost of Batteries, $/kWh 0.60 Best wet cells Nominal Battery Capacity, Ah 300 (30 – 85)% (40 – 85)% 0.40 200 Golf cart (6V) 0.20 100 Example 0.00 0 0 20 40 60 80 100 0 25 50 75 100 125 150 Depth of Discharge, % Load, Ah/day 42 Batteries
Sizing the Alternator After a deep discharge, batteries will accept very high The three curves show the dramatic savings that can rates of charge. AGM and gelled-electrolyte batteries be realized by matching the alternator to its load. Min- typically accept up to 0.5C (50% of capacity per hour), imum engine/fuel cost is achieved by deep discharge while healthy wet-acid batteries safely accept up to of AGM or gelled-electrolyte batteries and recharge at 0.25C. Once a battery has been recharged to 75% of 0.5C (220 A for the example of paralleled 8D batteries). its capacity, the charging rate must be reduced in order For a pair of 8D wet-acid batteries, the matched alter- to prevent gassing in all batteries, as was shown in Fig- nator would be rated at 110 A. ure 3.14. Solar and wind power will be discussed in Chapter The total cost per kilowatt-hour produced and 10, but costs per kilowatt-hour for solar and wind-pro- stored is the sum of battery cost (Figure 3.17) and en- duced power have been included in Figure 3.19 for gine/fuel costs. Figure 3.19 compares battery and comparison. The solar system is assumed to cost $480 engine/fuel costs. Engine/fuel costs assume: per 60-watt panel, last 10 years, and be used all year in • Consumption = 0.5 gallon per hour Miami. The wind machine has a 5-foot blade, costs • Fuel price = $2.20 per gallon $1,500, lasts 10 years, and is used all year in 10-knot • Engine life = 10,000 hours average winds. • Engine price = $7,000 Solar and wind costs per kilowatt-hour are indepen- • Maintenance = $0.20 per hour dent of discharge depth, assuming the systems are matched to the daily load. It is interesting to note that typical utility rates are $0.10 to $0.15 per kilowatt-hour. Fig. 3.19 Total Costs per kWh of Generated Power 4.00 ENGINE COSTS: Charging two 8D batteries (440 Ah) to 85% using: 3.50 55-amp alternator 3.00 Battery and Charging Costs, $/kWh 2.50 110-amp alternator 2.00 220-amp alternator 1.50 BATTERY COSTS: Gelled AGM 1.00 ALTERNATE ENERGY Best wet cells COSTS: Golf cart (6V) Wind 0.50 Solar 0.00 0 10 20 30 40 50 60 70 80 90 100 Depth of Discharge, % Sizing the Alternator 43
Series vs. Parallel A battery bank consists of one or more batteries, con- Fig. 3.20 Battery Size Selector nected to act as a single 12-volt unit. Two common questions are: (1) should a large bank consist of one + very large battery, two smaller 12-volt batteries in par- 12V allel, or two 6-volt batteries in series; and (2) assuming Single 185AH 122 lb Rolls 4D two banks, should both be on all the time, or should 12V, 185Ah – they be alternated? First, how large a bank do you need? Some say that your battery capacity can never be too large, but con- sider two facts: 12V + 12V + 1. Batteries should not be left in even a partially Parallel 90AH 90AH 62 lb 62 lb discharged condition any longer than necessary. 2 Rolls Size 27 – – 2. The cost of charging batteries is greater than the 12V, 180Ah amortized cost of any battery, and unless a bat- tery is discharged at least to 50%, recharging cur- rents are restricted and charge times elongated. + + 6V 6V These are both reasons to size each battery bank for Series 180AH 180AH 72 lb 72 lb a single day's load. If your daily load is less than about 2 Deka 8G6V200 – – 100 Ah, you can get by with a single 4D battery (185 12V, 180Ah Ah) by cycling between 85% and 30%. The problem— unless you are young and a weight lifter—is the weight of such a large battery. As you can see from Table 3.1, 4D batteries typically weigh 125 pounds, while 8Ds The second question was whether, in the case of two weigh in at around 160 pounds. The option is to break battery banks, to leave the battery selector switch per- the bank into smaller, more manageable, units. manently in the "Both" position. Here are arguments for the single battery, the series Reasons "Both" is better: connection, and the parallel connection (Figure 3.20). • Current drain from each battery is less, so less energy A single battery is better: is lost to internal resistance. This is important when • Because there is just one case, you get the maximum using an electric windlass or a microwave oven. Ah in a given space. • Each battery receives only half of the charge currents, • Two battery cables and terminals are eliminated. so both batteries can be charged in half of the time. If using solar or wind, charging near 100% capacity Parallel connection of smaller batteries is better: will less likely cause gassing. • Assuming isolation diodes (page 58) are used, the bad battery can be removed, and the remaining bat- Reasons alternating banks are better: tery still has full voltage at half capacity. • A catastrophic short circuit, or leaving the anchor • The stronger battery cannot drive a weaker battery light on for a week, will not result in total loss of into cell reversal. capacity. The reason for two banks is redundancy. • Without an expensive Ah meter, battery health can Series connection of 6-volt batteries is better: be accurately assessed only after a 24-hour rest • Failure of a single cell will be apparent as a sudden 2- period. Switching banks allows better monitoring of volt drop, but voltage will still be sufficient for engine capacity and performance. starting. • Failure of a single cell in one battery will not draw Recommendation: alternate banks daily, but switch down the voltage in a paralleled battery. to "Both" when charging with the engine, starting the • 6-volt golf cart batteries are the cheapest sources of engine, hauling the anchor with an electric windlass, or battery power. running other high loads, such as microwave ovens. 44 Batteries
Battery Boxes There are three good reasons to house batteries in other objects from accidently shorting the battery ter- sturdy covered battery boxes: (1) to capture and vent minals. overboard explosive hydrogen gas generated in the case Battery boxes can be purchased in a few sizes ready- of overcharging, (2) to contain electrolyte that may be made, or you can construct one to custom fit your spilled in rough seas, and (3) to prevent metal tools and bank. Making your own has the advantage of fitting both the space and the batteries better. Building a Battery Box Fig. 3.21 DIY Battery Box Building a battery box is an excellent way to learn basic 23.5\" 22\" fiberglass techniques. No curved surfaces are required, appearance is not critical, and the plywood core forms the All sides 3/4\" mold. exterior plywood 20.5\" Bottom (1) 19\" Figure 3.21 shows the construction of a box large Cover (1) enough to hold two 12-volt D4s (330 Ah total) or four 6- volt T-105 golf cart batteries (440 Ah total). Batteries weigh about 0.75 pound and contain 2 23.5\" 19\" ounces of acid per Ah. While you are making the box, con- sider the consequences of 330 pounds of batteries and 28 Long 12\" Short 12\" quarts of battery acid breaking loose in a storm. Also pic- side (2) side (2) ture installing or removing batteries weighing up to 165 pounds each. 3 layers FRP inside 3 1. Mark cuts on ⁄4-inch AC-Exterior plywood. & outside corners 2. Apply a layer of fiberglass to both sides of the uncut plywood using epoxy or polyester resin. 3. Cut the panels and apply resin to edges. Fill with epoxy paste 4. Glue and nail the box together. 2 layers FRP over 5. Sand round all outside edges and fill inside corners all inside surfaces with an epoxy paste. Round all corners 6. Apply at least three overlapping strips of fiberglass reinforced plastic (FRP) cloth at each inside and outside corner, making sure there are no voids. 7. Apply two complete layers of fiberglass cloth over the entire outside and finish with epoxy paint. Min. distance to fuel 8. Fasten the box firmly to the hull with countersunk 12\" system or component stainless steel, flat-head (SS FH) bolts. (see USCG regulations) 9. Apply two additional layers of fiberglass cloth to Vent hole Nylon web straps (2) the inside and finish with white epoxy paint. 10. Drill a vent hole near the top of the side most con- Cover locating pins venient to venting. The hole diameter should pro- Fits D4s vide a press fit for a length of garden hose. or 1 11. lnsert batteries using ⁄4-inch nylon line, leaving the Golf cart line for later extraction. 12. Fasten the cover down and run the vent hose to a point outside the hull. SS FH machine screws (FRP over) for securing Battery Boxes 45
ABYC Standards for Batteries Adapted from ABYC Standard E-10, Standards and NOTES: Recommended Practices for Small Craft, dated Decem- 1. Terminal insulation or battery covers do not comply ber, 1996. ABYC standards conform with Title 33, Code with this requirement since during installation or of Federal Regulations, Part 183—Boats and Equipment. removal of a battery, these protective devices are usually removed in order to connect the cables. E-10.6. Battery Capacity 2. Any nonconductive material may be used for shielding as long as it is durable enough to withstand accidental a. Cranking batteries shall have at least the cold crank- contact by a tool or the battery terminals during servic- ing performance rating (CCA @ 32°F) or marine ing, installation or removal. cranking performance rating (MCA @ 32°F) amper- e. Each battery shall not be installed directly above or age required by the engine manufacturer. below a fuel tank, fuel filter, or fitting in a fuel line. b. Accessory batteries and cranking batteries used as accessory batteries shall have a rated reserve capacity in NOTE: This does not prohibit a battery from being minutes determined by the calculations in ABYC E-11, installed directly above or below an uninterrupted fuel DC Electrical Systems Under 50 Volts. line; however, if this fuel line is within the twelve inch envelope of the top surface of the battery it shall be shielded dielectrically as required in ABYC E-10.7.d. E-10.7. Installation f. A vent system or other means shall be provided to a. Batteries shall be secured against shifting. permit the discharge from the boat of hydrogen gas b. An installed battery shall not move more than one released by the battery. Battery boxes whose cover inch in any direction when a pulling force of ninety forms a pocket over the battery shall be vented. pounds or twice the battery weight, whichever is less, NOTE: These provisions also apply to installations of is applied through the center of gravity of the battery as sealed batteries. follows: g. If the mounting surfaces or components of the boat (1) Vertically for a duration of one minute. in the immediate vicinity of the battery location are of (2) Horizontally and parallel to the boat's center a material attacked by the electrolyte, a mounting line for a duration of one minute fore and one means shall be provided that is made of a material that minute aft. is not damaged by electrolyte. (3) Horizontally and perpendicular to the boat's h. Fasteners for the attachment of battery boxes or trays center line for a duration of one minute to star- shall be isolated from areas intended to collect spilled board and one minute to port. electrolyte. c. To prevent accidental contact of the ungrounded battery terminal to ground, each battery shall be pro- tected so that metallic objects cannot come into contact E-10.8. Wiring with the ungrounded battery terminal. This may be a. Connectors to battery terminals shall be made with accomplished by means such as: fitted connectors providing secure mechanical and (1) Covering the ungrounded terminal with a boot electrical connections. Spring clips or other temporary or nonconductive shield. clamps shall not be used. (2) Installing the battery in a covered battery box, or b. A soldered connection that joins a battery terminal (3) Installing the battery in a compartment spe- connector to a conductor may be used if the length of cially designed only for the battery(ies). the soldered joint is at least 1.5 times the diameter of d. Each metallic fuel line and fuel system component the stranded portion of the battery conductor. within twelve inches and above the horizontal plane of c. Battery supply conductors must be sized to satisfy the battery top surface as installed shall be shielded the load calculations as outlined in ABYC E-11.10. [See with dielectric material to protect against accidental Chapter 6.] short-circuiting. 46 Batteries
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4 CHAPTER Alternators – + – + – + F F GND GND + 48 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
A n alternator is a rotary current machine that transforms mechanical rotation into AC cur- rent. The AC current produced by the alterna- tor coils is rectified by diodes into DC current for charging the ship's batteries. In order not to overcharge the batteries we need a regulator for controlling the alternator. Whether the regulator field-coil wire is connected to the positive or to the negative battery terminal determines whether it is a type-P or type-N alternator. The methods of pow- ering the voltage regulator and supplying excitation current to the field coil vary as well. Regulator bypass controls, allowing more rapid bat- tery charging, are popular among cruisers, the most sophisticated of all being the Link 2000-R Charge Controller. The electrical demands of boats vary widely, so a variety of charging setups have evolved, from the sim- plest one alternator/one battery of the day boater to the multiple alternators/multiple batteries of the dedicated liveaboard cruiser. Since most engines are equipped with light-duty alternators, cruisers and liveaboards having large bat- tery banks very often upgrade to higher-output mod- els, requiring guidance on alternator installation. Despite the great number of alternator models and charging setups, the basic principles and components are largely the same, allowing for simple troubleshoot- ing procedures. 49
A Galley Alternator If you had fun making the galley battery in Chapter 3, to minus and back to plus again is called a cycle.The try making the galley alternator in Figure 4.1. All you number of cycles per second is the frequency, measured need are an analog voltmeter or ammeter (a multime- in Hertz (Hz). Utility power in the United States is ter with many ranges is best), a large steel nail or bolt, delivered at 60 Hertz; in Europe, at 50 Hertz. several feet of insulated copper wire, and a magnet. Wrap a dozen turns of the wire around the nail and Fig. 4.1 A Galley Alternator connect the bare ends to the meter. If you are using a multimeter, start with the highest amps scale. Hold the magnet as close to the head of the nail as possible with- out actually touching it. Now move the magnet rapidly back and forth, as shown in the illustration. The nee- dle of the meter should jump back and forth across zero. N S - + If the needle doesn't move, switch the meter to a lower scale. If the needle still doesn't move, increase the number of turns of wire until it does move. What's going on? As Hans Oersted discovered in 1820, an electric current is induced in a wire whenever the magnetic field around the wire changes. Our mov- + ing magnet induces magnetism in the nail. As the per- manent magnet moves back and forth, the magnetism in the nail alternates in direction, so the magnetic field Amps 0 through the coiled wire alternates as well. The alter- nating field produces pulses of current of alternating polarity as shown in the graph at the bottom of Figure - 4.1. The scale of the graph is not important to our experiment, but you should know that the current is Fig. 4.2 A Rotary Current Machine directly proportional to the strength of the magnetic field, the rapidity of the magnet motion, and the num- ber of turns in the coil. N Simple Two-Pole Magnet Instead of passing the magnet back and forth across the - + head of the nail, we can make a rotating machine to do the same thing. Figure 4.2 shows a straight bar S magnet pivoted about its center between two series- connected coils. The coils are wound in opposite direc- tions, so that the opposite poles of the magnet produce current in the same direction. As the magnet turns, however, each coil sees alternating poles, so the cur- + One Cycle rent changes polarity as shown in the graph. This type of current is called alternating current, or AC. Chapters 7 through 9 of this book deal with AC Amps 0 power on boats. All we need to know about AC at this point is that both voltage and current reverse, usually many times per second. One complete swing from plus - 50 Alternators
A Rotary Current Machine More Poles and Coils Fig. 4.3 Multiple Poles and Coils We can make our rotary current machine more effi- A cient by placing more magnets on the rotating shaft and by adding a corresponding number of coils of wire, as shown in Figure 4.3. With three times the number of magnets and coils, the result is three times as much S generated power. N N With three times as many magnet poles, each revo- lution of the shaft produces three times as many cycles. All of the coils still produce current in synchrony, how- S S ever, so the forms of the output current and voltage N remain the same as before. + A Amps 0 - Three-Phase Current Fig. 4.4 A Rotary Current Machine Let's call the entire series-connected coil of Figure 4.3 C B coil A. Now let's add coils B and C, identical in form to A coil A, but rotated one-third and two-thirds of the gap between the small coils of coil A, as shown in Figure 4.4. The poles of the rotating magnet will pass each set S of small coils in the order: A, B, C, A, B, C, etc. The cur- N N rents induced in coils A, B, and C will therefore be off- set by one-third and two-thirds of a cycle as shown at the bottom of Figure 4.4. We now have three identical S S alternating currents, offset in phase by 120° (one com- N plete cycle equals 360°). We call this three-phase AC. Why would we want to complicate our rotary cur- rent machine in this way? 1. We can triple power output without increasing + the size of the wire in the coils. A B C A 2. It is easier to wind closely spaced coils than to increase the number of magnetic poles. Amps 0 3. The three phases result in a better (smoother) output, as we'll see later. - A Rotary Current Machine 51
Rectification As we saw in Chapter 3, batteries produce direct cur- Fig. 4.6 The Galley Alternator with Rectifier rent (DC), which is always of the same polarity. To recharge batteries we need DC. The rotary current machine is of no use unless we convert its three-phase AC output to DC. Enter the diode. As its circuit symbol (Figure 4.5, + - top) indicates, the diode allows current to flow only in the direction of the arrow. If you like analogies, you can think of a diode as the equivalent of a check valve in a N S - + water-supply system, allowing water to flow in one direction but not the opposite. Fig. 4.5 Diodes and the Diode Symbol + – Diode symbol + Passed by diode Signal diode Power rectifier diode Amps All diodes have the following three ratings: 0 maximum forward current—maximum current in Blocked by diode the forward direction peak inverse voltage—maximum voltage at which - diode will block current flow in reverse direction forward voltage drop—voltage in the direction of the arrow at which diode begins to conduct current Diodes come in different sizes and shapes, depend- Fig. 4.7 Half-Wave Rectification ing on their intended uses. Tiny signal diodes are intended for low-current applications. Large rectifying A diodes are used in high-current applications such as alternators. A typical alternator diode might have rat- ings of 50 amps, 50 volts, and 0.6 volt. If you haven't yet put away your galley experiment, S insert a diode into the circuit as shown in Figure 4.6. N N Now when you pass the magnet back and forth, the needle should deflect only in the positive direction. If S S you get a negative deflection, either the meter leads are reversed, or the diode is pointing in the wrong direc- N tion. As the current plot shows, the magnet and wire coil are still producing negative pulses, but the pulses are blocked by the diode. Figure 4.7 shows how a diode would similarly block + negative current in our rotary current machine. The A process of passing current of one polarity but block- Passed ing current of the opposite polarity is called rectifica- by diode tion. Passing only the positive halves of an AC wave is Amps 0 called half-wave rectification. Rectification would be twice as efficient if we could Blocked by diode pass both halves of the AC wave. This is accomplished - 52 Alternators
with a four-diode full-wave rectifier (Figure 4.8). No through diode 1, into the positive terminal, through the matter the polarity of current and voltage through the external load, into the negative terminal, through diode wire coil, there are always two of the four diodes seeing 3, and back to the coil. reverse voltage and acting as if they were open circuits. The second half-wave travels Path 2: from the coil, Follow the currents in Figure 4.9 as they flow through diode 2, out the positive terminal, through the through the coil, the diodes of the rectifier, and the external load, into the negative terminal, through diode externally connected load in the alternating closed cir- 4, and back to the coil. cuits labeled Path 1 and Path 2. An obvious extension would be to provide each of The first half-wave travels Path 1: from the coil, the coils in Figure 4.4 with their own full-wave recti- fiers, as shown in Figure 4.10. This would be fine if we Fig. 4.8 Full-Wave Rectification desired three separate outputs to recharge three sepa- rate batteries or to power three independent DC cir- + cuits, but we don't. We'd rather have a single DC sys- tem, and, although we might have three batteries, we'd rather charge them in parallel from a single source. It would be needless torture to force you through the logic, but it turns out that connecting the ends of - the three coils produces a felicitous simplification. S N Fig. 4.10 Three Full-Wave Rectifiers + + + N S C B A S N - - - + A Amps S 0 N N - Fig. 4.9 Rectifier Current Paths S S PATH 1 PATH 2 N + + 1 2 1 2 Load Load + A B C A B C A B C 4 3 4 3 - - Amps 0 - Rectification 53
Rectification Figure 4.11 shows the two common ways to connect Figure 4.12 shows the ends of the coils connected to the coils: the Delta and the Y. With the coils connected, a single pair of output terminals. The currents combine half of the twelve diodes can be eliminated. With either in such a way that total output current approximates configuration, we are left with only three coil terminals, steady DC. Our rotary current machine has finally each of which is connected to a diode pair. evolved into a DC-output alternator. Fig. 4.11 Delta and Y Coil Arrangements Fig. 4.12 Delta and Y Connections in a Real Alternator - + + A B A B + - DELTA Configuration C C - + - + - + Y Configuration - A B + A B C C - + - + A B C A B C A B C + A B C A B C A B C Amps Amps 0 0 54 Alternators
Controlling the Alternator As you will recall, the output of the galley alternator in Fig. 4.13 Electromagnets Figure 4.1 depended on three variables: 1. Strength of the magnet S N 2. Number of turns of wire 3. Speed of magnet movement Field coil The alternators in Figure 4.12 are similar. We can S N vary their outputs only by changing engine rpm, which is inconvenient. The problem of control in a real alternator is solved by varying the strength of the magnet. Instead of the N S N S permanent magnet in Figure 4.1, we use an electro- magnet as in Figure 4.13. The iron core concentrates the magnetic field, which is generated by a current S N through the coil. The strength of the field generated is proportional to the current flowing in the field coil. Thus, alternator output can be controlled by varying current through the field coil. Figure 4.13 also demonstrates a phenomenon you Fig. 4.14 Alternator Rotor and Brushes can verify with your galley magnet and two or more N S Slip rings nails: A magnet will induce magnetism of opposite polarity in a second piece of iron in close proximity. For example, in Figure 4.13, two additional iron bars N placed at the ends of the core also become magnets. S This can be verified with either iron filings or a small compass. S N Figure 4.14 shows the added iron bars replaced by iron disks with fingers that have been bent around and interleaved. In this way, current through a single field N Field S coil wrapped around the shaft results in alternating coil magnetic fingers around the circumference. It also shows how current can be fed to the field coil through N S Carbon brushes carbon brushes riding on copper slip rings fixed to the shaft. Figure 4.15 shows a typical alternator rotor with its interleaving magnetic poles, slip rings, and field coil Fig. 4.15 Typical Alternator Rotor wrapped around the inside shaft. This rotor assembly rotates inside the collection of stationary coils, known N as the stator. S The device that controls field-coil current, and thus alternator output, is known as the voltage regulator. N How it came to be known as a voltage—rather than a current—regulator, is lost in history. We will not change its name. Just remember that it controls out- S put current, not voltage. N Controlling the Alternator 55
Controlling the Alternator Voltage Regulators Fig. 4.16 Older Electromechanical Voltage Regulator We'll start with the old-fashioned electromechanical voltage regulator still found in some older boats (Fig- Ignition or Adjust Battery + ure 4.16). The field current flows through the relay arm that pivots about F and contacts the points labeled Relay arm "Ignition" and "Ground.""Ignition" is connected to the battery + terminal through the engine ignition switch. F The relay arm is held up against the ignition contact by the adjusting spring. With full field current flow- ing, the alternator quickly produces its maximum cur- Field rent. If the battery voltage is low enough, the alterna- Relay coil tor continues to pump out maximum current. When coil battery voltage rises to a set value (between 13.8 and 14.2 volts), the increased current flowing from igni- Ground tion to ground through the relay coil pulls the arm down and opens the contact. Field current drops to zero, alternator output drops to zero, battery voltage Fig. 4.17 Solid-State (Transistorized) Voltage Regulator drops, and the relay arm is pulled up to the ignition contact to start the cycle again. Battery Ignition or or + auxiliary The greater the voltage of the battery, the greater the percentage of time the contact remains pulled down into the open position. Alternator output switches between full and zero output hundreds of times per 2 second. The average voltage approaches a constant, while average charging current falls toward zero (plus 1 3 whatever load is being drawn at the same time). Battery voltage is adjusted by turning the adjusting spring. Adjust It is easy to check a voltage regulator. With the engine running, and after output current has dropped F to a trickle, turn on a heavy load. If the regulator is Field coil working, voltage will remain the same, but alternator current will increase by the amount of the added load. Gnd Electromechanical regulators have been replaced by solid-state regulators. Although they can be destroyed by reversing battery and ground leads and by excessive heat, they never wear out. Figure 4.17 shows a solid- Fig. 4.18 How an NPN Transistor Works state equivalent of the electromechanical regulator. The operation of a solid-state regulator is easily Collector (C) understood once you understand how a transistor works. Figure 4.18 shows the most common type of transistor—the NPN. It has three leads: base (B), emit- ter (E), and collector (C). It can be thought of as an amplifying valve. The current flowing into the base Base (B) Collector to emitter controls the current flowing from the collector to the Base current emitter. Because the junction between base and emitter current is essentially a diode in the direction of the arrow, no current flows until the base-to-emitter voltage reaches about 0.5 volt.Above that voltage, the output current is 20 to 100 times the base current. Thus the transistor can be used as an electronic switch or current amplifier. Emitter (E) 56 Alternators
Type-P and Type-N Alternators In Figure 4.17 assume the battery voltage is low. The Both type-P and type-N voltage regulators draw base of transistor 1 is therefore at a low voltage and power from the battery + terminal. If the power is not transistor 1 is off. With transistor 1 acting as a high interrupted when the engine stops, the voltage regulator/ resistance between the base of transistor 2 and ground, alternator coil will slowly drain the battery. the voltage of transistor 2 base is high and transistor 2 Figure 4.20 shows three small diodes (the diode is on. Transistor 3 amplifies the collector-to-emitter trio) connected to the three coil terminals in a type-N current of transistor 2 by twenty times or more, caus- alternator. These diodes feed a terminal labeled "Aux." ing a large current through the field coil and maximum When the alternator is not turning, there is no current alternator output. to power the regulator, so there is no drain on the bat- Soon battery voltage increases, however, and tran- tery. Reverse current flow from the battery to the aux- sistor 1 switches on. The resistance from the base of iliary terminal is prevented by the charge diodes. transistor 2 to ground decreases, and transistors 2 and Fig. 4.20 Diode Trio 3 switch off, cutting off the current to the field coil. With no field current, alternator output ceases. + The transistors switch on and off hundreds of times per second, with the ratio of on-to-off times control- ling the average field current and alternator-output Diode current. The analogy between electromechanical and trio solid-state voltage regulators is obvious. Note that the solid-state regulator of Figure 4.17 Aux A B had two positive terminals: 1. Battery, or +, is for sensing the voltage of the bat- Field coil tery so that it can be charged at the correct volt- age. F C 2. Ignition, or auxiliary, supplies the field current. to Reg Not to be confused with NPN and PNP transistors, - alternators and regulators can be connected in two dif- ferent ways called type-P and type-N (Figure 4.19). Figure 4.21 shows a second method of supplying In type-P alternators and regulators, the regulator is regulator current. A large isolation diode is placed connected to the positive end of the field coil. In type- between the three charge diodes and the alternator + N alternators, the voltage regulator is located between output terminal. This isolation diode prevents reverse the negative end of the field coil and ground. current flow from the battery to the regulator. Fig. 4.19 Type-P and Type-N Regulators Fig. 4.21 Isolation Diode + Battery + Battery + Isolation diode Field coil TYPE P (in alternator) Voltage Aux regulator F Field coil A B F TYPE N F Voltage regulator to Field coil Reg (in alternator) C Gnd Gnd - Type-P and Type-N Alternators 57
Powering the Voltage Regulator Battery Isolation Diodes Fig. 4.22 Battery Isolation Diodes Do not confuse the diode trio or the alternator isola- + To alternator tion diode with battery isolation diodes. The first two Isolator Isolator are internal parts of the alternator and will not be seen unless the case is opened. If a boat has battery isola- tion diodes (Figure 4.22) they will appear as large + Battery 1 - + Battery 2 - diodes mounted on a finned heat sink. Their purpose, if present, is to prevent paralleled batteries from dis- charging each other. Not all marine systems have bat- tery isolation diodes. Exciting the Alternator Did you spot a problem with the circuits of Figures Fig. 4.23 A Common Alternator Excite Circuit 4.20 and 4.21? If we actually wired an alternator and regulator as shown in either of the figures, the alterna- + - tor would never come on. An alternator will not gen- Ignition Battery erate an output current without an input field current, switch but there will be no field current until there is an alter- nator output! To solve this chicken-or-egg dilemma, Charge alternators that derive their field currents from inter- light nal-diode trios or isolation diodes require a tempo- R + rary source of field current called the excite current. Figure 4.23 shows a typical excite circuit added to Isolation diode the alternator of Figure 4.21. Its operation will be Aux familiar to anyone who owns an automobile. When the ignition switch is turned on, current flows from the battery, through the lamp and paralleled resistor, to the alternator auxiliary terminal, and then Field through the field coil. As soon as the engine starts, coil however, the alternator begins generating current, A B which then makes the voltage at the auxiliary terminal 0.5 to 1.0 volt higher than the battery voltage. With F to only 0.5 to 1.0 volt across its terminals, the 12-volt Reg charge-indicator lamp goes out. If it stays on or comes C on again, you know that the alternator in not produc- ing current. A resistor is placed in parallel with the lamp in order to provide excite current in case the lamp filament burns out. An alternate and common solution is to feed the charge indicator lamp from the engine oil-pressure – switch rather than the ignition switch, so that the alter- nator is excited as soon as oil pressure climbs. An advantage of this system is keeping the load on the engine low until it is up to speed. 58 Alternators
Regulator Bypass Controls Alternators with fixed-voltage regulation are not ideal Fig. 4.24 Example of Optimally Fast Charging for boats. Without modification, they are simply cur- rent-limited, fixed-voltage chargers set at compromise Bulk Absorption Float voltages between 13.8 and 14.2 volts. As we saw in 15.0 cycle cycle cycle Chapter 3, 13.8 to 14.2 volts is higher than the recom- V=14.4 mended float voltage and lower than the recommended 14.0 80% 90% fast-charge absorption voltage. An alternator con- Charging Voltage I=25%C Constant 13.5V trolled by a standard regulator will never fully charge a battery in typical operation, yet will overcharge if run 13.0 for days on end. Cruising boats, particularly sailboats, impose large 12.0 Time loads on their batteries but run their engines only a few hours per day. Worse, when a boat is at anchor the engine is usually run for the sole purpose of charging the batteries. We need a way to control the alternator output for optimally fast charging (Figure 4.24). Fig. 4.25 Regulator Bypass Hookups Figure 4.25 shows regulator bypasses installed + + across both type-P and type-N voltage regulators. Note that the original voltage regulators remain in place. The Type P Field coil bypass regulators simply control field current in order Voltage Regulator bypass to control alternator output. After the regulator bypass regulator F has accomplished its task and is switched off, the orig- inal voltage regulator resumes control. F Regulator Voltage Type N Voltage Some regulator bypasses are manual, requiring dili- bypass regulator regulator gent monitoring of battery-charge current and voltage. Field coil The simplest automatic bypasses come on when the engine is started, provide a constant-current bulk Gnd Gnd charge, then switch off when the battery reaches a pre- set voltage. More sophisticated regulator bypasses (see next page) automatically cycle through bulk, absorp- tion, and float stages every time the engine is started. An equalization charge can also be selected when desired. Fig. 4.26 A Manual Regulator Bypass Before discussing the most sophisticated regulators (charge controllers), Figure 4.26 shows a simple man- + + ual-control regulator bypass you can build yourself. On/ Off Note that the bypass circuit is the same whether used Field with a type-P or type-N alternator. The on/off switch Type P 25W coil Regulator 2 Ω Voltage allows the bypass to be switched into or out of the cir- regulator bypass cuit. The 2-ohm, 25-watt fixed resistor limits the max- F 20 Ω On/ imum field current. The 20-ohm, 100-watt rheostat 100W Off (variable power resistor) allows the field current to be Type N 2 Ω varied over a wide range. F Voltage 25W Warning! Manual regulator bypasses should never Regulator regulator bypass be used without diligent monitoring of both battery 20 Ω charging current and voltage. It is easy to destroy a Field 100W $300 battery with a $30 homemade regulator bypass. coil If you do not have the discipline to continuously mon- itor the charging process, you should either forgo the Gnd Gnd fast-charge option or invest in one of the sophisticated automatic models. Regulator Bypass Controls 59
Link 2000-R Charge Controller The Xantrex Link 2000-R Charge Controller (Figure ing routine is truly ideal for any given battery type and 4.27) is a dedicated computer that monitors and con- conditions. trols both an inverter/charger (any of the Xantrex Free- dom series) and an alternator. Parameters monitored Fig. 4.28 Four-Cycle Charging for a Wet-Cell Battery at 70°F include: 16.0 Charge Acceptance Float • battery voltage • amps being drawn 15.0 • amp-hours withdrawn Constant 14.4V Equalize • amp-hours remaining Charging Voltage • time remaining to discharge 14.0 Constant 13.5V • number of battery charges Full Current When either inverter or engine is turned on, the 13.0 2000-R initiates the four-cycle optimum charge rou- 12.0 tine: charge, acceptance, float, and equalize (Figure Time 4.28). Charging Operation Fig. 4.27 Link 2000-R Charge Controller Panel The status of the four-step charging process is indi- cated by the horizontal row of LEDs at the bottom of the control panel (Figure 4.27 again). Link 2000-R Charge cycle (red LED ON). After a 2-second engine- Control Battery Invert 1 start delay, the field current is ramped up over 20 sec- Idle Mode Reset A hrs onds until the alternator reaches its full output. Charg- Charger 2 ing at full current continues until either battery bank Pwr Share Data reaches the acceptance voltage. Setup Volts Amps A hrs Time Acceptance cycle (orange LED ON). Charging contin- Charged V Charged % Batt Cap Function ∆ Equalize ues at the fixed acceptance voltage until charging cur- Status: AC In Charge Accept Float rent drops to 2% of the battery nominal capacity. At this point the regulator goes into an acceptance-hold status during which the acceptance voltage is main- tained and the charging current is monitored. If voltage Either one or two battery banks may be monitored and current remain steady for 10 minutes, or if voltage and controlled. Voltages for the four charge cycles are holds steady but current rises during 20 minutes, the tailored both to the type of battery and to the real-time regulator goes into the float stage. If, however, battery temperature of the battery (Table 4.1). Thus, the charg- voltage drops to below the acceptance voltage for 2 minutes, the entire charge cycle is restarted. Table 4.1 Voltage Settings for the Link 2000-R Float cycle (green LED ON). Battery voltage is main- Type 0 Type 1 Type 2 Type 3 tained at the float voltage. The alternator supplies cur- Temp. Wet-Cell Gel-Cell 1 Gel-Cell 2 AGM rent up to its full output in order to supply current °F Accept Float Accept Float Accept Float Accept Float draw and maintain the float voltage. If battery voltage 120 12.5 12.5 13.0 13.0 13.0 13.0 12.9 12.9 drops to below the float voltage for 2 minutes, the 110 13.6 12.7 13.5 13.0 14.0 13.4 13.9 12.9 100 13.8 12.9 13.7 13.2 14.1 13.5 14.0 13.0 charge cycle is restarted. 90 14.0 13.1 13.8 13.3 14.2 13.6 14.1 13.1 Equalize cycle (red LED FLASHING). This is initiated 80 14.2 13.3 14.0 13.5 14.3 13.7 14.2 13.2 manually by pressing a combination of buttons. Charge 70 14.4 13.5 14.1 13.6 14.4 13.8 14.3 13.3 current is held at a constant 4% of capacity while volt- 60 14.6 13.7 14.3 13.8 14.5 13.9 14.4 13.4 age increases to 16.0 volts (or the acceptance voltage for 50 14.8 13.9 14.4 13.9 14.6 14.0 14.5 13.5 gelled batteries). Equalization terminates in 3.5 hours 40 15.0 14.1 14.6 14.1 14.7 14.1 14.6 13.6 30 15.2 14.3 14.7 14.2 14.8 14.2 14.7 13.7 or when charging current drops to 2% of capacity at 16.0 volts. 60 Alternators
Charging Setups No battery/alternator setup is ideal for every vessel. Fig. 4.29 Simplest One-Battery System Cost is a big issue for most boaters, but pattern of use and degree of vulnerability when dead in the water are To starter also considerations. Here are a variety of setups, from F F among dozens, demonstrating the possibilities and the GND GND + To panel issues involved. Note that bilge pumps (and any other device that must never be shut off) are wired and fused C directly to a battery. 1 OFF - + To bilge Figure 4.29 shows the most common configuration in pump small recreational boats. All electrical loads except the bilge pump are disconnected from the battery with the Battery 1 simple ON/OFF switch. Regardless of setup, an important consideration is that the alternator-to-battery + connection must never be broken while the alternator is generating current. Fig. 4.30 Simplest Two-Battery System Otherwise the energy stored in the alternator's induc- tive coils would produce a large voltage spike, possibly To starter destroying both the alternator rectifier diodes and any To panel F connected electronics. Three solutions are a voltage GND GND F snubber from alternator output to ground, a warning + C sign on the switch, and, in the case of a four-pole 1 OFF switch, a built-in field disconnect. B 2 To bilge pump - + - + Figure 4.30 shows a common configuration in small cruising boats. Here two batteries are charged from the same alternator. Depending on the position of the Battery 1 Battery 2 four-pole switch, the charge can be directed to either battery or both batteries at the same time. Similarly, the discharge can be from either or both. The batteries may be of unequal size—a small start battery and a large house battery—but they must be of Fig. 4.31 Two Batteries with Alternator Protected the same type. If one were a gel and the other a wet- acid, for example, either the gel would be overcharged To panel To starter and destroyed, or the wet-acid would be undercharged with the same long-term result. F F GND GND + C Figure 4.31 shows a setup where the alternator is per- 1 B 2 OFF manently connected to the house battery, so there is no danger of damage from interrupting the alternator To bilge pump output.As shown the starting battery can be charged in - + - + parallel with the house battery with the switch in the "Both" position. If, instead, the alternator were wired directly to the House Starting "Common" terminal of the switch, the setup would be the same as in Figure 4.30, with the attendant danger of interrupting the alternator output. Charging Setups 61
Charging Setups Figure 4.32 shows a pair of isolation diodes. The diodes Fig. 4.32 Batteries Isolated with Diodes make it possible to leave both batteries connected directly to the alternator output without the danger of To panel one battery draining the other. Because the diodes look F F like closed circuits in the forward direction, they also GND GND + To solve the open-alternator problem. starter To bilge pump The big problem with isolation diodes is that they C 2 drop the voltage from alternator to battery by 0.6 to 1.0 OFF 1 volt, requiring the voltage regulator to be adjusted upward by the same amount to compensate. - + - + Most boaters are not aware of the voltage drop, so their batteries are chronically, severely undercharged Starting House and suffer early demise. Figure 4.33 shows a setup incorporating a series regula- tor. When house and starting batteries are of different size or type, one of the batteries will end up over- Fig. 4.33 System with Series Regulator charged while the other is undercharged, shortening the lives of both. Isolation To A series regulator, such as Ample Power's Elimina- F GND switch panel F tor, is designed to solve this problem. The alternator's GND + regulator is set up for the optimum charging of the Parallel To house battery. At the same time the series regulator, set switch starter up for the characteristics of the starting battery, siphons some of the charging current to charge it. Series The parallel switch can be used either to bypass the To bilge pump Regulator series regulator or to combine the battery outputs. - + - + Figure 4.34 shows one way to charge two batteries from two alternators. This is useful both when the batteries House Starting are of different size and/or different type and when the batteries are larger than can be charged quickly from a single alternator. It also provides redundancy in case one of the alternators fails. Commonly the starting battery is charged Fig. 4.34 Two Batteries and Two Alternators by the engine's original alternator, and a high- To To output alternator with multistep regulator is starter(s) panel added to charge the much larger house bank. F F F GND + F GND + GND C Paralleling C GND OFF switch 2 OFF 1 To bilge pump - + - + Battery 1 Battery 2 62 Alternators
Alternator Installation When changing alternators there are four critical phys- Fig. 4.35 Mounting Configurations (Balmar) ical considerations: (1) mounting configuration, (2) pulley alignment, (3) belt size, and (4) belt tension. Figure 4.35 illustrates four Balmar mounting con- figurations designed to be compatible with most marine engines. Most often a combination of washers, Single 1\" Foot spacers, and bushings can compensate for an imper- (Model 71) 6.7\" fect fit. Figure 4.36 shows how to bring the alternator pul- ley into alignment with the engine drive pulley. Hold a straightedge against the faces of the two pulleys, and shim the alternator foot (or feet) with washers until the 1\" faces are in the same plane. 3 Alternators of up to 80 amps output can use ⁄8-inch 1 belts (width of outside belt face), up to 110 amps ⁄2- inch belts, and over 110 amps dual belts. Proper belt tension can be determined in two ways: 1. Turn the alternator pulley retaining nut with a Single 2\" Foot 6.7\" (Model 712) wrench. If the belt slips it is too loose. 2. Press on the belt with moderate force (Figure 1 4.37). Deflection should be between ⁄4 inch and 5 ⁄16 inch. Fig. 4.36 Aligning Engine and Alternator Pulleys 2\" ENGINE Straightedge against face of pulley Dual Foot 3.15\" ID 6.7\" (Model 70) Misalignment .5\" 3.15\" .5\" Fig. 4.37 Testing Belt Tension Belt Deflection 7.6\" 1/4\" to 5/16\" Dual Foot 4\" ID (Model 95) .6\" 4\" .6\" Alternator Installation 63
Troubleshooting When an engine fails to turn over or batteries go flat, the charging/starting system is made easier if you the fault may be in the batteries, the alternator, an understand how each of the components work, so read external voltage regular, or the wiring. Troubleshooting Chapters 3 and 4 before using the charts and proce- dures that follow. Troubleshooting 1: Engine Won't Turn Over Is voltage at battery >12 volts? NO Battery dead or discharged YES Is voltage at input terminal of Defective + (red) battery cable battery switch >12 volts? NO YES Is voltage at common terminal NO Battery switch OFF or defective of battery switch >12 volts? YES Is voltage at input to ignition Defective conductor to ignition switch switch 12 volts? NO or blown engine fuse YES Is there >10 volts at output terminal of ignition switch with ignition key on and start button NO Defective key switch or push-button switch depressed? YES Is there >10 volts at solenoid input with ignition key on and NO Defective conductor from ignition switch start button depressed? YES Is there >10 volts at starter input with ignition key on and start NO 0 volts = defective solenoid; button depressed? low voltage = low battery or terminal corrosion YES With compression released, can you turn engine over using NO Engine seized or water in cylinder wrench on crankshaft nut? YES Starter motor defective or jammed 64 Alternators
Voltage regulator set too low. Adjust or replace. Run engine 2 hours. Is voltage now > 14.0 vol YES Diminished battery capac Equalize or replace batte Corrosion in charging cab or engine ground connec NO Run engine 2 hours. NO Is voltage now > 14.0 volts? YES Diminished battery capacity. Equalize or replace battery. Corrosion in charging cable NO or engine ground connection. NO NO Leakage current is draining battery. Repeat test, discon- necting circuits one at a time to find leak. Alternator OK. Turn on all lighting circuits. Is voltage now < 13.0 volts? YES With engine running, measure voltage between alternator B+ terminal and battery + terminal. Is voltage < 0.3 volt? Troubleshooting 2: Batteries Not Charging Fully Tighten or replace NO NO NO NO NO . YES Broken field wire or oil pressure switch. Defective alternator. Turn off all circuits and set battery switch to tested battery. Disconnect cable from battery + terminal. Measure resistance from cable end to battery – terminal. Is reading > 100 ohms? YES Reconnect battery cable. Start engine and bring to 1,200 rpm. Measure voltage between battery terminals. Is voltage < 13.0 volts? YES Alternator not charging. Is alternator belt tight? . YES Are there > 2.0 volts at the voltage regulator field terminal? YES Increase (if external) voltage regulator setting. Does charging voltage increase? YES You have solved the problem. . Troubleshooting 65
Troubleshooting Troubleshooting 3: The Alternator 1. There will be no spare part you might have over- Variations in appearance, arrangement of terminals, looked. For example, what if the problem were a and internal connections number in the hundreds. It broken mounting flange? is beyond the scope of this book to detail the differ- 2. You don't have to carry special tools such as a ences, but an alternator is an alternator, and, whatever bearing puller, press, or heavy-duty soldering its name, it works on the principles above. iron. There are two basic approaches to alternator repair. 3. Replacement takes minutes; repair takes hours. The first is to carry replacements for the components 4. The cost of the whole alternator (with trade-in) most likely to fail in the field: charge diodes, diode trio, is probably no greater than the cost of a com- isolation diode, brushes, bearings, and voltage regula- plete set of spare components. tor. The second is to carry an exact replacement for the entire alternator, including the voltage regulator if The following troubleshooting guide should help external. I favor the second approach for the following you to discover whether the problem is with the wiring, reasons: the alternator, or the regulator. Check the Wiring from Alternator to a Battery with Battery Isolation Diodes STEP 1. Fig. 4.38 Wiring with Isolation Diodes Turn the engine off and the battery-select switch off. The multimeter should read: - + • Battery + to Ground, 12 V or more • Alternator + to Ground, 0 V V – + If Alternator + to Ground reads 12 V, suspect a shorted isolation diode. STEP 2. - + Turn the engine on with the battery-select switch on. The multimeter should read: F GND F • Alternator + to Battery +, 0.5 to 1.0 V GND + • Battery + to Ground, about 1 V higher than with the engine off If not, suspect the isolation diode feeding the battery. STEP 3. To check a battery isolation diode definitively, discon- nect it from the batteries and read resistance across the diode, reversing leads. • An open-circuit diode reads 1 both directions ∞ • A shorted diode reads near 0 1 both directions • A healthy diode reads near ∞ 1 in one direction and 0 1 in the other direction 66 Alternators
Check Wiring from an Alternator to a Battery with No Battery Isolation Diodes STEP 1. Fig. 4.39 Wiring with No Isolation Diodes Turn the engine off and the battery-select switch on. The multimeter should read: • Alternator + to Battery +, 0 V • Alternator – to Battery –, 0 V V – + On the resistance scale the multimeter should read: • Alternator + to Battery +, 0 1 • Alternator – to Battery –, 0 1 - + If not, suspect corrosion or a broken wire. F F GND STEP 2. GND + Turn the engine on and the battery-select switch on. The multimeter should read: • Alternator + to Battery +, < 0.5 V • Alternator – to Battery –, < 0.5 V If not, suspect corrosion or a broken wire. Check Alternator and Battery Voltage with No Battery Isolation Diodes STEP 1. Fig. 4.40 Alternator and Battery Voltage Turn the engine off and turn the battery-select switch to the battery being tested (repeat tests for other batter- ies). On the voltage scale the multimeter should read: • Battery + to Ground, 12 to 13 V. If not, the bat- tery may be bad. – + – + • Alternator + to Ground, 12 to 13 V. If not,Alterna- tor + to Battery + cable is bad. STEP 2. - + Turn the engine on and turn the battery-select switch to the battery being tested (repeat tests for other batter- F F ies). On the voltage scale the multimeter should read: GND GND + • Battery + to Ground, about 1 V higher than with the engine off. • Alternator + to Ground, at least 1 V higher than with the engine off. If not, the alternator is not charging. Troubleshooting 67
Troubleshooting Check Alternator and Battery Voltage with Battery Isolation Diodes STEP 1. Fig. 4.41 Voltages with Isolation Diodes Turn the engine off and turn the battery-select switch to the battery being tested (repeat tests for other bat- teries). On the voltage scale the multimeter should V V read: – + – + • Battery + to Ground, 12 to 13 V. If not, the bat- tery may be bad. • Alternator + to Ground, 0 V. If not, suspect a - + shorted isolation diode. STEP 2. Turn the engine on and turn the battery-select switch to the battery being tested (repeat tests for other batter- + ies). On the voltage scale the multimeter should read: - F • Battery + to Ground should be about 1 V higher F GND than with the engine off. If not, the alternator is GND + not charging. • Alternator + to Ground should be 0.5 to 1.0 V higher than Battery + to Ground. If not, suspect a shorted isolation diode. Check a Type-N Alternator with No Output STEP 1. Fig. 4.42 Checking a Type-N Alternator Turn the engine off, measure the voltage from Battery + to Ground, and note its value. STEP 2. A – + Remove the wire from Alternator Terminal F. STEP 3. Connect a test light (minimum 12 W,such as an anchor light) from Terminal F to Ground. + - STEP 4. F F GND GND + Start the engine and measure the voltage from Battery + to Ground again. If the voltage is about 1 V higher than it was when the engine was off, then the alternator is OK, but its regulator is bad. 68 Alternators
Check a Type-P Alternator with No Output STEP 1. Fig. 4.43 Checking a Type-P Alternator Turn the engine off, measure the voltage from Battery + to Ground, and note its value. A STEP 2. – + Remove the wire from Alternator Terminal F. STEP 3. Connect a test light (minimum 12 W, such as an anchor light) from Terminal F to Battery +. + - STEP 4. F Start the engine and measure the voltage from Battery GND GND F + to Ground again. If the voltage is about 1 V higher + than with the engine off, then the alternator is OK, but its regulator is bad (see next test). Check the Excite Circuit for a Type-P Alternator Regulator If the type-P regulator tested bad above, the problem Fig. 4.44 Flashing a Type-P Alternator may lie not in the regulator but in its excite circuit. To test the excite circuit: – Voltage regulator STEP 1. F + Start the engine. STEP 2. - Measure the voltage from Battery + to Ground. + F F GND GND + STEP 3. Momentarily connect the test light between Battery + and Alternator Terminal F. If the voltage from Battery + to Ground is now about 1 V higher than with the engine off, the alternator and regulator are OK, but the excite circuit is bad. You can either repair the excite circuit, or you can create an excite circuit temporarily by placing a 12 W lamp between the engine oil-pressure switch and Alter- nator Terminal F. Troubleshooting 69
5 CHAPTER Bonding DCV ACV Ω mA – + Reference electrode Proposed zinc 70 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
B onding is a somewhat controversial, and often poorly understood, wiring practice. As usual, we start by answering a basic question—what is bonding? The purposes of bonding are threefold: (1) electrical system grounding, (2) lightning protection, and (3) corrosion protection. The bonding controversy stems from the possibility of its encouraging stray-current corrosion. So—to bond, or not to bond—that is the question we address in detail. Fortunately, there are simple methods for testing your protection against corrosion. These, and the ABYC standards for the general application of cathodic protection, should protect your boat's underwater met- als. Though neither caused nor prevented by bonding, other types of corrosion are explained as well. 71
What Is Bonding? No marine wiring topic causes more confusion than grounded conductors are held to the same voltage bonding. That is because there are at least three sepa- (ground, or zero volts) by being connected to the DC rate and compelling reasons for electrically connecting, negative bus and, ultimately, to the battery negative ter- or bonding, metal objects aboard a boat: minal. So that people are not accidently exposed to live 1. Electrical system grounding 2. Lightning protection voltage from a piece of equipment shorted to a live 3. Corrosion protection wire, the metal enclosures of all electrical equipment are connected to ground by grounding conductors. At the same time, there are reasons for not bonding These conductors are in addition to the grounded con- certain items. As they occur, these exceptions will be ductors and carry current only in the case of an elec- discussed. Note that the grounding of AC systems is trical fault. covered separately in Chapter 9, AC Standards and Bonding conductors are also separate from, and in Practices.You will find there, however, that AC ground- addition to, the grounded conductors. As elaborated ing is related to DC grounding in a simple way. later in this chapter, they play important roles in both lightning and corrosion protection. They should take as short and direct routes as possible to the substantial Grounded, Grounding, Bonding common-bonding conductor, which usually runs near Ideally, ground is the voltage of the water in which the the fore-and-aft centerline of the boat. Each bonding boat is immersed. Unfortunately, voltage in the water conductor should be at least as large as the current-car- may vary slightly due to stray electrical currents. As we rying positive and negative conductors that serve the will see, one of the purposes of the bonding system is to equipment. force the voltage of and within the hull to be as uni- The engine-bonding conductor should be at least as form as possible through the use of low-resistance con- large as the largest bonding conductor in the rest of ductors and connections. the bonding system and large enough to carry starting As defined by the ABYC and shown in Figure 5.1: current. Twin engines with crossover starting systems • Grounded conductors are the current-carrying con- should be bonded to each other, as well, with a conduc- ductors that connect to the side of the source tor large enough to carry the starting current. (almost universally the battery negative terminal), The large common-bonding conductor should be which is intentionally maintained at ground bare or green. If wire, it may consist of bare, stranded, potential. tinned copper or insulated stranded wire of minimum • Grounding conductors are normally non-current- size 8 AWG. If solid, it may be uninsulated copper, carrying conductors, provided to connect the bronze strip, or copper pipe at least 0.030 inch thick exposed metal enclosures of electric equipment and 0.5 inch wide. The copper, bronze strip, or pipe to ground, the primary function of which is to may be drilled and tapped, provided it is thick enough minimize shock hazard to personnel. to provide at least three full threads for terminal • Bonding conductors are normally non-current- screws, or it may be unthreaded for machine screws carrying conductors used to connect the non- and locknuts. current-carrying metal parts of a boat and the Equipment to be bonded includes: engines and non-current-carrying parts of direct-current transmissions, propellers and shafts, metal cases of devices on the boat to the boat's bonding system. motors, generators and pumps, metal cabinets and All DC electrical devices receive their power control boxes, electronics cabinets, metal fuel and water through a pair of positive and negative input terminals, tanks, fuel-fill fittings, electrical fuel pumps and valves, served by a pair of conductors. Current flows into the metal battery boxes, metal conduit or armoring, and positive terminal from a positive conductor (wire) large nonelectrical metal objects as recommended in from the DC distribution panel and, ultimately, from the Lightning Protection section. the positive (+12 V) terminal of the battery. Ideally, Note that you may choose not to bond electrically the same amount of current returns to the battery neg- isolated through-hull fittings, as will be discussed fur- ative terminal through the grounded conductor. All ther in the Corrosion Protection section. 72 Bonding
Fig. 5.1 Typical DC Negative System and DC Grounding System (Adapted from ABYC Standard E-11, Figure 18) Windlass + – Distribution Panel FOR – + Wiper SYSTEM GROUNDING – + Horn Blower Float switch Grounding AND bonding conductor – + Bilge pump Float switch Overcurrent DC negative bus – + protection Grounded conductors Main feed + Overcurrent Parallel switch protection House Accessory or solenoid battery negative – bus Battery Battery switch Engine switch negative + terminals + Start Engine Engine Start battery battery – – DC main negative bus AC grounding bus Grounding conductor Grounding conductor Fill Gauge Gauge Fill Fuel tank Grounding bus Bonding Fuel tank conductors Seacock Large metal objects FOR CORROSION Seawater strainer Chainplates PROTECTION FOR LIGHTNING Sacrificial zinc Electronics PROTECTION ground plate Lightning down conductor (from lightning mast) Immersed lightning ground plate or strip What Is Bonding? 73
Lightning Protection At any moment, there are approximately 2,000 light- Fig. 5.2 Discharge of Cloud Charge ning storms in progress around the earth, producing 100 strikes every second. In some regions lightning is + + + + + + + + + + + + a rarity. In others it is an almost daily occurrence. + + To put the danger in perspective, there are approxi- mately 24,000 lightning deaths per year in the world, 100 in the United States. From 1959 to 2003, recorded deaths in the United States included: • Florida 425 • Texas 195 • North Carolina 181 • Ohio 136 • New York 134 – – – – – – – – – – – – – – – – • Tennessee 133 – – – – – – – – Where the deaths occurred: • In or around the home 20% • In vehicles (mostly open) 19% ++ • Taking refuge under trees 15% +++++ +++++ • In boats 13% • Everywhere else 33% Ionization proceeds in steps of about 100 feet. Elec- Considering the significant percentage of deaths trons flow downward through the ionized path and occurring in boats and the low number of people in cause a faint blue-white glow, similar to the flow of boats at any given time, it is apparent that the poten- electrons in the ionized gas of a neon sign. Each step tial for lightning strikes on boats is a serious matter. In requires only about 0.00005 second to ionize and fill, so fact, the ABYC devotes all of Standard E-4 to the matter that the stepped leader traverses a distance of 10,000 of lightning protection. feet, from the base of a cloud to ground, in about 0.005 second. The final step to ground is of most interest to a What Is Lightning and How Does It Act? boater. Up to the last step, the presence of a boat has In all lightning theories, a combination of vertically no influence on either the location or the direction of moving water droplets and air currents results in the the discharge. When looking for that final connection buildup of large quantities of oppositely charged par- to earth, however, the lightning will head for the closest ticles within clouds and between clouds and the accumulation of positive charge. That generally means ground (Figure 5.2). The electrical potential differences the highest point within a radius of 100 feet. If that between charges may be as high as 100,000,000 volts. point is you, chances are you will be struck. If it is the By comparison, the voltage on the power lines running tip of your mast, your mast will be struck. along a street is a mere 12,000 volts. After the ionization of the column has been com- In particular, the base of a cloud becomes negatively pleted by the leader, there exists a short circuit from charged. Since opposite charges attract, the surface of cloud to earth. The resulting rush of accumulated the earth directly beneath the cloud becomes positively charge from cloud to earth is what we see as the light- charged. People standing in this positively charged area ning bolt—an ionized column of air, heated to under a cloud sometimes report feeling their hair 50,000°F, conducting a typical current of 50,000 amps. standing on end due to the static charge just before a The resulting rapid heating of the air produces a super- lightning strike. What initially prevents the charges sonic air-pressure wave heard as thunder. The entire from combining is the extreme electrical resistance of 0.005-second process may be repeated several or even air. Some scientists believe that lightning strikes are dozens of times during the following second, depend- triggered by cosmic rays knocking electrons from air ing on the initial size of the accumulated charge. molecules. The freed electrons accelerate in the volt- Direct strikes are the most dangerous. Consider that age field, causing the release of more electrons and ion- the largest circuit breaker or fuse on your boat is prob- izing the air. ably rated at less than 100 amps, and that the cranking 74 Bonding
current to your starter motor is probably on the order Zones of Protection of 200 amps. Now consider what 50,000 to 200,000 Metal masts tend to draw the final step of a leader to amps might do to that same wiring. Although the peak themselves within a radius equal to their height. The current lasts only 0.0001 second, the resistive heating conical zone beneath the tip is known as the zone of is often sufficient to burn insulation, melt components, protection. A person or object entirely within this zone even vaporize conductors. is substantially protected from a direct strike. Much lightning damage occurs from near-hits, Figure 5.3 shows zones of protection for a power- however. It is not uncommon for one boat to suffer a boat with a lightning-protective mast and with the direct strike and for boats in adjacent slips to lose elec- mast extended by a grounded air terminal. Powerboat tronic equipment. Just as a current-carrying wire pro- hulls do not generally fall entirely within their zones duces a magnetic field, and a varying magnetic field of protection unless either their masts are extended by produces current in a conductor (the principle behind grounded antennas or outriggers, or they have more the alternator), lightning currents produce extreme than one grounded mast. magnetic fields, which then induce currents in nearby Figure 5.4 shows the zone of protection for a sail- wires. These induced currents are often sufficient to boat mast less than 50 feet. A sailboat hull will usually destroy sensitive electronic circuits. lie entirely within the zone of protection. To qualify as Just any copper conductor will not suffice to con- a lightning-protective mast, the mast must either be duct currents of 50,000 amps. The conductor must be metal or be equipped with an air terminal and metal large and conductive enough to present the path of conductor to ground (see Figure 5.6). least resistance to ground (the surrounding water, in Figure 5.5 shows the zone of protection for a boat the case of a boat). Small-diameter wire, corroded con- with a lightning-protective mast more than 50 feet. nections, and too small a ground plate (area of metal in With more than one mast, zones are drawn for each contact with the water) may cause the lightning to seek mast. The combined protective zone includes all areas additional paths to ground, resulting in dangerous side under one or more of the individual zones. To qualify flashes. The recommendations in ABYC Standard E-4 as lightning protective, each mast must be grounded. are intended to minimize both danger and damage Multihulls require grounding plates in each hull. from lightning. Fig. 5.3 Lightning-Protective Zone for Motorboat with Lightning-Protective Mast or Mast with Approved Extension Protected zone with solid antenna Solid antenna extending the height of the lightning mast to protect nearly the entire boat Lightning mast Protected zone with lightning mast only H2 H1 H1 H1 H2 H2 Lightning Protection 75
Lightning Protection Fig. 5.4 Lightning-Protective Zone for Sailboat Mast Less Than 50 Feet H H H Fig. 5.5 Lightning-Protective Zone for Sailboat Mast Over 50 Feet or More Than One Mast Zone for taller mast Zone for shorter mast Masts more than 50 ft (15 m) 100 ft 100 ft 76 Bonding
The Safe Path to Ground Fig. 5.6 The Safe Path to Ground Regardless of any lightning rod or charge dissipator, if Air terminal your mast is the highest object in the vicinity it will be struck. The purpose of the safe path to ground is to provide a path to ground (the water) as short, straight, and conductive as possible to prevent side flashes to Parallel path Parallel path alternate routes. The path consists of two parts: the lightning-protective mast and the lightning-ground con- nection. Primary Lightning-Protective Mast lightning conductor Metal masts qualify as protective masts. If nonconduc- (4 AWG) tive, however, a mast must be provided with a ground- ing conductor running from an air terminal 6 inches above the mast in as straight a line as possible to the lightning-ground connection. The conductor must be securely fastened to the mast and consist of either a 4 AWG conductor stranded-copper wire of minimum size 4 AWG or a short as possible with 8\" min. radius bends metal strip of conductivity equal to that of 4 AWG cop- Metal tank per wire and thickness of at least 0.030 inch. Engine Joints, including that to the lightning-ground con- nection, must not be subject to immersion. In the case of 4 AWG wire, the connection must be strong enough to support a 45-pound weight for 1 minute. To avoid Bonding conductors corrosion, all bolts, nuts, washers, and lugs must be gal- Secondary (6 AWG) lightning vanically compatible with the conductor. conductor Immersed (6 AWG) A stainless steel radio antenna may serve as an air ground plate or strip (1 sq. ft.) terminal provided it has either a means for direct connection to ground, or a lightning-protective gap the engine, transmission, and shaft may lead to (closely spaced electrodes, which lightning will easily extremely large currents through main-engine- and jump). If not disconnected when the antenna is transmission-output bearings, to their detriment. If the grounded, the antenna feed line should also have a shaft and propeller are to be bonded, it should be lightning arrestor, or transient voltage surge suppres- through a brush riding on the shaft. sor. Sintered bronze plates, intended to serve as ground Lightning-Ground Connection plates for SSB radios, are questionable as lightning A lightning-ground connection may be any underwa- grounds. Due to their porosity, these plates do have ter metal surface of at least 1-square-foot area. Metal wetted areas greater than the areas of their envelopes, hulls, centerboards, and external (not encased in fiber- but evidence suggests that they are not significantly glass) keels are excellent. Although metal rudders qual- more effective than plain copper plate of the same area. ify in area, the connection from mast to rudder is too In fact, it is theorized that edge length is more impor- long. tant than area in lightning ground plates.A 12 foot by 1 1 Where the lightning-ground connection is an inch by ⁄4 inch copper strip would be six times more immersed ground plate at the base of the mast, the effective than a 1 foot by 1 foot square copper plate. backstay and other large aft metal objects, because of In order, the best lightning-ground connections are: the distance, should be grounded to the engine instead 1. Metal hull of the ground plate. 2. External metal keel (attach to keel bolts) 1 It is commonly believed that the large surface areas 3. External 12 foot by 1 inch by ⁄4 inch copper of the propeller and shaft provide adequate lightning strip grounding. While true, relying on the conductivity of 4. Large sintered bronze plate Lightning Protection 77
Lightning Protection Protecting Electronics Fig. 5.7 Protecting Electronics from Lightning Surges A well-protected boat may lose electronics. The prob- Alternative 1: Short the Surges lem is that today's solid-state electronics are very intol- erant of voltage surges. It doesn't matter whether the Solid whip surge comes from a direct lightning hit or from current induced in the antenna, microphone, or power leads by Lightning bypass gap the magnetic field pulse of a nearby strike. bridging loading coil Two basic approaches to protecting electronics are: Long coax run (1) shorting the surges, and (2) disconnecting all the leads. Transient voltage surge suppressor (TVSS) 2' – 3' distance Shorting the Surges + Electronic Figure 5.7 shows an antenna at the top of the mast. For equipment MOV Battery a solid-wire antenna with base-loading coil to be an – effective air terminal, there must be a lightning-bypass Microphone gap between the solid wire and the base of the antenna. If not, the inductive base coil resists the lightning cur- Alternative 2: Disconnect All Leads rent, and the lightning-protective mast originates at the base of the antenna. If the antenna is fiberglass with a Alternative 2: Disconnect All Leads Solid whip less than 8 AWG conductor, its conductivity is insuffi- cient, and the lightning protection again originates at Solid whip Antenna loading coil the top of the mast. A coaxial conductor from antenna to radio can pick Long coax run Antenna loading coil up current, either as part of a direct strike, or induced by the magnetic field of a nearby strike. This surge is Long coax run shorted to ground by a transient voltage surge suppres- + Electronic sor (TVSS) several feet from the electronics enclosure. equipment Battery Surges on the power supply line are shorted to Electronic + – ground by a metal oxide varistor (MOV), which typi- equipment Microphone Battery cally acts in less than 1 microsecond. Both TVSS and – MOV devices are available at ham- and marine-radio If any of your electronics have aluminum cases, dealers. place them in a steel box, which will shield them from There remain several problems with the approach: magnetic fields. 1. Insertion of the TVSS in the antenna-feed line results in some loss of transmitted power. Protecting People 2. By shorting the cable to ground, the TVSS makes it more likely that the coaxial line will be dam- Assuming all of the protective measures above are in aged by a strike. place, you can minimize the lightning danger to peo- 3. By shorting the antenna feed to ground, the ple aboard your boat by following these rules: TVSS leads lightning current closer to the elec- 1. Keep everyone inside the boat. tronics than if the cable were disconnected. 2. Do not allow any part of anyone's body in the water. Disconnecting Leads 3. Keep everyone at least 6 feet from the lightning- TVSS and radio manufacturers agree the best way to protective mast. protect electronics is to remove all leads, including the 4. Don't allow anyone to touch any part of the microphone. Switching a circuit breaker won't work spars, standing rigging, metal rails, or metal life- because lightning will easily bridge the small breaker lines. gap. 5. Don't allow anyone to touch any two grounded objects with two hands. 78 Bonding
Corrosion Protection Every boatowner knows about corrosion. That is, they switching the meter to amps and placing a 1.5-volt know it happens. Everywhere they look they see stain- lamp in series with the meter + lead, we find that cur- ing, pitting, powdering, and disintegration. Corrosion rent is flowing from + terminal to – terminal as is so pervasive on a boat that it's easy to throw up your expected. Since electrons are negative, the electrons are hands and accept it, like death, as inevitable. But cor- actually flowing in the opposite direction, from – rosion is not inevitable. Corrosion can be prevented. to +. As with most problems, a solution comes only with If we were to leave the lamp connected to the bat- understanding, and understanding requires an invest- tery long enough, the battery voltage and current ment of mental energy. If you really, truly want to stop would eventually drop to zero. Upon examination, we the corrosion on your boat, get a cup of coffee or tea, would find that all of the zinc coating had disappeared find a comfortable reading spot, and clear your mind. (it had corroded). On the other hand, if we discon- nected the lamp so that there was no electrical closed What Is Corrosion? circuit between the carbon and the zinc, the zinc would not corrode, and the battery would retain its voltage for In general terms, corrosion is the deterioration of a material by chemical or electrochemical reaction with a very long time. its surroundings. As boatowners, we are most familiar You have just witnessed galvanic corrosion in a gal- with galvanic corrosion—the deterioration of the vanic cell. The common carbon-zinc battery is a conve- anode of a galvanic couple resulting from the flow of nient example, but it is just one example of a common ions from the anode to the cathode through an elec- phenomenon. trolyte. Relax! Those are just fancy words to describe a very Another Galley Experiment common phenomenon—the chemical reaction that Performing the experiment in Figure 5.9 will do won- takes place inside a battery. ders for your understanding of corrosion on your boat. Figure 5.8 shows a carbon-zinc flashlight battery Gather a plastic container of fresh water, a table- (the inexpensive type that comes with electrical toys). If spoon of salt, a multimeter, two test leads with alligator we were to slice the battery in half, we would see a car- clips, and an assortment of metal items. I used a stain- bon rod in an electrically conductive paste, all inside a less bolt, a small piece of aluminum pie plate, and a zinc-coated can. At A we measure the voltage between shaft zinc. the carbon rod and the zinc can as 1.5 volts. At B, Fig. 5.9 Measuring Galvanic Voltage and Current Fig. 5.8 The Battery—a Useful Form of Corrosion - mV + B Meter set to Amps Zinc Stain- – + less A Meter set to Volts - mA + + I - I Zinc e Electrolyte - Carbon Zinc e Stain- less Zn ++ Corrosion Protection 79
Corrosion Protection Switch the multimeter to volts. Using the test leads, Fig. 5.10 What Happens When Zinc Corrodes connect the negative (–) lead to the zinc and the posi- tive (+) lead to the stainless bolt and lower both pieces into the water. Surprised? The meter will indicate a Zn voltage. Atom Now switch the meter to milliamps. You may or may not read any current, but hold on. Dump the tablespoon of salt into the fresh water and stir. Depend- ing on the sizes of the electrodes, you will now proba- bly measure a current of about a milliamp flowing e - from the stainless bolt to the zinc. Zn ++ What's going on? When two dissimilar metals are - Ion placed together in an electrolyte (electrically conduc- e tive medium), one of the metals will assume a higher potential than the other. In Chapter 1 we learned that current flows only in a closed circuit. Two electrodes, immersed in electrolyte, form an open circuit, and no current flows. But when we connect the two electrodes, either with a wire or by letting them touch, we com- plete the circuit and current flows. In this case, the current flowing through the meter is from the stainless steel electrode into the zinc elec- The values in the table are between a metal and a trode. (Since electrons carry negative charge, the elec- silver-silver chloride electrode.Values between any two tron flow is actually in the opposite direction, but never metals are found as the differences between the table mind.) values for the two metals. Figure 5.10 shows what is happening to the zinc on Example: What is the corrosion (galvanic) poten- an atomic level. Zinc atoms are changing into positively tial between silicon bronze and zinc? From Table 5.1 we charged zinc ions by giving up two electrons. These find the corrosion potential of silicon bronze vs. the released electrons are flowing from the zinc to the reference to be –0.26 to –0.29 volt (average –0.28 volt) stainless through the meter leads, and the newly and zinc vs. the reference to be –0.98 to –1.03 volt formed zinc ions are departing the zinc electrode and (average –1.00 volt). Thus the corrosion potential migrating into the electrolyte—the zinc is corroding. between silicon bronze and zinc is –0.72 volt. Continue the experiment if you wish by substitut- By now you may be thoroughly alarmed at the ing other pairs of dissimilar metals. As long as the elec- thought of all the underwater metallic components on trode metals are different in composition, they will your boat—stainless bolts, stainless or bronze shaft, always generate a potential difference, and current will brass Cutless bearing shell, and aluminum outboard always flow into the lower-voltage metal. The voltage drive. And well you should be, with all that potential difference will be the same, whether the water is salt or (no pun intended) for corrosion. But let's press on. fresh. The currents, however, will be much greater in Before continuing our galley experiment, let's salt water due to its greater conductivity. review what we have learned. We have found that any The potential difference between any two dissimilar two dissimilar metals or alloys immersed in water will metals can be predicted by consulting a table of gal- generate a potential difference.We have also found that vanic potentials. The table lists the potential differences if the two metals are isolated (neither physically touch- measured between the metal in question and a refer- ing nor electrically connected by wire), no current or ence electrode, typically silver-silver chloride. Table 5.1 corrosion will occur. Good. But what if they cannot be reproduces the values listed in Table I of ABYC Stan- separated (a bronze prop on a stainless shaft), or what dard E-2 for metals and alloys in seawater flowing at 8 if we have bonded them for lightning protection (a to 13 feet per second (4.7 to 7.7 knots), and at temper- steel rudder, several bronze through-hulls, and a cop- atures of 50°F to 80°F. per ground strip)? Have we shot ourselves in the foot? 80 Bonding
Table 5.1 ABYC Standard E-2, Galvanic Series of Metals in Seawater Referenced to Silver-Silver Chloride Half Cell (Seawater flowing at 8 to 13 ft./sec. [4.7 to 7.7 kn.], temperature range 50°F to 80°F—except as noted) Metals and Alloys (Anodic or Least Noble—Active) Corrosion Potential, Volts Magnesium and Magnesium Alloys –1.60 to –1.63 Zinc –0.98 to –1.03 Aluminum Alloys –0.76 to –1.00 Cadmium –0.70 to –0.73 Mild Steel –0.60 to –0.71 Wrought Iron –0.60 to –0.71 Cast Iron –0.60 to –0.71 13% Chromium Stainless Steel, Type 410 (active in still water) –0.46 to –0.58 18-8 Stainless Steel, Type 304 (active in still water) –0.46 to –0.58 Ni-Resist –0.46 to –0.58 18-8, 3% Mo Stainless Steel, Type 316 (active in still water) –0.43 to –0.54 Inconel (78% Ni–13.5% Cr–6% Fe) (active in still water) –0.35 to –0.46 Aluminum Bronze (92% Cu–8% AI) –0.31 to –0.42 Nibral (81.2% Cu–4% Fe–4.5% Ni–9% Al–1.3% Mn) –0.31 to –0.42 Naval Brass (60% Cu–39% Zn) –0.30 to –0.40 Yellow Brass (65% Cu–35% Zn) –0.30 to –0.40 Red Brass (85% Cu–15% Zn) –0.30 to –0.40 Muntz Metal (60% Cu–40% Zn) –0.30 to –0.40 Tin –0.31 to –0.33 Copper –0.30 to –0.57 50-50 Lead–Tin Solder –0.28 to –0.37 Admiralty Brass (71% Cu–28% Zn–1% Sn) –0.28 to –0.36 Aluminum Brass (76% Cu–22% Zn–2% AI) –0.28 to –0.36 Manganese Bronze (58.5% Cu–39% Zn–1% Sn–1% Fe–0.3% Mn) –0.27 to –0.34 Silicon Bronze (96% Cu max–0.8% Fe–1.5% Zn–2% Si–0.75% Mn–1.6% Sn) –0.26 to –0.29 Bronze-Composition G (88% Cu–2% Zn–10% Sn) –0.24 to –0.31 Bronze ASTM B62 (thru-hull) (85% Cu–5% Pb–5% Sn–5% Zn) –0.24 to –0.31 Bronze-Composition M (88% Cu–3% Zn–6.5% Zn–1.5% Pb) –0.24 to –0.31 13% Chromium Stainless Steel, Type 410 (passive) –0.26 to –0.35 Copper Nickel (90% Cu–10% Ni) –0.21 to –0.28 Copper Nickel (75% Cu–20% Ni–5% Zn) –0.19 to –0.25 Lead –0.19 to –0.25 Copper Nickel (70% Cu–30% Ni) –0.18 to –0.23 Inconel (78% Ni–13.5% Cr–6% Fe) (passive) –0.14 to –0.17 Nickel 200 –0.10 to –0.20 18-8 Stainless Steel, Type 304 (passive) –0.05 to –0.10 Monel 400, K-500 (70% Ni–30% Cu) –0.04 to –0.14 Stainless Steel Propeller Shaft (ASTM 630:#17 and ASTM 564:#19) –0.03 to +0.13 18-8, 3% Mo Stainless Steel, Type 316 (passive) 0.00 to –0.10 Titanium –0.05 to +0.06 Hastelloy C –0.03 to +0.08 Stainless Steel Shafting (Bar) (UNS 20910) –0.25 to +0.06 Platinum +0.19 to +0.25 Graphite +0.20 to +0.30 (Cathodic or Most Noble—Passive) Corrosion Protection 81
Corrosion Protection To find out if we are in trouble, let's continue our Fig. 5.11 How a Sacrificial Zinc Anode Works galley corrosion experiment. First repeat the zinc vs. stainless test in Figure 5.10. Next add a piece of alu- - - minum as a third electrode. Using alligator clip leads, e I I=0 I e connect the zinc, stainless, and aluminum electrodes, as mA mA mA shown in Figure 5.11. Now set the multimeter to mil- liamps and insert it, one at a time, in each of the leads to detect current flow. Amazing! Electric current is flowing out of the stainless electrode and into the zinc electrode, but no Zinc Alum Stain- current at all is flowing either into or out of the alu- less minum electrode. Since metal is lost only by an elec- trode that receives current, it seems that the zinc is pro- Zn ++ tecting the aluminum by sacrificing itself. You can repeat this experiment with any three met- als you wish, and the results will always be the same: when dissimilar metals in an electrolyte are mechani- Fig. 5.12 Two Examples of Zinc-Anode Protection cally or electrically bonded, the only metal to corrode will be the one highest in the galvanic series. The metal most used in boats for this purpose is zinc. The phenomenon just observed is called cathodic Bond protection, and the zinc masses are called zinc anodes Zinc or just zincs. Aluminum Figure 5.12 shows two examples of cathodic protec- tion using zincs.At top is an outboard engine mounted on the transom of a boat. A large zinc is bolted directly to the transom underwater, and a wire is run from the Bond mounting bolts of the zinc to the outboard. The zinc protects the outboard. The zinc could also have been— Zinc collar Bronze and often is—bolted directly to the underwater shaft of Stainless the outboard. At the bottom of Figure 5.12 is a sailboat with a zinc on the propeller shaft. The zinc is mechanically (and Fig. 5.13 An Assortment of Zincs thus electrically) connected to the shaft. Protection is extended to the rudder shaft by a conductor from rud- der to engine block. Rudder, rudder shaft, engine, SHAFT ZINCS ENGINE ZINCS transmission, prop shaft, and prop are all connected and thus protected by the zinc. The presence of a non- conductive plastic or rubber shaft coupling would require a jumper strap across the coupling. It should be KEEL AND noted that the ABYC also permits shafts and rudders RUDDER ZINCS to be protected separately, each by its own zinc anode. Figure 5.13 shows a variety of zincs commonly found in chandleries. Many more shapes and forms are available from specialty suppliers. Engine zincs are mounted inside the cooling systems of engines. The TRANSOM ZINC "GUPPY" ZINC guppy is used at anchor or in a marina slip and will be discussed below. 82 Bonding
Stray-Current Protection Even if you're flushed with your recent mastery of Fig. 5.14 Experiment Setup the subject of galvanic corrosion, I suggest you take a break at this point because we have to start all over - mV + again. It turns out there is more than one way to create a potential difference between underwater metals. We have another dragon to slay—stray-current corrosion. - mA + Galley Experiment, Continued I=0 0 Volts I=0 OK, back to work. As a refresher, place two identical aluminum electrodes in the saltwater solution, as in Al Al Figure 5.14. Using the multimeter, measure the voltage between the electrodes. Then switch the multimeter to A B milliamps and measure the current in the wire between the electrodes. The result should be the same in both cases: zero. Next place a 1.5-volt battery between the same two aluminum electrodes, A and B, as in Figure 5.15. Now, of course, you will measure the battery's 1.5 volts across Fig. 5.15 Impressing (Forcing) Current with a Voltage the electrodes and, with the meter placed in series with Source the battery, a current flowing from the battery positive - + (+) terminal into electrode B. If you let the experiment 1.5V go on long enough, you will observe that the electrode into which the current flows is corroding, just as it did I I with galvanic corrosion. It is apparent that it makes no difference whether the potential difference between the electrodes is due to their being of dissimilar metals or due to a voltage impressed on them from an outside source—the electrode receiving current always cor- A B rodes. When the impressed voltage is accidental (as from a poorly insulated electrical connection), the cor- rosion is termed stray-current corrosion. Since stray, or accidental, voltage sources can be much greater than galvanic potentials (up to 12 volts, compared to a few tenths of a volt), stray current corrosion can be much more damaging than galvanic corrosion. Fig. 5.16 Stray Current Impressed by Voltage Field Finally, we'll use four aluminum electrodes as shown in Figure 5.16. As in the previous test, Figure 5.15, we'll use electrodes A and B to force a current in the seawater. Now insert the connected pair, C and D, between A and B. Measure the current between C and D. It will be approximately the same as in the previous experiment. Likewise, electrode C will eventually show signs of corrosion. Now you see why this insidious phenomenon is termed stray-current corrosion. Two perfectly innocent metal objects, if electrically bonded, can pick up stray current flowing through the electrolyte and partici- pate in the corrosion process! Stray-Current Protection 83
Stray-Current Protection Figure 5.17 shows a boat floating in an external flows into the ground plate, through the bonding sys- voltage and current field (perhaps due to an adjacent tem and out of the propeller. And since the current is boat). The voltage difference, from left to right across flowing into the propeller from the bonding system, the the illustration, is 1.0 volt. propeller will corrode. Since the electrical resistance of the path from Figure 5.18 shows that a sacrificial zinc on the shaft ground plate to bonding wire to engine to shaft to pro- will divert the current flow to itself and save the prop. peller is less than that of the water path, electric current Fig. 5.17 Stray-Current Corrosion Caused by an External Voltage Field 0V 0.5V 0.5V 1V Radio No zinc—prop Bonding corrodes wire I Ground plate Fig. 5.18 Cathodic Protection from Stray-Current Corrosion Caused by an External Voltage Field 0V 0.5V 0.5V 1V Radio Zinc—prop protected Bonding wire I Ground plate 84 Bonding
Figure 5.19 shows a stray current originating the water outside the hull, and back through the prop, entirely inside the boat. Both a bilge pump and a shaft, and engine path to ground. Since the through- bronze through-hull are sitting in bilge water. The hull is receiving current, it is also giving up ions to the unbonded pump develops a short from its positive sea (corroding). If the pump housing had been electri- power lead to its housing, establishing the pump hous- cally bonded, the short would have tripped the circuit ing at 12 volts. Current flows from the electrified hous- breaker, preventing corrosion and alerting the boat- ing, through the bilge water, into the through-hull, to owner to the short. Fig. 5.19 Stray-Current Corrosion Caused by Shorted Bilge Pump Inside Hull 12V 0V Stray current Battery Through- Pump hull 0V Stray current Figure 5.20 shows stray current originating from a stray current finds its way back to ground by way of the terminal strip in the bilge. A single 12-volt/ground pair through-hull–seawater connection. If the through-hull is shown here, but there are usually several pairs, serv- were, instead, bonded to ground, the stray current ing anchor light, steaming light, and spreader lights on would flow back to ground by way of the bonding and the mast. The terminal strip is wet, and some of the not result in corrosion. Fig. 5.20 Stray-Current Corrosion Caused by Wetted Terminal Strip in Bilge Panel 12V 0V Stray current Battery Through- Terminal hull strip Stray current Stray-Current Protection 85
To Bond or Not to Bond We have just seen three cases of stray-current corro- Bond and Protect sion. Two would have been prevented by bonding, but Figure 5.21 shows the bond-and-protect principle. one was, in fact, caused by bonding. In general, bonding Every underwater mass is connected to the boat's of immersed metal components prevents corrosion due bonding system. To protect against stray currents out- to stray currents from inside the hull, but it causes cor- side of the hull, sacrificial anodes are connected to the rosion due to stray currents from outside the hull. bonding system and placed where they may best pro- Two opposite solutions to this dilemma are to: (1) tect all underwater masses. bond everything and protect, and (2) unbond every- thing and isolate. Fig. 5.21 The Bond-and-Protect Approach 12V 0V Common Radio ground Battery Bonding Through- Ground Zinc plate hull Unbond and Isolate The Pros and Cons of Bonding Figure 5.22 shows the alternative unbond-and-isolate Bonding and protecting offers the advantage of greater principle. Underwater masses are isolated so neither wetted surface area for the lightning and radio galvanic nor outside stray current can flow between grounds. them. The only bonded underwater mass is the light- On the other hand, proponents of the unbond-and- ning and radio ground. Masses entirely within the hull isolate approach claim that the lightning ground strip (engine, transmission, metal tanks, and mast) are or plate provides adequate ground for both lightning bonded to the boat's bonding system. The shaft is iso- and SSB radio, and that electrochemical reactions at lated by an insulating flexible coupling. The prop is bonded wooden hull through-hulls dangerously soften protected by a shaft zinc if prop and shaft are of dissim- the surrounding wood. The ABYC favors the bond- ilar metals. and-protect approach, but specifically states that elec- trically isolated through-hull fittings need not be bonded. Fig. 5.22 The Unbond-and-Isolate Approach 12V 0V Radio Battery Bonding Through- hull Ground Zinc Isolating plate flexible Unbonded coupling Isolated 86 Bonding
Sizing the Anode(s) The ABYC recommends a method (in Standard E-2, Fig. 5.23 ABYC Method for Sizing Cathodic Protection Appendix 3) using a silver-silver chloride reference electrode for determining the amount of cathodic pro- STEPS 1–6 tection (size of aggregate zinc anodes) required to pro- DCV ACV Ω mA tect the underwater metals of a boat. The method DMM on DC volts assumes the use of zincs meeting Military Specification MIL-A-18001 (99.2% zinc minimum), excellent – + (metal-to-metal) electrical contact between anode and metal to be protected, and no paint on the anode. The standard further points out that cathodic pro- tection requirements increase with boat speed, salinity (if salt water), acidity (if fresh water), frequency of use of the boat, and deterioration over time of the anode. ABYC Method 1. Assemble your materials: No zinc • silver-silver chloride reference electrode with lead (widely available on the Web or at West Reference Marine stores for about $80) electrode • digital multimeter (DMM) having at least 10 MW input impedance (even inexpensive DMMs do) • several high-quality zinc anodes of appropri- ate type (shaft collar, prop, or hull zincs) • two 20-foot test leads with strong clips 2. Starting with the hull free of all zinc anodes, lower the silver-silver chloride electrode into the water near the metal to be protected. STEPS 7–9 3. Set the DMM to the 2 Volts DC setting. 4. Connect the lead from the reference electrode DCV ACV Ω mA to the DMM – input. 5. Using a test lead, connect the metal to be pro- – + tected to the DMM + input. Make sure the test lead clip makes a clean electrical connection to the metal. 6. Note the DMM reading (example: –0. 720 volt). 7. Using the second test lead, connect one of the zinc anodes to the metal to be protected and lower the zinc into the water. 8. Note the new DMM reading. The zinc is ade- quate if it has lowered the voltage by at least 0.200 volt (example: from –0.720 volt to –0.920 volt or less). 9. If the second reading isn't at least 0.200 volt more negative than the first, the zinc is not suf- Reference electrode ficient. Increase either the zinc area or the num- Proposed zinc ber of zincs and retest. Sizing the Anode(s) 87
Testing Your Protection Test 1: Stray Currents Fig. 5.24 Test for Stray Current Inabondedsystem,straycurrentwillbecapturedby the boat's bonding conductor. Stray current in a through-hull or other accessible underwater mass can Digital meter be measured with a digital multimeter on the mil- on milliamps setting liamps (mA) setting as shown in Figure 5.24. DCV ACV Ω mA Disconnect the bonding conductor and place the meter between the end of the conductor and the metal of the through-hull. Current into or out of the through- + – hull will now flow through the meter. Repeat the test with each fitting, as well as the rudder shaft, prop shaft, and strut or shaft log. Remember that current flowing from the bonding conductor into the fitting, as shown, Bonding is causing corrosion of the fitting. Current of as little as conductor 1 milliamp is reason for concern as it will, over the 8,766 hours in a year, cause serious damage to the fitting. Test 2: Corrosion Potentials This test (Figure 5.25), using a digital multimeter and a silver-silver chloride reference electrode, will deter- Table 5.2 Interpreting Corrosion Test Voltages mine whether the boat's present sacrificial zincs are Underwater Under- Over- protecting the boat's underwater metallic masses: Metal protected Protected protected Bronze < 0.44 V 0.44–0.70 V > 0.70 V 1. Set the multimeter to measure DC volts. Steel < 0.75 V 0.75–0.95 V > 0.95 V 2. Connect the meter's + input to an underwater Aluminum < 0.90 V 0.90–1.10 V > 1.10 V metallic mass or, if there is a common bonding system (as shown), to engine negative ground. 3. Connect the reference electrode to the meter's – Readings in excess of 1.10 volts usually indicate a input, and lower the electrode into the water. voltage field in the water surrounding the boat. If you can't eliminate or reduce the external field, consider Compare the reading to those of Table 5.2 to see unbonding and isolating the underwater fittings, as whether the zinc anodes are adequate. If the readings shown in Figure 5.22. indicate underprotection, replace or add zinc anodes. Digital multimeter Fig. 5.25 How to Evaluate Your Boat's Corrosion Potential DCV ACV Ω mA on DC volts + – 12V 0V Common Radio Battery ground Bonding Ground Through- Zinc plate hull Silver- silver chloride electrode 88 Bonding
Noncathodic Corrosion We have addressed the types of corrosion that can be Fig. 5.26 Dezincification of Brass eliminated by cathodic protection. There are further annoying types of corrosion on a boat that must be addressed by other means. Dezincification Figure 5.26 shows the dezincification of brass screws. Brass consists of a mixture of copper and zinc. Com- Dezincification mon yellow brass contains 65% copper and 35% zinc. (loss of zinc In the presence of moisture (a very common electrolyte and strength) around boats!), the zinc and copper react galvanically, just as they would underwater, although more slowly. The result is a loss of zinc and loss of strength. When a badly dezincified screw is removed, the screw head often snaps off. The lesson: use only stainless or bronze screws around a boat. A second instance of dezincification occurs in bronze (an alloy of copper, tin, and zinc) propellers. Loss of zinc is evidenced by a telltale change of the metal from bright yellow to a pinkish hue. Stainless Screws in Aluminum Fig. 5.27 Seizing of Stainless Screws in Aluminum Figure 5.27 shows what happens when a fitting of any material, metallic or nonmetallic, is attached to an alu- minum mast or boom with stainless screws. Regard- less of how well machined the threads are, there are Capillary moisture results in corrosion always microscopic spaces between the screw and the body. If salt water finds its way into these capillary spaces, an ideal galvanic cell is set up with resulting loss Stainless screw of aluminum in the area of the threads. Ultimately, the stainless screw seizes in the hole or, worse, falls out under load. Filling both sets of threads with silicone sealant or grease before fastening will fill the capillary Fitting spaces around the threads and prevent the intrusion of salt water. No seawater—no electrolyte—no corro- sion. Aluminum mast Silicone sealant or grease in threads (exaggerated) Stainless screw Noncathodic Corrosion 89
Noncathodic Corrosion Stainless Pitting Fig. 5.28 Pitting of Stainless Steel Figure 5.28 shows how stainless (pronounce "stain- less") steel develops corrosion pits. Stainless steel is Stainless steel passivated principally an alloy of iron and chromium. When by layer of chromium oxide exposed to the oxygen in air, the chromium oxidizes and forms a shiny protective skin (the stainless is then said to be passivated). The chromium oxide skin is very noble in the galvanic series (see Table 5.1, entry 18-8, Barnacle or dirt 3% Mo Stainless Steel, Type 316 [passive]), so it resists corrosion and protects the iron beneath. Stainless steel activated If the surface is immersed in or covered with an by lack of oxygen oxygen-free liquid, however, the chromium loses its oxygen, the passive skin is lost, and the iron is free to rust. In Figure 5.27 a barnacle has attached itself to a stainless surface, depriving the chromium-oxide skin of oxygen. The unpassivated area and the surrounding passivated area then act as a galvanic couple, resulting Anode Cathode in corrosion of the iron under the barnacle. The same sort of corrosion occurs between stainless stanchions and their water-retaining bases, explaining the mysterious rust stains often seen in these areas. Deep pit leads to continued corrosion Cavitation Erosion Finally, Figure 5.29 shows cavitation erosion of the Fig. 5.29 Erosion Due to Cavitation trailing edge of a propeller. Cavitation is the rapid for- mation and collapse of vapor bubbles just behind pro- peller blades. Cavitation is not galvanic corrosion. Instead, the propeller is turning so quickly that the water immediately behind the blade is left behind, Cavitation forming water vapor (gaseous form of water) bubbles. erosion As these bubbles subsequently collapse, the water hits the blade like thousands of tiny hammers.You can hear the sharp popping sound underwater when a boat passes. The result is mechanical destruction and ero- sion of the metal at the trailing edge of the blade. The solution is to increase the area of the blade, thereby reducing the pressure difference across the blade. In contrast, a bronze propeller or any other bronze fitting suffering from galvanic corrosion displays a rosy-pink color instead of its normal brassy-yellow color. Galvanic corrosion selectively removes the zinc Cavitation erosion from the bronze, leaving the reddish copper behind. 90 Bonding
The ABYC on Cathodic Protection The following general recommendations are taken h. In general, the use of several anodes instead of one large from ABYC Standard E-2, Cathodic Protection of Boats, anode will tend to provide better distribution of the protec- Section E-2.4. tive current. Sacrificial anodes may be mounted remotely; a. Although cathodic protection will, depending on the cur- the best current distribution will be obtained with the anode(s) positioned to be as equidistant as possible from rent capability of the system, help to minimize stray- the metals to be protected. current corrosion when it exists, stray-current corrosion should be controlled by: i. Anodes should be faired and, if possible, arranged in a lon- (1) Minimizing DC and AC electrical leakage levels from gitudinal row to minimize drag.After installation, peripheral crevices should be sealed. electrical products, and (2) The use of a bonding system in accordance with j. Anodes shall be mounted on a sloping surface that cannot ABYC E-1,"Bonding of Direct Current Systems." entrap gas bubbles. b. Factors that affect the type and degree of cathodic pro- k. If anodes are located near through-hull fittings they shall tection required: be positioned forward of discharge fittings and aft of intake (1) Water Velocity—Cathodic protection current re- ports.Anode locations that disturb the flow of water past the propeller should be avoided. quirements increase with water velocity past the hull. The current requirements can be as high as 30 times l. All metals which are to receive cathodic protection from that required in still water. the cathodic protection system must have good electrical (2) Boat Usage—More frequently operated vessels continuity to the boat bonding system. Galvanic anodes, if require more cathodic protection than vessels infre- used, must be affixed in a manner that electrical continuity is quently used. maintained with the metals they are to protect, either (3) Fresh and Sea Water—Current requirements increase through their mounting means or through the boat's bond- with salinity but higher driving potentials are ing system. required in fresh water. (1) Propeller shafts do not provide reliable electrical con- (4) Deterioration of Protective Coatings—Current re- tinuity to the boat's bonding system. quirements increase as protective coatings deterio- (2) Rudder posts shall be cathodically bonded by means rate. of a flexible conductor positioned to allow full rudder c. The need for a cathodic protection system for metal movement without stressing the cathodic bonding appendages on nonmetallic hulls may not be justified if the conductor or its connection. metals coupled are galvanically compatible. m. In general, sacrificial anodes may be mounted directly d. Hull-mounted metallic trim tabs may be electrically iso- on the metal to be protected, but the best current distribu- lated from the boat's bonding system to reduce the load on tion will be obtained by remote mounting with the anode(s) the boat's cathodic protection system, providing the trim positioned to be as equidistant as possible from the metals to tabs are also electrically isolated from their electrical actuat- be protected. ing mechanism. If the trim-tab system is connected to the n. The negative potential (–1,050 millivolts as compared to boat's bonding system the cathodic protection system's mil- silver-silver chloride reference electrode) that can be liampere rating will have to be increased to provide the addi- achieved by some corrosion control systems will result in tional protection. some decrease in the effectiveness of antifouling paints. e. A cathodic protection system shall be capable of inducing Because the decrease in the effectiveness increases with and maintaining a minimum negative shift of 200 millivolts higher negative voltages, the negative potential should be in the potential of the composite cathode being protected. kept as close to the optimum value as possible. A reference potential reading in excess of –1,100 millivolts indicates f. Since the area relationship of metals in a galvanic cell will excessive cathodic protection. affect current density and therefore corrosion rate, the immersed cathodic metal surfaces may be coated to obtain o. Anodes and reference electrodes shall be positioned to a more favorable anode to cathode area relationship. Coat- avoid contact with lifting slings and chocks when the boat is ings shall not contain pigments that will form galvanic cou- hauled. ples with the substrate. Coatings on substrate and coatings p. The electrical interconnection that occurs via shore-power on surfaces must be able to tolerate alkali generated by the cables or metal mooring cables between two vessels or cathodic reaction. between a vessel and submerged metal or the dock may g. Impressed-current anodes shall have the words "DO NOT result in galvanic corrosion of steel or aluminum hulls and PAlNT" on a visible surface when installed. aluminum underwater appendages. An isolator or an isola- NOTE: Anodes are ineffective if painted. tion transformer can break this couple. The ABYC on Cathodic Protection 91
6 CHAPTER DC Standards and Practices DUAL BATTERIES + 72\" max. Battery Fuse – or breaker + 72\" max. Battery – Cranking-motor conductor (no length restriction) 7\" max.or 40\" max. No limit Solenoid Starter 92 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
S tandards and recommended practices for the wiring of boats are promoted by the American Boat and Yacht Council (ABYC). This chapter delineates and explains these standards. Preliminary to the standards, however, we first explain the wisdom of creating wiring diagrams for your boat's electrical sys- tems. The standards and practices start with the specifica- tion of acceptable marine wire. The ABYC DC load cal- culation method allows you to calculate the maximum current expected to flow in a conductor and to use the tables for allowable amperage of conductors and con- ductor sizes for allowable voltage drops. Wiring and, later, troubleshooting are both facili- tated by the proper identification of conductors, as well as the proper installation of wire runs. As in a home, overcurrent protection, in the form of fuses and circuit breakers, guards against overheating and possible fire. The marine environment, characterized by mois- ture, salt, and vibration, makes conductor connections critical. The lethal mixture of gasoline vapors and open flame or electric spark dictates the ABYC-adopted Coast Guard requirements for ignition protection. 93
Wiring Diagrams When you first bought your boat, you probably judged A proper wiring diagram shows every electrical its wiring on appearances. Either it looked good or it device: circuit breaker, fuse, switch, terminal, and con- did not. You never gave it another thought—until ductor, as well as wire size, color, and label. It makes something went wrong. Then you discovered whether troubleshooting a snap. If a light doesn't come on, the or not the boat had a wiring diagram. Chances are, if diagram shows exactly where to check for voltage, all your boat was American made, it did not. the way from the lamp back to the distribution panel.A The person who wired your boat didn't need a circuit diagram also shows the best place to tie in addi- wiring diagram. First, yours was probably one of tional electrical equipment, what spares to carry, and dozens, if not hundreds, he had wired just like it. Sec- whether or not you are fused correctly. ond, he assumed he would not be there when some- Best of all, if you create your circuit diagram by thing went wrong. Troubleshooting would be your visually inspecting your existing wiring, you will have problem. looked systematically at every component and may be One summer I worked in a boatyard rigging and able to spot potential problems before they become stepping masts. One of my jobs was to check the mast problems underway. wiring before the mast was stepped. Some masts had combined tricolor, anchor, and strobe light (four con- ductors), masthead or steaming light (two conductors), Creating a Wiring Diagram spreader lights (two conductors), windvane light (two Circuit symbols are, like international road signs, conductors), plus a windspeed indicator (six wires in a intended to convey meaning at a glance. Unlike inter- cable) and a VHF coaxial cable—a total of ten individ- national signage, however, there is no rigorous stan- ual conductors plus two cables. dard for wiring symbols. Figure 6.1 shows commonly It seemed as if every second mast had a problem. A used symbols for most of the simple devices encoun- bulb was burned out or not properly seated, connectors tered in a boat. If these don't work for you, feel free to were corroded, or a wire was broken. The symptoms invent your own. For example, you may elect to show were obvious—a light at the top of the mast did not a fan as a fan blade and a fuse as a simple rectangle. come on. Finding the cause, however, was an art. With- If you possess the repair manual for your engine (a out a wiring diagram, labeled terminals, and color- minimal and wise investment), it probably contains a coded conductors, finding the fault sometimes wiring diagram for the starting motor, alternator, and required an hour of labor for two workers: one at the instrument panel. If so, you are in luck; you are already top end reading voltage or watching the light, the other halfway there. Consider the engine diagram to be the at the bottom applying voltage to successive pairs of first of your circuit diagrams and adopt its style for the conductors. Did you know that the number of possi- rest of your diagrams. ble pairs of n wires is n(n – 1)/2? For 10 wires we had Breaking the total system into a set of circuits has to check 45 pair combinations! the added advantages of smaller sheets of paper, less Sometimes we found that a light that had worked confusion, and the ability to make changes without on the ground no longer worked with the mast up. redrawing the entire system. Now there were even more possibilities! Something A complete set of circuit diagrams for a typical could have happened inside the mast during stepping, pleasure boat might include: or the problem could lie between the distribution panel • Engine wiring and the base of the mast. It was here that we sometimes • Engine-starting circuit encountered the case of the chameleon conductor. A • Cabin lights and accessories wire would leave the distribution panel with blue insu- • Navigation lights lation, disappear into the bilge or behind a liner, and • Instrumentation and radios emerge at the base of the mast with yellow insulation! • 110 VAC system One of my associates had worked for one of the best • Main distribution panel boatbuilders in the United States. Over lunch I related • Mast wiring the case of the chameleon wire. • Water pumps "Oh, sure," he said,"we used to run a wire until the Don't worry if several of your diagrams overlap. spool ran out. Then we'd grab another spool of what- The intent is to locate the general area of a fault and ever color and splice it in." then to isolate the exact location within that area. 94 DC Standards and Practices
Fig. 6.1 Wiring Symbols Switch (SPST) Earth single-pole ground single-throw F Fan Resistor Equipment ground Switch (SPDT) single-pole Variable double-throw M Motor resistor Conductors, no connection Switch (DPST) double-pole single-throw Capacitor Conductors, A Ammeter connected Switch (PBNO) push-button normally open Battery, Variable + single cell capacitor or voltage V Voltmeter – source Circuit breaker + Battery, multi-cell Fuse Lightbulb Diode – (lamp) rectifier A Starter-Motor Circuit Fig. 6.2 Typical Starter-Motor Circuit Figure 6.2 shows a very simple diagram of an engine starter-motor circuit. If one day you turn on the igni- – – tion switch, push the start button, and nothing hap- pens, this is the circuit diagram you will need. A com- plete engine wiring diagram would probably contain the same information, but it would also contain all of the meters, idiot lights, and alternator wiring, adding +12V +12V considerable visual confusion. Engine panel For the starter-motor circuit all you need to see are 1 2 ON–OFF Fuse on the: Battery engine (30A) Key switch switch • Battery switch • Fuse between battery switch common terminal START and engine panel Push button • On/Off switch • Momentary start switch • Wire from starting switch to solenoid • Heavy positive cable from battery-select common Solenoid terminal to solenoid • Heavy negative cable from battery negative termi- Starter nal to engine negative terminal. If the engine won't turn over, the problem proba- Engine bly lies somewhere in this diagram. For guidance, see ground page 64. Wiring Diagrams 95
Wiring Diagrams A Cabin Lighting Circuit Fig. 6.3 Typical Cabin Lighting Circuits Although it shows 15 separate lights and fans, the cabin lighting diagram in Figure 6.3 is even simpler in con- PORT STARBOARD cept than the engine starter circuit. The diagram con- sists of two similar, but separate, branch circuits. V-berth V-berth fan On the right is the starboard cabin lighting circuit, F originating at a 10-amp circuit breaker in the DC dis- tribution panel and running forward to serve all of the lights and fans on the starboard side. The positive con- ductor is a red AWG (American Wire Gauge) 14 wire Main labeled "27." The negative conductor is a black AWG V-berth forward 14 wire labeled "28."Except for the two paralleled main cabin lights, each light and fan is controlled by an indi- vidual single-pole, single-throw switch. You may wish to include model numbers and specifications for each Main Main device so that you can calculate current draws and find forward aft replacement parts. The devices are drawn on paper as laid out in the boat so that we can physically pinpoint a problem. For example, if the chart table light failed, but the main aft Main Chart light still worked, the circuit diagram would allow us to aft table immediately isolate the problem to either the chart table light or the lamp's controlling switch. On the other hand, if the main aft, main forward, and V-berth lights failed as well, we would suspect the Head Night problem to be in either the positive or negative conduc- fluorescent light tors or the connections between the night light and the chart table light. On the left is the similar port cabin lighting circuit, Galley originating at a 10-amp circuit breaker in the DC dis- fluorescent Quarter berth tribution panel and running forward to serve all of the lights and fans on the port side. The positive conductor is a red AWG 14 wire labeled "29." The negative con- ductor is a black AWG 14 wire labeled "30." Galley Quarter incandescent fan F AWG 14 black #28 Galley fan F AWG 14 red #27 Stbd lights, 10A Port lights, 10A AWG 14 red #29 AWG 14 black #30 96 DC Standards and Practices
Marine Wire Real circuits consist not of pencil lines on a sheet of neers) conductors and the minimum numbers of paper, but of real metal conductors having finite elec- strands specified by the ABYC for AWG 18 through trical resistance. The conductors and their installations AWG 4/0 (0000) conductors. should satisfy a number of criteria: 1. Construction should be such that the conduc- Insulation tor will not break under continuous vibration or an accidentally imposed force. All single-conductor and cable insulations should be 2. Insulation should be appropriate for the one of the types listed in Table 6.2, appropriate to its expected maximum ambient (surrounding air) expected exposure to temperature, moisture, and oil. temperature and degree of exposure to sunlight, The letters in the designations stand for: T moisture, and air. M thermoplastic 3. Ampacity (current-carrying capacity) should be W oil resistant sufficient to avoid overheating. H moisture resistant 4. Conductor size should be selected considering HH heat resistant to 75°C conductor length and current in order that volt- high-heat resistant to 90°C age drop not impair the functioning of the load An insulated jacket or sheathing may qualify for devices. more than one rating and be labeled as such. The most commonly available cable suitable to all applications in the typical boat is probably UL 1426 boat cable. Construction Table 6.2 Acceptable Insulation Types The ABYC calls for most conductors to be stranded and of size AWG 16 minimum. An exception is sheathed Type Description AWG 18 conductors that do not extend more than 30 CONDUCTORS inches beyond their sheath. THW Moisture and Heat Resistant, Thermoplastic Because copper wire becomes brittle with flexing, TW Moisture Resistant, Thermoplastic solid wire (as used in house wiring) is not allowed at HWN Moisture and Heat Resistant, Thermoplastic all. Type II stranding is the minimum allowed for gen- XHHW Moisture and High-Heat Resistant, Cross-Linked eral boat wiring, and Type III stranding should be used Synthetic Polymer wherever vibration is expected, such as on an engine. MTW Moisture, Heat, and Oil Resistant, Thermoplastic AWM Moisture, Heat, and Oil Resistant, Thermoplastic, Table 6.1 shows the minimum circular-mil areas (a Thermosetting circular mil is the area of a 0.001-inch-diameter circle) UL 1426 Boat Cable for both AWG and SAE (Society of Automotive Engi- SAE CONDUCTORS Table 6.1 Minimum Circular-Mil (CM) Areas and Stranding GPT Thermoplastic Insulation, Braidless HDT Thermoplastic Insulation, Braidless Conductor Minimum Minimum Minimum Strands Gauge CM for AWG CM for SAE Type II Type III SGT Thermoplastic Insulation, Braidless STS Thermosetting Synthetic-Rubber Insulation, 18 1,6201,537 16 – Braidless 16 2,5802,336 1926 HTS Thermosetting Synthetic-Rubber Insulation, 14 4,1103,702 1941 Braidless 12 6,5305,833 1965 SXL Thermosetting, Cross-Linked Polyethylene 10 10,380 9,343 19105 Insulation, Braidless 8 16,51014,81019168 6 26,24025,91037266 FLEXIBLE CORDS 4 41,74037,36049420 SO Hard-Service Cord, Oil Resistant 2 66,36062,450127665 ST Hard-Service Cord, Thermoplastic 1 83,69077,790127836 STO Hard-Service Cord, Oil Resistant, Thermoplastic 0 105,60098,9801271,064 SEO Hard-Service Cord, Oil Resistant, Thermoplastic 2/0 133,100125,100 1271,323 SJO Junior Hard-Service Cord, Oil Resistant 3/0 167,800158,600 2591,666 SJT Hard-Service Cord, Thermoplastic 4/0 211,600205,500 4182,107 SJTO Hard-Service Cord, Oil Resistant, Thermoplastic Marine Wire 97
ABYC DC Load Calculation Ampacity Main feed conductors for distribution panels and Branch circuit conductors should be sized to carry the switchboards should be determined using the ABYC maximum currents drawn by their loads. In the case procedure, shown in Table 6.3 (a sample calculation is of motors, maximum current should be for the locked- shown). rotor, or stalled, condition. Table 6.3 ABYC Load Calculation Method (for total electrical loads for minimum sizes of panelboards, switchboards, and main conductors) NOTE: Calculations are based on the actual operating amperage for each load and not on the rating of the circuit breaker or fuse protecting that branch circuit. Column A Column B List each of the loads that must be available for use on a List the intermittent loads. The largest load or 10% of the continuous basis. total, whichever is greater, will be carried to Column A. Equipment Amperes Equipment Amperes Navigation lights 5.5 Cigarette lighter 0.0 Bilge blower(s) 2.0 Cabin lighting 10.0 Bilge pump(s) 4.2 Horn 6.3 Wiper(s) 0.0 Additional electronics 10.0 Largest radio (transmit mode) 2.5 Trim tabs 0.0 Depth sounder 0.9 Power trim 0.0 Radar 7.5 Heads 0.0 Searchlight 12.0 Anchor windlass 80.0 Instruments 2.3 Winches 0.0 Alarm system (standby mode) 0.5 Freshwater pumps 5.8 Refrigeration 5.5 Other: Microwave 60.0 Other: Autopilot 3.5 Total of Column B 172.1 10% of Column B 17.2 Total of Column A 46.4 Largest item in Column B 80.0 Enter Total from Column B 80.0 Larger of above two lines— 80.0 Enter in both Column A and Column B Sum of Totals (Total Load) 126.4 98 DC Standards and Practices
Allowable Conductor Amperage Having the maximum load current in amps and the temperature rating of the conductor insulation, the minimum required conductor size is selected from Table 6.4. Table 6.4 Allowable Amperage of Conductors for Under 50 Volts (Adapted from ABYC Standard E-11, Table IV) Conductor Temperature Rating of Conductor Insulation Size, AWG 60°C (140°F) 75°C (167°F) 80°C (176°F) 90°C (194°F) 105°C (221°F) 125°C (257°F) 200°C (392°F) Outside Engine Spaces 18 10 10 15 2020 25 25 16 15 15 20 2525 30 35 14 20 20 25 3035 40 45 12 25 25 35 4045 50 55 10 40 40 50 5560 70 70 8 556570708090100 6 80 95 100 100120 125 135 4 105 125 130 135160 170 180 2 140 170 175 180210 225 240 1 165 195 210 210245 265 280 1/0 195 230 245 245285 305 325 2/0 225 265 285 285330 355 370 3/0 260 310 330 330385 410 430 4/0 300 360 385 385445 475 510 Inside Engine Spaces 18 5.8 7.5 11.7 16.417.0 22.3 25.0 16 8.7 11.3 15.6 20.521.3 26.7 35.0 14 11.6 15.0 19.5 24.629.8 35.6 45.0 12 14.5 18.8 27.3 32.838.3 44.5 55.0 10 23.2 30.0 39.0 45.151.0 62.3 70.0 8 31.948.854.657.468.080.1100.0 6 46.471.378.082.0102.0111.3135.0 4 60.9 93.8 101.4 110.7136.0 151.3 180.0 2 81.2 127.5 136.5 147.6178.5 200.3 240.0 1 95.7 146.3 163.8 172.2208.3 235.9 280.0 1/0 113.1 172.5 191.1 200.9242.3 271.5 325.0 2/0 130.5 198.8 222.3 233.7280.5 316.0 370.0 3/0 150.8 232.5 257.4 270.6327.3 364.9 430.0 4/0 174.0 270.0 300.3 315.7378.3 422.8 510.0 Allowable Conductor Amperage 99
Allowable Voltage Drop All wire has resistance. As current flows through the where: CM = conductor circular mils (Table 6.1) wire, voltage drops according to Ohm's Law. If power is I = current in amps supplied to a circuit by a 12.0-volt battery and the volt- L = round-trip length in feet age drops 0.5 volt in the positive conductor going to the E = voltage drop in conductor, volts load and another 0.5 volt in the negative conductor Example: What size conductor is required for an back to the battery, then the voltage across the load is anchor light drawing 0.9 amp at the top of a 50-foot mast not 12.0 volts, but 12.0 – 0.5 – 0.5 = 11.0 volts. The with a 15-foot run from panelboard to base of the mast? voltage drop in the total length of conductor to and The light is a navigation light, so the allowed voltage from the load is thus 1.0/12.0 = 8.3%. drop is 3% of 12 volts or 0.36 volt. The length of the The ABYC specifies two allowable percentage drops, conductor from panelboard to the light and back to the depending on the effect on safety: panelboard is 15 feet + 50 feet + 50 feet + 15 feet = 130 • 3% for panelboard feeds, bilge blowers, electron- feet. The minimum circular-mil area of the conductor ics, and navigation lights is thus • 10% for general lighting and other noncritical applications CM = 10.75 0.9 × 130/0.36 = 3,494 × Required conductor size may be determined from: Table 6.1 tells us a #14 AWG conductor is required. CM = 10.75 I L/E Alternatively, we can find the answer in Table 6.5. × × Table 6.5 Conductor Sizes (Minimum Circular Mils Converted to AWG by Table 6.1) for Allowable Voltage Drops in 12-Volt Systems (Adapted from ABYC Standard E-11, Tables X and XI) Current, Round-Trip Conductor Length, ft. Current, Round-Trip Conductor Length, ft. Amps 10 20 30 40 60 80 100 120 140 Amps 10 20 30 40 60 80 100 120 140 3% Voltage Drop 10% Voltage Drop 1 18 18 18 18 16 14 14 1412 1 18 18 18 18 18 18 18 1818 2 18 18 16 14 14 12 10 10 8 2 18 18 18 18 18 18 16 1614 5 18 14 12 10 10 8 6 6 6 5 18 18 18 16 14 14 12 1210 101410108 6 6 4 42 10 18 16 14 14 12 10 10 8 8 1512108 6 6 4 2 21 15 18 14 12 12 10 8 8 6 6 20108 6 6 4 2 2 10 20 16 14 12 10 8 8 6 6 6 25106 6 4 2 2 1 02/0 25 16 12 10 10 8 6 6 4 4 30106 4 4 2 1 02/03/0 301412108 6 6 4 42 40 8 6 4 2 1 02/03/04/0 4014 108 8 6 4 4 22 50 6 4 2 2 02/03/04/0 – 50 12 10 8 6 4 4 2 2 1 60 6 4 2 1 2/0 3/0 4/0 – – 60128 6 6 4 2 2 11 70 6 2 1 0 3/0 4/0 – – – 70108 6 6 2 21 1 0 80 6 2 1 0 3/0 4/0 – – – 80108 6 4 2 2 1 02/0 90 4 2 0 2/0 4/0 – – – – 90106 6 4 2 1 0 02/0 100 4 2 0 2/0 4/0 – – – – 100106 4 4 2 1 02/02/0 100 DC Standards and Practices
Identification and Installation Conductor Identification Installation of Wire Runs The ABYC states,"Each electrical conductor that is part When both AC and DC conductors are run in the same of the boat's electrical system shall have a means to area and direction, the AC conductors should be kept identify its function in the system." separate from the DC conductors by bundling, sheath- Two means of identification are insulation color ing, or other means. and labels (numbers and/or letters) applied near the terminal points. The use of both is recommended. Continuous Support In general, DC conductor insulation should follow In order to minimize flexing from vibration, conduc- the color scheme: tors should be supported continuously or every 18 inches minimum by clamps or straps (Figure 6.4). DC Positive Red (R) Nonmetallic clamps and straps should not be used in DC Negative Black (B) or Yellow (Y) locations where failure would result in a hazard, such as DC Grounding Green (G) or Green over engines, shafts, or passageways. with Yellow (GY) Metal clamps should be lined with moisture-, The ABYC goes on to recommend colors for spe- gasoline-, and oil-resistant material, or have smooth, cific DC positive conductors. If these colors are not rounded edges. The cable beneath unlined metal used, a wiring diagram should be provided showing the clamps should be protected by a wrapping to protect conductors and their identifiers. Table 6.6 lists the rec- the conductors. ommended colors for both general and specific con- ductors. Fig. 6.4 Cable Support Devices Standard Mounting Identification Table 6.6 DC Wiring Color Code cable ties cable ties cable ties (Adapted from ABYC Standard E-11, Tables XIV and XV) Color Use Conductor Green or green with General DC grounding yellow stripe(s) Black or yellow General DC negative Red General DC positive Yellow with red stripe Starter switch to solenoid Brown with yellow Fuse or switch to blower—If DC stripe, or yellow negative is yellow, positive must be brown with yellow stripe Dark gray Fuse or switch to navigation lights Tachometer sender to gauge Brown Generator armature to regulator Auxiliary terminal to light and regulator Fuse or switch to pumps Orange Ammeter to alternator or generator output and accessory fuses or switches Distribution panel to accessory switch Purple Ignition switch to coil and electrical instruments Distribution panel to electrical instru- ments Dark blue Fuse or switch to cabin and instru- ment lights Light blue Oil-pressure sender to gauge Tan Water-temperature sender to gauge Plastic cable clamps Metal cable clamp Pink Fuel-gauge sender to gauge Green/stripe, Tilt and/or trim circuits except G/Y Identification and Installation 101
Identification and Installation Exposure to Damage Fig. 6.5 Chafe Protection Material Conductors should be protected from chafing by rout- ing clear of engine and steering shafts and control link- Strip grommet Grommet (bulkheads) (panels) ages. In exposed areas conductors should be protected by conduit, raceway, or equivalent wrap. Holes in pan- els, bulkheads, or other structural members (Figure 6.5) should be lined. Protecting Connections Spiral wrap Enclosures with electrical connections should be in dry locations or be weatherproof. If wet locations are unavoidable, nonmetallic enclosures are preferred, but metal enclosures can be mounted to prevent accumula- tion of moisture between the enclosure and adjacent PVC conduit 1 surfaces, such as by providing a space of at least ⁄4 inch. Wiring in the Bilge The simplest routing of conductors is often through the bilge, but more than 90% of all electrical problems are due to corrosion, and nothing leads to corrosion more quickly than water—particularly of the salt vari- Wood raceway Wood raceway ety. Current-carrying conductors should be routed as high as possible above bilge water. If routing through the bilge cannot be avoided, connections must be watertight. Sources of Heat Drill through-deck Cable through-deck Conductors should be kept away from and never run (multiple conductors) (split insert) directly above engine exhaust pipes and other similar sources of heat. Minimum recommended conductor clearances are 2 inches from wet-exhaust pipes and components and 9 inches from dry-exhaust compo- nents, unless equivalent thermal insulation is provided. Battery Cables Unless battery cables are overcurrent protected, they should be run above bilge-water level, away from metal Fig. 6.6 Wiring Near Magnetic Compasses fuel-system components, such as fuel line and fuel fil- ters, and away from the engine, transmission, and shaft. The grounded battery cable is excepted because contact between the grounded engine and a grounded conduc- tor does not pose a danger. Wiring Near Compasses Direct current flow through a wire produces a concen- tric magnetic field, which may disturb a nearby com- pass (Figure 6.6). The direction of the magnetic field changes with current direction, so twisting positive and negative conductor pairs negates the overall magnetic field.All conductor pairs within 24 inches of a compass should be twisted, unless they are coaxial. 102 DC Standards and Practices
Overcurrent Protection Circuits That Require Protection Circuits Branching from a Panel Every ungrounded conductor originating in the panel Distribution Panels and Switchboards (branch circuit) should be protected at its point of ori- A distribution panel or switchboard (Figure 6.7) should gin unless its rating is the same as that of the main or be protected at its source of power (battery, battery sub-main protection. The overcurrent protection rat- switch, or starter solenoid) by either a fuse or a trip-free ing should not exceed 150% of the conductor ampac- circuit breaker of capacity not exceeding the capacity of ity. the panel or the ampacity of the feed conductors. Except for engine-starter motors, all motors should If there is also a sub-main fuse or breaker on the be protected either internally or at the panel. The over- panel that does not exceed the panel or feeder ampac- current protection rating should be low enough to pre- ity, then the protection at the source of power may be vent a fire, in the case of a stalled motor rotor, for up rated up to 150% of the feeder capacity. to 7 hours. Fig. 6.7 Panelboard and Switchboard Overcurrent Protection Switch + Feeder Panelboard Main-circuit Sub-main Battery protection breaker Fused Equipment – Main breaker Branch breaker Main breaker Branch breaker Branch breaker Main fuse Unprotected Length Limits Sources of power for positive-feed conductors can be a • Connected directly to a battery terminal—72 battery terminal, battery-select common terminal, or inches feed to the starter. The maximum allowed unprotected • Connected to other than a battery terminal, but lengths of positive feeder conductors, as shown in Fig- contained within a sheath or enclosure—40 inches ure 6.8, are: • All others—7 inches Fig. 6.8 Maximum Unprotected Lengths for Positive Feeder Conductors SINGLE BATTERY DUAL BATTERIES + 72\" max. + 72\" max. Battery Battery Fuse – Overcurrent – or protection breaker (fuse or breaker) + 72\" max. Cranking-motor conductor (no Battery length restriction) – Cranking-motor conductor (no length restriction) 7\" max.or 40\" max.* No limit 7\" max.or No limit 40\" max.* Solenoid Solenoid * NOTE: Up to 40\" is allowed if the conductor, throughout this distance, is contained in a Starter sheath or enclosure, such as a junction Starter box, control box, or enclosed panel. Overcurrent Protection 103
Overcurrent Protection DC Circuit Breakers Fig. 6.9 Circuit Breakers As shown in Figure 6.7, by definition the first breaker Blue Sea (Bussman) Ancor CE World surface-mount or fuse in a circuit connected in series with the battery thermal circuit breaker trip-free AC/DC circuit breaker is considered to be the main circuit breaker or fuse. All 1.9\" 1.64\" other breakers or fuses in the circuit, including sub- main breakers and fuses, are considered to be branch circuit breakers and fuses. Note that breakers and fuses HI–AMP may be mixed in the same circuit. It is possible, for Buss ® 2\" 70A example, to use a main fuse ahead of a panel containing 2.89\" branch circuit breakers. When installing a breaker panel, the breakers and WATERPROOF 185035F panel should be from the same manufacturer to insure compatibility. Most manufacturers offer two sizes of breaker—small for up to 50 amps, and large for over 50 Ratings, Amps amps. Either size may be used for main or branch break- Ratings, Amps 5 ers, although many larger panels are designed to accept 25 80 10 the larger size breaker for the main and the smaller 30 90 15 breaker for the branches. Figure 6.9 shows the dimen- 35 100 20 25 40 110 sions and available current ratings for Ancor brand 50 120 30 breakers up to 50 amps and Blue Sea Systems (Bussman) 60 135 40 surface-mount breakers rated up to 150 amps AC or DC. 70 150 50 Fuses Figure 6.10 shows a wide variety of fuses for boats. The 300 amps, ANL ignition-protected fuses from 50 to 675 electronic types (AGC and AGU) are available from 0.25 amps, and Class T fuses from 175 to 400 amps. to 30 amps, and the automotive types (ATC and ATM) Fuses may be mounted in equipment, fuse blocks, dis- are rated from 5 to 30 amps. Sea Fuses run from 100 to tribution panels, and in-line fuse holders. Fig. 6.10 Common Marine Fuses and Fuse Blocks AGC AGU ATC ATM Sea Fuse ANL Class T In-line AGC Panel-mount AGC Fuse block AGU Fuse block with common hot AGC and MDL In-line ATC & ATO 104 DC Standards and Practices
Conductor Connections Tools Professional electricians use ratcheting crimp tools. Most wiring failures occur at the connections. When A single-crimp ratchet crimps just the barrel.A double- copper corrodes it forms a layer of greenish copper crimp ratchet crimps both the barrel and the sleeve. oxide. Because it is thin, the oxide does little to the con- The advantage of the ratchet is that the tool will not ductivity of the wire, but, because it is nonconductive, release until the terminal has been crimped to the per- it forms a resistive barrier at surface-to-surface connec- fect degree. It is almost impossible to under- or over- tions. Most remaining wiring failures are due to physi- crimp terminals designed for use with this tool. cal stresses on connections, such as engine vibration, or Lugs are terminals for large conductors. The lug a pull on the conductor when an object or person acci- crimper in Figure 6.11 is actuated either by squeezing dentally strikes it. in a vise or by striking with a hammer. Many boatowners spend as little as possible on spe- Diagonal wire cutters ("diagonal pliers") distort the cialized electrical tools. Instead, they attempt to make cut end, making it difficult to insert the wire into the do with what they have. This is false economy. proper size connector barrel. The wire and cable cut- Although it is possible to make bad connections with ter shown shears the wire, resulting in cleaner cuts. good tools, it is virtually impossible to make good con- Most soldering problems are due to insufficient heat. nections with bad tools. It is better to get in and out quickly than to linger on a Figure 6.11 shows a variety of specialized wiring connector while the iron struggles to reach 400°F. The tools. The cut, strip, and crimp tool should be your pocket-size butane soldering iron can produce all the minimal investment. This tool is found in both hard- heat you'll need, short of soldering battery lugs. It will ware and electronics stores in a wide range of quali- burn for several hours on a filling and, best of all, free ties. Two key considerations are: you from trailing cords. Heated to 275 to 300°F, heat-shrink tubing shrinks 1. The stripper holes should line up perfectly (try to a third or less of its original diameter, gripping the stripping a few wires before purchasing). conductor tightly. If the tubing contains adhesive, the 2. The tool should match the brand of terminals melted adhesive seals out moisture and strengthens the you will be crimping. Ideally you should be able connection at the same time. to get both the crimp tool and connectors from Heat guns (not hair dryers) achieve temperatures in the same manufacturer. excess of 500°F and shrink the shrink tubing quickly. Fig. 6.11 Special Tools for Wiring Cut, strip, and crimp Single-crimp ratchet Lug crimper Wire and Butane Heat gun (650°F) cable cutter soldering CUT 22–14 iron 22–14 INSUL INSULATED 4/0 12–10 INSUL 12–10 NON INSUL 22–10 6-–32 4-–40 BUTANE 3/0 8-–32 10-–32 10-–24 2/0 CUT STRIP SOL 22–20 18 18 16 16 14 14 12 12 10 10 8 6 4 2 1 1/0 Conductor Connections 105
Conductor Connections ABYC-Approved Connectors Fig. 6.12 Connectors for Marine Use Marine connectors differ from residential wiring con- nectors in being subject to vibration and other stresses. Figure 6.12 is self-explanatory and shows both Splice Butt approved and disapproved types of connectors. Note 3-Way Wire nut specifically that the ubiquitous wire nut, so popular in household wiring, is not approved for marine use. Friction-type connectors (blade and bullet connec- Friction Blade Bullet tors, shown in Figure 6.12) can be used provided they or snap resist a pull in the direction of the conductor of at least 6 pounds for 1 minute. The other connectors in Figure 6.12 must resist the tensile forces shown in Table 6.7 for Terminals Plain at least 1 minute. Ring Locking Flanged spade spade spade Solder Set Screw The use of solder in marine connections is controver- Indirect-bearing Direct-bearing sial. Some experienced electricians feel that soldered connections are the most secure and best at eliminating terminal corrosion. Others point out that the solder in Table 6.7 Tensile Test Values for Connections an overheated terminal may melt and allow the con- (Adapted from ABYC Standard E-11, Table XVI) ductor to pull out of the terminal. A further problem Conductor Force, Conductor Force, is wicking of solder into the stranded conductor, result- Size, AWG lb. Size, AWG lb. ing in a rigid portion that is liable to break like a solid 18 10 4 70 conductor. 16 15 3 80 The ABYC states that solder should not be the sole means of mechanical connection in any circuit; the 14 30 2 90 only exception is battery lugs with a solder-contact 12 35 1 100 length of not less than 1.5 times the conductor diameter. 10 40 0 125 8 45 2/0 150 6 50 3/0 175 Solderless Heat-Shrink Connectors 5 60 4/0 225 Terminal systems are available that resolve all of the above problems (Figure 6.13). Although expensive (about twice the price of the usual automotive-grade materials), anything less in the hostile marine environ- Fig. 6.13 Adhesive-Lined Heat-Shrink Tubing ment is false economy. STEP 1: Strip insulation from wire 1. Pretinned, stranded conductors are available in all gauges and recommended colors. Pretinning (coating individual strands with solder) prevents STEP 2: Slip heat-shrink tubing over wire oxidation of the strands, eliminates the need to cut a conductor back several inches when repair- STEP 3: Insert wire into terminal ing, and facilitates soldering. 2. Heat-shrink tubing with adhesive coating, applied over both terminal and conductor, seals STEP 4: Crimp barrel of terminal out moisture, makes the connection more secure, and insulates the terminal shank all at the same time. The shrink tubing may be purchased STEP 5: Position heat-shrink and heat separately or already attached to terminals. 106 DC Standards and Practices
Other Termination Considerations shanks should be insulated to prevent acciden- Figure 6.14 illustrates the remaining ABYC specifica- tal shorting to adjacent terminals. tions for wiring connections: 4. Connections should be in locations protected from weather or in weatherproof enclosures. If 1. The openings of ring and captive spade termi- immersion is possible, connections should be nals should be of the same nominal size as the watertight. stud. 5. Terminal studs, nuts, and washers should be cor- 2. An extra length of conductor should be provided rosion resistant and galvanically compatible with at terminations in order to relieve tension, the conductor and terminal lug. Aluminum and permit fanning of multiple conductors, and unplated steel are unsuitable. allow for future repairs that might shorten the 6. No more than four conductors should be conductor. attached to a single terminal stud. If necessary, 3. Except for grounding conductors, terminal two or more terminal studs may be connected by jumper straps. Fig. 6.14 Proper Terminations Ground bus Hot bus Insulated shanks 09A No more than four 11B connectors per screw 11A All conductors 07A uniquely labeled 05B Terminal, studs, nuts, and washers all corrosion resistant and Waterproof galvanically compatible 05A or watertight enclosure Connector and screw 02B same nominal size 02A Drip loop, tension relief, and extra length for future repair Strap conductors @ 18\" minimum to support against vibration Conductor Connections 107
Conductor Connections Coaxial Connectors Table 6.8 Coaxial Cables Coaxial cable consists of an insulated center conduc- Specification RG-58/U RG-59/U RG-8X RG-8/U RG-213 tor surrounded by a concentric (coaxial) grounded- Nominal O.D. 3 ⁄16\" 1 ⁄4\" 1 ⁄4\" 13 ⁄32\" 13 ⁄32\" shield conductor (either fine, braided strands or foil), all protected by an outer insulating jacket. Because the Conductor AWG #20 #23 #16 #13 #13 outer conductor (the shield) is grounded and com- Impedance, ohms 50 75 50 52 50 pletely surrounds the center conductor, coaxial cables Attenuation/100', neither radiate nor pick up much electrical noise. dB "Coax" is primarily used to connect antennas to elec- @ 50 MHz 3.3 2.4 2.5 1.3 1.3 tronic equipment, such as VHF and HF transceivers, @ 100 MHz 4.9 3.4 3.7 1.9 1.9 and GPS receivers. @ 1,000 MHz 21.5 12.0 13.5 8.0 8.0 Like the wire used for DC wiring, coaxial cable for marine use should have pretinned, stranded center Figure 6.15 shows just a few of the UHF, VHF, and conductor and braid. UHF/VHF coaxial adapters available from such sources Table 6.8 lists the characteristics of five types of as RadioShack. coaxial cable found on a boat: Figure 6.16 shows the assembly of UHF connectors • RG-58/U is very thin and is typically used only for on both large and small coaxial cables. interconnecting electronics where lengths are Figure 6.17 demonstrates the similar assembly of short and signal attenuation is not a problem. BNC connectors on RG-58/U, RG-59/U, and RG-8X • RG-59/U is used to connect television antennas coaxial cables. and cable service. Although there are solderless versions of connec- • RG-8X is typically used to connect VHF and HF tors, they are not recommended for marine applica- antennas up to lengths where attenuation becomes tions except in protected locations (inside cabin) due to excessive. corrosion. After assembly, it is a good idea to apply a • RG-8/U and RG-213 are both used to conduct moisture-displacing lubricant. If the connection is maximum power to VHF and HF antennas. exposed to weather, the connection should be wrapped Marine coaxial cables are usually terminated at in a good quality plastic electrical tape to exclude mois- both ends with PL-259 8UHF connectors. It is ture. important to know how to install this type of con- ductor, which has so many applications on a boat. Fig. 6.15 A Few Coaxial Adapters The significance of each of the specifications in the PL-258 M359 table is: UHF double-female UHF 90 male/female Conductor (size) AWG is important for heavy cur- rent flows, such as the output of SSB and ham radio transmitters. Impedance is the high-frequency equivalent of resis- M-348 tance and must match the output impedance of the UHF T-adapter transmitter in order to achieve maximum output power. (All VHF and SSB radios are designed with UHF male/ 50 W output impedance.) BNC female Attenuation is the loss of transmitted power between the radio and the antenna, where each 3 decibels (dB) represents a 50% loss of power. UHF female/ UHF double-male BNC male 108 DC Standards and Practices
Fig. 6.16 Assembly of PL-259 (UHF) Connectors Fig. 6.17 Assembly of BNC Connectors ON RG-58/U, RG-59/U, AND RG-8X CABLES ON RG-58/U, RG-59/U, AND RG-8X CABLES FEMALE CONNECTOR STEP 1: Slip on shell and adapter; strip outer jacket back 5/8\" STEP 1: Cut cable end even and 5/8\" strip outer jacket back 5/16\" 5/16\" STEP 2: Slide clamp nut and pressure sleeve over cable; straighten braid ends STEP 2: Bend back braided shield STEP 3: Fold braid back; insert ferrule inside braid; cut dielectric back 13/64\"; tin conductor STEP 3: Slip adapter under braided shield 13/64\" STEP 4: Trim excess braid; slide insulator over conductor STEP 4: Strip center conductor 1/2\" and tin into ferrule; slide female contact over conductor and solder 1/2\" STEP 5: Screw on body and solder tip and braid STEP 5: Slide body over ferrule and press all parts through holes in body into body; screw in the nut tightly STEP 6: Screw shell onto body MALE CONNECTOR STEP 1: Cut cable end even and strip outer jacket back 5/16\" 5/16\" STEP 2: Slide clamp nut and pressure sleeve over cable; straighten braid ends ON RG-8/U AND RG-213 CABLES STEP 1: Slip on shell and strip to center of conductor and back 3/4\" 3/4\" STEP 3: Fold braid back; insert ferrule inside braid; cut dielecric back 13/64\"; tin conductor 13/64\" STEP 2: Strip outer jacket additional 5/16\" 3/4\" 5/16\" STEP 4: Trim excess braid; slide insulator over conductor into ferrule; slide male contact over conductor and solder STEP 3: Slip on body, making sure shield does not contact center conductor, and solder tip and shield through holes STEP 5: Slide body over ferrule and press all parts into body; screw in the nut tightly STEP 4: Screw shell onto body Conductor Connections 109
Ignition Protection Gasoline and propane explosions are among the lead- Isolation of Ignition Sources ing causes of marine loss of life. For this reason, the Ignition sources located in the same spaces as gasoline ABYC has adopted the ignition protection standards engines, gasoline tanks, and gasoline fuel joints and of the U.S. Coast Guard as described below. fittings must be ignition-protected unless the compo- nents are isolated from the fuel sources. An electrical Fuels component is considered isolated from a fuel source if: Boats using only diesel fuel are exempt. Boats using just 1. It is separated by a bulkhead of full width and a single LP (propane) or CNG appliance may exempt 1 the gas appliance from the ignition protection standard height that leaks no more than ⁄ 4 ounce of water provided: per hour with a water height of 12 inches or one- third the bulkhead height (whichever is less), 1. Gas tank connections and regulators are outside and has no higher opening with greater than ⁄ 4- l of the hull or are located in an enclosure that is inch gap around its perimeter. vapor-tight to the interior of the boat and vented 2. The electrical component is separated by a floor, overboard. deck, or other type of enclosure. 2. The gas supply can be shut off at the tank by a 3. The distance between the electrical component control that is part of or located near the appli- and the fuel source is at least 2 feet, and the space ance. Manual controls must provide a warning between is open to the atmosphere, where when the supply valve at the tank is open. "open" means 15 square inches of open area per cubic foot of net compartment volume. Boats using gasoline as a fuel for either propulsion or auxiliary generator are subject to the ignition pro- Figures 6.18 through 6.24 illustrate these require- tection standards shown here. ments for a variety of installations. Fig. 6.18 Bulkheads (Adapted from ABYC Standard E-11, Figure 8) Seepage of not more than 1/4 fl oz/hr permitted below water- resistant height. This includes bulkhead fastenings and space around hatches, doors, access panels, & items passing through the bulkhead. Openings above the water-resistant height may not have more than 1/4\" annular space around items passing through the openings. Bulkhead extends full height 1/4\" annular Bulkhead extends space maximum full width Not more than 1/4\" annular space Fuel source this Water- side of bulkhead resistant height Sealed Electrical components Maximum this side height of of bulkhead 1/3 max. 12\" bulkhead height Plugged drain 110 DC Standards and Practices
Fig. 6.19 Isolation of Ignition Sources (Adapted from ABYC Standard E-11, Figure 1) Ignition-protected engine and blower Ignition protection not required —ignition source and gasoline Fuel tank source separated by bulkheads and deck Annular space less than 1/4\" Ignition- Spaces requiring ignition- Watertight bulkhead to 1/3 protected protected equipment height or 12\", whichever is less pump Fig. 6.20 Isolation of Ignition Sources (Adapted from ABYC Standard E-11, Figure 2) Ignition-protected engine and blower 2' Ignition protection not required 2' —ignition source and gasoline source separated by 2 feet Fuel tank Annular space less than 1/4\" Ignition- Spaces requiring ignition- Watertight bulkhead to 1/3 protected protected equipment height or 12\", whichever is less pump Ignition Protection 111
Ignition Protection Fig.6.21 Isolation of Ignition Sources (Adapted from ABYC Standard E-11, Figure 5) Ignition-protected components not required—enclosure provided Sealed wire-way Fuel tank Spaces requiring ignition- Ignition-protected protected equipment engine and components Fig. 6.22 Isolation of Ignition Sources (Adapted from ABYC Standard E-11, Figure 3) Ignition-protected components— no separation from fuel sources Openings—annular space no more than 1/4\" Ignition-protected H engine & components Fuel tank Pump—ignition protection not required Bulkhead—watertight to 12\" or 1/3 height, Spaces requiring ignition- whichever is less protected equipment 112 DC Standards and Practices
Fig. 6.23 Isolation of Ignition Sources (Adapted from ABYC Standard E-11, Figure 6) Ignition-protected components not Ignition- required—2' open space to fuel source protected —compartment open to atmosphere blower 2' Fuel tank Area of opening at least Fuel 15 sq. in./cu. ft. of net tank compartment volume Spaces requiring ignition- Ignition-protected pump Ignition- protected equipment below fuel sources protected engine Instrument panel may be an ignition Instrument panel may be an ignition source unless ignition-protected source unless ignition-protected 15 sq. in. open area per each 15 sq. in. open area per each cu. ft. of net compartment volume cu. ft. of net compartment volume Fuel connection is source 2' 2' 2' Toe Fuel 2' Fuel board tank tank Cockpit deck Partial bulkhead to isolate fuel source from ignition source Fig. 6.24 Isolation of Electrical Components (Adapted from ABYC Standard E-11, Figure 4) Ignition-protected com- Engine-cover ponents—no separation seams less from fuel sources than 1/4\" Bulkhead watertight to 12\" or 1/3 height, whichever is less Fuel tank Alternate Pump not required to be ignition protected Spaces requiring ignition- protected equipment Ignition-protected components not required— enclosure must provide equivalent ignition protection Ignition Protection 113
7 CHAPTER AC Basics Ω – + Current Load, Voltage Impedance 114 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
B oaters are increasingly demanding the conve- nience of onboard AC power. We are familiar with DC power from Chapters 1 through 6. Now we need to know how alternating current differs. In the Will the Real Voltage Please Stand Up? sec- tion we see why 120-volt AC is variously called 110, 112, 115, 117, or even 125 volt, but in fact is none of the above! We'll find that phase is as important as voltage and frequency. Some systems have only a single phase. Oth- ers utilize three separate phases and are called three- phase. Because voltage and current in a conductor may differ in phase, a concept termed the power factor is needed to calculate AC power. AC safety is largely a function of grounding. Because mistaking a hot wire for a ground wire can prove fatal, conductor identification is extremely important. Even with proper conductor identification, however, we need ground fault devices to guard against breaks in the ground system. AC is more flexible than DC because of the trans- formations we can achieve using (what else?) trans- formers. As with DC, instruments for AC measurements per- mit troubleshooting AC circuits in order to uncover problems, including checking polarity of the incoming shore-power conductors. 115
Alternating Current Alternating current electricity (AC) is easily under- Will the Real Voltage Please Stand Up? stood once you have grasped the fundamentals of Read the labels on the under- or backside of your AC direct current electricity (DC). If you understand the electric appliances, tools, and entertainment devices. relationships between voltage, current, and resistance Which is correct: 110, 112, 115, 117, 120, or 125 volts? in DC circuits, then you are ready for the very similar There is no universal agreement as to standard AC volt- relationships in AC circuits. If you are unfamiliar with age. Different utility companies aim at different nomi- Ohm's Law, however, first review the DC concepts pre- nal voltages. In addition, the voltage delivered to your sented in Chapters 1 and 2. home is likely to vary by a few volts, depending on the Figure 4.2 showed us the output of a rotary current other loads in your neighborhood and the total load on machine. Rotation of a magnet between coils of wire the grid. In this book, we will adopt a nominal standard induces a sinusoidal current in the wire. Because the of 120 volts. current alternates polarity, it is known as alternating The first electric service supplied by utilities was in current. If we used a meter to measure the voltage the form of 120 volts DC. The change to AC was made across, instead of current through, the coils, we would because AC power is easily transformed (by transform- see that the voltage is of the same sinusoidal form as the ers) to higher voltage and correspondingly lower cur- current (Figure 7.1). All modern generators and alter- rent. Since voltage drop in a wire is proportional to cur- nators produce this sinusoidal current and voltage rent and not voltage, greater voltage results in reduced prior to rectification. loss in transmission. To take advantage of this fact, the Fig. 7.1 Alternating Voltage/Current power company distributes power over the grid at extremely high voltages (several hundred thousand), One cycle then transforms it down in progressive steps to the 120 + volts AC that enters your home. Electric lights, the first electric devices used in the home, work equally well on AC and DC, provided the power dissipated in the filament is the same. As we Voltage 0 learned in Chapter 1, electrical power is the product of voltage and current, P= V I × where: P = power consumption in watts V = volts across the load – I = amps through the load Using Ohm's Law, which works equally well for DC One full oscillation of voltage or current—plus, and AC with purely resistive loads, we can also express 2 minus, and back to plus—is a cycle. The number of power as P = V /R. Since the resistance, R, of a lamp fil- cycles completed in one second is the frequency. The ament is purely resistive, equal AC and DC power dissi- unit of frequency (cycles per second) is Hertz, abbre- pation reduces to: viated Hz. Utility electricity in the United States is pre- 2 2 ) ) cisely regulated at 60 Hertz and in Europe at 50 Hertz. (V DC ave = (V AC ave If you plugged a U.S.-built synchronous-motor electric In other words the average value of the squared AC clock into a European outlet, it would advance 50 min- voltage must equal the average value of the squared DC utes per hour instead of 60. voltage. Many people still have not adopted the term Hertz, It is easier to think in terms of equivalent DC volt- first introduced in the 1960s. They use the colloquial age, so we say, cycles, as in 60 cycles per second, instead of the proper 2 1/2 60 Hertz. Little harm is done, though, since everyone Equivalent V DC = (V AC ave ) knows what is meant. The equivalent DC voltage is computed as the square root of the mean value of the squared AC voltage (the root mean square [RMS] value of the AC voltage). 116 AC Basics
In the case of a sinusoidal AC voltage, the peak AC volt- V AB =V – V B A age is simply (2) 1/2 , or 1.414, times the equivalent DC = 120 V AC – (–120 V AC ) voltage. As shown in Figure 7.2, the peak voltage of 120 = 240 V AC volts AC is actually 1.414 120 volts = 170 volts. Thus from the three incoming supply conductors, × Fig. 7.2 Peak and RMS (Effective) AC Voltages we actually derive three different voltage sources: 120 170 V AC , 120 V AC , and 240 V AC . The phase, Ø, of a sinusoidal wave is its horizontal 120 position along the sinusoidal wave, as shown in Figure Peak 7.4. Consider waveform A starting at the left. At Ø = RMS 0°, the voltage is passing through 0 volts and rising. At Voltage 0 Peak Ø = 90°, the voltage is at its maximum positive value. to At Ø = 180°, the voltage is zero again but decreasing. peak At Ø = 270°, the voltage is at its most negative value. Finally, at 360° the voltage has come full cycle. This waveform is called single-phase (abbreviated as 1Ø) because, although changing, there is only one –170 phase present at any time. Figure 7.4 shows two additional waveforms, labeled Phase B and C. Waveform B lags waveform A by 120°, while If you look at the wires coming into your home, you'll waveform C lags A by 240°. Where all three phases are see three. Two are covered with heavy rubber insulation present in the same voltage source (shore-power cable, and are "hot." The third, forming a shield around the generator output, distribution panel, etc.), the power other two, is "neutral" and maintained at the electrical is said to be three-phase or 3Ø. potential of the earth or ground. If we plot the voltages between the three wires, they Fig. 7.4 Three-Phase AC look as in Figure 7.3. Between wires A and C, we have + 120 volts AC, just as in Figure 7.2. Between B and C, A B C we also have 120 volts AC, but the polarity is opposite that of A and C. That is, when the voltage of wire A is at Voltage its maximum positive value, the voltage of wire B is at its maximum negative value. If we ignore the neutral wire, C, and look at the instantaneous voltage between the two hot wires,A and – 180 B, we see it is the difference, or twice 120 volts AC. 0 90 Phase, Degrees 270 360 Fig. 7.3 120/240 AC Voltages Using the same logic, the 120/240 volts AC power A & B coming into your home (Figure 7.3) should be termed A Black (hot) two-phase. For whatever reason, however, it is consid- B Red (hot) ered and termed single-phase. C Bare (neutral) A & C Small boats with minimal AC equipment use only 120 VAC, 1Ø shore power, essentially that provided by a heavy-duty 120 VAC extension cord. Larger boats Volts often use 120/240 VAC, 1Ø hookups to double the available power and to operate large appliances, such as electric ranges and water heaters. The largest boats may B & C use 120/240 volts AC, 3Ø or 120/208 VAC, 3Ø hookups to increase the power even further in order to operate large appliances and take advantage of the higher effi- ciencies of 3Ø electric motors. Alternating Current 117
Power Factor Figure 7.5 shows a simple AC circuit without the com- Fig. 7.6 Three-Phase AC plications of a grounding wire. Until a load is plugged into the receptacle, the circuit from the hot (black) wire + ∅ to the neutral (white) wire remains open. Although Current voltage exists between hot and neutral, no current Voltage/Current flows because the circuit is not complete. Voltage Fig. 7.5 A Simple AC Circuit Hot wire (Black) Power Factor = cos ∅ – 0 90 180 270 360 90 Shore-power 15A/120V Phase Angle, Degrees connection receptacle The relationship between voltage and current is usefully expressed by the load's power factor, PF. Neutral wire (White) PF = Watts ⁄ (Volts Amps) × where: Watts = true power consumed Current Volts = measured volts Amps = measured amps Load, Were the load purely resistive, voltage and current Voltage Z would be in phase, watts would equal volts times amps, and the power factor would be 1.0. Since the load has an inductive component, however, voltage and current are never simultaneously at their maximum values, so the true power (instantaneous product of voltage and At the bottom we have plugged a load (a motor, for current) is less than the maximum voltage times the example) into the receptacle with a two-prong plug. maximum current, and the power factor is less than Now current flows because the circuit has been closed, 1.0. or completed, through the load. As shown in Figure 7.6, PF equals cos Ø, the cosine Note that the load is labeled Z instead of R. Z is the of the phase angle between voltage and current. For symbol for impedance, the AC equivalent of resistance. purely resistive loads such as incandescent lamps, Ø = Impedance consists of a combination of the load's DC 0°, so PF = 1.0. In the example shown, current lags resistance and its reactance (transient reaction to behind voltage by 60° (Ø = 60°), so PF = cos 60° = 0.5. changing voltage). We won't go into the mathematics, The definition of PF can also be written as but capacitors accept voltage changes readily, while inductors (coils) oppose voltage change. For this rea- Amps = Watts/(Volts PF) × son, the relationship between voltage and current in The above equation indicates the problem with an AC circuit is not one to one, as it is in DC circuits, small PF. For the same wattage of useful power, halv- but is a function of frequency. ing PF doubles amps. Greater amps means larger sup- Figure 7.6 shows plots of both voltage and current ply conductors, greater voltage drops, greater resistive in our AC motor circuit. In this example, the motor heating, and decreased efficiency. load possesses inductance, so the current lags behind The power factor of an electric motor can be very the voltage by phase angle Ø. If the load were more small when the rotor is stalled. As a result, locked-rotor capacitive than inductive, voltage would lag current, and start-up currents can be three to five times nor- and Ø would be negative. mal running current, a factor which must be consid- ered when protecting motor circuits. 118 AC Basics
AC Safety Electricity is dangerous yet indispensable in our lives. Fig. 7.7 The Dangers of Electrical Shock Unfortunately the marine environment both worsens the hazards and degrades the materials. Understand- Safe: Standing on nonconductive surface ing AC electricity and its effects on the body should convince you of the importance of AC wiring stan- dards, such as those promoted by the ABYC. The basic safety problem stems from the fact that the human body is an electrochemical/mechanical sys- tem. At the center of this system is an advanced com- puter—the brain. External stimuli are converted to electrical signals by transducers, such as the eyes (light to electricity), ears (sound to electricity) and nerves (touch and temperature to electricity). The electrical signals are conducted to the brain through nerve fibers acting much like conducting wires. The brain processes Unpleasant: Hot and ground in same hand the incoming information and then sends out appro- priate electrical signals in response. The most obvious effect of the outgoing signals is the stimulation and contraction of muscles. Herein lies the danger of exter- nally applied electrical current. Because the fluids in your body have the same approximate composition as salt water, your body has the same electrical conductivity. If you bridge an elec- trical circuit, you becomes a part of that circuit, and electric current flows through it. Muscles in your body, including your heart, cannot distinguish between elec- trical signals from the brain and the electric current we call a shock. Lethal: Hot and ground in opposite hands If you are fortunate, the involuntary muscle con- traction propels you away from the source.A less fortu- nate reaction would be contraction of the muscles in the hand and a rigid grip on the source. Worst of all would be current through the chest and heart muscle, resulting in interruption of your heartbeat. Figure 7.7 compares the dangers of various current paths through the body. The second panel shows a shock that, although painful and possibly resulting in a burn, is not usually life-threatening. Since both hot and neutral or ground conductors are in the same hand, current flow is limited to the hand muscles. Lethal: Standing in/on conductive ground Herein lies the danger of electrical shock. The third figure explains why electricians often work with one hand in ticklish situations. If one hand were to contact a hot wire or case and the other hand a ground, the resulting current flow would be directly through the chest. The bottom figure illustrates the second dangerous situation: contact with a hot wire or case while standing on a wet and conductive ground. The current flow is again directly through the chest and heart. AC Safety 119
Grounding Figure 7.7 showed what happens when a person con- back at the power source, runs parallel to the neutral tacts a hot (live) wire or equipment case while standing wire throughout the circuit. This green grounding wire on a grounded conductive surface. The body serves as a is connected to the exterior metallic case of every elec- parallel return conductor to ground. trical device. If the hot wire were to short to the case, But who would ever grasp a hot wire? Figure 7.8, the green grounding wire would offer the stray current top, shows that it is not always necessary to touch a hot a nearly zero-resistance return path to ground, thus wire directly to receive a potentially lethal shock. The preventing significant current through the more resis- hot (black) and neutral (white) wires of the motor cord tive human body. are intended to be isolated from each other and from If the short circuit from the hot conductor to the the metal case. Unfortunately, through chafe or over- case were of low enough resistance, the short circuit heating of its insulation, the hot wire has shorted to the current would blow the fuse or trip the circuit breaker motor case. Operation of the motor may be unaffected, in the black conductor. Even were the current insuffi- but when you contact the case, the result is the same as cient to trip the breaker, however, the green wire would touching the hot wire directly. provide a low-resistance safety path. It should be obvi- Figure 7.8, bottom, shows the solution: the green ous that this green grounding conductor should never grounding wire, connected to the white neutral wire be interrupted by a switch, fuse, or circuit breaker. Fig. 7.8 The Green Grounding Wire TWO-WIRE SYSTEM Return to ground: case hot Hot wire (Black) Short to metal case Neutral wire (White) THREE-WIRE WITH GROUND Short to metal case Return to ground: case not hot Hot wire (Black) Grounding wire (Green) Neutral wire (White) 120 AC Basics
Conductor Identification With each conductor playing an assigned role in safety, but what if the green wire breaks, or the device is used it is critical that they not be accidentally confused and on a two-wire extension cord with no grounding con- reversed. For that reason, the ABYC assigns specific col- ductor? There are numerous ways that the purpose of ors to the insulation of each conductor in an AC cir- the green wire can be circumvented. To protect against cuit. Table 7.1 shows the color code for AC conduc- these accidents, an ingenious type of circuit breaker is tors. It is fortunate for those versed in residential wiring recommended for all AC outlets located in head, gal- that the colors are the same. ley, machinery space, or on deck. Table 7.1 Color Code for AC Conductors Figure 7.10 demonstrates the operation of a ground fault circuit interrupter (GFCI). In a normally func- Source Grounding Neutral Hot tioning AC circuit, current flow through the hot (black) 120 V, 1Ø green or bare white black and neutral (white) conductors is equal and opposite. The green grounding conductor is connected to the 120/240 V, 1Ø green or bare white black, red neutral conductor at the point of origin (the distribu- 120/240 V, 3Ø green or bare white black, red, blue tion panel), but not at the individual receptacles and 120/208 V, 3Ø green or bare white black, red, blue devices. Thus, the green wire does not normally carry any current. Every electron flowing in the hot conduc- To prevent accidental reversal of the conductors at tor is intended to be returned by the neutral conductor. plug and socket connections, both sockets and plugs Any difference in current between the hot and neutral are designed so that they can be connected in only one conductors must, therefore, represent a stray (danger- way, and each screw terminal is assigned a color match- ous) current. ing its conductor. In the GFCI both hot and neutral conductors pass Figure 7.9 shows the most familiar example: the through a circular magnet. Current in the hot conduc- 15 A/120 VAC polarized receptacle used in both resi- tor induces a magnetic field in the magnet, but the dential and marine applications. Notice that the rectan- equal and opposite current in the neutral conductor gular sockets and prongs are of different sizes. It is induces the opposite magnetic field. The net magnetic impossible to insert the mating polarized plug the field is thus zero. wrong way and reverse the hot and neutral conductors. All screw terminals are color coded to insure proper Fig. 7.10 Ground Fault Circuit Interrupter (GFCI) installation. The terminal for the hot (black) conductor is darkest; the neutral (white) terminal is silver; the Hot grounding (green) terminal is tinted green. Line Neutral Fig. 7.9 Polarized 120 VAC Duplex Receptacle Neutral (white Detect and wire/silver amplify screws) Hot (black or difference red wire and between dark screws) hot and neutral A difference in the two currents, however, produces a net magnetic field, which induces a current in the detecting coil. This current activates a solenoid that opens either the hot conductor (single-pole GFCI) or Ground (green wire/ both hot and neutral conductors (double-pole GFCI). green screw) The Class A GFCI recommended for marine use opens on a current difference of only 0.005 amp—far less than a lethal current to humans. Although the sensi- Added Safety: Ground Fault Devices tivity of these devices can be annoying when trying to The green grounding conductor of Figure 7.8 goes a establish a shore-power connection, it is better to be long way toward providing safety from electrocution, annoyed than dead. Conductor Identification 121
Transformers AC to AC Fig. 7.11 A 1:1 Transformer The great advantage of AC over DC power is the pos- Shore side Ship side sibility of increasing and decreasing voltage simply. Figure 7.11 shows a simple transformer. It consists Hot Hot of two insulated coils, both wound around the same (Black) (Black) iron core. AC current flowing in the input coil induces an alternating magnetic field in the core which, in turn, induces an AC current in the output coil. If the number of turns in the input and output coils are identical, out- Neutral Neutral put voltage is identical to input voltage. This trans- (White) (White) former preserves the identity of the conductors and the Grounding Grounding phases of the input and output by tying the neutral (Green or Bare) (Green) conductors together. The green grounding wire is sim- ilarly uninterrupted and is bonded to the transformer case. Figure 7.12 shows a step-down (voltage reducing) transformer. The number of turns in the output coil is Fig. 7.12 A Step-Down Transformer less than the number of turns in the input coil. The voltage induced in the output coil is, therefore, less than Shore side Ship side the voltage in the input coil. (The ratio of voltages sim- ply equals the ratio of turns.) Hot (Black) As with Figure 7.11 the identities of the input and output conductors and phases are preserved by tying Hot the neutral conductors together. The green grounding (Black) wire is again bonded to the transformer case. Figure 7.13 shows an isolation transformer. Here Neutral Neutral (White) (White) neither neutral nor grounding conductors are con- nected. The neutral (white) and grounding (green) Grounding Grounding (Green or Bare) (Green) conductors on the output side are connected, however, so that the transformer output acts as an independent electrical source, isolated from shore ground. The green grounding wire from the shore-power side is connected to the shield between the input and output coils. Other common configurations include Fig. 7.13 An Isolation Transformer connection of the grounding wire to an inside case or to an outside case. In any case, follow the manufac- Shore side Ship side turer's recommendation. Hot The isolation transformer is ideal for shore-power (Black) Hot (Black) hookups because it interrupts the green grounding wire from the shore-power circuit, which might other- wise provide a path for stray corrosion currents between boats sharing the same shore-power circuit. Neutral Neutral Isolation transformers will be discussed further in (White) (White) Chapter 9. Grounding Grounding (Green or Bare) (Green) Shield— insulated from Metal case case and core 122 AC Basics
Converting AC to DC Fig. 7.14 The Half-Wave Rectifier As we saw in Chapter 4, alternating current can be con- + verted to direct current. In Figure 7.14, a diode in the output allows current to flow only in the direction of Input Output the symbolic arrow. As a result, the positive current half-waves are conducted while the negative half-waves are blocked. Although not constant, the output cur- – rent never reverses polarity and is, thus, direct current. The full-wave rectifier in Figure 7.15 employs a diode bridge of four interconnected diodes to conduct both positive and negative half-waves. During the pos- Fig. 7.15 The Full-Wave Rectifier itive current half-wave, the two diodes at the top con- duct. During the negative current half-wave, the bot- tom two diodes conduct. Since the input and output Input + coils are electrically isolated, both half-waves appear as positive when seen at the output. The output voltages of both the half-wave and the Output full-wave rectifier still look to the eye more like alter- – nating current than direct current, due to the extreme amount of ripple. The DC power supply in Figure 7.16 employs a large capacitor across the output to filter, or smooth, the pulses for a nearly ripple-free output. The simple battery charger in Figure 7.17 uses the Fig. 7.16 A Filtered DC Power Supply battery itself, instead of a capacitor, to smooth the rip- ple. As we saw in Chapter 4, the rectified output of an Hot alternator is similarly smoothed by the large capacity of the battery it charges. + Neutral + Ground – Fig. 7.17 A Battery Charger Hot + Neutral Battery – Ground Transformers 123
AC Measurements The common multimeter can be used for AC as well as DC measurements, although with fewer ranges and with reduced accuracy. Fortunately, accuracy is rarely of importance in AC measurements. While a differ- ence of just 0.1 VDC represents about 10% of the capacity of a 12-volt battery, an acceptable range of shore-power voltage may be 110 to 125 volts AC. AC Voltage Fig. 7.18 Measuring AC Voltage Figure 7.18 shows a multimeter being used to measure AC voltage. The meter employs the same internal cir- cuitry to measure and display both AC and DC volt- ages, except that the AC voltage is first rectified by an V internal diode bridge. In some multimeters the positive – AC test lead must be switched to a separate AC jack that feeds the diode bridge.Attempting to measure AC volts on a DC volts setting will do no harm but will likely result in a reading of 0 volts, since the numerical aver- age of AC voltage is zero. Current Load, AC Impedance Voltage Impedance As we saw earlier, impedance may vary with frequency and, in the case of AC motors, with the speed of the motor. Such measurements are beyond the scope of this book and the pocketbooks of most boaters. What we can measure, however, is the resistive component of the impedance. To do so, the load must be isolated from the rest of the circuit as shown in Figure 7.19. Fig. 7.19 Measuring the Resistive Component of Impedance Simply disconnecting one of the leads effects electrical isolation. The resistance component of many AC loads is quite small, so be sure to zero the meter first by touch- ing the test leads together and adjusting the zero-ohms knob. In digital multimeters zeroing is automatic. Ω – + Current Load, Voltage Impedance 124 AC Basics
AC Amps Fig. 7.20 Measuring AC Currents Inexpensive multimeters can measure up to 250 mil- mA liamps (0.25 amp) of AC current directly, as shown in Figure 7.20, top. To make the measurement, make sure DIRECT the multimeter switches and leads are in the correct positions. Then disconnect the hot conductor from the – AC load and insert the multimeter leads between the con- ductor and the load. The trick employed in high-current ammeters can Current be used to measure AC currents greater than 0.25 amp. Figure 7.20, middle, shows a shunt inserted in the cur- Load, rent-carrying conductor. A shunt is a low-ohm preci- Voltage Impedance sion resistor that generates a voltage drop in accor- dance with Ohm's Law. Shunts are specified by the ratio of voltage drop across to the maximum current through the shunt. For example, a 50 mV per 100 A shunt is intended for currents of up to 100 amps and produces 50 millivolts across its terminals at full cur- mV rent. From Ohm's Law, we calculate the resistance of ACROSS this shunt to be: SHUNT *Shunt may be R = V/I internal or = 0.050 volt/100 amps external to meter – + = 0.0005 ohm More expensive multimeters usually contain inter- nal shunts allowing direct current AC measurements of Current up to 10 amps. Shunt* If your multimeter does not have this capability, or if you wish to measure currents greater than 10 A, you Voltage Load, can purchase a 100 millivolts per 100 amps, 50 milli- Impedance volts per 200 amps, or other shunt for less than the cost of another ammeter. You can then use your multime- ter on a millivolts setting to read amps flowing through the shunt. If you have money to spare, a more expensive, but 400 A MAXIMUM less accurate, special-purpose AC meter employs a clamp that is placed around the hot conductor (Figure 7.20, bottom). The magnetic field around the conduc- CLAMP-ON tor induces a current in the clamp. The current is then AMMETER OFF AMPS read as in any other type of test meter. HOLD The advantage of the clamp-on meter is the ability to read current without disconnecting or cutting the AC VOLT conductor.A limitation is the requirement of physically separating the hot and neutral conductors. If both hot Current and neutral conductors are enclosed by the clamp, the opposing currents cancel so the meter reads zero. A second disadvantage of the clamp-on meter is Voltage Load, lack of sensitivity.While direct, in-line meters can mea- Impedance sure microamps, the clamp-on meter is useful only down to milliamps. AC Measurements 125
Troubleshooting AC Circuits Testing an AC circuit is no more difficult than testing meter reads zero, shift the probe from the larger rectan- a DC circuit, provided you keep in mind the functions gular socket to the U-shaped socket. If the meter now of each of the conductors in the circuit. To review the shows 120 VAC, there is a fault somewhere in the neu- color code for AC conductors: tral conductor. If the meter still shows zero, the fault is • Black conductors should be hot (120 VAC). likely in the hot conductor, including an open circuit • Red (and blue if present) conductors should also breaker or fuse. be hot (120 VAC), but of different phase than the The test for the second circuit is identical to that black conductors. for the first. Simply substitute red for black and repeat • White conductors should be at 0 volts relative to the tests. boat ground. At the right, we are testing the 240-volt leg of the • Green or bare conductors should be at 0 volts rel- 120/240-volt system. The meter is measuring the volt- ative to boat ground. age difference between the two hot wires. Each hot wire Figure 7.21 shows three receptacles representing the should be at 120 volts, but opposite in polarity, so that three different possible voltage sources in a 120/240 the difference is 240 volts. If the meter displays zero, VAC system. there is a fault in either the black or the red conductor. Set the meter to 250 VAC. At the left, insert the test To discover which conductor is not working, shift one probes in the two rectangular holes. Since the black of the probes to the grounding socket. The meter conductor should be at 120 VAC and the white conduc- should read 120 VAC. If not, the other (unshifted) tor at 0 VAC, the meter should display 120 VAC. If the probe is on the defective conductor. Fig. 7.21 Troubleshooting AC Circuits with a Multimeter 120 VAC 120 VAC 240 VAC VAC VAC VAC – + – + – + Hot (Black) Neutral (White) Hot (Red) Grounding (Green) 126 AC Basics
Checking Polarity In spite of rigorous adherance to the color code, AC one of its leads is in the hot socket and the other in conductors can sometimes become switched. Most either the neutral or grounding socket. If the lamp often the fault lies in a homemade shore-power cord lights when the leads are in the large rectangular and where the mirror-image male and female plugs and U-shaped sockets,then either the neutral or the ground- receptacle patterns are easily confused. ing conductor is hot and the polarity is reversed. Fix the Reverse polarity is a dangerous situation. The boat's polarity immediately before someone is injured or elec- ground is inadvertently raised to 120 VAC, along with trocuted! the seawater immediately surrounding the boat via the A proper shore-power hookup will have a reverse- bonding of underwater metal. A person swimming polarity warning light in the AC-distribution panel near the boat could be electrocuted. (required by ABYC). If yours doesn't, you can install Unfortunately, most AC electrical equipment will one as described in Chapter 14. operate normally with reverse polarity. We need some Alternatively, you can purchase a plug-in polarity way to test for proper polarity when establishing a tester at any hardware store for about $5. Plug it into an shore-power connection. onboard AC receptacle each time you establish a shore- Figure 7.22 shows how you can perform the test power connection. It may save someone's life. with a 120-volt lamp. The lamp should light whenever Fig. 7.22 Testing the Polarity of an AC Circuit with a Lamp If this lamp lights, polarity is reversed! Insulated sleeve Hot (Black) Neutral (White) Grounding (Green) Checking Polarity 127
8 CHAPTER Inverters and Generators Battery DC Shore power External transfer AC Inverter in Generator switch AC out Large-load Small-load panel panel Air cond Stb out Water htr Port out Range Stereo Spare Spare 128 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
W hy have AC power on a boat? Because AC appliances add quality to life aboard. Possi- ble AC sources include shore power, invert- ers, and generators. In order to select an inverter or generator you first need to determine your AC budget, or how much AC power you will likely consume. Modern inverters can supply all the clean, regulated AC power you wish, along with the conveniences of automatic battery charging and transfer switching between shore power and battery. Generators can do the same but, before choosing a generator over an inverter, you should verify that it is really necessary! 129
Why Have AC Power? I was cruising the Bahamas a few years ago. There's not AC Sources much radio or TV programming in the Bahamas so I, You have three options for getting AC power: like most other cruisers (and Bahamians as well), was • Shore power idly listening to other boaters' conversations on VHF. • Diesel or gasoline generator Two women were chatting about the weather, their • DC-to-AC inverter plans for the afternoon, etc. Suddenly one said, "Whoops, gotta go; the toast is up." Shore Power There was a long pause. Then,"You have a toaster?" Shore power is the same power as in your home. Essen- "Sure," said the other, "I have toast or an English tially, you connect your boat to the utility company via muffin every morning." an extension cord. Unlike in your home, however, there Another long pause. Then,"I'm going to kill you." are significant safeguards that should be installed to My sentiments exactly. Though there is a certain protect against dangerous shocks and stray-current pristine beauty in adherence to the old ways—reading corrosion of your boat's underwater metals. These by oil lamp, navigating by sextant, boiling coffee installation safeguards are discussed in Chapter 9. grounds in a pot—for most liveaboards the ascetic life wears thin after a season or two. Considering the high Generators performance and low cost of modern inverters, the Generators can supply large currents—enough to question should be,"Why not have AC on your boat?" power an electric range. Unless your boat is a 100-foot yacht with a soundproof engine room (not compart- ment), generators are too smelly and noisy to be run 24 AC Versus DC hours per day. You may become immune to the noise, You've probably already experimented with one or but boaters anchored near you in Paradise Lagoon will more DC appliances. Your first galley appliance may probably consider you an inconsiderate jerk. have been the 12 VDC blender you saw in a marine cat- If you really must have an electric range, water alog. Under the Christmas tree came the 12-volt hair heater, and air conditioner at anchor or underway, dryer and coffee grinder. The first season, however, the install a generator, but concentrate the heavy loads for blender screeched to a halt and the other two appli- an hour in the morning and an hour in the evening. ances melted in a cloud of smoke. You learned why the Smaller loads can be run off your batteries via an appliances in our homes run on 120 VAC, not 12 VDC. inverter. You may also have noticed that the 12-volt blender, for which you paid $89.95, goes for $19.95 in its AC Inverters incarnation at Wal-Mart. Several generalizations can be Inverters are silent sources of AC that draw battery made about DC versus AC appliances: power derived from the engine alternator, a generator, or wind, water, or solar chargers. Many modern invert- 1. AC appliances cost much less because there are at least 1,000 times as many manufactured. ers are designed specifically for marine or mobile use, 2. AC appliances last longer because they are are nearly 100% efficient, are better regulated in voltage designed to survive 20 years rather than a few than your local utility, and are capable of more sophis- seasons. ticated battery charging than stand-alone battery 3. You can only get serious power (for toasters, chargers. microwaves, hair dryers) with AC. If you spend much time dockside, you'll want a sub- stantial shore-power hookup. Even if you spend most There are also a few exceptions to the AC/DC rule. of the time anchored or moored, however, the cost of Nearly all electronic circuits run on DC.A piece of elec- the most common hookup (30 A/120 VAC, 1Ø) is so tronic equipment designed specifically for DC can small that you should install it anyway. eliminate the internal AC-to-DC power supply and With an inverter, you'll be able to cast off the dock actually be more efficient than its AC equivalent. The and shore-power lines and continue to use all of your automobile CD player is the best example. Even with small AC appliances without interruption. the biggest and best inverter or generator aboard, your If you have cloned your home with air conditioner, stereo should be powered by DC, just like all of your refrigerator, freezer, and electric range, however, you'll navigation electronics. also need a substantial generator. 130 Inverters and Generators
Figuring Your AC Budget The first task is to determine how much AC power you Table 8.1 Typical Appliance Power Consumption will need. Table 8.1 lists the typical power consump- Typical TypicalHours tions of AC appliances and tools you may consider. The Appliance Watts Use Per Day listed figures are representative and intended to be used for preliminary planning. If you already have the appli- Air conditioner, 5,500 Btu/h 750 12 ances, use their actual ratings instead. Air conditioner, 11,000 Btu/h 1,500 12 300 On every tool and appliance is a nameplate listing Blender 0.02 its electrical consumption. The amps and watts shown Broiler 0.25 1,400 are the maximum steady-state values at the specified Computer, desktop (w/o monitor) 60 2 voltages. Motor-driven devices often draw start-up cur- Computer, laptop 60 2 rents several times larger than their nameplate ratings. Computer monitor, 17-inch CRT 65 2 This is usually of small concern with inverters and gen- erators, since both are capable of surge currents far in Computer monitor, 15-inch LCD 30 2 excess of their continuous ratings. If your inverter or Printer, inkjet 15 0.05 generator is sized to run within its steady-state capacity, Printer, laser 800 0.05 it should have little trouble starting a motor. Drill, ⁄8-inch 0.02 3 350 To convert appliance ratings from amps to watts Dryer, hair 1,200 0.05 and vice versa, remember: Fan, 6-inch 25 8 Watts = Volts Amps Fan, 20-inch 250 8 × Example: On the bottom of your toaster it says,"115 Fry pan 1,200 0.25 volt AC, 10 amps." First, ignore the fact that the volt- Heater, space 1,200 12 age is listed as 115 (or 110 or 125) instead of 120. Heater, water 1,500 1.3 Although your toast will brown more quickly on 120 Iron 0.15 1,100 than 115 volts, the toaster will function on any voltage Light 4 25–75 between 110 and 125 volts AC. Microwave, 0.6 cu.ft. 800 0.15 To convert from amps to watts we use the formula: Microwave, 1.5 cu.ft. 1,200 0.25 Watts = Volts Amps Mixer 0.05 240 × = 115 volts 10 amps Percolator 0.25 600 × = 1,150 watts 1,200 Range/element 1 The voltage of your onboard source may actually be Refrigerator, 6 cu. ft. 80 10 120 volts AC, in which case the toaster will draw slightly Refrigerator, 14 cu. ft. 140 10 more than 10 amps and 1,150 watts, but we are just estimating our needs at this point. Soldering iron 100 0.02 Column 3 of Table 8.1 lists typical operating times TV, 7-inch B&W 20 4 for each appliance.You may not have a listed appliance, TV, 7-inch color 35 4 or you may have it but rarely use it. The figures in col- TV, 16-inch color 100 4 umn 3 are suggested operating times in hours per day Toaster 0.15 1,100 when applicable. These figures obviously depend on VCR/DVD, play-only 20 2 lifestyle. For example, the table lists 1.3 hours per day VCR/DVD, play/record 80 2 for a 1,500-watt water heater. A single-handed boater might halve the listed time, but a family with teenagers Vacuum cleaner 800 0.05 might quadruple the listed 1.3 hours. After assembling your list of planned appliances, their rated wattages, and estimated hours of use, you are ready to compile your estimated daily electric load. Table 8.2, on the next page, provides a blank form you can photocopy and complete to determine your typical daily consumption in watt-hours. Figuring Your AC Budget 131
Figuring Your AC Budget Table 8.2 Daily Electrical Consumption Rated Typical Use, Watt-Hours Peak Watts Appliance Watts Hours/Day per Day 1 Inverter 2 Generator 3 Totals 1 Watt-hours supplied by inverter. 2 Peak watts supplied by inverter with generator off. 3 Peak watts supplied by generator. 132 Inverters and Generators
Tables 8.3 through 8.5 show example budgets of This minimal budget requires an inverter with a low, medium, and high AC-power use. maximum continuous rating of only about 500 watts, The low daily budget in Table 8.3 represents a tradi- which draws about 35 Ah per day from the batteries. tional weekend cruiser with alcohol- or propane-fueled Total battery consumption is 33 Ah (35 Ah consid- cooking, mechanical or 12-volt refrigeration, but 120- ering inverter efficiency), plus the sum of the daily DC volt-AC entertainment. loads. Table 8.3 Example of Low Daily Electrical Consumption Rated Typical Use, Watt-Hours Peak Watts Appliance Watts Hours/Day per Day 1 Inverter 2 Generator 3 Blender 300 0.02 6 300 — Computer 100 2.00 200 100 — 3 Drill, ⁄8-inch 350 0.02 7 — — Soldering iron 100 0.02 2 — — TV, 7-inch color 35 4.00 140 35 — VCR/DVD 20 2.00 40 — — Totals 395 435 (33 Ah) 1 Watt-hours supplied by inverter. 2 Peak watts supplied by inverter with generator off. 3 Peak watts supplied by generator. The medium budget in Table 8.4 adds a small (0.6 occurs in short bursts, and since inverters can put out cu. ft.) microwave, 120-volt-AC refrigerator, and hair much larger currents for short periods, a 1,000-watt dryer. continuous inverter would probably suffice. These significant additions require an inverter rated Total battery drain consists of the 125 Ah inverter at about 1,300 watts continuous that draws about 125 drain plus all DC loads. Ah from the batteries. Since microwave use most often Table 8.4 Example of Medium Daily Electrical Consumption Rated Typical Use, Watt-Hours Peak Watts Appliance Watts Hours/Day per Day 1 Inverter 2 Generator 3 Blender 300 0.02 6 300 — Computer 100 2.00 200 100 — 3 Drill, ⁄8-inch 350 0.02 7 — — Hair dryer 1,200 0.05 60 — — Microwave, small 800 0.15 120 800 — Refrig., 6 cu. ft. 80 10.00 800 80 — Soldering iron 100 0.02 2 — — TV, 7-inch color 35 4.00 140 35 — VCR/DVD 20 2.00 40 — — Totals 1,375 1,315 1 Watt-hours supplied by inverter. (115 Ah) 2 Peak watts supplied by inverter with generator off. 3 Peak watts supplied by generator Figuring Your AC Budget 133
Figuring Your AC Budget The high budget shown in Table 8.5 includes all of This large budget requires a 6-kilowatt generator the conveniences of the home. Demand in the evening during the hours of peak use and an inverter rated at is beyond the capability of standard inverters, so a gen- about 3,000 watts continuous or more.Allowing for the erator is added to supply the largest loads, which are efficiency of the inverter, the inverter alone draws about concentrated for an hour in the morning and an hour 280 Ah per day from the batteries. in the evening. Table 8.5 Example of High Daily Electrical Consumption Rated Typical Use, Watt-Hours Peak Watts Appliance Watts Hours/Day per Day 1 Inverter 2 Generator 3 Air conditioner, 11,000 Btu/h 1,500 12.00 — — 1,500 Blender 300 0.02 6 300 — Computer 100 2.00 200 100 — 3 Drill, ⁄8-inch 350 0.02 7 — — Hair dryer 1,200 0.05 60 1,200 1,200 Water heater 1,500 1.30 — — 1,500 Lights 50–500 4.00 1,000 250 250 Microwave, large 1,200 0.25 — — 1,200 Range element 1,200 1.00 — 1,200 — Refrig., 14 cu. ft. 140 10.00 1,400 140 140 Soldering iron 100 0.02 2 — — TV, 19-inch color 100 4.00 400 100 100 VCR/DVD 20 2.00 40 20 20 Vacuum 800 0.05 40 — — Totals 3,155 3,310 5,910 1 Watt-hours supplied by inverter. (263 Ah) 2 Peak watts supplied by inverter with generator off. 3 Peak watts supplied by generator. 134 Inverters and Generators
Inverters How Inverters Work Fig. 8.2 Inverter Waveforms Compared Figure 8.1 shows, in simplified form, how an inverter Sine wave transforms DC battery power into AC power. S ,S , 170V 2 1 and S are all solid-state transistors, which act as fast 3 switches. Fig. 8.1 Simplified Inverter Schematic S2 P2 Square wave Output S3 120V P1 S1 Storage Battery – + Pulse width varied to maintain 120 volts RMS Modified sine wave 150V The sequence of electrical events for a single AC cycle is shown in Table 8.6. The actual circuitry is far more complex, but the switching sequence demon- strates the principle. Table 8.6 Transistor Switching in an Inverter ment, the square wave appears to be a group of sinu- S 1 S 2 S 3 Action Result Closed Open Open 12V applied to + Output soids at multiples of the fundamental 60 Hertz. primary coil P 1 Whether these higher-frequency components interfere Open Open Closed primary shorted 0 Output depends a great deal on the quality of the equipment's grounding, shielding, and power-supply filtering. Open Closed Open 12V applied to – Output primary coil P 2 High-quality, pulse-width-modified, sine-wave Open Open Closed primary shorted 0 Output inverters emit less harmonic power but sometimes still cause difficulty in sensitive equipment. For zero inter- ference and hum, pure-sine-wave inverters are available Figure 8.2 compares the outputs of three inverter at significantly higher cost. types: square wave, pulse-width-modified sine wave, My experience in operating computers, GPS, VHF, and pure sine wave. Note the differences in peak voltage SSB, and television receivers concurrently with a pulse- for the nominal 120-volt AC waves. width-modified, sine-wave inverter is that the com- The pulse-width-modified sine wave has two puter and GPS seemed unaffected, the television advantages over the square wave. First, it appears displayed minor interference patterns, and the trans- slightly more sinusoidal in shape to a load. Second, by missions of both VHF and SSB contained noticeable varying the width of the output pulse, the average out- hum. I have not found the interference to be serious put voltage (area under the voltage curve) can be held enough to install line filters, however. constant as the input battery voltage and output peak Chapter 13 contains all of the information you voltage drop. require to filter the supply lines of affected equipment. Square-wave inverters are notorious for causing 60 If you are still concerned you can make your purchase Hertz hum and interference. To the antenna or input of a pulse-width-modified, sine-wave inverter conti- transformer of a piece of sensitive electronic equip- gent on acceptable interference levels. Inverters 135
Inverters Inverter Specifications Output Voltage Table 8.7 lists the specifications of four popular invert- The outputs of both Freedom inverters in Table 8.7 are ers in a range of sizes. pulse-width-modified sine waves, where the duration of the pulses are adjusted to produce a constant RMS Input Voltage (root mean square) voltage. The actual peak voltages Most inverters accept a range of input voltage of about corresponding to 120 volts AC RMS are as shown in 10 to 15.5 volts DC. To avoid problems, you should Figure 8.2: make sure the voltage regulators of your engine alter- • Sine wave 170 volts nator and solar and wind chargers are set to less than • Square wave 120 volts 15.5 volts, measured on the battery side of any isolation • Modified sine wave 150 volts diodes. If you wish to bypass the regulators and equal- Since the normal range of shore-power voltage is ize your batteries with a voltage greater than 15.5 volts, from 110 to 125, or 117 ±7% VAC, any regulation of first turn the inverter off. 7% or better is acceptable. The low voltage cutoff of approximately 10 volts The frequency regulation of most inverters is good DC is designed to prevent destructive 100% discharge enough to keep time by. The Freedoms' ±0.005% of the batteries. Some inverters sound an audible alarm equates to ±4 seconds per day! before cutting off. Table 8.7 Inverter Specifications Specification Prosine 2.0 Xantrex MS2000 Freedom Marine 10 Freedom Marine 25 Minimum input voltage, DC 10.0 10.0 10.0 10.0 Maximum input voltage, DC 16.0 15.5 15.5 15.5 Output waveform true sine wave true sine wave modified sine wave modified sine wave Output voltage, AC 117 120 120 120 Output frequency, Hz 60 60 50 or 60 50 or 60 Frequency regulation, % ±0.05 ±0.05 ±0.005 ±0.005 Output, continuous watts 2,000 2,000 1,000 2,500 30-minute watts — — 1,800 2,800 Surge watts (5 seconds) 4,500 5,000 3,000 5,200 Efficiency, peak, % 89 92 93 93 Efficiency, full load, % 81 87 85 87 Standby drain, searching, watts 2 14.4 1.5 1.5 Standby drain, inverting, watts 25 48 — — Battery charging current, amps 100 100 50 130 Battery charging stages 3 + manual equal. 3 + manual equal. 3 + manual equal. 3 + manual equal. Weight, lb. 24 68 34 50 Transfer switch, AC amps 30 30 30 30 Optimal temperature range, °F 32–104 32–104 32–104 32–104 136 Inverters and Generators
Output Power Fig. 8.3 Rated Output of Heart EMS-1800 When sizing an inverter, be careful. It was common 3500 practice in the past to define "continuous watts" as Continuous output 1100 VAC @13 VDC and 25˚C "continuous for up to 30 minutes"! For example, the 3000 maximum continuous output power of the older Heart EMS-1800 was not 1,800 watts, as you might assume, 2500 but 1,100 watts—40% less. The manufacturers no doubt reasoned that many of the larger inverter loads, 2000 such as microwaves, hair dryers, and clothes irons, Output, VAC lasted 30 minutes or less, so a 30-minute rating was 1500 appropriate. It may have been appropriate, but it was also misleading. Fortunately it appears that most man- 1000 ufacturers have now adopted a "continuous" continu- ous rating. 500 Figure 8.3 shows how the maximum output of the 0 EMS-1800 varied with duration. The curve reflects the 0 0.5 1 1.5 2 buildup of internal heat, not depletion of the battery, Time Until Thermal Shutdown, Hr which is assumed to be a constant 13.0 volts DC. The output power versus time curves of all inverters are of similar shape. Fig. 8.4 Efficiency of Heart EMS-1800 Surge current is the momentary current drawn by electric motors at startup. As a rule of thumb, surge 100 currents of inverters are approximately 250% of the continuous-rated currents. In fact, many manufactur- 80 ers specify surge current in terms of the size of motor they will start. 60 Efficiency and Standby Power Efficiency, % The percentage of battery power converted to AC 40 power depends on two factors: • Efficiency is the percentage of power converted 20 while the inverter is in operating mode • Standby power is the drain on the battery while the 0 inverter is in standby mode, waiting for a load to be 0 0.3 0.6 0.9 1.2 1.5 1.8 connected Output Power, x1000 Watts Pulse-width-modified, sine-wave inverters are typi- cally extremely efficient at mid- to upper-output levels. Figure 8.4 shows efficiency versus output power for level, as may be the case with a small nicad battery the Heart EMS-1800. Most inverters achieve efficien- charger. To overcome the standby mode, I recharge sev- cies in excess of 90% over most of their output ranges. eral nicads at once. Efficiency drops dramatically, however, at very low The standby-drain specification is important power levels. For this reason, most inverters remain in because it results in a constant drain on the batteries. standby mode (on, but not producing power) until Freedom's 1.5 watts amounts to 3 Ah per day. With they sense a significant load. their more complex circuitry, pure-sine-wave inverters For Freedom inverters the minimum load required can draw an amp or more on standby, wasting at least to trigger the "on"state is only 1.5 watts. Since the turn- 24 Ah per day. For example, the Xantrex MS2000 on is instantaneous, the user is usually not aware of standby drain of 14.4 watts drains a hefty 28.8 Ah per the standby mode unless the load is less than the trigger day. Inverters 137
Inverters Battery Charging Fig. 8.5 Typical (Heart EMS-1800) Three-Stage Charging The most sophisticated inverters offer shore-power 100 battery charging. In effect running backward, when external AC power is applied from either shore power 80 or an onboard generator, a 30-amp internal transfer Constant I = 65A switch connects inverter loads directly to the external 60 AC-power source and, at the same time, begins charg- Charging Current, Amps Tapering I to V = 14.3 ing the battery. The battery-charging circuitry is as sophisticated as many multicycle stand-alone chargers 40 costing nearly as much as the inverter. The economy is Floating constant V Constant realized through the use of many of the same compo- 20 nents for both modes. Charger off V Figure 8.5 shows the battery-charging cycles of the 0 12.5 13.0 13.5 14.0 14.5 15.0 12.0 older Heart EMS-1800 inverter. More modern inverters Battery Charging Voltage are even more flexible, allowing operator choice of charging voltages, depending on the type of battery. Bulk Absorption Float and cycle cycle equalize Bulk cycle. Assuming the battery is moderately dis- charged, the charging current of the EMS-1800 starts at Equalize once/mo. V=15.3 for 8 hr. 65 amps (100 amps for the EMS-2800). Charging cur- 15 rent remains constant until the battery voltage reaches Voltage 13.0 volts. From 13.0 to 14.3 volts the charging current 14 V=14.3 to I=10A tapers from 65 amps to about half, or 30 amps. Charging 65A to 13V; taper to 14.3V Absorption cycle. During the absorption cycle, voltage 13 Float at 13.3V is held constant at 14.3 volts, while the battery current acceptance drops from 30 amps to 10 amps. Referring 12 to the recommended optimally fast charging routine 8 Hours Maximum for wet lead-acid batteries, shown in Figure 3.14 of Chapter 3, the 10-amp cutoff seems wise, correspond- ing to a 200 Ah battery (size 8D). Float cycle. Once the current at 14.3 volts drops to 10 amps, the charger reverts to a float state, at a constant 13.3 volts. In the float state, the charger will provide up to its maximum output of 65 amps (100 amps for the EMS-2800) while maintaining 13.3 volts. Current demands over 65 amps are drawn from the battery. Equalization cycle. As discussed earlier, the useful life of a battery can be increased by periodic equalization. Equalization consists of overcharging the battery, resulting in shedding of hardened lead sulfate from the plates. EMS inverters can be manually triggered after reaching the float state to maintain a constant 15.3 volts for 8 hours. They then revert to the float state at 13.3 volts. Note that sealed and gelled-electrolyte bat- teries should not be equalized because they cannot vent the generated hydrogen gas, and lost water cannot be replaced. 138 Inverters and Generators
Transfer Switching Many inverters offer a transfer switch either as standard Fig. 8.6 A Transfer Switch equipment or as an option. An inverter transfer switch Transfer switch automatically switches boat AC loads to shore power or generator output when available, and back to the AC input 1 inverter output when the external source is removed. AC output This is a great convenience on a boat that goes into and out of slips a great deal. AC input 2 Boats with onboard generators require an addi- tional transfer switch to select between shore power and generator output. Figure 8.6 shows the internal configuration of a transfer switch. Input 1 is connected to AC source 1 Fig. 8.7 Transfer Switch with Automatic Battery Charging (shore power, for example). Input 2 is connected to AC source 2 (internal connection to inverter output).With Shore Inverter no AC at the terminals of input 1, power is routed from Power input 2 (inverter) to the output. When shore power ON Battery appears at input 1, however, the solenoid pulls the switch up, and power is routed from input 1 to the out- Internal put. AC input transfer Charger switch Operation of a shore-power/generator transfer switch can be either manual or similarly automatic. AC output Figure 8.7 shows the operation of an inverter with both an internal transfer switch and automatic battery Shore Inverter charging. Power With shore power on, the shore-power AC is con- OFF nected to the AC output and the inverter is turned off. Battery Simultaneously, AC power is applied to the inverter's Internal built-in battery charger, which draws its power from AC input transfer Charger the battery. switch The inverter and battery combination thus operates AC output as an "AC battery," supplying AC power when shore power is not available and recharging the batteries when it is. Figure 8.8 shows the operation of a shore-power generator-inverter combination. Fig. 8.8 Shore-Power Generator-Inverter When shore power is available, the external trans- Switching with Transfer Switches Battery fer switch feeds shore power to both inverter and large- load panel. The inverter's transfer switch shunts the shore power through to the small-load panel and simultaneously charges the battery. Shore power External DC When shore power is not available, the external transfer AC Inverter in transfer switch selects the generator output, which is Generator switch AC out fed to both the inverter and the large-load panel. The inverter's internal transfer switch shunts generator power to the small-load panel and continues to charge Large-load Small-load the battery. panel panel When neither shore power nor generator power is Air cond Stb out available, the inverter stops charging the battery and Water htr Port out Stereo Range comes on to supply the small-load panel. In this mode Spare Spare there is no power at the large-load panel. Transfer Switching 139
Generators Prior to the advent of efficient, low-cost, solid-state tors, the field current is generated through rectifica- inverters, the generator was the only source of AC tion of a portion of the AC output and fed to the rotor power away from the dock. Now, for loads up to about through brushes—just as in the automotive alternator. 2 kW, a combination of a large battery and inverter and Most generators, however, are brushless. An exciter coil a means for charging (such as engine alternator, solar in the stator induces AC current in the rotor field coils, panel, or wind machine) will produce AC power at half which is then rectified by a diode. of the cost of power from the most economical gener- Figure 8.9 shows a simplified brushless alternator- ator. For loads greater than 2,000 watts there is still no type generator. There are two large windings that pro- substitute for a generator. For boats with large power vide the main generator output. These may be in phase budgets a generator-inverter combination is ideal. The or out of phase. If in phase, there will be two 120-volt two types of AC generator are: AC outputs. If out of phase, there will be two 120-volt AC outputs of opposite polarity, which can be com- 1. Alternator-type, in which the output is gener- ated by the stator. bined for 240 volt AC. The small coil to the right pro- 2. Armature-type, in which the output is generated vides excitation for the field coils of the rotor. The small by the rotor. coil to the left provides input to a bridge rectifier, which provides 12 volts DC for charging the generator's start- ing-motor battery. Both main windings and the exciter winding are Alternator-Type Generators provided with multiple taps as shown at A, B, and C in In an alternator-type generator the magnetic field is Figure 8.9. Output voltage varies slightly with rpm and created by magnets and controlling field coils on the load, but the nominal voltage is changed by selecting rotor. Output current is induced in fixed stator coils different taps. Output frequency can be controlled only located around the inside of the case. In some genera- by adjusting engine rpm. Fig. 8.9 Alternator-Type Generator 240VAC 12VDC 120VAC 120VAC Voltage regulator A A B C Auxiliary Main Main Exciter winding winding winding winding STATOR ROTOR Field coil Field coil 140 Inverters and Generators
Armature-Type Generators rent, the stator magnets are designed to retain a degree All generators and alternators rely on the fact that an of permanent magnetism. A few generators solve the electric current is induced in either a moving wire in a same problem by taking the current for the stator magnetic field or a stationary wire in a magnetic field windings directly from the ship's batteries. that is changing in intensity. Generators with a single 120-volt AC output gener- In an armature-type generator, the magnetic field is ally have two brushes, as shown in Figure 8.10. One created by a controlling field current flowing through brush/terminal is hot (black conductor); the other fixed coils that are placed around the stator (station- brush/terminal is neutral (white conductor) and is ary coil). The stator is anchored to the outside case of connected to the case of the generator and to ship's the generator. ground via the green grounding conductor. Note that Output current is induced in multiple coils wound single-voltage European versions produce 240 volts AC on the rotor, which is driven at a constant 3,600 rpm rather than 120 volts AC. (3,000 rpm in 50 Hz European models) by the speed Generators having both 120-volt AC output and governor of the generator's engine. Large-capacity slip 240-volt AC output have either three or four brushes. rings and brushes transfer the large output currents Figure 8.11 shows a four-brush generator. Brushes 2 from the moving rotor to the generator-output termi- and 3 (neutral) are tied together to the case and to nals. The output of the generator is sinusoidal in wave ship's ground. Brushes 1 and 4 are hot. The voltages form. between brush 1 and neutral and between brush 4 and The small DC field current is usually taken from a neutral are both 120 volts AC, but of opposite polarity. rectifier bridge connected across a pair of output ter- The voltage between brushes 1 and 4 is thus 240 volts minals. To get around the chicken-or-egg dilemma of AC. requiring a stator field in order to begin generating cur- Fig. 8.10 Two-Brush Armature Generator Fig. 8.11 Four-Brush Armature Generator Field winding Armature Brush 1 4 2 1 2 3 240 VAC 120 VAC 120 VAC 120 VAC 1 2 1 2 3 4 Armature Field Field Armature Armature Generators 141
Generators Frequency and Voltage Regulation Fig. 8.12 A Simple AC-Frequency Meter As you will see below, the output frequency of a gener- 100K 0.2mF 1N914 ator is the key indicator of its proper operation. For this Hot reason the importance of a frequency meter cannot be 6.2V overstated. Most generators intended for permanent zener 1N914 10K 0–100 µΑ A installation are equiped with frequency meters in their pot. control panels, whether at the generator or in the AC distribution panel. If yours does not have such a meter, Neutral you can easily construct one from a 100-microamp panel meter and a handful of inexpensive components, as shown in Figure 8.12 and in Project 3, Chapter 14. Fig. 8.13 Generator Frequency vs. Load In a pinch you can press an old-fashioned synchro- nous electric clock into service. Such a clock advances 63 in proportion to the frequency of its power supply: 60 minutes for 60 Hertz, 50 minutes for 50 Hertz, etc. Sim- 62 ply plug the clock into an outlet and let it run for an hour (as timed by your watch). At the end of the hour 61 it will read the average frequency in minutes. Hz In both alternator- and armature-type generators, 60 the output is taken from the output windings and thus Frequency, corresponds directly with the rotation of the rotor. Fre- quency is therefore directly proportional to rpm. This 59 is why fixed-drive generators cannot be driven directly by a boat's propulsion system. Hydraulic drives and 58 variable-speed clutches are available for matching gen- erator and propulsion engine, but they are not as pop- 57 ular as dedicated engines. 0 20 40 60 80 100 Engine rpm is controlled by a mechanical gover- % Load nor on the engine.As the engine slows under increasing load, a centrifugal weight acts to open the throttle. Fig. 8.14 Generator Voltage vs. Load Mechanical governors require an rpm deviation in 130 order to effect a throttle adjustment. The more fuel required, the larger the required deviation in rpm. Thus, generator frequency is necessarily affected by the load. Figure 8.13 shows the typical frequency versus 125 load relationship. Output voltage is affected by both engine rpm and Voltage output load. Since rpm is affected by load, we can think 120 of output voltage as being affected by load. Figure 8.14 Output shows a typical 110- to 130-volt AC variation in out- put voltage from no load to full load. Voltages greater than 130 volts AC shorten the lives of resistive compo- 115 nents, such as lamp filaments and heater elements. Low voltages cause motors to draw excessive currents and overheat, or not start at all. 110 0 20 40 60 80 100 % Load 142 Inverters and Generators
Troubleshooting Generators WARNING: The output terminals of a working generator Troubleshooting Guide are protected by neither a fuse, circuit breaker, nor ground fault circuit interrupter. At 120 or 240 volts AC, contact Voltage Erratic with a terminal and a grounded part of the vessel at the STEP 1. Check the brushes for wear. Replace if same time could be lethal. If you are not highly versed in dealing with generators, don't attempt measurements on more than 50% worn. STEP 2. Check slip rings for burning and/or pit- the generator while it is running. As a further precau- tion, disable any remote-start circuitry. ting (requires services of a machine shop). The owner's manuals of high-quality generators Voltage High (over 130 volts) usually contain extensive maintenance and trou- STEP 1. Check the frequency for normal range (57 bleshooting guides for the specific model. If yours doesn't, purchase a copy of the shop manual, which will to 63 Hertz). STEP 2. Adjust the voltage regulator if possible. have the guides. STEP 3. Have the voltage regulator checked. Con- The troubleshooting guide included here is general and not intended to replace a manufacturer's guide. sult the manual for terminal changes. Most generators have sealed bearings, which require Voltage Low (below 110 volts) no lubrication. This does not include the generator engine, which must be maintained to the same degree STEP 1. Check the voltage at the generator termi- as the boat's propulsion engine. Crankcase oil should nals. If OK, the problem is voltage drop in connec- be changed every 100 hours of operation and just prior tors or conductors. to any extended layup. STEP 2. If the voltage is OK initially, then drops, If the boat is in the north and the generator is not check the temperature of the voltage regulator. It removed from the boat, the engine will require win- should be cool enough to touch. terization, as well. If the engine is gasoline-fueled, the STEP 3. Adjust the voltage regulator if possible. spark plugs should be replaced every year. STEP 4. Consult manual for terminal change. If the generator contains brushes, check the brushes Frequency Erratic for excessive wear (more than 50%) and the slip rings for burning and pitting. Replace worn brushes with STEP 1. Check for loads that cycle on and off. exact replacements from the manufacturer and follow STEP 2. If erratic with no load connected, check the the directions for seating the new brushes. engine governor. The troubleshooting guide applies to both arma- Frequency High (over 63 Hertz) ture- and alternator-type generators. You will need to measure output AC volts, AC amps, and frequency. A STEP 1. Adjust the engine governor and clean and proper generator installation should include AC volts, lubricate its linkage. AC amps, and frequency panel meters in the AC dis- STEP 2. Consult the engine manual. tribution panel. For smaller generators use a multime- Frequency Low (below 57 Hertz) ter to measure volts and amps. If you don't have a fre- quency meter, purchase one or build the one in Project STEP 1. Reduce the load. If frequency increases to 3, Chapter 14. normal range, the generator is overloaded. STEP 2. Adjust engine governor and clean and lubricate linkage; consult manual. Troubleshooting Generators 143
9 CHAPTER AC Standards and Practices Black Black White White Green Common green wire Green Dock float Boat Boat ground ground Galvanic current 144 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
A s with Chapter 6, its DC equivalent, this chapter is essentially an amplification of the ABYC stan- dards for AC power aboard boats. We start with sources of AC power: shore power, generators, and inverters, all of which feed the AC main panelboard. Two primary AC safety considerations are ground- ing (including ground faults) and overcurrent protec- tion. Load calculations and ampacity tables allow us to size the overcurrent protection and to select both the approved wire and cable and receptacles for the appli- cation. The probability of moisture, salt, and vibration, as well as the possibility of gasoline vapors, mandate stan- dards for the installation of conductors. As with DC wiring, the issue of galvanic protection and grounding raises the question of what to do with the green wire. The two solutions—isolating diodes and isolation transformers—are incorporated into ABYC-approved shore-power circuits. 145
Shore Power The ABYC standards for AC electrical systems are the inlet must be insulated from a metal hull or any designed to prevent electrical fires and shock. You metal parts connected to the boat's ground. should not assume that familiarity with residential wiring qualifies you to do marine wiring, however. The Cable Wiring standards for boats are more stringent than those for homes for three major reasons: Standards for shore-power cable are more stringent than those for cords you find in building supply outlets. 1. Boats sit in an electrically conductive medium. The cable must be one of the types listed in Table 9.1. 2. Metal parts of boats, including electrical wiring and connections, are subject to corrosion. Table 9.1 Shore-Power Cable 3. Boats are subject to fatiguing vibration and Type Description Temp.Rating impact. SOW Hard-service cord, 60°C, 75°C A boat's source of AC may be shore power, an oil-resistant compound onboard generator, a DC-to-AC inverter, or a combina- STW Hard-service cord, thermoplastic 60°C, 75°C tion. The nature and operation of generators and STOW, Hard-service cord, 60°C, 75°C inverters were covered in Chapter 8. The proper instal- SEOW oil-resistant thermoplastic lation of the three sources is covered here. STOOW Extra-hard-usage cord, 105°C oil-resistant thermoplastic Shore Power Current-carrying conductors (hot and neutral) Sooner or later someone will use the shore-power cable must be sized for the capacity of the shore-power cir- as a dockline, perhaps from grasping for the nearest cuit, as shown in Table 9.2. object while headed for the water, or maybe someone forgot to unplug the power when getting underway. Table 9.2 Ampacity of AC Conductors Plus, plugs and receptacles are subject to rain and spray Conductor Two Conductors 1 Three Conductors 2 from washdown hoses. For these reasons the ABYC Size, AWG Maximum Amps Maximum Amps standards for shore-power cables and inlets are rigor- 14 18 15 ous. 12 25 20 10 30 25 8 40 35 The Boat Connection 6 55 45 4 70 60 The inlet on the boat end (Figure 9.1) must be a male 2 95 80 connector. If in a location subject to rain, splash, or 1 spray, it must be weatherproof, regardless of whether the Not including the green grounding wire, which is considered non- conducting. cable is connected. If the location is subject to submer- 2 For four to six conductors, reduce current rating a further 20%. sion, no matter how brief, the inlet must also be water- tight—again, whether the cord is connected or not. A green grounding wire is required in all shore- If the boat's AC system includes an isolation trans- power cables, but since the grounding wire is consid- former or a galvanic isolator, the metal components of ered normally non-current-carrying, it may be of smaller size than the current-carrying conductors. Fig. 9.1 Shore-Power Boat Connection Commonly, it is one size smaller. The shore end of the cable must have a locking and grounding cap with the proper male (plug) connector that matches the female shore receptacle (see Figure 9.2). The boat end of the cable must have a locking and grounding cap with the proper female (receptacle) con- nector to match the boat's male power inlet. Figure 9.3 shows the boat and shore ends of a 30 A/120 VAC, 1Ø shore-power cable. The weatherproof sleeves slide over the connectors. 146 AC Standards and Practices
Fig. 9.2 Matching AC Plugs and Receptacles (U.S.) Fig. 9.3 30 A/120 VAC Shore-Power Cable 120 Volts 15A, 120V 20A, 120V 20A, 120V Boat end Straight blade Straight blade Locking 2 pole, 3 wire 2 pole, 3 wire 2 pole, 3 wire W W W G G G Receptacle Receptacle Receptacle W W W G G G Plug Plug Plug 30A, 120V 50A, 120V Locking Locking 2 pole, 3 wire 2 pole, 3 wire W G W G Receptacle Receptacle W G G W Plug Plug 240 and 208 Volts 50A, 120/240V 30A, 120/208V 3ØY Locking Locking 3 pole, 4 wire 4 pole, 5 wire Y X G W Y G X W Z Receptacle Receptacle Y X G Y W W X G Z Plug Plug 100A, 120/240V 100A, 120/208V 3ØY Pin and sleeve Pin and sleeve 3 pole, 4 wire 4 pole, 5 wire G W Z X Y G Y W X Receptacle Receptacle G W Z Y X G Y W X Shore end Plug Plug Shore Power 147
Generator and Inverter Sources Transfer Switch nected at the generator, at the inverter, and (not shown) Connections to shore power, onboard generators, and at the shore-end source. inverters must be such that no more than one source A galvanic isolator serves to block stray current in can be connected to a circuit simultaneously. Switching the shore-power grounding wire. Thus, regardless of between power sources must be made with a transfer the source of power, the neutral is grounded only at its switch, which prevents arc-over between the contacts of source. Further, the neutral and grounding conductors the different sources. are always maintained at boat ground, which is critical for the safety of anyone on board. Grounded Neutral Boat AC systems use a grounded neutral, as do residen- Ampacity tial systems. Where the neutral (white conductor) and An onboard generator or inverter must be rated to sup- grounding (green or bare conductor) are connected is ply the entire load, as calculated later, unless the sys- critical. The neutral (white) must be grounded (con- tem is designed to isolate certain loads from connec- nected to the green or bare conductor) only at the tion. power source: an onboard generator or inverter, the sec- In either case, the feed conductors from the gener- ondary of an isolation or polarization transformer, or ator or inverter must be of sufficient ampacity to carry the shore-power receptacle. the maximum rated output. In addition, the generator Figure 9.4 shows a system consisting of shore or inverter output must be protected at its output with power, onboard generator, and inverter. A two-pole an overcurrent device, rated at no more than 120% of transfer switch selects the power source. Note that the the rated output, unless the generator or inverter is self- neutral (white) and grounding (green) wires are con- limiting to the same degree. Fig. 9.4 Typical Use of the Transfer Switch Shore-power cable G W B Main shore-power disconnect To engine negative Galvanic circuit breaker terminal (boat ground) isolator G B + + Auxiliary W W generator Inverter Battery B G – – Shore Inv Gen O Black To branch circuit protective devices White Green 148 AC Standards and Practices
Main Panelboard All AC systems must have a main panelboard, which of polarity indication devices must be at least 25k ohms. may (it usually does) also serve as the AC distribution Figure 9.5 shows a simple polarity-indicating circuit panel. The panelboard must be easily accessible and that satisfies the 25k ohm criterion. A green light indi- either weatherproof or in a location protected from the cates correct polarity (voltage between the hot and weather. neutral conductors). A red light indicates incorrect The panelboard must be clearly and permanently polarity (either neutral or grounding conductor hot). marked with the system voltage and frequency. Two common markings are "120VAC" and "120V-60Hz." If Fig. 9.5 A Simple Polarity-Indicating Circuit (see Project there are either AC motors or an AC generator aboard, 1, Chapter 14) the panelboard should also include an AC voltmeter. It Hot (black) is recommended that the voltmeter display upper and Neutral (white) lower operating voltage limits. The main panelboard should also contain a shore- Ground (green) power polarity indicator that warns of reversed polar- ity in the shore-power connection with either a contin- R1 R1 uous sound or light. A polarity indicator must be N1 installed if: 1. Any of the boat's branch circuits have overcur- N2 N1 rent protection in the ungrounded conductor Green Red only, or 2. Polarity is critical to the operation of any of the Plug-in polarity indicators, no larger than a three- AC devices on the boat. prong adapter, are available at hardware stores for around $5. If your AC panel doesn't have a built-in A polarity indicator is not needed, however, if the polarity indicator, one of these devices can be used to shore power feeds through an isolation transformer, quickly check for damaging reverse polarity when since the transformer acts as a separate source of power establishing a shore-power connection. Such a device on the boat, and its output conductors are permanently does not satisfy the ABYC requirement, however. wired. A permanent waterproof warning placard must be In order to limit current on the normally non- displayed prominently at all shore-power inlets. Figure current-carrying green grounding wire, the impedance 9.6 shows the wording suggested by the ABYC. Fig. 9.6 ABYC Suggested Wording for Shore-Power Connection WARNING To minimize shock and fire hazards: 1. Turn off the boat's shore connection switch before connecting or disconnecting shore cable. 2. Connect shore-power cable at the boat first. 3. If polarity warning indicator is activated, immediately disconnect cable. 4. Disconnect shore-power cable at shore outlet first. 5. Close shore-power inlet cover tightly. DO NOT ALTER SHORE-POWER CABLE CONNECTORS Main Panelboard 149
AC Load Calculations Instructions Motors and Heaters (Lines 8–12) The ABYC suggests a method for determining the min- For Lines 8 through 27, you will need the amps listed imum sizes of AC panelboards, supply conductors, and on the nameplates of each piece of equipment. The AC power sources. The total load may be supplied by: nameplate is usually found on the backside of the equipment. 1. A single shore-power cable of required ampacity. LINE 8. Add and enter the total amps for all fans. 2. Multiple shore-power cables, provided each inlet LINE 9. Total the amps for all air conditioners. If is marked with volts, amps, phase (if 3Ø), and there are two units, enter the larger number. If there the load it serves. are three or more units, multiply the total by 0.75. If 3. One or more onboard generators of continuous the total is less than Line 10, leave Line 9 blank. rating equal to the load. LINE 10. Total the amps for electric, gas, and oil 4. Shore power plus generators and inverters of heaters. If this total is less than the total in the pre- combined capacity equal to the load, provided vious step (before multiplying by 0.75), leave Line the loads connected to each are isolated. 10 blank. Table 9.3 is a form that follows the ABYC-recom- LINE 11. Enter 25% of the nameplate amps for the mended procedure for calculating AC loads. As you largest motor in any of the appliances involved in read the instructions below, you may also find it help- Lines 8 through 10. ful to refer to Table 9.5, the completed example. LINE 12. Enter total of Lines 8 through 11. Lighting and Small Appliances (Lines 1–7) Fixed Appliances (Lines 13–28) Lighting includes all AC-powered lights on the boat. LINES 13–27. For each of the appliances shown, Small appliances are those used in the galley and dining multiply the amps listed on the nameplates by the areas that have power cords and plugs, such as blenders, use factors listed after the appliance name. If the mixers, and toasters. unit is a 240-volt appliance, enter the result in both LINE 1. Add the total square feet of all of the living Columns A and B. areas on the boat, not counting storage and engine LINE 28. Enter the total of Lines 13 through 27, but spaces, and multiply by 2.0. if there are more than three appliances listed in LINE 2. Multiply the number of 20-amp circuits Lines 13 through 27, first multiply Line 28 by 0.6. used for small appliances in the galley and dining areas by 1,500. Free-Standing Range (Lines 29–31) LINE 3. Add Lines 1 and 2. LINE 29. A free-standing range is one that contains LINE 4. Subtract 2,000 from Line 3, and multiply both surface burners and an oven. First, read the by 0.35 (enter 0 if negative). watts listed on the range nameplate. Enter the cor- LINE 5. Add Lines 3 and 4. responding "load watts" from Table 9.4. LINE 6. Divide Line 5 by the system voltage (either LINE 30. Enter the range voltage (from the name- 120 or 240). plate). LINE 7. If your shore-power inlet is 120 VAC, enter LINE 31. Divide Line 29 by Line 30 and enter value Line 6 in Column A. From this point on, use only in both Columns A and B. the left-hand (Column A) lines. If instead you have a 240-volt AC system that splits into two onboard Total AC Load (Line 32) 120 VAC branches, enter half of Line 6 in Columns LINE 32. Total Lines 7, 12, 28, and 31 separately for A and B. From this point on, you will have to enter Columns A and B. The Total AC Load in Amps is values in Columns A and B separately, depending the larger of A and B. on which branch of the 240 circuit the load is on. 150 AC Standards and Practices
Table 9.3 ABYC AC Load Calculation Form Line Loads Column A Column B LIGHTING AND SMALL APPLIANCES 1. Lighting and receptacles: Living area sq.ft. × 2 __________ __________ 2. Small appliances: number of 20-amp circuits × 1,500 __________ __________ 3. Line 1 + Line 2 __________ __________ 4. (Line 3 – 2,000) × 0.35 (Enter 0 if less than 0) __________ __________ 5. Line 3 + Line 4 __________ __________ 6. Line 5/System voltage (either 120 or 240) __________ __________ 7. If 120 VAC, enter Line 6 in Column A; if 240 VAC, enter 50% of Line 6 in both A and B __________ __________ MOTORS AND HEATERS (total nameplate amps) 8. Exhaust and supply fans __________ __________ 9. Air conditioners (If two, enter larger number; if three or more, enter 75% of total; omit if less than Line 10) __________ __________ 10. Heaters (If two, enter larger number) (If figure is less than Line 9, enter 0) __________ __________ 11. 25% of largest motor in Lines 8–10 __________ __________ 12. Total of Lines 8–11 __________ __________ FIXED APPLIANCES (nameplate amps) 13. Disposal × 0.1 __________ __________ 14. Water heater × 1.0 __________ __________ 15. Wall oven × 0.75 __________ __________ 16. Stovetop cooking unit × 0.75 __________ __________ 17. Refrigerator × 1.0 __________ __________ 18. Freezer × 1.0 __________ __________ 19. Ice maker × 0.5 __________ __________ 20. Dishwasher × 0.25 __________ __________ 21. Clothes washer × 0.25 __________ __________ 22. Clothes dryer × 0.25 __________ __________ 23. Trash compactor × 0.1 __________ __________ 24. Air compresser × 0.1 __________ __________ 25. Battery charger × 1.0 __________ __________ 26. Vacuum system × 0.1 __________ __________ 27. Sum of other fixed appliances __________ __________ 28. Total of Lines 13–27; if more than three fixed appliances, × 0.6 __________ __________ FREE-STANDING RANGE 29. Load watts from Table 9.4 __________ __________ 30. Nameplate volts (either 120 or 240) __________ __________ 31. Line 29 divided by Line 30 __________ __________ 32. Sum of Lines 7, 12, 28, and 31; TOTAL is larger of A and B __________ __________ AC Load Calculations 151
AC Load Calculations Example Fixed Appliances (Lines 13–28) Use Table 9.5 to calculate the 120 VAC load for a boat Our fixed appliances include the 12-amp water heater, with 240 square feet of enclosed space (not including 0.7-amp refrigerator, 3.5-amp battery charger, and 1- engine compartment or chain locker), one 20-amp amp air compressor. The first three have a duty factor small appliance circuit, and: of 1.0, so we enter their amps directly. The compressor • 50-watt (0.4 amp) ventilation fan has a duty factor of only 0.10, so we enter 0.10 1.0 × • 1,500-watt (12 amp) water heater amp = 0.1 amp on Line 24A. • 85-watt (0.7 amp) refrigerator • 120-watt (1 amp) air compressor Adding Lines 13 through 27 we get 16.3 amps. Since • 420-watt (3.5 amp) battery charger there are more than three fixed appliances, we multi- ply the sum by the factor 0.60 and enter the result, 9.8, Lighting and Small Appliances (Lines 1–7) on Line 28. The lighting load is 2 240 square feet = 480 watts, × which we enter on Line 1. Total AC Load (Line 32) Adding Line 7 (16.5 amps), Line 12 (0.5 amp), Line 28 The small appliance load for one 20-amp circuit is 1 × (9.8 amps), and Line 31 (0.0 amps), we get 26.8 amps. 1,500 watts = 1,500 watts, which we enter on Line 2. Since our system has only a single phase and, thus, a single branch, our total AC load for sizing the main The sum of lines 1 and 2 is 1,980 watts, which is less AC panelboard is 26.8 amps. Rounding up, we'll call it than 2,000 watts, so we enter 1,980 watts on Line 3 and 30 amps. 0 watts on Line 4. Table 9.4 Load Watts for Free-Standing Ranges (For use in Table 9.5, Line 29) We divide 1,980 watts by 120 volts to get 16.5 amps. Since 120-volt shore power only has one branch, we Nameplate Watts Load Watts enter the 16.5 amps on Line 7A. 0–10,000 80% 10,001–12,500 8,000 Motors and Heaters (Lines 8–12) 12,501–13,500 8,400 We have only one motor—the 0.4-amp fan, which we 13,501–14,500 8,800 enter on Line 8. Adding 25%, we get 0.5 amp, which 14,501–15,500 9,200 we enter on Line 12A. 15,501–16,500 9,600 152 AC Standards and Practices
Table 9.5 ABYC AC Load Calculation Form (filled-out example) Line Loads Column A Column B LIGHTING AND SMALL APPLIANCES 480 1. Lighting and receptacles: Living area sq.ft. × 2 __________ __________ 1500 2. Small appliances: number of 20-amp circuits × 1,500 __________ __________ 1980 3. Line 1 + Line 2 __________ __________ 0 4. (Line 3 – 2,000) × 0.35 (Enter 0 if less than 0) __________ __________ 1980 5. Line 3 + Line 4 __________ __________ 16.5 6. Line 5/System voltage (either 120 or 240) __________ __________ 7. If 120 VAC, enter Line 6 in Column A; if 240 VAC, enter 50% of Line 6 in both 16.5 A and B __________ __________ MOTORS AND HEATERS (total nameplate amps) 0.4 8. Exhaust and supply fans __________ __________ 9. Air conditioners (If two, enter larger number; if three or more, enter 75% of total; omit if less than Line 10) __________ 10. Heaters (If two, enter larger number) (If figure is less than Line 9, enter 0) __________ __________ 0.1 11. 25% of largest motor in Lines 8–10 __________ __________ 0.5 12. Total of Lines 8–11 __________ __________ FIXED APPLIANCES (nameplate amps) 13. Disposal × 0.1 __________ __________ 12.0 14. Water heater × 1.0 __________ __________ 15. Wall oven × 0.75 __________ __________ 16. Stovetop cooking unit × 0.75 __________ __________ 0.7 17. Refrigerator × 1.0 __________ __________ 18. Freezer × 1.0 __________ __________ 19. Ice maker × 0.5 __________ __________ 20. Dishwasher × 0.25 __________ __________ 21. Clothes washer × 0.25 __________ __________ 22. Clothes dryer × 0.25 __________ __________ 23. Trash compactor × 0.1 __________ __________ 0.1 24. Air compresser × 0.1 __________ __________ 3.5 25. Battery charger × 1.0 __________ __________ 26. Vacuum system × 0.1 __________ __________ 27. Sum of other fixed appliances __________ __________ 9.8 28. Total of Lines 13–27; if more than three fixed appliances, × 0.6 __________ __________ FREE-STANDING RANGE 29. Load watts from Table 9.4 __________ __________ 30. Nameplate volts (either 120 or 240) __________ __________ 31. Line 29 divided by Line 30 __________ __________ 26.8 32. Sum of Lines 7, 12, 28, and 31; TOTAL is larger of A and B __________ __________ AC Load Calculations 153
Overcurrent Protection Amp Ratings Branch-Circuit Protection All fuses and circuit breakers must be rated at or less Branch circuit breakers and fuses should be rated at or than the ampacity of the conductors of the circuit less than the ampacity of the smallest current-carrying being protected. Exception: if no breaker of correct conductor in the circuit. If there is no matching breaker ampacity is available, the breaker rating may exceed the or fuse rating, the next larger may be used, provided it ampacity of the conductors by up to 150%. doesn't exceed 150% of conductor ampacity. For boats wired with 120 VAC, 1Ø, both current- Circuit Breaker Specifications carrying conductors (hot and neutral) must be pro- tected by a pair of simultaneous-trip circuit breakers. All circuit breakers must meet the standards of either Exception: the ungrounded conductor alone may be UL 489 or UL 1077, be of the manual-reset type (except protected, provided: if integral to a piece of equipment), and be of the trip- free type (cannot be held closed while the overcurrent 1. The entire system is polarized, including lighting condition persists). fixtures, and there is a polarity indicator between the shore-power inlet and the main circuit breakers, or Main Supply Protection 2. The neutral and grounding conductors are con- Specifications for overcurrent protection of the main nected at the secondary of an isolation or polar- supply conductors include: ization transformer. 1. The shore-power feeder conductors should be All motors must be protected by either an overcur- protected by multi-pole breakers. In a 120 VAC rent or a thermal device unless they do not overheat, system the breakers should protect both the even when the motor is stalled (rotor locked). ungrounded (black) and the neutral (white) conductors. In any system containing either 240 Fuse or Breaker Location VAC or 208 VAC, there should be breakers in all The fuses or circuit breakers for a circuit must be of the ungrounded conductors. Note that the placed at its power source, except: green grounding conductor is never interrupted. 2. If there are isolation or polarization transform- 1. If impractical, within 7 inches of the source. ers in the shore-power feed, primaries should be 2. If impractical within 7 inches, then within 40 protected by a circuit breaker that opens both inches, provided the conductor is contained in a primary feeders simultaneously and that is rated protective sheath or enclosure. at no more than 125% of the primary rating. If the secondary provides 120/240 VAC, it also Ground Fault Protection should be protected by a circuit breaker that opens both secondary feeders simultaneously GFCI Breakers and that is rated at no more than 125% of the GFCI breakers must meet the same requirements as cir- rated secondary current of the transformer. cuit breakers of the same rating. They may be used to 3. The maximum unprotected conductor length protect individual branch circuits, or they may protect a from boat inlet connector to circuit breaker group of associated circuits. Like other circuit breakers, must not exceed 10 feet. If the length is greater they are permitted to interrupt only the ungrounded than 10 feet, add additional slow-blow fuses or conductor, provided the system is polarized and has a breakers within 10 feet of the inlet. If additional polarity indicator, the system has an isolation or polar- fuses or circuit breakers are provided, they must ization transformer, or the system is 120/240 VAC. be larger, but not more than 125% larger, than the main shore-power disconnect breaker. GFCI Receptacles 4. The maximum unprotected conductor length GFCI receptacle devices must be two-pole and meet from an AC generator must be less than 7 inches. all of the requirements of standards UL 943 and UL However, up to 40 inches is allowed if the con- 498. They may protect either a single receptacle or mul- ductor is protected by a sheath or enclosure. tiple receptacles in the same circuit. 154 AC Standards and Practices
Approved Wire and Cable No conductor may be smaller than 16 AWG, except 18 Table 9.8 Minimum AC Conductor Stranding AWG inside panelboards and equipment enclosures, Conductor Minimum Minimum Minimum Strands serving DC electronics at less than 1 amp, as less than Gauge CM for AWG CM for SAE Type II 1 Type III 2 7-inch panelboard pigtails, and extending less than 30 18 1,6201,537 16 – inches outside a sheathed bundle. The temperature rat- 16 2,5802,336 19 26 ings of all conductors and flexible cords should be at 14 4,1103,702 19 41 least 140°F (60°C), except 167°F (75°C) in engine 12 6,5305,833 19 65 spaces. Individual conductor insulations must be rated 10 10,380 9,343 19 105 at 600 volts minimum. Flexible cords may be rated at a 8 16,51014,810 19 168 minimum of 300 volts. 6 26,24025,910 37 266 Conductors must be one of the types listed in Table 4 41,74037,360 49 420 9.6. Flexible cords must be one of the types listed in 2 66,36062,450 127665 Table 9.7. Both conductors and flexible cords must also 1 83,69077,790 127836 0 be of the stranding as shown in Table 9.8. 2/0 105,60098,980 1271,064 127 1,323 133,100125,100 The ABYC-recommended color code for AC wiring 3/0 167,800158,600 259 1,666 is shown in Table 9.9. 4/0 211,600205,500 418 2,107 1 Conductors with at least Type II stranding to be used for general- purpose boat wiring. Table 9.6 Acceptable Conductor Types for AC Wiring 2 Conductors with Type III stranding to be used where frequent flex- ing is expected. Damp Oil Extra-Hard Hard Type Location Resistant Usage Usage SE, SEW X X Table 9.9 Color Code for AC Wiring SEO, SEOW X X X Conductor Colors (Preferred First) SJ, SJW X X SJE, SJEW X X Ungrounded Black or Brown SJEO, SJEOW X X X Grounded Neutral White or Light Blue SJO, SJOW X X X Grounding Green, Green with Yellow Stripe SJOO, SJOOW X X X SJT, SJTW X X Additional Ungrounded Red, Blue, Orange SJTO, SJTOW X X X Black with Red Stripe SJTOO, SJTOOW X X X Black with Blue Stripe SO, SOW X X X Black with Orange Stripe ST, STW X X STO, STOW X X X STOO, STOOW X X X Ampacity The minimum ampacities of AC current-carrying con- Table 9.7 Acceptable Flexible Cord Types for AC Wiring ductors are shown in Tables 9.10 through 9.15 on the following pages. Type Description SO, SOW Hard-Service Cord, Oil Resistant ST, STW Hard-Service Cord, Thermoplastic STO, STOW Hard-Service Cord, Oil Resistant, Thermoplastic SEO, SEOW Hard-Service Cord, Oil Resistant, Thermoplastic SJO, SJOW, Junior Hard-Service Cord, Oil Resistant SJTW SJT, SJTW Hard-Service Cord, Thermoplastic SJTO, SJTOW Hard-Service Cord, Oil Resistant, Thermoplastic Approved Wire and Cable 155
Ampacity Tables Table 9.10 Allowable Amperage of No More Than Two Bundled Conductors (Adapted from ABYC Standard E-11, Table VII-A) Temperature Rating of Conductor Insulation Size 60°C 75°C 80°C 90°C 105°C 125°C 200°C AWG 140°F 167°F 176°F 194°F 221°F 257°F 392°F Outside Engine Spaces 18 10 10 15 20 20 25 25 16 15 15 20 25 25 30 35 14 20 20 25 30 35 40 45 12 25 25 35 40 45 50 55 10 40 40 50 55 60 70 70 8 55 65 70 70 80 90 100 6 80 95 100 100 120 125 135 4 105 125 130 135 160 170 180 2 140 170 175 180 210 225 240 1 165 195 210 210 245 265 280 1/0 195 230 245 245 285 305 325 2/0 225 265 285 285 330 355 370 3/0 260 310 330 330 385 410 430 4/0 300 360 385 385 445 475 510 Inside Engine Spaces 18 5 7 11 16 17 22 25 16 8 11 15 20 21 26 35 14 11 15 19 24 29 35 45 12 14 18 27 32 38 44 55 10 23 30 39 45 51 62 70 8 31 48 54 57 68 80 100 6 46 71 78 82 102 111 135 4 60 93 101 110 136 151 180 2 81 127 136 147 178 200 240 1 95 146 163 172 208 235 280 1/0 113 172 191 200 242 271 325 2/0 130 198 222 233 280 316 370 3/0 150 232 257 270 327 364 430 4/0 174 270 300 315 378 422 510 156 AC Standards and Practices
Table 9.11 Allowable Amperage of Three Bundled Conductors (Adapted from ABYC Standard E-11, Table VII-B) Temperature Rating of Conductor Insulation Size 60°C 75°C 80°C 90°C 105°C 125°C 200°C AWG 140°F 167°F 176°F 194°F 221°F 257°F 392°F Outside Engine Spaces 18 7 7 10 14 14 17 17 16 10 10 14 17 17 21 24 14 14 14 17 21 24 28 31 12 17 17 24 28 31 35 38 10 28 28 35 38 42 49 49 8 38 45 49 49 56 63 70 6 56 66 70 70 84 87 94 4 73 87 91 94 112 119 126 2 98 119 122 126 147 157 168 1 115 136 147 147 171 185 196 1/0 136 161 171 171 199 213 227 2/0 157 185 199 199 231 248 259 3/0 182 217 231 231 269 287 301 4/0 210 252 269 269 311 332 357 Inside Engine Spaces 18 4 5 8 11 11 15 17 16 6 7 10 14 14 18 24 14 8 10 13 17 20 24 31 12 10 13 19 23 26 31 38 10 16 21 27 31 35 43 49 8 22 34 38 40 47 56 70 6 32 49 54 57 71 77 94 4 42 65 71 77 95 105 126 2 56 89 95 103 125 140 168 1 67 102 114 120 145 165 196 1/0 79 120 133 140 169 190 227 2/0 91 139 155 163 196 221 259 3/0 105 162 180 189 229 255 301 4/0 121 189 210 221 264 295 357 Ampacity Tables 157
Ampacity Tables Table 9.12 Allowable Amperage of Four to Six Bundled Conductors (Adapted from ABYC Standard E-11, Table VII-C) Temperature Rating of Conductor Insulation Size 60°C 75°C 80°C 90°C 105°C 125°C 200°C AWG 140°F 167°F 176°F 194°F 221°F 257°F 392°F Outside Engine Spaces 18 6 6 9 12 12 15 15 16 9 9 12 15 15 18 21 14 12 12 15 18 21 24 27 12 15 15 21 24 27 30 33 10 24 24 30 33 36 42 42 8 33 39 42 42 48 54 60 6 48 57 60 60 72 75 81 4 63 75 78 81 96 102 108 2 84 102 105 108 126 135 144 1 99 117 126 126 147 159 168 1/0 117 138 147 147 171 183 195 2/0 135 159 171 171 198 213 222 3/0 156 186 198 198 231 246 258 4/0 180 216 231 231 267 285 306 Inside Engine Spaces 18 3 4 7 9 10 13 15 16 5 6 9 12 12 16 21 14 7 9 11 14 17 21 27 12 8 11 16 19 23 26 33 10 13 18 23 27 30 37 42 8 19 29 32 34 40 48 60 6 27 42 46 49 61 66 81 4 36 56 60 66 81 90 108 2 48 76 81 88 107 120 144 1 57 87 98 103 125 141 168 1/0 67 103 114 120 145 162 195 2/0 78 119 133 140 168 189 222 3/0 90 139 154 162 196 218 258 4/0 104 162 180 189 227 253 306 158 AC Standards and Practices
Table 9.13 Allowable Amperage of Seven to 24 Bundled Conductors (Adapted from ABYC Standard E-11, Table VII-D) Temperature Rating of Conductor Insulation Size 60°C 75°C 80°C 90°C 105°C 125°C 200°C AWG 140°F 167°F 176°F 194°F 221°F 257°F 392°F Outside Engine Spaces 18 5 5 7 10 10 12 12 16 7 7 10 12 12 15 17 14 10 10 12 15 17 20 22 12 12 12 17 20 22 25 27 10 20 20 25 27 30 35 35 8 27 32 35 35 40 45 50 6 40 47 50 50 60 62 67 4 52 62 65 67 80 85 90 2 70 85 87 90 105 112 120 1 82 97 105 105 122 132 140 1/0 97 115 122 122 142 152 162 2/0 112 132 142 142 165 177 185 3/0 130 155 165 165 192 205 215 4/0 150 180 192 192 222 237 255 Inside Engine Spaces 18 2 3 5 8 8 11 12 16 4 5 7 10 10 13 17 14 5 7 9 12 14 17 22 12 7 9 13 16 19 22 27 10 11 15 19 22 25 31 35 8 16 24 27 28 34 40 50 6 23 35 39 41 51 55 67 4 30 46 50 55 68 75 90 2 40 63 68 73 89 100 120 1 47 73 81 86 104 117 140 1/0 56 86 95 100 121 135 162 2/0 65 99 111 116 140 158 185 3/0 75 116 128 135 163 182 215 4/0 87 135 150 157 189 211 255 Ampacity Tables 159
Ampacity Tables Table 9.14 Allowable Amperage of 25 or More Bundled Conductors (Adapted from ABYC Standard E-11, Table VII-E) Temperature Rating of Conductor Insulation Size 60°C 75°C 80°C 90°C 105°C 125°C 200°C AWG 140°F 167°F 176°F 194°F 221°F 257°F 392°F Outside Engine Spaces 18 4 4 6 8 8 10 10 16 6 6 8 10 10 12 14 14 8 8 10 12 14 16 18 12 10 10 14 16 18 20 22 10 16 16 20 22 24 28 28 8 22 26 28 28 32 36 40 6 32 38 40 40 48 50 54 4 42 50 52 54 64 68 72 2 56 68 70 72 84 90 96 1 66 78 84 84 98 106 112 1/0 78 92 98 98 114 122 130 2/0 90 106 114 114 132 142 148 3/0 104 124 132 132 154 164 172 4/0 120 144 154 151 178 190 204 Inside Engine Spaces 18 2 3 4 6 6 8 10 16 3 4 6 8 8 10 14 14 4 6 7 9 11 14 18 12 5 7 10 13 15 17 22 10 9 12 15 18 20 24 28 8 12 19 21 23 27 32 40 6 18 28 31 32 40 44 54 4 24 37 40 44 54 60 72 2 32 51 54 59 71 80 96 1 38 58 65 68 83 94 112 1/0 45 69 76 80 96 108 130 2/0 52 79 88 93 112 126 148 3/0 60 93 103 108 130 146 172 4/0 69 108 120 126 151 169 204 160 AC Standards and Practices
Table 9.15 Allowable Amperage of Flexible Cords 1,2 (Adapted from ABYC Standard E-11, Table XIII) Outside Engine Space Inside Engine Space Size, Nominal CM 30°C Ambient 50°C Ambient AWG Area Three Conductors Two Conductors Three Conductors Two Conductors 16 2,580 10 13 6 8 14 4,110 15 18 9 11 12 6,530 20 25 12 15 10 10,380 25 30 15 20 8 16,510 35 40 20 25 6 26,240 45 55 30 35 4 41,740 60 70 35 40 2 66,360 80 95 50 55 1 Current ratings are for flexible cords containing no more than three conductors. For four to six conductors, reduce ampacity to 80%. 2 Shore-power cables rated at 86°F (30°C). Ampacity Tables 161
Conductor Installation Note that the conductor specifications and wiring tech- Fig. 9.7 ABYC Approved and Disapproved Marine Connectors niques for DC and AC systems are nearly identical. Some of the illustrations used in Chapter 6 are repeated here to save the reader from having to flip back and forth. Splice Butt 3-Way Wire nut Connections Fabrication and installation of wiring connections Friction should not damage the conductors. Special tools (see Blade Bullet or snap Figure 6.10 and discussion in Chapter 6) are available for making approved crimp-on connections. All connection components (conductors, terminals, Terminals studs, washers, and nuts) should be galvanically com- Locking Flanged Plain patible and corrosion resistant. Specifically, aluminum Ring spade spade spade and unplated steel are not appropriate for studs, nuts, and washers. Set Screw Marine connectors also differ from the more com- mon electronic-type connectors in that they must Indirect-bearing Direct-bearing withstand vibration and tensile stresses. Figure 9.7 shows the types of connectors approved for marine use, along with several types specifically disapproved. Table 9.16 Tensile Test Values for Connections Friction connectors (the blade and bullet variety in (Adapted from ABYC Standard E-11, Table XVI) Figure 9.7) are allowed, provided they resist a 6-pound Conductor Force, Conductor Force, pull. The other approved connectors must resist the Size, AWG lb. Size, AWG lb. pulls shown in Table 9.16 for at least 1 minute. 18 10 4 70 Although not specified in the ABYC standard, pre- 16 15 3 80 tinned conductors are preferred in marine use. The rea- 14 30 2 90 son will be apparent when you attempt to repair a con- 12 35 1 100 ductor that has been on a boat for a few years. Chances 10 40 0 125 are, if it is untinned, it will be corroded far up into the 8 45 2/0150 insulating sleeve, due to capillary wicking of moisture 6 50 3/0175 into the stranded conductor. Soldering corroded cop- 5 60 4/0225 per wire is ineffective and definitely not recommended. Although solder can make a strong connection, the ABYC states that solder must not be the sole means of mechanical connection in any circuit. One reason is Fig. 9.8 Adhesive-Lined, Heat-Shrink Tubing that the solder may melt if the terminal overheats, due to either an overcurrent condition or high resistance STEP 1: Strip insulation from wire in the connection. Without any other means of attach- ment, a melted solder connection may separate. If you STEP 2: Slip heat-shrink tubing over wire wish to use solder (and many professionals do), first crimp the connector to the conductor, then flow sol- STEP 3: Insert wire into terminal der into the crimped joint. As an altemative to solder, adhesive-lined, heat- shrink tubing is available. It seals out moisture, STEP 4: Crimp barrel of terminal mechanically strengthens the connection, and electri- cally insulates the terminal shank at the same time. Fig- ure 9.8 shows how to make a terminal connection using STEP 5: Position heat-shrink and heat adhesive-lined, heat-shrink tubing. 162 AC Standards and Practices
Conductor Protection Conductor Routing Exposed conductors must be protected by conduit, Route conductors well above the bilge or any other area self-draining loom, tape, raceway, or equivalent means. where water might accumulate. If routing through such Loom materials must be self-extinguishing. an area cannot be avoided, both the conductors and the Except for battery cables up to 36 inches in length connections should be watertight. and outboard engine cables, conductors must be either Conductors should also be kept clear of exhaust supported continuously or secured every 18 inches pipes and other heat sources. Minimum clearances, maximum with clamps or straps. except for engine wiring and exhaust-temperature sen- Nonmetallic clamps are allowed except over an sor wiring, should be 2 inches for wet exhausts and 4 engine, shaft, machinery, or passageway, where clamp inches for dry exhausts, unless equivalent heat barriers failure could result in danger. Clamp materials must are provided. also be resistant to oil, gasoline, and water. Conductors should also be kept clear of sources of Metal clamps must have smooth, rounded edges, chafing such as engine shafts, steering cable and link- and the cable must be protected from the metal by tape ages, steering gears, and engine controls. or other wrapping to protect the conductors. If AC and DC conductors are run together, the AC Conductors should be clamped close to their con- conductors must be sheathed or bundled separately nections to remove strain from the connections. from the DC conductors. Receptacles Fig. 9.9 Polarity Provisions in AC Receptacles Maintaining Polarity Neutral (white AC receptacles (Figure 9.9) must be of the grounding wire/silver type with one terminal connected to the green ground- screws) Hot (black or red wire and ing wire. To prevent polarity reversal all plugs and dark screws) receptacles must match and must not be interchange- able with plugs and receptacles of the DC system. Ter- minals must be identified either by letter or by using the color scheme shown in Table 9.17: Table 9.17 AC Wiring Color Code Conductor Wire Color Terminal Color Ground Ungrounded Black, Red Dark (Copper/Brass) (green wire/ Grounded White Light (Silver) green screw) Grounding Green Tinted Green Fig. 9.10 Receptacle Placement in Galleys Location Galley receptacles should be placed so that appliance cords do not cross a stove, sink, or traffic area, as shown Electric in Figure 9.10. Range appliance Receptacles that are located in the head, galley, machine spaces, or above deck should be protected by a Type-A (trip-on fault current of 5 milliamps [0.005 amp]) GFCI. Receptacles normally should be installed in loca- tions that are protected from weather, spray, and flood- ing. If not, they should be protected when not in use Traffic Sink area by a spring-loaded cover. Receptacles subject to sub- mersion must be watertight. Conductor Installation 163
The Green Wire The green wire in AC circuits provides a life-saving Fig. 9.11 What the Green Wire Protects Against return path for stray electric currents. Figure 9.11 illus- trates the danger the green wire is designed to protect against. The engine, through the transmission, shaft, and water surrounding the boat, is at earth potential. In the illustration one of the hot conductors of a piece of Engine electrical equipment (a water heater) has short- AC (ground) water circuited to its metal case. With one hand on the metal heater engine and the other on the water heater jacket, the person in the illustration serves as a return-to-ground path for the AC current. Were there a green grounding wire connected to the heater jacket and to the engine, it would provide a very-low-resistance return path for the return current and hold the case and engine at the same potential. With no driving potential difference, there would be no reason for electrical current to flow through the person. Boaters familiar with residential wiring often assume that a boat is just like a house. On that assump- tion, they connect the neutral (white) and grounding (green) shore-power conductors at the boat's AC panel. grounding conductor, and—via the boat's grounded Figure 9.12 shows what can happen in such a case. underwater metal—the seawater. As always, all of the current in the hot (black) conduc- If resistance or a break develops in the white and tor somehow finds its way back to the shore-power green conductors, much of the return current could ground. In a properly wired system, the sole return be through the water, exposing a person in the water path would be the neutral (white) conductor. In the near the boat to great danger. system shown, however, the return current flows Principle: Connect the green and the white conductors through three paths: the neutral conductor, the green at the source, be it shore power, generator, or inverter. Fig. 9.12 Mistake #1: Connecting White (Neutral) and Green (Grounding) Conductors on a Boat Black White Short Green to case Motor Boat ground Parallel path for leakage current 164 AC Standards and Practices
Figure 9.13 shows a second mistake. This time the wire will carry current. If there is, however, resistance in white and green wires are properly separated on the the green wire and its connections, the equipment case boat, but, intending to prevent stray-current corrosion may still be above ground potential. A person contact- of the boat's underwater hardware, the misguided ing both the equipment case and a piece of metal owner has cut the green wire to the boat's ground underwater hardware may be shocked (literally) to find (engine and metallic underwater hardware). If a short that he is a parallel return path through the water. develops in a piece of electrical equipment, the green Principle: Connect the green wire to the boat's ground. Fig. 9.13 Mistake #2: Not Connecting the Green Grounding Conductor to Boat Ground Black White Short Green to case Leakage Motor Voltage Parallel path for leakage current We have found that the green and white wires must to each other through the common shore-power con- not be connected on a boat, but that the green wire nection. must be connected to the boat's ground. Unfortunately, We have now created a galvanic cell: one boat is the we still may experience a problem.We may have unwit- anode and the other boat is the cathode. Even were the tingly created a galvanic cell, which, as we saw in Chap- underwater metals of the two boats of identical com- ter 5, leads to corrosion of underwater metals. position, they could suffer from impressed-current cor- Figure 9.14 shows two boats in a marina on shore rosion were there a voltage field in the water. power. The green wires are properly connected to their Woe is us; is there ANY safe solution which doesn't respective boat grounds, but they are also connected cause corrosion? Actually, there are two. Fig. 9.14 Galvanic Cell Created by Marina Common Ground Black Black White White Green Common green wire Green Dock float Boat Boat ground ground Galvanic current The Green Wire 165
The Green Wire Solution 1: The Galvanic Isolator Solution 2: The Isolation Transformer A galvanic isolator, placed on the ship's green ground- If we had a source of electricity that acted like an ing wire immediately after the shore-power connector, onboard generator, there would be no need for a green blocks DC current. Figure 9.15 shows how it works. At wire to run back to the shore-power ground, and we top is a simple pair of parallel and reversed diodes. could break the galvanic connection to other marina- Diodes pass current in the direction of the arrow but bound boats. An isolation transformer is the answer, block current in the opposite direction. In the forward regenerating onboard power without direct electrical direction a small voltage drop (0.6 volt for a silicon connection to shore power. diode) occurs. Thus the pair of diodes will block cur- Figure 9.16 shows an isolation transformer. To meet rent until the voltage reaches 0.6 volt in both direc- ABYC requirements, isolation transformers must be tions. tested and labeled by an independent laboratory. Adding diodes in series doubles the voltage rating. The primary coil is connected to the hot and neu- Parallel and reversed diode pairs will thus block current tral shore-power conductors. The secondary coil is until the voltage reaches 1.2 volts in either direction. connected to the hot and neutral ship's-power conduc- Finally, a nonpolarized capacitor allows AC current tors. to pass, while still blocking DC currents up to ±1.2 A metal shield, electrically isolated from all other volts. parts of the transformer, is placed between the primary and secondary coils, and a lead is brought out from the ABYC Galvanic Isolator Recommendations shield. The shield must withstand a voltage of 4,000 According to the ABYC, a galvanic isolator should: volts AC, 60 Hz, for 1 minute, applied between the • be tested by an independent testing laboratory shield and other components such as windings, core, • have a current rating not less than that of the main and outside enclosure. shore-power disconnect circuit breaker The transformer case must be metal and have a • not introduce a voltage drop greater than 2.5 volts grounding terminal. at 100% of the shore-power cable ampacity rating The ship's neutral (white) and grounding (green) • not pass less than 0.030 ampere at DC voltages of conductors are connected at the transformer output, 1.2 volts in either direction since the transformer secondary is a new source of elec- • not pass less than 0.030 ampere at DC voltages of tricity. As you will see on the following pages, connec- 0.5 volt in either direction with 3.0 amperes RMS tions between shield, conductor, transformer case, AC current superimposed shore-power ground, and ship's ground vary with the In addition the galvanic isolator should provide transformer. Follow the manufacturer's directions. audible or visible status monitoring indicating: • shorted or open diode • failure to block galvanic current at 1.1 volts DC Fig. 9.16 Isolation Transformer • continuity of the shore grounding circuit • operational status of the monitoring device Shore side Ship side Hot Hot Fig. 9.15 Galvanic Isolators Single Diodes Blocks ± 0.6 VDC Block 0.6 VDC Neutral Neutral Blocks ± 1.2 VDC Double Diodes & Block 1.2 VDC Grounding Capacitor Grounding Passes AC Passes 120 VAC Shield— insulated from Metal case case and core 166 AC Standards and Practices
Approved Shore-Power Circuits The following pages contain a variety of shore-power cuit incorporates galvanic protection in the form of circuits, adapted from ABYC Standard E-11. They either a galvanic isolator or an isolating transformer. range from the simplest and most common small-boat, For ease in finding the appropriate circuit for your 120-volt AC, 30-amp circuit to the heavy-duty 120/240 application, here is a guide: VAC systems found on large power yachts. Each cir- Figure Volts Phases Galvanic Protection ABYC Reference 9.17 120 1 Galvanicisolator E-126.96.36.199.1 9.18 120 1 Galvanic isolator and generator E-22.214.171.124.1 9.19 120 1 Galvanic isolator and polarity indicator E-18.104.22.168.1 9.20 120/240 1 Galvanic isolator and generator E-220.127.116.11.2 9.21 240 1 Polarization transformer and generator E-18.104.22.168 9.22 120 1 Isolationtransformer E-18.104.22.168 9.23 120 1 Isolationtransformer E-126.96.36.199 9.24 120 1 Isolation transformer and GFCI E-18.104.22.168 9.25 240 1 Isolationtransformer E-188.8.131.52 9.26 240 1 Isolationtransformer E-22.214.171.124 9.27 240 1 Isolation transformer and GFCI E-126.96.36.199 9.28 120 1 Polarization transformer and galvanic isolator E-126.96.36.199 9.29 240 1 Isolationtransformer E-220.127.116.11 Approved Shore-Power Circuits 167
Approved Shore-Power Circuits Fig. 9.17 Single-Phase, 120-Volt System with Shore-Grounded Neutral and Grounding Conductors Ungrounded Grounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Galvanic isolator (optional) Main shore-power disconnect breaker To Engine Negative terminal or its bus Ungrounded Grounded Grounding Breaker (typical) 120 VAC grounding 168 AC Standards and Practices
Fig. 9.18 Single-Phase, 120-Volt System with Shore-Grounded Neutral and Grounding Conductors Ungrounded Grounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Galvanic isolator (optional) Main shore-power 120 VAC disconnect breaker generator Transfer switch GEN–OFF–SHORE To Engine Negative terminal or its bus Ungrounded Grounded Grounding Breaker (typical) 120 VAC grounding Approved Shore-Power Circuits 169
Approved Shore-Power Circuits Fig. 9.19 Single-Phase, 120-Volt System with Shore-Grounded Neutral and Grounding Conductors Ungrounded Grounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Galvanic isolator (optional) Polarity indicator Main shore-power disconnect breaker To Engine Negative terminal or its bus Ungrounded Grounded Grounding Breaker (typical) Breaker (typical) 120 VAC 120 VAC device grounding 170 AC Standards and Practices
Fig. 9.20 Single-Phase, 120/240-Volt System with Shore-Grounded Neutral and Grounding Conductors Ungrounded Grounded Ungrounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Galvanic isolator (optional) Main shore-power 120/240 VAC disconnect breaker generator Transfer switch GEN–OFF–SHORE To Engine Negative terminal or its bus Ungrounded Grounded Ungrounded Grounding Double Branch Branch circuit breaker circuit breaker circuit breaker 240 VAC 120 VAC 120 VAC device grounding device receptacle Approved Shore-Power Circuits 171
Approved Shore-Power Circuits Fig. 9.21 Polarization Transformer System with Single-Phase, 240-Volt Input, 120/240-Volt Output, and Generator Ungrounded Grounded Ungrounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Galvanic isolator (optional) Main shore-power disconnect breaker Encapsulated single-phase 1:1 polarization transformer with metal case To Engine Negative terminal or its bus 120/240 VAC Transformer secondary generator overcurrent protection Transfer switch GEN–OFF–SHORE Ungrounded Grounded Ungrounded Grounding Double Branch circuit breaker circuit breaker 240 VAC 120 VAC 120 VAC device grounding device receptacle 172 AC Standards and Practices
Fig. 9.22 Isolation Transformer System with Single-Phase, 120-Volt Input and 120-Volt Output Ungrounded Grounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Main shore-power disconnect breaker Transformer case ground and shield connection Encapsulated single-phase 1:1 isolation transformer iinsulated from boat by a ventilated non-conductive enclosure Transformer shield Transformer enclosure To Engine Negative terminal or its bus Ungrounded Grounded Grounding Branch circuit breaker 120 VAC 120 VAC grounding device receptacle Approved Shore-Power Circuits 173
Approved Shore-Power Circuits Fig. 9.23 Isolation Transformer System with Single-Phase, 120-Volt Input and 120-Volt Output Ungrounded Grounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Main shore-power disconnect breaker Transformer shield (insulated from case and core) Encapsulated single-phase 1:1 isolation transformer with metal case Transformer case ground connection Transformer case To Engine Negative terminal or its bus Ungrounded Grounded Grounding Branch circuit breaker Branch circuit breaker 120 VAC 120 VAC grounding device receptacle 174 AC Standards and Practices
Fig. 9.24 Isolation Transformer System with Single-Phase, 120-Volt Input and 120-Volt Output with Ground Fault Protection Ungrounded Grounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Main shore-power disconnect circuit breaker with GFP Transformer shield Encapsulated single-phase 1:1 isolation transformer with metal case Transformer case ground and shield connection Transformer case To Engine Negative terminal or its bus Ungrounded Grounded Grounding Branch circuit breaker Branch circuit breaker 120 VAC 120 VAC device grounding receptacle Approved Shore-Power Circuits 175
Approved Shore-Power Circuits Fig. 9.25 Isolation Transformer System with Single-Phase, 240-Volt Input and 120/240-Volt Output Ungrounded Grounded Ungrounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Main shore-power disconnect breaker Metal transformer case ground and shield connection Encapsulated single-phase 1:1 isolation Transformer shield transformer insulated from boat by a ventilated nonconductive enclosure Transformer secondary overcurrent protection To Engine Negative terminal or its bus Ungrounded Grounded Ungrounded Grounding Double Branch circuit breaker circuit breaker 240 VAC 120 VAC device device 176 AC Standards and Practices
Fig. 9.26 Isolation Transformer System with Single-Phase, 240-Volt Input and 120/240-Volt Output Ungrounded Grounded Ungrounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Main shore-power disconnect breaker Transformer shield Encapsulated single-phase 1:1 isolation transformer with metal case Transformer case ground and shield connection Transformer secondary overcurrent protection To Engine Negative terminal or its bus Ungrounded Grounded Ungrounded Grounding Double circuit breaker Branch circuit breaker 240 VAC 120 VAC 120 VAC device grounding device receptacle Approved Shore-Power Circuits 177
Approved Shore-Power Circuits Fig. 9.27 Isolation Transformer System with Single-Phase, 240-Volt Input and 120/240-Volt Output with Ground Fault Protection Ungrounded Grounded Ungrounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Main shore-power disconnect breaker Transformer shield grounded to case Encapsulated single-phase 1:1 isolation transformer with metal case Transformer secondary overcurrent protection To Engine Negative terminal or its bus Ungrounded Grounded Ungrounded Grounding Double circuit breaker Branch circuit breaker 240 VAC 120 VAC 120 VAC device grounding device receptacle 178 AC Standards and Practices
Fig. 9.28 Polarization Transformer System with Single-Phase, 120-Volt Input and 120-Volt Output Ungrounded Grounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Optional galvanic isolator Main shore-power disconnect breaker Transformer case ground connection Encapsulated single-phase 1:1 polarization transformer with metal case To Engine Negative terminal or its bus Ungrounded Grounded Grounding Branch circuit breaker Branch circuit breaker 120 VAC 120 VAC device grounding receptacle Approved Shore-Power Circuits 179
Approved Shore-Power Circuits Fig. 9.29 Polarization Transformer System with Single-Phase, 240-Volt Input and 120/240-Volt Output Ungrounded Grounded Ungrounded Grounding Shore-power connection Shore-power cable Shore-power cable connector SHORE SIDE BOAT SIDE Power inlet (insulated from boat if isolator installed) Optional galvanic isolator Main shore-power disconnect breaker Encapsulated single-phase Transformer case 1:1 isolation transformer ground connection with metal case Transformer secondary overcurrent protection To Engine Negative terminal or its bus Ungrounded Grounded Ungrounded Grounding Branch circuit breaker 240 VAC 120 VAC 120 VAC device grounding device receptacle 180 AC Standards and Practices
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10 CHAPTER Conservation for Liveaboards PL 4-Pin Thin-Lite Single Short, Compact Replacement 8 Watts 12VDC, 13 Watts LED All-Round Light Mini Reading Light 3 Watts 10 Watts Halogen Mini-Spot 5 Watts 182 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
T he cost per kilowatt-hour of power generated on a boat is high, whether in dollars or in aggrava- tion. It is easily shown that the dollar cost of a kilowatt-hour saved is less than that of a kilowatt-hour generated, no matter the shipboard source. This chapter shows you how to reduce your use of electricity for lighting, refrigeration, and several other areas. The bottom line is that most boaters can cut their onboard power consumption by at least half with little or no compromise in lifestyle. 183
Costs per Kilowatt-Hour Before considering solar and wind power, the live- Solar Power: aboard boater should consider the less expensive alter- • Used all year native form of energy—conservation. • Size, 50 watts peak output Put yourself to the following test.Your already leaky • Price including controls, $400 boat becomes more leaky. Which solution first comes • Life, 10 years to your mind? If it is to install a second or larger bilge • Average daily sunshine, 5.2 hours pump, then forget conservation, solar, and wind, and • Annual maintenance, $0 get yourself to a slip where you can tap into shore power. If fixing the leak seems more logical to you, Wind Power: however, then read on. • Used all year If we have learned anything in the past 20 years, it • Size (blade diameter), 5 feet is that, with modest investment and attention to detail, • Price including controls, $1,500 we can save a lot of expensive energy in our homes and • Life, 10 years offices. The same is true of boats. • Average wind speed, 10 knots If your boat is typical, this chapter can show you • Annual maintenance, $100 how to reduce the drain on your batteries by half with Assuming the alternators cycle the battery between virtually no effect on your lifestyle. By cutting con- the charge states of 50% and 90%, the relative produc- sumption in half, you will also reduce the required sizes tion costs per kilowatt-hour shown in Figure 10.1 of and costs of the solar and wind systems you may be electricity are: considering adding to your boat. In fact, you may • 220-amp alternator, $1.25 reduce your consumption to the point where you never • 110-amp alternator, $2.30 need run your engine again just to charge your batter- • 55-amp alternator, $4.10 ies! • Solar panel, $0.42 The old saying "A penny saved is a penny earned" • 5-foot wind machine, $0.59 has its analog in energy conservation:"A kilowatt saved is a kilowatt made." If we can save energy without dimishing lifestyle, then it is fair to compare the cost The Costs of Conserving Electricity of saving a kilowatt-hour to the cost of producing a Now let's compare the costs per kilowatt-hour of elec- kilowatt-hour in order to see which is the better deal. tricity saved by two simple changes: switching from incandescent to fluorescent lighting, and halving the losses of a DC-powered refrigerator. Costs of Producing Electricity Figure 10.1 shows the costs per kilowatt-hour of elec- Lighting Conversion tricity produced by: An 8-watt fluorescent fixture puts out nearly as much • 220-amp alternator on a 20 hp diesel light as a 40-watt incandescent lamp. Assume each • 110-amp alternator on a 20 hp diesel replacement fluorescent fixture costs $30. Fluorescent • 55-amp alternator on a 20 hp diesel bulbs cost four times as much as incandescent bulbs, • Solar panel at $8 per peak watt but they last proportionally longer, so the cost of bulb • 5-foot wind machine at $1,500 replacement is the same. The assumptions used include: Assuming a 10-year fixture life, and that the lamp is operated an average of 2 hours per day throughout Diesel Power the year, the lifetime savings of the fluorescent replace- • Used at anchor ment fixture is 124 kilowatt-hours. The cost per kilo- • Fuel consumption, 0.5 gallon/hour watt-hour saved is $30/124 = $0.24—half the cost of • Fuel price, $2.20/gallon electricity produced by the cheapest alternative means, • Price including controls, $7,000 and one-tenth the cost of the 110-amp alternator • Life, 10,000 hours power. • Maintenance, $0.20/hour 184 Conservation for Liveaboards
Fig. 10.1 Costs per Kilowatt-Hour of Generated Power (based on 10 years of daily consumption) 4.00 ENGINE COSTS: Charging two 8D batteries (440 Ah) to 85% using: 3.50 55-amp alternator 3.00 Electricity, $/kWh 2.50 110-amp alternator of 2.00 220-amp alternator Cost 1.50 Wind 1.00 Solar Utility 0.50 0.00 0 10 20 30 40 50 60 70 80 90 100 Depth of Battery Discharge, % Refrigerator Losses The first method has the advantage of simplicity, Assume that our 8-cubic-foot refrigerator with 2-inch but reduces the volume of the box. The second method foam insulation draws 5.5 amps at 12 volts DC and has retains the box dimensions, but its effectiveness is a 40% duty cycle. Its daily consumption would be: 5.5 uncertain without disassembly of the cabinetry. amps × 24 hours 0.40 = 52.8 Ah, or 0.63 kilowatt- Method one could be accomplished for about $50 × hour. in materials and $200 in labor by a reasonably compe- If we were to double the insulation of the refrigera- tent fiberglass technician. Cost per kilowatt-hour saved tor walls to 4 inches, install a better door gasket and is thus $250/1,186 kilowatt-hours = $0.21/kilowatt- install a trap in the drain, we would probably reduce hour. the refrigerator's total heat loss by half, or 0.315 kilo- Both of our retrofits are at least twice as cost effec- watt-hour/day. Over 10 years of continuous use, the tive as adding solar and wind power, and ten times savings would amount to 1,186 kilowatt-hours. cheaper than generation by shipboard diesel. The most effective way to double the refrigerator Caveat: The above calculations assume year-round insulation would be to line the inside of the box with 2- use of the boat for 10 years. If you use your boat only inch polyurethane foam board and then glass over the 10% of the year, then solar and wind costs per kilowatt- foam. If accessible, cavities between the box and the hour should be multiplied by a factor of 10. That is why hull and cabinetry can be filled with expanding foam. this chapter is titled Conservation for Liveaboards. Costs per Kilowatt-Hour 185
Lighting Savings Most boats come from the factory equipped with Fig. 10.2 Efficacy of Light Sources incandescent lighting. Both the bulbs and the fixtures 100 are inexpensive, but it is a false economy for the owner. You can reduce your lighting load by a full two-thirds 90 through three simple retrofits (see Figures 10.3 and 80 10.4): fluorescent galley and head fixtures, halogen 70 reading-light fixtures, and, for those who anchor out a lot, a light-actuated anchor light switch or a 3-watt 60 LED all-around light. Efficacy, Lumens per Watt 50 Green Fluorescent Fixtures 40 Red White The galley requires bright lighting, but 8-watt fluo- 30 Orange rescent slim-line fixtures cast as much light as common 40-watt incandescent fixtures. For serious chefs, larger 20 fluorescents rated at 13 watts (65 W), 16 watts (80 W) 10 and 26 watts (130 W) are available. The head is another good location for the same types of fluorescent lighting. 0 Incandescent Halogen Fluorescent LED If you have 120 VAC light fixtures aboard, you can Anchor Lights convert them with compact fluorescent screw-in replacement bulbs and then run these fixtures from a International navigation law requires boats less than 20 DC-to-AC inverter for similar savings. meters long to display an anchor light that is visible If the fluorescent fixtures affect any of your elec- for at least 2 nautical miles. The required luminance is tronics, install the filters described in Chapter 13. equivalent to that produced by a 10-watt incandescent lamp. Halogen Spot Fixtures The battery-powered "marker lights" many boaters Many of the lights below deck are for reading. The employ do not meet the 2-mile requirement. Simply most common small incandescent fixtures spread the reducing incandescent lamp wattage puts your boat in light from 15-watt bulbs over an area ten times that of jeopardy—at least from the standpoint of liability. a page. These lamps can be directly replaced with 5- or Two legal, energy-saving alternatives are: 10-watt halogen spot-task lamps, which achieve the 1. Using an automatic anchor light switch same light intensity by concentrating the beam from a 2. Switching to an LED all-round light high-efficiency halogen bulb onto a page or task. You can save further lighting energy by installing Anchor light switch. To run the light from sunrise to the solid-state dimmer circuit described in Chapter 14. when you wake up (or when you first remember the You can then dim the lights for a warmer ambience, light is on, which may be considerably longer) is waste- save electricity, and double the lifetime of the lamps, all ful, however. The automatic anchor light switch in at the same time. Chapter 14 turns the anchor light on and off precisely at sunset and sunrise, saving about 2 Ah per day. If you LEDs leave your boat unattended it will save an average of The future of marine lighting is all about LEDs. While about 10 Ah per day. If building the circuit yourself Figure 10.2 shows the present efficacy range of LEDs isn't your idea of a fun way to spend a weekend, sev- as 22 to 42 lumens per watt (about twice that of incan- eral commercial versions are also available. descents and half that of fluorescents), there is little LED all-around light. Perko (no doubt others will fol- doubt that 60 to 100 lumens per watt will ultimately low suit) has developed an LED all-round light that sat- be achieved. isfies the 2 nm visibility requirement for vessels under The same efficiency as fluorescents, 10 to 100 times 20 meters. The design takes advantage of both the the life of halogens and incandescents, indestructible LED's inherent efficiency (two times that of incandes- packaging, and easily and efficiently dimmed: sounds cents) and its narrow beam (±5°) to focus the light at like a no-brainer. the horizon. The result is a 75% power reduction, from 10 to 12 watts to only 3 watts. 186 Conservation for Liveaboards
Fig. 10.3 Bulbs for Boats FLUORESCENTS Compact Replacement T-5 T-8 INCANDESCENTS 12VDC, 13 Watts min. bipin med. bipin Spherical Bayonet Bayonet Med. Screw-Base Single-Contact Double-Contact PL 2-Pin Festoon PL 4-Pin LEDS HALOGENS Cluster Bayonet Replacement G4 G9 Single Fig. 10.4 A Collection of Efficient Fixtures Perko LED All-Round Light 3 Watts West Marine Aqua-Signal Mini Reading Light Halogen Mini-Spot 10 Watts 5 Watts Thin-Lite Single Short, 8 Watts Thin-Lite Single Long, 13 Watts Thin-Lite Dual Short, 16 Watts Thin-Lite Dual Long, 26 Watts Lighting Savings 187
Refrigeration Savings Fig. 10.5 Pressure-Temperature Curve for ES-12a How Refrigeration Works Refrigerant If you know that water boils (turns from a liquid to a 140 gas) at 212°F at normal atmospheric pressure, but that 120 Condensation its boiling temperature rises at higher pressure (such as in a pressure cooker), and that evaporating water 100 absorbs a lot of heat (think of getting out of the water 80 GAS on a windy day), then you are well on your way to 60 understanding how refrigerators, air conditioners, and Temperature, ° F heat pumps work. 40 LIQUID Unfortunately, the boiling point of water is too high 20 to use it as a refrigerant, but other fluids exist that boil at below the freezing point of water! One such refrig- 0 Evaporation erant is ES-12a (see Figure 10.5), one of many refrig- -20 erants developed to replace R-12 (Freon), now banned -40 90 due to its adverse effect on the earth's ozone layer. 0 30 60 Pressure, psi 120 150 180 As shown in Figure 10.5, at atmospheric pressure (15 psi), ES-12a boils at about –26°F. If we compress it Condenser to a pressure of 150 psi, its boiling temperature rises to Efficient condenser operation requires efficient heat about 110°F. Since this rise approximates the range removal from the tubing. Air-cooled condensers uti- from freezer temperature to maximum atmospheric lize metal fins on the tubing and air flow over the fins to temperature, ES-12a may prove useful. remove the heat. The efficiency of such an arrangement In the refrigeration system in Figure 10.6, the refrig- depends on both the temperature of the air and the rate erant is sucked into a compressor. The compressor of airflow. A stuffy engine compartment is obviously works like the piston of an internal combustion engine, not a good location for the condenser. except power is applied to the piston by the crankshaft instead of the other way around. The piston com- Evaporator presses the gas to about 150 psi, in the process raising The evaporator shown has little heat-storage capacity. its temperature to about 120°F. As a result the compressor will cycle on and off every The hot, compressed gas then flows through the few minutes. A lot of energy is lost starting the com- discharge line to a condenser—a heat exchanger— pressor, so the efficiency is relatively low. A better sys- where it is cooled to below its condensation point and tem encloses the evaporator coil in a holding plate filled changes back to a liquid. In order to condense the with a liquid having a low freezing point. The compres- 120°F gas, the condenser must be located in a cool sor runs until all of the holding-plate liquid freezes. space or be cooled by seawater. The holding plate then functions like a block of ice. From the condenser the hot liquid first passes Properly sized for the refrigerator box, a holding-plate through a drier, which assures no water contaminates system requires running the compressor just once a day the refrigerant, then on to an expansion valve. for an hour or so. By running such a system only when The function of the expansion valve is to control the the engine is running, all of the considerable load is release of the hot liquid into the low pressure of the removed from the boat's batteries. evaporator coil. When the fluid emerges from the expansion valve, the dramatic drop back to near atmo- Controls spheric pressure causes it to boil (evaporate) at about A small temperature-sensing bulb on a capillary tube is –25°F, absorbing heat from the evaporator coil. The attached to the suction end of the evaporator coil. The evaporator coil is the frost-covered tubing you see in an temperature-dependent pressure in the tube controls older refrigerator or freezer. the rate of fluid flow through the valve, and thus the From the evaporator the now-cool gas is again temperature of the evaporator coil.When the tempera- sucked into the compressor, and the cycle is repeated. ture of the refrigerator box rises, a thermostat switches Now for some details: the compressor on to move and compress refrigerant, cooling the box. 188 Conservation for Liveaboards
Fig. 10.6 How Refrigerators Work Low-pressure gas (cold) Evaporator Expansion valve Low-pressure liquid Insulation THE BOX Suction line Compressor Discharge line High-pressure gas Condenser Dryer High-pressure liquid (hot) Refrigeration Savings 189
Refrigeration Savings Calculating the Cooling Load Fig. 10.7 Conductive Heat Loss First, two definitions: • Btu = heat that changes the temperature of 1 ∆ T pound of water by 1F°. • Heat of fusion of water (heat absorbed by 1 pound Tinside Toutside of ice when it melts) = 144 Btu. A Next, Figure 10.7 shows the basic equation of con- ductive heat loss: H H R H= A ×∆ T/R where: H = heat loss through A, in Btu/hour A = area of surface in square feet T = temperature difference, T – T F° ∆ outside inside R = thermal resistance To this conductive heat loss through the refrigerator walls we have to add the losses of infiltration (air leak- age through the lid and drain) and cooldown (heat that Fig. 10.8 Typical Refrigerator Box must be removed from warm objects added to the Before Retrofit box). 28\" The Refrigerator Box Figure 10.8 shows the dimensions of a typical 8-cubic- foot refrigerator. The walls are constructed of 2-inch urethane foam, lined with fiberglass. Plugging the numbers into the heat-loss equation above: 24\" 28\" A = 28 square feet (insulation mid-plane) T = 75°F outside – 40°F inside 24\" ∆ = 35F° R = 2 inches R-6/inch 24\" × = 12 H = 28 35/12 28\" × = 82 Btu/hour After Retrofit If this box had a perfect lid and we never opened it, 28\" it would melt 82 Btu/hour/144 Btu/pound = 0.57 pound of ice per hour or 13.7 pounds of ice per day. If we add another third (27 Btu/hour) to the heat loss for infiltration and cooldown, our totals become 109 Btu/hour and 18 pounds of ice per day. How much electricity will it take to replace the ice? The answer is—it all depends. It depends primarily on 28\" 20\" the efficiency of the refrigeration system, the refrigera- 20\" tor's coefficient of performance (COP), defined as: 20\" COP = watts removed/watts used We'll also need a conversion factor: Ah/day = 0.586 Btu/hour 28\" × 190 Conservation for Liveaboards
COP depends on how hard the compressor has to Fig. 10.9 Refrigerator COP vs. Temperature work pumping heat from the evaporator (cold) side to 3 the condenser (hot) side. When the temperatures of evaporator and condenser are the same, the compres- sor can remove about 3 Btu of heat energy, using the equivalent of 1 Btu of electrical energy, yielding a COP 2 of 3.0. At the opposite extreme, the typical refrigerator is capable of moving heat across a maximum difference Coefficient of Performance (COP) of about 150F°, at which point its COP becomes zero. Figure 10.9 shows the relationship between COP 1 and condenser temperature for a typical small refrig- erator, assuming the evaporator is at 20°F. The temperature of the condenser depends on its type and location. Table 10.1 shows typical condenser 0 20 40 60 80 100 120 140 160 operating temperatures and resulting COPs for differ- Condenser Temperature, °F ent condenser types and locations in the boat. Assume the condenser is located in free air at 75°F but has no fan. According to Table 10.1, its COP will Table 10.1 Refrigerator COP vs. Location be about 1.3. Our example refrigerator will then draw 190 Btu/hr 0.586/1.3 = 49 Ah/day. Condenser × Condenser/Location Temp., °F COP Air-cooled in 110°F engine 140 0.6 A Typical Refrigerator Retrofit compartment, no fan To reduce the refrigeration load we can take three steps: Air-cooled in 110°F engine 120 1.0 compartment with fan 1. Increase wall insulation. Air-cooled in 75°F free air with no fan 105 1.3 2. Decrease infiltration with a better lid gasket and a drain trap. Air-cooled in 75°F free air with fan 85 1.7 3. Increase condenser COP with a fan. Water-cooled, intake water 75°F 85 1.7 Water-cooled, intake water 60°F 70 2.0 Wall Insulation At the cost of 3.4 cubic feet of interior space, we can double the insulation of all surfaces and increase their R-values to R-24. Because we also have decreased the heat loss area (measured at the midpoint of the insula- marine and RV refrigeration manufacturers offer such tion) to 24 square feet, conductive heat loss is decreased fans as an option. If not, small fans that run on 12 VDC by 47 Btu/hour to 35 Btu/hour. are readily available at electronics stores, such as RadioShack. DIY Project 13 (Chapter 14) is a circuit Infiltration to control such a fan. By installing a better gasket on the lid and a better melt- Manufacturers also sometimes offer water cooling, water drain trap, we might decrease the losses due to air where the condenser is cooled by water circulated to a leaks by half, or 13 Btu/hour, and the total heat loss by heat exchanger mounted on the bottom of the hull. 60 Btu/hour to 49 Btu/hour. While more efficient in cooler waters, such systems are susceptible to becoming fouled with growth. Condensor COP By installing a thermostatically controlled 12-volt DC Net Refrigerator Savings fan to move air through the condenser coils, we can With the above improvements, our new refrigeration increase the condenser COP from about 1.3 to 1.7 at load becomes 60 Btu/hour 0.586/1.7 = 20.7 Ah/day— × the cost of about 2 Ah per day to power the fan. Most a decrease of more than 50%. Refrigeration Savings 191
Other Savings Cabin Fans tional to the area of the screen (diameter squared). The most efficient way to cool a hot cabin is with a From a 19-inch CRT to a 6-inch LCD there is a 65-watt, wind chute attached to a hatch, but its use assumes a or 5-amp, difference. If you are an average 4-hour-per- breeze and that the boat is free to swing into it. day boob-tube watcher, the daily difference is greater On hot, still nights, small fans directed at your body than the drain of the anchor light. An excellent way to can make the difference between sleeping and not. The save energy is, therefore, to install a 6-inch LCD televi- typical 6-inch cabin fan draws about 1 amp, but the sion and sit closer! most efficient fans draw only 0.3 amp. In 8 hours the VCRs and DVD players are becoming very popular accumulated difference is more than 5 Ah per fan. on boats. In fact, trading videotapes and DVDs is nearly as common as trading paperback books. The Electronics typical 120-volt AC record/play VCR/DVD machine The power consumption of a sound system depends draws about 17 watts. Portable 12-volt DC play-only more on the efficiency of the speakers than that of the models draw 10 watts. electronics. Therefore, look for speakers designed to be driven by computers, as they are the most efficient. No one is willing to watch black and white televi- The Bottom Line sion any longer, so the choice is between the older stan- Table 10.2 shows, as promised, how the daily power dard cathode-ray (CRT) color television and the newer, consumption of a typical cruising boat can be reduced solid-state LCD versions. Wattage is roughly propor- by half with no significant degradation of lifestyle. Table 10.2 Power Consumption of a Typical versus an Energy-Efficient Liveaboard Boat Hours/ TypicalEfficient Area Device WattsAmpsDayAhAh 5500.156.9 Galley Microwave 45.8 6.9 Toaster 66.70.04 800 Blender 14.6 0.1 1750.010.1 Coffee grinder 160 13.3 0.01 Refrigerator 2\" insul. 60 5.0 10.00 49.0 4\" insul 60 5.0 5.00 20.7 Head Hair dryer 1,200 100.0 0.03 Lights Reading 2 incand., 15 W 30 2.5 2.00 5.0 2 halogen, 5 W 10 0.8 2.00 1.6 Galley 2 incand., 25 W 50 4.2 2.00 8.4 2 fluor., 8 W 16 1.4 2.00 2.8 Anchor manual, 10 W 10 0.8 14.00 11.2 auto., 10 W 10 0.8 11.00 8.8 Fans Typical 6-inch, 100 cfm 12 1.0 5.00 5.0 Most efficient, 100 cfm 4 0.3 5.00 1.5 Electronics Stereo 20 W/channel 60 5.0 1.00 5.0 7 W/channel 35 3.0 1.00 3.0 Television, color, 19\" CRT 80 6.7 2.00 13.4 15\" LCD 36 3.0 2.00 6\" LCD 15 1.25 2.00 2.5 VCR or DVD Typical 120-volt AC 17 1.4 1.0 1.4 12-volt DC play-only 10 0.8 1.0 0.8 Totals 105.4 48.7 192 Conservation for Liveaboards
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11 CHAPTER Solar Power E D B A C 194 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
I s solar for you? Would the power produced by solar panels pay back their cost? There is quite a collection of commercially available photovoltaic panels. Interpreting specifications requires that we first understand how photovoltaic panels work. We also need to consider panel orienta- tion in estimating daily output. Once the decision has been made, mechanical instal- lation is quite simple. Electrical installation integrates the panels into the existing 12-volt DC alternator/ battery system. Following the rules for solar success virtually guar- antees your solar satisfaction. 195
Is Solar for You? A solar, or photovoltaic, installation is a one-time Fig. 11.1 Solar Energy Production among 71 Cruisers investment with a fuel- and maintenance-free lifetime of 10 years or longer. Whether a photovoltaic system 100 would prove cost effective on your boat, however, depends very much on how you use the boat. If you live 80 aboard and are away from the dock at least half of the time, the answer is a definite "yes." If you cruise 1 60 month each summer, the answer is probably "no." Percent of Load Generated Figure 11.1 shows the percentage of daily electrical 40 load supplied by photovoltaic panels among 71 live- aboard cruisers surveyed in Florida and the Bahamas. 20 The average installation was far smaller than optimal, yet the average percentage of power supplied was a sig- 0 nificant 40%. Had the array sizes been optimal, I am None Solar Wind & Solar Only sure the power supplied would have been in the 80 to 100% range. Also note from Figure 11.1 that cruisers who had both solar and wind systems garnered more than 90% of their power from the combination. Those having wind power, but no solar, generated 60% from the wind. Figure 10.1 compared the costs per kilowatt-hour of electricity produced by photovoltaic panels, wind machines, and engine-driven alternators. The photo- voltaic cost of $0.42/kilowatt-hour assumed: • System used year-round • Panel size—50 watts peak output • Price including controls—$400 • Life—10 years • Average daily sunshine—5.2 hours • Maintenance—$0 Such a panel would produce on average 5.2 hours 50 watts = 0.26 kWh per day, or 95 kWh per year. An × alternative source of power would be a high-output, 110-amp alternator, charging batteries on a 50 to 85 percent-of-charge cycle. This, according to Figure 10.1, would produce power at a cost of $2.30 per kilowatt- hour. Compared to the cost of alternator power, solar sav- ings would be $2.30 – $0.42 = $1.88 per kilowatt-hour. At 95 kilowatt-hours per year, annual savings would be $179, and the photovoltaic system would pay for itself in $400/$177 = 2.2 years. That amounts to receiv- ing a tax-free return on investment of 45%. Try to match that at your local bank! On the other hand, if the boat were used but 1 month out of the year, the payback would be 27 years— longer than the projected life of the system. 196 Solar Power
How Photovoltaics Work Figure 11.2 shows how a photovoltaic panel works. Fig. 11.2 How Photovoltaics Work Solar energy in the form of photons penetrates the photovoltaic material. Each photon transfers enough energy to the photovoltaic atoms to release an electron. If we connect the grid on the sunlit side to the conduct- ing base on the backside, the free electrons will flow through the external conductor and load to rejoin atoms having missing electrons. Each free electron has a potential of about 0.6 volt. A panel typically consists of from 30 to 36 cells, con- Tempered nected in series to produce an open-circuit voltage of glass from 18 to 22 VDC. The theoretical maximum effi- Conducting ciency of this conversion of light energy to electrical grid energy is about 28%. As we will see, however, the effi- ciencies achieved in manufacture are improving but still fall far short of theory. Photovoltaic collector materials take three common forms: monocrystalline silicon, polycrystalline silicon, and amorphous silicon. Crystalline silicon is grown in the form of large crystals, which are sawn into thin wafers to form the cells. Monocrystalline cells consist of single, large crystals grown and drawn from melted silicon in the form of large rods. Due to their crystalline perfection, they have the highest efficiencies, ranging from 14 to 17%. N-semiconductor Polycrystalline silicon is formed by pouring melted PN junction silicon into blocks, the molten silicon forming many P-semiconductor small crystals on cooling. These polycrystalline blocks are then sawn into cells. Because of defects between Conducting layer the crystals, the conversion efficiency of polycrystalline silicon ranges between 13 and 15%. Amorphous silicon is produced by the less expen- sive process of depositing vaporized silicon onto a metal substrate. In addition to being less expensive to produce, amorphous silicon can be fabricated into semirigid and flexible panels. Semi-rigid panels attached to a thin steel backing can be adhered to a deck and stepped on without damage. Flexible panels with a heavy fabric backing can be attached to boat canvas. Unfortunately, the efficiency of amorphous sil- icon is only 5 to 7%, so twice as much collector area is required as for crystalline panels. Most crystalline photovoltaic panels are warranted for 20 years, but there is no reason, barring physical damage, that they would not last 30 years or longer. Amorphous silicon panels, because they are not enclosed in a rigid, protective frame, are generally war- ranted for only 5 years. How Photovoltaics Work 197
Photovoltaic Panels Table 11.1 lists the specifications of the most popular deck. Flexible panels may be draped anywhere. On photovoltaic panels. All panel output ratings are for average you can expect (in 2005) to pay about $6 per 25°C (86°F). Rigid panels are in aluminum frames, and rated watt for rigid panels, $8 for semirigid, and $12 for can be mounted to davits, bimini frames, and stan- flexible. Add about $2 per rated watt for controls and chions. Semirigid panels may be adhered directly to the mounting hardware. Table 11.1 Photovoltaic Panel Specifications 1 Rigid (R) Open- Short- Semirigid (S) Dimensions, Rated Rated Circuit Circuit Warranty Flexible Model (F) 2 inches Watts Amps VoltsAmps Years ICP Solar Pro 3 Plug'n'Play 30 R 41 x 12.4 30 2.00 — — Life Plug'n'Play 50 R 41.3 x 20 50 3.30 — — Life Plug'n'Play 75 R 50 x 23.3 75 5.00 — — Life Plug'n'Play 100 R 60.3 x 28 100 6.70 — — Life Solara SM40M S 16.6 x 10.7 10 0.50 21.0 — 20 SM60M S 24.4 x 9.8 15 0.90 21.0 — 20 SM80M S 16.9 x 17.7 20 1.10 21.0 — 20 SM120M S 23.2 x 17.7 30 1.70 21.0 — 20 SM160M S 29.0 x 17.7 40 2.20 21.0 — 20 SM225M S 29.5 x 24.0 56 3.00 21.0 — 20 United Solar (Unisolar) USF-5 F 21.3 x 9.7 5 0.30 16.5 0.33 5 USF-11 F 21.3 x 16.7 11 0.62 16.5 0.69 5 USF-32 F 55.8 x 16.7 32 1.94 16.5 2.10 5 Kyocera KC35 R 18.5 x 25.7 35 2.33 18.8 2.50 25 KC40 R 20.7 x 25.7 40 2.34 21.5 2.48 25 KC50 R 25.2 x 25.7 50 3.00 21.5 3.10 25 KC60 R 29.6 x 25.7 60 3.55 21.5 3.73 25 KC70 R 34.1 x 25.7 70 4.14 21.5 4.35 25 KC80 R 38.4 x 25.7 80 4.73 21.5 4.97 25 KC120-1 R 56.1 x 25.7 120 7.10 21.5 7.45 25 Shell Solar (Siemens) SM20 R 22.3 x 12.9 20 1.38 18.0 1.60 10 SM46 R 42.7 x 13 46 3.15 18.0 3.35 25 SM55 R 50.9 x 13 55 3.15 21.7 3.45 25 SM75 R 47.3 x 20.8 75 4.40 21.7 4.80 25 SM110 R 51.8 x 26 110 6.30 21.7 6.90 25 BP Solar (Solarex) BP MSX5L S 10.8 x 10.5 4.5 0.27 20.5 0.30 5 BP MSX10L S 17.5 x 10.5 10 0.58 21.0 0.65 5 BP MSX20L S 17.5 x 19.5 20 1.17 21.0 1.29 5 BP MSX30L S 24.3 x 19.5 30 1.75 21.0 1.94 5 BP MSX40 R 29.9 x 19.7 40 2.37 21.0 2.58 20 BP MSX60 R 43.5 x 19.7 60 3.56 21.0 3.80 25 1 All ratings at 25°C (86°F). 2 Flexible panels for mounting directly to deck. 3 Plug'n'Play panels include a charge controller. 198 Solar Power
Interpreting Specifications Figure 11.3 shows the voltage-current curve for a typi- Fig. 11.4 Typical Photovoltaic Output vs. Number of Cells cal 30-cell photovoltaic panel in full sunlight.With out- and Panel Temperature put terminals shorted, the panel put out its short- 4.0 circuit current (here 3.3 amps). With output terminals 30 Cell Panel not connected, current is zero, but output voltage is the open-circuit voltage (here 18.0 volts). Maximum power 3.0 output is achieved at the knee of the curve where the Current, Amps rated current (3.0 amps) times the rated voltage (14.7 2.0 Output @ 68°F volts) equals the panel's rated power (44 watts). @ 86°F Output @ 104°F Fig. 11.3 Typical Photovoltaic Panel Output Curve 1.0 @ 122°F 4.0 Short circuit amps Rated 0 0 5 10 15 20 25 power Output Current, Amps 2.0 14.7V 4.0 33 Cell Panel 3.0 3.0 A point Output Volts 1.0 Open- 3.0 circuit Current, Amps volts Output @ 68°F 0 2.0 0 5 10 15 20 25 @ 86°F Output Volts @ 104°F Figure 11.4 shows how the voltage-current curves Output 1.0 @ 122°F vary both with number of cells and with panel tem- perature. Panel specifications are given for a panel (not 0 air) temperature of 25°C (86°F). Both voltage and cur- 0 5 10 15 20 25 rent decrease at higher temperatures. For this reason, Output Volts panels should be mounted with free airflow beneath to minimize operating temperature. Panels in the trop- 4.0 36 Cell Panel ics should have higher voltage ratings as well. The effect of shading is not shown in manufactur- 3.0 ers' voltage-current curves. Shading the panel from direct sun does not affect open-circuit voltage, but Current, Amps reduces power output under load roughly in propor- 2.0 Output @ 68°F tion to the percentage of shaded area. @ 86°F Finally, unless built in, you should install a Schottky Output @ 104°F blocking diode to prevent reverse-current flow from 1.0 @ 122°F the batteries at night. Better yet, install a regulator that opens the circuit whenever the panel voltage is less than 0 that of the battery. 0 5 10 15 20 25 A common mistake in selecting solar panels is fail- Output Volts ing to account for all of the voltage drops. Select a panel whose rated voltage at your expected operating tem- perature is at least 14.8 volts, since 14.8 volts – 0.4 volt (blocking diode drop) = 14.4 volts, the voltage required for fully charging lead-acid batteries. In order to equal- ize the batteries, the blocking diode can be temporar- ily shorted with clip leads, raising the voltage to 14.8. Interpreting Specifications 199
Panel Orientation To understand how panel orientation affects the output shortest (December 21) days. On June 21, if we are of a photovoltaic system, we must consider how the sun both smart and mobile, we will be at, or around, lati- moves through the sky, both throughout the day and tude 40°N. Figure 11.6 shows that a horizontal panel with the seasons. will collect 119% of the radiation collected by a fixed Figure 11.5 shows the track of the sun over a boat panel tilted south at 40°. located at latitude 24°N (southern Florida) at the spring On December 21 we hope to be in the neighbor- and fall equinoxes (March 21 and September 21), and hood of Miami, where our horizontal panel will col- the summer and winter solstices (June 21 and Decem- lect 72% as much radiation as a fixed panel tilted south ber 21). On June 21, the sun reaches its highest noon at 24°. elevation, 90°. On December 21, the sun reaches its Thus we see, averaged over the year, a horizontal lowest noon elevation, 43°. Further, the sun is above the panel will perform as well as a fixed, south-tilted panel. horizon approximately 16 hours in June but only 8 "But," you say, "if I were at a dock, I could tilt my hours in December. We would, therefore, expect a lot panels toward the noon sun." But if you were at a dock, less solar input in December than in June. you wouldn't need photovoltaic panels. Panel output ratings assume full sunlight with the Further, if you were on a mooring or anchor, your sun's rays normal (perpendicular) to the panel surface. boat would swing without regard for the position of Panels in large utility "solar farms" are mounted on the sun. Any fixed orientation you selected might be frames that continuously track the sun's orbit for max- perfectly right at one moment but perfectly wrong an imum output. hour later. There is only one orientation that doesn't What can we do about orientation on a boat? You're change as a boat swings: horizontal (facing straight up). obviously not going to install a tracking mechanism, To show the effect of compass direction, Figure 11.7 and most people would get tired of adjusting panel ori- compares the solar radiation on horizontal panels and entation three or four times a day. So the question is: vertical panels facing north, east, south, and west. what fixed tilt is best? Although vertical east and west panels collect signifi- Figure 11.6 compares the solar radiation on a hori- cant amounts of radiation in morning and afternoon zontal surface (tilt = 0°) and surfaces tilted to the south respectively, both collect for only half a day, so their at the latitude angle, for latitudes 24°N (Miami) and total collection is small. Conclusion: the only practical 40°N (New York), on both the longest (June 21) and solar panel orientation on a cruising boat is horizontal. Fig. 11.5 Track of the Sun Through the Day and the Seasons June Mar Sep Dec Noon altitude Noon 90 ° altitude 67 ° altitude E 43 ° Noon N S W 200 Solar Power
Fig. 11.6 Hourly Radiation on Horizontal and Tilted Surfaces JUNE 21 DEC 21 24°N 24°N hr. 300 hr. 300 Btu/sq.ft./ 200 Btu/sq.ft./ 200 Insolation, 100 Horizontal (total 2574) Insolation, 100 24° Tilt (2058) 0 24° Tilt (total 2230) Horizontal (1474) 0 0 6 7 8 9 10 11 12 1 2 3 4 5 6 6 7 8 9 10 11 12 1 2 3 4 5 6 AM Hour of Day PM AM Hour of Day PM 40°N 40°N hr. 300 hr. 300 Btu/sq.ft./ 200 Btu/sq.ft./ 200 Insolation, 100 Horizontal (total 2648) Insolation, 100 40° Tilt (1634) 40° Tilt (total 2224) Horizontal (782) 0 0 6 7 8 9 10 11 12 1 2 3 4 5 6 6 7 8 9 10 11 12 1 2 3 4 5 6 AM Hour of Day PM AM Hour of Day PM Fig. 11.7 Hourly Radiation on Horizontal and Vertical Surfaces JUNE 21 DEC 21 hr. 300 24°N hr. 300 24°N Btu/sq.ft./ 200 Horizontal Btu/sq.ft./ 200 So. vert. East vert. Insolation, 100 No. vert. West vert. So. vert. Insolation, 100 Horizontal East vert. 0 West vert. North vertical 0 0 6 7 8 9 10 11 12 1 2 3 4 5 6 6 7 8 9 10 11 12 1 2 3 4 5 6 AM Hour of Day PM AM Hour of Day PM 40°N 40°N hr. 300 hr. 300 Btu/sq.ft./ 200 Horizontal Btu/sq.ft./ 200 So. vert. East vert. East vert. West vert. Insolation, 100 No. vert. So. vert. Insolation, 100 West vert. No. vert. Horizontal 0 0 6 7 8 9 10 11 12 1 2 3 4 5 6 6 7 8 9 10 11 12 1 2 3 4 5 6 AM Hour of Day PM AM Hour of Day PM Panel Orientation 201
Estimating Output Because the fixed horizontal orientation is the most Table 11.2 Average Daily Radiation on a Horizontal Sur- practical on a non-stationary platform, solar-availabil- face, in Equivalent Hours of Full Direct Sunlight ity tables and maps often show total radiation on a hor- izontal surface. Figure 11.8 contains such seasonal Highest Lowest Annual maps. Table 11.2 lists, for selected locations, more pre- State City Month Month Average cise values of average daily solar radiation falling on AK Fairbanks 5.87 2.12 3.99 horizontal surfaces during: AK Matanuska 5.24 1.74 3.55 • the sunniest month (Highest Month) CA La Jolla 5.24 4.29 4.77 • the least sunny month (Lowest Month) CA Los Angeles 6.14 5.03 5.62 • the entire year (Annual Average) The values are in equivalent hours of full sunlight, CA Santa Maria 6.52 5.42 5.94 2 where full sunlight is defined as 1,000 watts/meter . DC Washington 4.69 3.37 4.23 These values allow easy estimation of solar panel FL Apalachicola 5.98 4.92 5.49 performance: the average daily output is simply the FL Belle Is. 5.31 4.58 4.99 panel rating in watts times the equivalent hours of full FL Miami 6.26 5.05 5.62 sunlight. FL Tampa 6.16 5.26 5.67 Example 1—always in a sunny location: How many HI Honolulu 6.71 5.59 6.02 kilowatt-hours of output can you expect over an IL Chicago 4.08 1.47 3.14 entire year from a horizontally mounted, 60-watt LA Lake Charles 5.73 4.29 4.93 panel in Miami, FL? In Table 11.2 we find for Miami LA New Orleans 5.71 3.63 4.92 an annual average figure of 5.62. Thus we can expect a 60-watt panel to produce an average of 60 MA Boston 4.27 2.99 3.84 watts × 5.62 hours = 337 watt-hours per day. Over MA E. Wareham 4.48 3.06 3.99 the entire year, we would expect 365 337 watt- MD Silver Hill 4.71 3.84 4.47 × hours = 123 kilowatt-hours. ME Portland 5.23 3.56 4.51 Example 2—Florida in winter and Maine in summer: NC Cape Hatteras 5.81 4.69 5.31 With the limited figures in Table 11.2, the simplest NJ Sea Brook 4.76 3.20 4.21 approximation would be to use the Lowest Month NY New York City 4.97 3.03 4.08 figure for Miami for the 6 months centered on win- NY Rochester 4.22 1.58 3.31 ter and the Highest Month figure for Portland, ME, OR Astoria 4.76 1.99 3.72 for the 6 months centered on summer. OR Corvallis 5.71 1.90 4.03 Miami, FL: 60 5.05 × 365/2 = 55.3 kWh OR Medford 5.84 2.02 4.51 × Portland, ME: 60 5.23 × 365/2 = 57.3 kWh RI Newport 4.69 3.58 4.23 × Annual total = 112.6 kWh SC Charleston 5.72 4.23 5.06 In Chapter 10, we retrofitted a boat to reduce its TX Brownsville 5.49 4.42 4.92 electrical load to 48.7 Ah per day. As we saw in the TX San Antonio 5.88 4.65 5.30 examples above, in a sunny climate, or for a liveaboard VA Richmond 4.50 3.37 4.13 boat following the sun, a solar array consisting of two 60-watt panels could be expected to provide an aver- WA Prosser 6.21 3.06 5.03 age of 2 112.6 = 225 kWh/yr. Dividing by 12 volts and WA Seattle 4.83 1.60 3.57 × 365 days, the array output averages 51.4 Ah/day or less than 100% of the boat's load. Provided the battery bank was sized at roughly four times the daily draw, this cruiser would rarely, if ever, have to use his engine for the sole purpose of charging the batteries. 202 Solar Power
Fig. 11.8 Maps of Average Daily Radiation on a Horizontal Surface, in Equivalent Hours of Full Direct Sunlight ANNUAL 4 5 MARCH JUNE 3 6 6 6 6 4 7 6 5 4 8 6 5 SEPTEMBER DECEMBER 4 4 4 4 4 5 6 2 3 3 Estimating Output 203
Mechanical Installation Fastening Fig. 11.9 Panel Clamp for Bimini or Dodger Frame Solar panels are extremely lightweight and strong. Their extruded aluminum frames make mechanical fastening a snap. Multiple panels can be fastened together loosely using stainless machine screws, lock- nuts, and rubber grommets as shown in Figure 11.9. The assembly of panels can then be fastened to the Panel frame stainless or aluminum tubing of a dodger, bimini, radar Rubber grommet arch, or davits. Alternately, each panel can be fastened Solar panel individually, or multiple panels can be fastened within a frame, and the frame fastened to the boat. Panel Location The critical part of panel installation is choosing the location. Figure 11.10 shows five locations for a system of four panels. Structural tubing Stanchion clamp Location A, on the deck just aft of the main mast, is shaded by both mast and boom, is in the way dur- ing mainsail operations, and is a target for objects dropped from the mast. panels offers no advantage.Worse is the fact that the Location B, on top of a pilot house, is a better loca- panels extend beyond the rail, where they are sub- tion than A because it is out of the way and farther ject to damage while docking. from the drop zone. And, to avoid shading, the Location D, in a horizontal frame on top of a radar boom could be swung to the side with a preventer. arch, is both out of the way and free from shade. Location C is often seen because solar suppliers offer Location E, in a similar frame fastened to dinghy the mounting hardware and because it allows tilting davits, is as good as Location D. It is shade-free, out of the panels. As we saw above, however, tilting the of the way, and very secure. Fig. 11.10 Candidate Panel Locations E D B A C 204 Solar Power
Electrical Installation Figure 11.11 shows a typical proper photovoltaic instal- current is less than 0.5% of total battery capac- lation. The important elements are: ity (2 amps for a 400 Ah battery bank), a charge controller is required to prevent overcharging 1. Fuse or circuit breaker. The positive leads from all charging sources except the alternator should be the batteries. A switch should be provided to overcurrent protected by fuses or circuit break- bypass the controller, however, so that a battery ers, as close to the battery as possible. The reason equalization charge might be applied occasion- is that unprotected leads might short, melting ally. If panel voltage is marginal, you might the conductor insulation, damaging the batter- install a switch to temporarily bypass the block- ies, and possibly starting a fire. Furthermore, if ing diodes as well. the output current of a short-circuited solar The simplest way to satisfy all three requirements panel could exceed the conductor capacity, the is to purchase a charge controller that contains all three charge controller should be fused, as well. features. The best controllers allow full current up to 2. Blocking diode. There should be blocking diodes about 14.4 volts, then taper to a float charge. Some con- between the battery and panel positive termi- trollers automatically switch excess panel output to a nals to prevent reverse flow at night (unless the resistance load, such as a 12-volt DC water heater ele- charge controller opens the circuit when panel ment, thereby extracting maximum use from the panel voltage is too low). The diodes should connect to output. the battery side of any isolation diodes from the Naturally, all DC wiring standards, such as conduc- alternator to avoid the double voltage drop of tor ampacity, stranding, insulation, and fastening, isolation diode and blocking diode. apply as well to solar installations. 3. Charge controller. Unless the total panel-rated Fig. 11.11 Electrical Hookup of Solar Panels (Wind Generator Optional) F + AUX GND GND – + – + Charge Charge controller controller DC AMPS DC AMPS + + - - These diodes and fuses may be omitted, provided charge controllers contain overcurrent protection and means for blocking reverse currents. Electrical Installation 205
Rules for Solar Success If you want a photovoltaic system to supply all or nearly all of your electrical energy needs, you must: 1. Reduce your average daily electrical consump- tion to 60 Ah or less. See Chapter 10 for sugges- tions. 2. Install sufficient panel area. Use Figures 11.8 through 11.10 to calculate the required panel wattage for the areas you plan to cruise. 3. Install the panels in a permanent, horizontal, shade-free location. 4. Do not depend on tilting of the panels, removing shading objects, or controlling boat orientation to increase panel output. 5. Select panels with sufficient rated voltage to overcome the voltage drops due to blocking diodes (if present), operating temperature, and anticipated shading. 6. Install a charge controller that does not require blocking diodes. 7. Make solid, corrosion-free electrical connections and protect with corrosion inhibitor. 8. Clean the panel surfaces of dust and salt spray regularly. 206 Solar Power
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12 CHAPTER Wind Power 208 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
I f not solar power, then is wind power for you? Again, calculating the economics will tell. Getting power from the wind explains how the kinetic energy of moving air can be converted to elec- trical energy. In order to estimate the daily output of a wind machine, we need to know how much wind there is where we will be cruising and the specifications of our wind machine. The most difficult part of mechanical installation is simply selecting the best location on the boat. As in the case of solar panels, the electrical installation of a wind machine requires integration with the existing alterna- tor battery system. At least one popular wind machine can be converted into a water generator—a feature long-distance cruisers may wish to consider. 209
Is Wind Power for You? The variables determining the viability of wind power Fig. 12.1 Wind Power Production on Cruising Boats on a boat are much more complicated than those for photovoltaics, but the general criteria remain the 100 same—if you live aboard, are away from the dock at least 6 months of the year, and actively seek out windy 80 areas, the answer is probably yes; if you use your boat only 1 month per year, the answer is no. Percent of Load Generated 60 Before delving into the economics of wind power production, you should note several non-economic 40 factors that are unique to wind: 20 1. Maintenance. Wind machines are of two types: the familiar alternator, and DC electric motors 0 running backward. Both produce AC electricity, None Wind Only Wind & Solar but rectify it (change AC to DC) in different ways.As we saw in Chapter 4, alternators employ Economics solid-state diode bridges. The DC-motor types, Figure 12.1 shows the percentage of daily electrical load however, rely on brushes and commutators, both supplied by wind among 71 liveaboard boats surveyed of which are subject to wear and maintenance. in Florida and the Bahamas. Most of the wind Also, both types contain bearings which will machines were of the large (60-inch blade diameter) require replacement. variety. The fact that 40% of the average daily load still 2. Noise. All wind machines make noise, ranging had to be supplied by running the engine shows that from the barely perceptible whisper of a small, wind is not constant. Decreasing the daily load through six-bladed Ampair, to the "woof, woof, woof" of conservation (see Chapter 10) and increasing battery a large, two-bladed, mizzen-mounted machine. capacity could increase the wind contribution to 80% Generally, the more power being generated, the or more. louder the noise. Some find the noise of a large An interesting alternative is the combination of machine satisfying, an audible reminder that wind and solar, which, as shown in Figure 12.1, sup- their batteries are being recharged for free. Oth- plied an average of 96% of the daily load. ers—particularly sailors on nearby boats—find Figure 10.1 compared the costs of power generated the sound annoying.You would be wise to spend by wind, solar, and alternators of various sizes. The time on a boat with a particular model before $0.59 kilowatt-hour cost of wind power assumed: purchasing. • Wind machine lifetime—10 years 3. Safety. The higher the wind speed, the greater the • Installed cost—$1,500 output of a wind machine. But wind speeds over • Annual maintenance—$100 about 30 knots pose several potential problems, • Blade diameter—60 inches particularly with the larger-diameter machines: • Conversion efficiency—30 percent (1) the high centrifugal forces and vibration on • Average wind speed—10 knots the blades may cause fatigue and failure (throw- Such a wind machine would produce 420 kilowatt- ing a blade), (2) the electrical output may hours per year in a steady 10-knot wind. One of the become too much for the batteries or charge reg- conventional alternatives, also shown in Figure 10.1, is ulator to handle, and (3) it may prove impossible a 110-amp engine alternator charging the batteries on a to shut the machine down, either manually (pic- 50 to 90% cycle at a cost of $2.25 per kilowatt-hour. ture trying to stop an airplane propeller) or The example wind machine savings would thus be automatically. All of the manufacturers have $2.25 – $0.59 = $1.66 per kilowatt-hour, or $697 per addressed this issue, but in various ways. Make year. The machine would pay for itself in a little over 2 sure you understand the shutdown mechanism years. Unfortunately for the majority of boaters, if the of the machine you are thinking of purchasing, wind machine were used only 1 month per year, the and talk to several owners about their experi- savings would fall to $58 per year, and the payback ences. period would increase to over 25 years. 210 Wind Power
Getting Power from the Wind The electrical power that a wind machine can extract Diameter, D, enters the equation squared. Doubling from the wind is: blade diameter quadruples power output. Most P = K E × D 2 × V 3 marine wind machines have blade diameters of × Where: P = power in watts either 1 m (39 inches) or 5 feet (1.52 m). Squaring K = 0.0653 the ratio of diameters shows that the theoretical E = mechanical efficiency in % maximum output of the 5-foot machines is 230% D = blade diameter in meters that of the 1 m machines. V = wind speed in knots Wind speed, V, is the most important factor of all because it enters the equation cubed. The difference Example: Calculate the power output of a wind between 8 knots and 10 knots may be barely notice- machine having a blade diameter of 5 feet (1.52 meters) able when sailing, but doubles the output of a wind and efficiency of 30% in a steady 10-knot wind. machine. Don't guess; use the wind-power maps 3 P = 0.0653 0.30 × 1.52 2 × 10 = 45 watts on the following pages when making the purchase decision. × The equation highlights the important factors in Figure 12.2 plots wind machine output versus wind selecting and sizing a wind machine to satisfy a boat's speed. The two theoretical curves (dashed) assume effi- electrical demand: ciencies of 30% and output at 14 volts. The curves for Efficiency, E, can never be 100%. If it were, the actual machines were drawn to fit manufacturers' data. blades would extract 100% of the kinetic energy of You would be wise to question the output figures the wind, bringing the wind to a complete halt. The claimed by wind machine manufacturers. The impor- maximum theoretical, aeronautical efficiency of a tant specification is continuous rated output at 14 wind machine is 59.3% but, due to losses in the VDC, not maximum output. generating coils, rotor bearings, and transmission Since average wind speeds are rarely above 15 knots, gearing, the actual efficiencies are around 30%. output at wind speeds in excess of 15 knots is not important in your choice of a wind machine. Fig. 12.2 Manufacturer-Claimed Output of Marine Wind Generators 20 Fourwinds II 5' diameter, 30% efficient machine 1 m diameter, 30% efficient machine Ferris WP200 Kiss Windbugger Aerogen 6 15 Fourwinds III Air-X Marine Output @14 VDC, Amps 10 Rutland 913 Aerogen 4 Pacific 100 (Ampair) 5 Rutland 503 Aerogen 2 0 0 5 10 15 20 25 Wind Speed, Knots Getting Power from the Wind 211
How Much Wind Is There? Figures 12.3 through 12.7 show average wind power, Fig. 12.8 Variation of Wind Speed and Power with Height in watts per square meter, from the Wind Energy 50 Resource Atlas of the U.S. The figures are the power con- Over Open Water tained in the wind and must be multiplied by wind 40 machine efficiency and area swept by the blades to pre- dict electrical output. 30 What is most striking about the maps is the pre- Height Above Water, Feet dominance of low average wind speed. While we all 20 know of places where the wind blows much harder, you would be well advised to ignore such places. In reality, 10 Relative wind power it is human nature to seek refuge from the wind. Since Relative wind speed most boaters seek shelter when on the hook, the wind 0 speeds shown may, in reality, be a little too high. 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 The wind speeds shown in the figures were 50 In a Harbor With observed in exposed locations, such as airports, and at Trees and Boats an average height above ground of 10 meters. Figure 40 12.8 shows how wind speed and power vary with actual height in both open-water and harbor locations. 30 Over open water a wind machine at a height of 10 Height Above Water, Feet feet will be exposed to 90% of the 10-meter wind speed 20 and produce about 72% as much power. In a protected Relative wind power harbor, the same 10-foot height will result in about 10 80% of the 10-meter wind speed and only 50% of the Relative wind speed power. 0 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 Fig. 12.3 Annual Average Power in Wind in W/m 2 ANNUAL W/m 2 mph knots 50 7.8 6.8 100 9.8 8.5 150 11.5 10.0 200 12.5 10.9 300 14.3 12.4 400 15.7 13.6 212 Wind Power
Fig. 12.4 Spring Average Power in Wind in W/m 2 SPRING W/m 2 mph knots 50 7.8 6.8 100 9.8 8.5 150 11.5 10.0 200 12.5 10.9 300 14.3 12.4 400 15.7 13.6 Fig. 12.5 Summer Average Power in Wind in W/m 2 SUMMER W/m 2 mph knots 50 7.8 6.8 100 9.8 8.5 150 11.5 10.0 200 12.5 10.9 300 14.3 12.4 400 15.7 13.6 How Much Wind Is There? 213
How Much Wind Is There? Fig. 12.6 Fall Average Power in Wind in W/m 2 FALL W/m 2 mph knots 50 7.8 6.8 100 9.8 8.5 150 11.5 10.0 200 12.5 10.9 300 14.3 12.4 400 15.7 13.6 Fig. 12.7 Winter Average Power in Wind in W/m 2 WINTER W/m 2 mph knots 50 7.8 6.8 100 9.8 8.5 150 11.5 10.0 200 12.5 10.9 300 14.3 12.4 400 15.7 13.6 214 Wind Power
Estimating Daily Output Selecting the right size wind machine for your boat is Fig. 12.9 Areas Swept by 5-Foot and 1 m Wind Generator not quite the same as designing a solar system. While Blades you have a variety of solar panel sizes to select from, 5' (60\") there are really only two sizes of wind machine: 1 meter, and 5 feet. So selecting a wind machine comes down to deciding whether one of the two available sizes is worth the investment. 2,827 Start by determining your average daily load in Ah, sq in just as in Chapter 11. Next, determine the available power in the wind for the areas you plan to cruise, using either the annual map (Figure 12.3) or the sea- sonal maps (Figures 12.4 through 12.7). Calculating the expected average electrical power from a wind machine is then a simple matter of multi- 1,217 plying the area swept by the blades by the machine effi- sq in ciency and the power shown in the map for the area(s) you intend to cruise. 2,827 The area of a circle is π × 2 1,217 = 232% D /4 (Figure 12.9), so Watts = π× D 2 × E × P/4 1m (39\") where: = 3.14 This wind machine would be well matched to the π D = blade diameter in meters load of the energy-efficient boat discussed in Chapter E = wind machine efficiency, 0.00 to 1.00 10. P = annual wind power in W/m 2 Note that the output of this wind machine could be increased by either of two steps: Assuming E = 0.30 (30%): Watts = 0.24 D 2 × P 1. Changing to a 33-foot mizzen mount would kWh/yr = 2.10 D 2 × P theoretically increase output by a factor of Ah/day = 0.44 D 2 × P 100%/60% = 1.67. 2. With the 12-foot mount, anchoring in unpro- Example 1: How much power can you expect from a tected locations would theoretically increase wind machine of 5-foot (1.52 m) blade diameter, 30% output by a factor of 75%/60% = 1.25. efficiency, and 12-foot height in protected harbors in New England in summer and the Florida Keys in win- Example 2: For the same conditions as in Example ter? 1, how much power would a 1 m wind machine pro- duce? Answer 1: Both locations have average wind power 2 of about 100 W/m at 33-foot height.Assuming harbor Answer 2: The ratio of blade diameter 1 to blade locations, at 12-foot height (Figure 12.8) the available diameter 2 is: power is 60% of the power at 33 feet. Therefore, D2/D1 = 1.00 m/1.52 m = 0.66 Watts = 0.24 D 2 × P = 0.24 1.52 2 × 0.6 × 100 The ratio of outputs is the ratio of diameters, × = 33 watts squared: kWh/yr = 2.10 D 2 × P (D2/D1) = 0.662 2 = 2.10 1.52 2 × 0.6 × 100 = 0.43 × = 292 kilowatt-hours Ah/day = 0.44 D 2 × P The output of a 1 m machine would therefore be: = 0.44 1.52 2 × 0.6 × 100 14 watts, 126 kilowatt-hours per year, and 26 Ah per × = 61 Ah day. Estimating Daily Output 215
Specifications Table 12.1 Wind Machine Specifications Number Blade Weight, Warranty, AmpsAmps of Blades Diameter pounds years @10 kn @15 kn Aerogen 2 (LVM) 5 23\" 11 3 0.3 0.9 Aerogen 4 (LVM) 6 34\" 24 3 1.4 3.5 Aerogen 6 (LVM) 6 48\" 28 3 3.0 6.6 Air-X Marine 3 45\" 13 3 1.3 5.8 Ferris WP200 2 60\" 19 1 4.0 11.2 Fourwinds II 3 60\" 22 3 5.6 10.7 Fourwinds III 3 40\" 20 3 3.0 6.0 Kiss 3 30\" 23 3 4.5 10.0 Pacific 100 (Ampair) 6 36\" 20 3 1.0 2.7 Rutland 503 6 20\" 8 2 0.3 1.0 Rutland 913 6 36\" 28 2 1.6 3.8 Windbugger 3 54\" 38 1 4.0 10.0 Table 12.1 lists the specifications for the wind machines Other Specifications included in Figure 12.2. As the manufacturers say, "specifications subject to change without notice,"so get Voltage the latest information before making your purchase. Some machines are regulated to produce constant volt- age. If so, select a regulator that can be adjusted for Number of Blades your battery type. As pointed out in Chapter 3, gelled- Theoretically, the efficiency of a wind machine is unre- electrolyte batteries can be ruined by long-term charg- lated to the number of blades. A two-bladed machine ing at over 14.1 volts DC. When a manufacturer claims can be as efficient as a six-bladed machine. However, its machine is "battery regulated," watch out! Such noise level decreases with increased number of blades, machines cannot be left unattended for long periods. and blade diameter.All six-bladed machines are quieter than the two- or three-bladed machines. Brushes If a machine is used continuously, it may require new Blade Diameter brushes every year. If this sort of maintenance doesn't As already discussed, power output varies with diame- appeal to you, check with the manufacturer, or go with ter squared, so a large diameter is necessary for large a brushless machine. output. On the other hand, weight, noise, and potential danger all increase with diameter as well. Slip Rings Slip rings pass current from a swiveling wind machine Weight to the power cables leading to the battery. Without slip Weight is a two-edged sword. Light weight makes the rings a wind machine cannot make more than a few machine easier to handle—particularly in the case of revolutions before fouling its cable. A ±180° swivel- a halyard mount—but light weight may equate to a mount has no slip rings but tracks the wind 99% of flimsier construction and smaller continuous rated the time. output. Amps at X Knots Shutdown Watch out! This may be the output when the machine This is the most important safety factor. A machine is cold, before self-regulation kicks in. Make sure the that must be manually secured in high winds is at best rating for maximum continuous output is at least as inconvenient and at worst dangerous. Even if the large as the claimed 15-knot output. machine has an automatic governor or brake, make sure the braking device is guaranteed to at least 50-knot winds. Otherwise, you are likely to have a broken or burned-out machine within a year. 216 Wind Power
Electrical Installation Figure 12.10 shows a wind machine electrical installa- no wind. Note that the blocking diodes are tion. Voltage and current meters are not shown but are installed downstream (down-current) of the often supplied with wind machines. If they are, simply alternator isolation diodes so that the voltage follow the manufacturer's directions for installation. drops are not additive. A solar system is also shown in the figure because 3. Charge controller. Unless the wind machine con- wind and solar are often combined. The installation is tains a voltage regulator, a charge controller designed so that the wind and solar systems are com- should be inserted in the output to prevent over- pletely independent, though complementary. Deleting charging of the batteries. The manual bypass the solar system has no effect on the wind system switch shown is provided to allow periodic hookup. equalization of the batteries. Elements of the installation include: Some charge controllers dump excess current into 1. Fuses or circuit breakers. Because a short circuit in heat-sinked transistors. Others divert current to an one of the battery positive leads could lead to fire external load, such as a 12-volt water heater element. In or explosion of the battery, all positive battery any case make sure the controller can handle the max- leads except those from the alternator are imum output current. required to be overcurrent-protected, as close to All of the DC wiring standards and practices dis- the positive battery terminals as possible. cussed in Chapter 6 apply to wind machine installations 2. Blocking diodes. Most wind machines are little as well. Make sure the ampacity of the output conduc- more than DC motors. Blocking diodes prevent tors exceeds the wind machine's maximum output. Siz- current from the batteries from spinning the ing the conductors for a 3% maximum voltage drop is wind machine backward in the absence of wind. not as important with wind machines as with solar pan- They also act as isolation diodes, preventing the els, however, since the open-circuit voltage in winds battery with greater charge from discharging over 10 knots is at least 20 volts and the voltage regula- into the battery with lesser charge when there is tor is clamped at less than 15 volts. I'd use a 10% drop. Fig. 12.10 Electrical Hookup of Wind Generator (Solar Optional) F AUX GND + GND – + – + Charge Charge controller controller DC AMPS DC AMPS + + - - These diodes and fuses may be omitted, provided charge controllers contain overcurrent protection and means for blocking reverse currents. Electrical Installation 217
Mechanical Installation Figure 12.11 shows a common large wind machine (the Halyard Mount 5-foot Fourwinds) mounted in all possible configura- While the ability to raise a wind machine to great tions on a 35-foot ketch. Most wind machines can be height would seem to promise the highest output, least mounted in several configurations with mounting noise, and greatest safety, a halyard-mounted machine accessories available from the manufacturer. Check should not be raised beyond the reach of a person with dealers for the possibilities. standing on deck. Shutdown or recovery of a halyard- mounted machine in a high wind can be exceedingly Pole Mount dangerous. In addition, the hassle of deployment, recovery, and storage at every anchoring makes them Of the three mounting options, the stern pole is the less popular. most common. The pole is usually of 2-inch schedule- In spite of these negatives, some owners swear by 40 or 80 pipe. Bracing is provided either by two lengths the halyard mount, claiming deployment and recovery of rigid stainless tubing to the deck or by one rigid in less than 3 minutes, as well as lowest initial cost. standoff to the backstay plus two guywires to the deck. Large halyard-mount machines are usually two- Pole height should be such that the blade clears the bladed because they are most conveniently stored in the head of the tallest crew, but can be secured without V-berth and handled through a forward hatch. standing on a pulpit rail. The advantages of the pole mount are that it is accessible from the deck and that it allows use while Radar Arch Mount under sail. Disadvantages include smaller output due to In line with the modern trend of mounting everything low height, relatively high noise level, and potential on an aft radar arch or on davits, the Fourwinds offers danger to unwary crew. a radar arch mount with 360° freedom. The mount makes logical sense, but many feel it compromises the Mizzen Mounts aesthetics of a sailing vessel. Mizzen mounts, for boats with a second mast, raise the wind machine for greater output and decreased danger. Noise In spite of the height, if an unbalanced machine is After safety, the most common concern about wind mounted near the midpoint of the mast, noise levels machines is the level of noise generated at moderate to may be even greater than those for the pole mount. high wind speeds. Manufacturers have made some Blade distance from the mast is also important in progress in recent years in abating noise. reducing noise levels. Note that Fourwinds offers four First, as pointed out earlier, the fewer the blades, the different mizzen mounts. greater the noise. Because of this, only one two-blade The four types of mizzen mounts differ chiefly in machine (the Ferris) remains on the market. The the ability to swivel into the wind: 0° (fixed in forward majority now offer either three or six blades. direction), 180°, and 360° (unlimited). The fixed Second, the more aerodynamic (more like an air- mount is extremely limiting, being useful only when foil) the shape of the blade, the less the noise. The the boat is anchored or on a mooring. The 180° mount blades of the newest machines closely resemble air- allows operation in all conditions except running plane propellers. downwind. This is a small disadvantage, however, since Third, mounting a machine rigidly on a pole or the apparent wind speed is reduced by the speed of the mast directly connected to the deck results in vibra- boat. If a lot of downwind sailing is contemplated, tion being transmitted to the deck. The deck then acts some wind machines (Fourwinds, Ferris, and Ampair) like a drumhead, amplifying the sound. Some manu- can be adapted to towing behind the boat. facturers now offer rubber shock mounts to decouple the vibrations before reaching deck level. 218 Wind Power
Fig. 12.11 Wind Generator Mounting Options MM-2 Top of mizzen 360° MM-3 Mizzen 360° MM-4 Mizzen 180° RA-1 Radar arch MM-1 360° Halyard Fixed 0° 360° PM-1 Pole 360° Mechanical Installation 219
Water Generators Many wind machines can be converted to water gen- Fig. 12.13 Aquair 100 Mounted on a Stern Rail erators. Figure 12.12 shows the outputs of four water generators versus water speed. All are sized to carry the Generating unit electrical load of a typical cruising boat at less than hull speed. The drag typically slows a boat by a small frac- tion of a knot, and they are usually deployed only as needed to recharge the batteries. They are popular with downwind passagemakers who are already equipped with wind machines, since relative airspeed downwind is low, but water speed is high. Most mount the generator on the stem rail and trail the propeller unit with a line sufficiently stiff to transmit the torque to the generating unit (Figure 12.13). Manufacturers generally recommend carrying several spare propeller units on long passages. The rea- son is obvious: the spinning prop looks suspiciouly like live bait to a large fish! The electrical installation for dual units is the same ANN for both wind and water operation, and is described in Figure 12.10. Propeller unit Fig. 12.12 Water Generator Output Curves 20 Ferris WP200 18 16 14 12 Fourwinds Output, Amps 10 II & III 8 Aquair 100, standard 6 4 Aquair 100, coarse 2 0 0 1 2 3 4 5 6 7 8 Water Speed, Knots 220 Wind Power
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13 CHAPTER Installing Electronics Stainless 3 dB whip (VHF) Radar Fiberglass 6 or 9 dB whip (VHF) GPS Stainless 3 dB whip (VHF) Insulated mizzen stay (SSB) Stainless whip (VHF) Backstay insulator Insulated backstay (SSB) Radar Fiberglass 6 dB whip (VHF) or 23' SSB Radar GPS 222 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
I f you can install a towel rack, you can install an electronic cabinet or case. But there is often more to a successful electronic installation than meets the eye. This chapter focuses on communication and navi- gation electronics—that is, electronics that use anten- nas. Antennas are intended to receive signals. It is important that the incoming signals not be attenuated, so much attention must be paid to antenna cable and connectors in addition to proper receiver and transmit- ter installation. Receivers and transmitters include VHF radio, GPS, SSB, and radar. The problem is they also receive electrical noise, so we give step-by-step procedures for identifying the sources and reducing the level with electrical filters. 223
Antennas Few things are as satisfying as installing your own elec- or smaller than, objects on the boat. Objects with a tronics. Repairing digital electronic circuitry is beyond diameter less than 1 inch (such as a mast) can reflect the abilities of most, but installation is not. or block the signal, creating blind zones. Installation requires only an understanding of the Finally, signals are at least partially absorbed by DC wiring standards and practices in Chapter 6, wire grounded rigging. Antennas placed too close to metal and connectors available through chandleries and standing rigging thus suffer loss of signal strength. The mail-order catalogs, and the principles outlined in this exception that proves the rule is the use of an insulated chapter. (ungrounded) backstay as a long SSB or ham antenna. With these in hand, you should be able to install any To avoid interference, antennas that are used to trans- piece of marine electronic equipment over a weekend, mit as well as receive should be spaced from other and as well as any professional. The obvious benefits antennas. are a significant costs saving and satisfaction at accom- plishing a professional job. The less obvious benefit Fig. 13.1 Marine Antennas occurs when something goes wrong, and you find that you are now able to retrace your steps and often locate the problem. The equipment covered in this chapter includes VHF and SSB radios, GPS, and radar. From an instal- lation standpoint, all marine electronics are similar. You'll find that the principles and techniques apply to stereos, televisions, depth sounders, and wind indica- tors, as well. Antenna Types NAVTEC You can find books on antenna design and specific antenna designs in electronics and ham radio maga- zines. My advice, however, is to start with the antenna recommended or supplied by the manufacturer of the equipment. Many antennas are designed to work only with a specific brand and model of equipment. After you have the equipment up and running, you may decide to experiment with a different antenna. The original antenna will then serve as a reference. 6 dB fiberglass VHF whip Backstay Antenna Location insulator Figures 13.1 and 13.2 show a variety of antennas and locations that will be referenced in the discussions of particular equipment types. Fixed base VHF and radar signals travel in straight lines, so GARMIN their antennas should be mounted high. GPS signals travel line-of-sight from outer space and, except for the requirement for a relatively clear view of the sky, are independent of height. SSB and ham signals arrive from space, having bounced one or more times off the ionosphere. While antenna performance is independent of height, their External GPS great lengths (23 to 60 feet) require height at one end. 3 dB stainless antenna Radar and GPS have wavelengths of the same order, VHF whip Ratchet mount 224 Installing Electronics
Fig. 13.2 Locating Antennas Stainless 3 dB whip (VHF) Radar Fiberglass 6 or 9 dB whip (VHF) GPS Stainless 3 dB whip (VHF) Insulated mizzen stay (SSB) Stainless whip (VHF) Backstay insulator Insulated backstay (SSB) Radar Fiberglass 6 dB whip (VHF) or 23' SSB Radar GPS Antennas 225
Antenna Cable and Connectors To minimize interference from shipboard electrical Fig. 13.3 Cable Adapter and Feed-Throughs noise, all antennas aboard a boat are, or should be, con- PL-258 M359 nected to their respective receivers with coaxial cable. UHF double-female UHF 90 male/female Table 13.1 lists the most common coaxial cable types and their specifications. Table 13.1 Coaxial Cables Specification RG-58/URG-8XRG-8/URG-213 Nominal 0.D. 3 ⁄16\" 1 ⁄4\" 13 ⁄32\" 13 ⁄32\" M-348 Conductor AWG #20 #16 #13 #13 UHF T-adapter Impedance, ohms 50 50 52 50 Attenuation per 100 Feet UHF double-male @ 50 MHz 3.3 dB 2.5 dB 1.3 dB 1.3 dB @ 100 MHz 4.9 dB 3.7 dB 1.9 dB 1.9 dB @ 1,000 MHz 21.5 dB 13.5 dB 8.0 dB 8.0 dB Conductor size (AWG) is important in transmitters where large currents may result in resistive loss of UHF male/ power in the cable. UHF female/ BNC female BNC male Impedance of the antenna cable should match the BNC Right-angle output impedance of the transmitter in order to adapter maximize signal strengths. Attenuation is the loss of transmitted power in the cable between transmitter and antenna. Each 3 decibels (dB) of loss is equivalent to a reduction in power at the antenna of 50%. Coax cables may have identical specifications, yet Deck Deck feed- vary greatly in quality. Cables aboard boats are exposed through cap feed-through to salt spray, sunlight, oil, and sometimes battery-acid SO-239 mist. Use only the highest-quality cable, consisting of Panel receptacle tinned center conductor and braid, solid polyethylene dielectric, and UV-resistant, non-contaminating outer jacket. Figure 13.3 shows the cable adapters and feed- throughs available at most chandleries and radio stores. Figure 13.4 shows the assembly of UHF connectors on both large and small coaxial cables. Figure 13.5 demonstrates the similar assembly of BNC connectors on RG-58/U, RG-59/U, and RG-8X coaxial cables. Drill through-deck Solderless versions are not recommended in marine Cable through-deck (multiple conductors) (split insert) applications due to the moist environment and the likelihood of corrosion, which solder excludes. After assembly the connector and cable should be sealed with adhesive-lined, heat-shrink tubing, as shown in Figure 13.6, to exclude moisture. 226 Installing Electronics
Fig. 13.4 Assembly of PL-259 Connectors ON RG-58/U, RG-59/U, AND RG-8X CABLES ON RG-8/U AND RG-213 CABLES STEP 1: Slip on shell and adapter; STEP 1: Slip on shell and strip to center of conductor strip outer jacket back 5/8\" and back 3/4\" 3/4\" 5/8\" STEP 2: Strip outer jacket additional 5/16\" STEP 2: Bend back braided shield 3/4\" 5/16\" STEP 3: Slip adapter under braided shield STEP 3: Slip on body, making sure shield does not contact center conductor, and solder tip and shield through holes STEP 4: Strip center conductor 1/2\" and tin STEP 4: Screw shell onto body 1/2\" STEP 5: Screw on body and solder tip and braid through holes in body STEP 6: Screw shell onto body Antenna Cable and Connectors 227
Antenna Cable and Connectors Fig. 13.5 Assembly of BNC Connectors ON RG-58/U, RG-59/U, AND RG-8X CABLES FEMALE CONNECTOR MALE CONNECTOR STEP 1: Cut cable end even and STEP 1: Cut cable end even and strip strip outer jacket back 5/16\" 5/16\" outer jacket back 5/16\" 5/16\" STEP 2: Slide clamp nut and pressure sleeve over cable; straighten braid ends STEP 2: Slide clamp nut and pressure sleeve over cable; straighten braid ends STEP 3: Fold braid back; insert ferrule inside braid; STEP 3: Fold braid back; insert ferrule inside braid; cut dielectric back 13/64\"; tin conductor 13/64\" cut dielectric back 13/64\"; tin conductor 13/64\" STEP 4: Trim excess braid; slide insulator over conductor STEP 4: Trim excess braid; slide insulator over conductor into ferrule; slide female contact over conductor and solder into ferrule; slide male contact over conductor and solder STEP 5: Slide body over ferrule and press all parts STEP 5: Slide body over ferrule and press all parts into body; screw in the nut tightly into body; screw in the nut tightly 228 Installing Electronics
Moisture Protection Moisture is the enemy of marine connectors. At least 2. Drip loops near the connector force water run- 90% of all marine electronics problems are due to cor- ning along the conductor to drop off before rosion in connectors and conductors. Water that pen- reaching the conductor. The loops cannot pre- etrates the connector wicks into the stranded center vent incursion of water falling directly on the conductor and shield and travels far into the cable. connector, but they minimize guttering. A sin- Corrosion turns copper into powdery copper oxide, gle drip loop at the base of a vertical run diverts thinning the conductors. In addition, the copper oxide water running down the mast. is an insulator, so resistance goes up and signal strength 3. Adhesive-lined, heat-shrink tubing seals the con- goes down. nector to the cable, preventing water leaks. The Figure 13.6 shows three defenses against moisture: heated tubing shrinks (up to 85%), and the adhesive flows, sealing the connection. 1. Making a nonwaterproof connection inside a waterproof box with the conductors entering the box from beneath. Fig. 13.6 Protecting Coax Connections Against Moisture Unsealed connection Watertight box Rubber grommet Unsealed connection Slip on adhesive-lined, heat-shrink tubing Apply heat to shrink Moisture Protection 229
VHF Radio Three factors affect how far a properly working VHF 2. Antenna gain. As shown in Figure 13.7, anten- radio can be heard: nas can be designed to concentrate the radiation toward the horizon to a greater or lesser degree. 1. Cable transmission loss. As indicated in Table 13.1, The concentration is expressed as gain in dB. power loss increases with frequency and decreases Generally, the longer the antenna, the greater the with cable diameter. At the VHF frequency of 157 gain. Popular models and their lengths are 3 MHz, the lengths of coaxial cable for a 3 dB (50%) dB—38 inches; 6 dB—8 feet; and 9 dB—19 feet. power loss are RG-58—49 feet; RG-8/X—66 feet; A masthead, 3 dB, 38-inch whip antenna is the and RG-8/U—111 feet. A sailboat with a 50-foot most appropriate for a sailboat because mast mast and a 16-foot run will lose half its VHF height compensates for low gain, and the less transmitting power if it uses RG-8X (most boats flattened pattern allows for heeling under sail. do). The loss would be reduced by 50% by switch- Bridge-mounted 6 dB and 9 dB antennas are best ing to the larger-diameter RG-8/U or RG-213. for powerboats because they do not heel. Fig. 13.7 VHF Antenna Gain 3 dB (x2) 9 dB (x8) 6 dB (x4) 3. Antenna height. VHF transmission is line of The distances in Table 13.2 are based on the formulas: sight. Transmit/receive distance is the same as D = 1.17 H the distance two observers at the same heights D + D = 1.17( H + H ) √ can see each other. Figure 13.8 demonstrates the 1 2 √ 1 √ 2 principle. Table 13.2 lists the distances, versus the where D is in nautical miles (nm) and H is in feet. heights, of the two antennas. Actual transmission distances are observed to be about 1.22 H, about 4% greater than the theoretical Table 13.2 Line-of-Sight Distance, D1 + D2, for VHF Radios √ values under average conditions. Thus, two sailboats Receiver Transmitter Height, feet with 60-foot masts can be expected to communicate Height, ft 5 10 20 40 60 80 100 200 400 about 19 nm. 5 5 6 8 10 12 13 14 19 26 Powerboaters sometimes make the mistake of rak- 10 6 7 9 11 13 14 15 20 27 ing a high-gain VHF antenna back to make the boat 20 8 9 10 13 14 16 17 22 29 look more streamlined. This leads to a radiation pat- 40 10 1113 15 17 18 19 24 31 tern that will be into space in the forward direction and 60 121314 17 18 20 21 26 33 into water aft. 80 131416 18 20 21 22 27 34 100 141517 19 21 22 23 28 35 Fig. 13.8 Line-of-Sight Transmit/Receive Distance for VHF Radio D1 D2 H1 H2 230 Installing Electronics
GPS and SSB GPS A second option, available on sailboats, is an insu- GPS receivers are supplied with matched antennas. lated backstay. The backstay, insulated with special fit- With signal frequencies of about 1.5 gigahertz, the tings at upper and lower ends, acts as a simple "long- wavelengths are about 8 inches, and the antennas tiny. wire" antenna. To protect crew from radiation burns, Location requirements are that the antennas have clear either the bottom insulator and electrical connection views of the sky and be located outside the radar beam should be placed at least 7 feet above the deck, or a and a few meters away from VHF and SSB antennas. length of rubber hose should be slid over the exposed Antenna power is low, so RG-58 cable is acceptable. lower portion. Both antennas require tuners to achieve maximum output. The tuners may be built into the radio chassis SSB or Ham or a separate unit installed near the antenna. Most ham Both marine single-sideband and ham HF transceivers operators feel the separate units work better in the rel- operate in the same approximate frequency bands. SSB atively low-frequency SSB bands. transmissions are restricted to designated SSB frequen- Both antenna types work well. The advantages of cies, and ham radio transmissions are restricted to the 23-foot whip include smaller size, lower cost, and a FCC-designated ham bands. The two transceiver types, vertical orientation for omnidirectional transmission. however, are otherwise functionally identical.Although The insulated backstay results in a cleaner deck and it is illegal to operate a ham transmitter as an SSB captures more incoming signals. transmitter (except in an emergency), removal of a sin- Use either RG-8 or RG-213 coax to connect trans- gle diode allows the ham radio to transmit on all fre- ceiver and tuner. Attenuation is less in the 2- to 12- quencies, from 300 kilohertz to 30 megahertz. megahertz SSB bands than in the 157-megahertz VHF There are two types of SSB antennas. A 23-foot band, but output currents are much greater for the whip antenna works well down to 4 megahertz on both 150-watt SSB than the 25-watt VHF, so we need a larger power- and sailboats. The antenna should be mounted center conductor. vertically and located out of easy reach, since touching it may result in radiation burns. Fig. 13.9 Single-Sideband (SSB) Antenna and Ground Connections Terminal GROUNDING IN ORDER OF EFFECTIVENESS: A Encapsulated metal keel Backstay insulator B Largest sintered groundplate C 100 sq. ft. of copper or bronze screening glassed to inside of 7-foot Insulated lead hull below waterline clearance minimum SSB radio GND ANT GND IN ANT 3-inch copper foil Antenna C tuner B A GPS and SSB 231
Radar As with GPS, radar units include matching antennas. The near distance can be calculated from: The transmission frequency of around 9,500 mega- N = H /tangent 20° 1 hertz (9.5 gigahertz) corresponds to a wavelength of 1 = 2.75 (H – H ) about 1 inch. The radar waves are therefore easily × 1 0 blocked by metallic objects, such as masts, greater than For example, a 40-foot-high antenna cannot see 1 inch in diameter. surface objects closer than 110 feet. Reducing the A second location requirement is that the antenna— antenna height to 20 feet reduces the blind zone radius essentially a microwave generator—be located a mini- to 55 feet. mum of 2 feet from humans. (The first microwave Note that it is the difference in height between the ovens were aptly named Radar Ranges!) Just forward antenna and the target that determines the blind zone. of the steering station on a flying bridge is not a good A 40-foot-high antenna can see a 20-foot-high target, location! such as another boat, at a distance of 55 feet. The third location criterion is height. Since radar The cable between the radar antenna assembly and transmission is line of sight and limited in distance by the display unit typically contains a dozen conductors. the curvature of the earth, the higher the antenna, the Use only the type of cable supplied with the unit. farther you can see. On the other hand, the radiation Assuming you are skilled at soldering multi-pin has a vertical beam width of about 40°, so objects more connectors, you can shorten the supplied cable by any than 20° below the horizontal will not be seen either. In degree. A longer cable can generally be ordered as well. choosing an antenna height, you thus need to balance A third option is to purchase an extension cable with the need to see large, distant targets and small, close matching connectors. objects. The extension cable is very useful in the case of Figure 13.10 shows both far (D + D ) and near mast-mounted antennas in sailboats. Provided the 1 2 (N ) distances. Table 13.3 lists the far distances (range) original cable and the extension cables join at the mast 1 for combinations of radar and target heights. Table 13.4 step, stepping and unstepping the mast requires only similarly shows the near distances (blind zone) for connecting and disconnecting the cable. In any case, combinations of radar and target heights. never locate cable connectors in the bilge, where they may be subject to corrosion. Table 13.3 Radar Line-of-Sight Range in Nautical Miles Table 13.4 Radar Near Range (Blind Zone), N1, in Feet Radar Target Height (H ), feet Radar Target Height (H ), feet 2 0 Ht (H ), ft 5 10 20 40 60 80 100 200 400 Ht (H ), ft 0 1 2 3 5 10 15 20 30 1 1 5 5 6 8 10 12 13 14 19 26 5 14118 5 – – – – – 27 10 6 7 9 11 13 14 15 20 27 10 25221914–––– 15 7 8 10 12 14 15 16 21 28 15 3836332714––– 41 20 8 9 11 13 14 16 17 22 29 20 55 52 49 47 41 27 14 – – 25 9 10 11 13 15 16 18 22 29 25 69 66 63 60 55 41 27 14 – 30 9 10 12 14 16 17 18 23 30 30 82 80 77 74 69 55 41 27 – 40 10 11 13 15 17 18 19 24 31 40 110 107 104 102 96 82 69 55 27 50 11 12 14 16 17 19 20 25 32 50 135132129124110968255 137 Fig. 13.10 Radar Range and Blind Zone vs. Heights of Antenna and Target D1 D2 ±20° N1 H0 H1 H2 232 Installing Electronics
Receiver/Transmitter Installation Location 12-Volt DC Power Hookup 1. Install in a dry location. As we saw in Chapter 3, 1. Do not install more than one radio on a single moisture serves as an electrolyte and promotes circuit. If you do,VHF and SSB radios may inter- corrosion. Salt spray has a way of infiltrating fere with each other through their power leads. anything located on deck or in the cockpit. A 2. GPS receivers contain memories that retain thin film of salt on a circuit board may have coordinates and reduce settling time consider- much lower resistance than many of the circuit ably. Turning off the equipment's power switch components, effectively shorting them out and does not disconnect the power to the memory, altering, if not disrupting, performance. In my but a drop in voltage may erase the memory. experience a standard enclosure in a dry location Powering navigation electronics from the house causes fewer problems than a "waterproof" battery rather than the engine-starting battery enclosure in a wet location. will help prevent memory loss. 2. Prevent overheating. Electronics are designed to operate in any temperature a person can tolerate. They are designed to dissipate internally gener- Grounding ated heat either by conduction through the case, If there is a separate chassis, or case, ground (usually a by natural convection through vents, or by fan- wing nut labeled "Gnd"), then: forced convection. The most common mistakes 1. Run a #10 AWG minimum green or bare copper are to restrict ventilation and to pile heat- grounding wire to ground. producing electronics on top of each other with 2. Run a separate ground from each chassis. insufficient space between. 3. Do not strain cables. Install the equipment so that 3. On a steel or aluminum boat, ground to the hull both antenna and power cables are secure but as close as possible to the equipment. On a wood not taut. Excessive tension on the conductors can or fiberglass boat, make the common ground pull the connectors apart. point either the engine negative terminal or an external ground plate. 4. Keep away from magnetic compasses. Direct cur- 4. SSB/ham transmitters require special attention rent produces a magnetic field around a conduc- tor. The fields can be reduced but not eliminated to ground (see Figure 13.9). Grounding conduc- if the power leads are either coaxial or twisted. tors should be of 3-inch-wide copper foil and Even stronger magnetic fields are caused by connected to a large area of bronze screening radio-speaker magnets and ferrite-rod radio epoxied to the inside of the hull, a large sintered antennas. copper external ground plate, or an internal 5. Secure firmly at a good viewing/listening angle. metal keel. Provided that all underwater metals Equipment cases are usually supplied with con- are bonded, the boat's ground may prove suffi- venient mounting brackets that allow either ver- cient. Remember, however, that bonding all tical or horizontal mounting. Secure the mount- underwater metals may increase corrosion. ing bracket to a bulkhead or overhead with panhead self-tapping stainless screws. Receiver/Transmitter Installation 233
Harnessing Electrical Noise Conducting a Noise Audit Curing Noise If you still have a loran set, don't deep-six it until you The first step in curing a noise problem is to recognize have first conducted a noise audit of your boat's electri- how electrical noise is generated and how it penetrates cal system. Most loran sets will display the signal-to- electronic equipment. Figure 13.11 shows that electri- noise ratio (SNR) of their received 100-kilohertz loran cal equipment can be divided into noise generators signals. In this mode, they are marvelous tools for (alternators, generators, ignitions, regulators, DC detecting radio frequency noise aboard your boat. motors, fluorescent fixtures, and some types of digital Here's how: electronics) and noise receivers (radios and electronic navigation devices). 1. Disconnect shore power. Sometimes a single piece of equipment falls into 2. Turn off all electrical equipment, including both categories. I am reminded of my autopilot, whose lights, refrigeration, receivers and transmitters, DC motor caused noise in my radios, but whose elec- inverter, generator, and engine. tronic control went crazy when I transmitted on a 3. Turn on the loran and let it settle. nearby handheld VHF. 4. Call up the SNR display (see your owner's man- ual). If any of the SNRs (at least one master and Fig. 13.11 Radio Frequency Interference (RFI) Generators three slave stations per master should be avail- and Receivers able anywhere in the United States for display) RFI GENERATORS is greater than 50, proceed to the next step. If all of the SNRs are less than 50, select another loran Motor, chain having greater SNRs. fathometer, fluorescent F 5. Note on a pad of paper the SNR values of one GND GND F of the stations for a few minutes, then average + the values to obtain the "clean-boat" reference – + SNR. 6. Start the engine and bring it up to its normal cruising rpm. Compare the SNR now displayed with the engine running to the previous aver- aged clean-boat reference SNR. If the SNR has – + dropped by more than 20% (from 50 down to 40, for example), your engine alternator or gen- erator is a source of noise. 7. Repeat Step 6 for each additional piece of equip- ment, one at a time; i.e., turn off the previous piece of equipment before testing the next item. Any item that causes a greater than 20% drop in SNR is a source of noise that needs to be cor- – + rected. Between each of the tests recheck the ref- erence SNR, with all equipment off, to make sure – + it hasn't changed. RFI RECEIVERS 234 Installing Electronics
Electrical Filters Cures fall into two categories: shielding and filtering. Figure 13.13 lays out a step-by-step attack on elec- Shielding consists of enclosing sensitive electronics tronic noise. The first six steps attack the noise sources, in a metal case and connecting the case to ground, since killing but a single source may reduce the noise to thereby shunting radiated noise to ground. By enclos- an acceptable level on all receivers. The last four steps ing power and signal leads in shielded cable and con- treat the receivers individually. necting the cable shield to the metal case, we shunt The plan also proceeds roughly in order of increas- noise induced in the leads to ground, as well. ing cost. It is assumed that, as each step is implemented, Filtering utilizes capacitors and inductors. Capaci- all previous cures are left in place. tors conduct AC but block DC, while inductors con- 1. Run separate grounding conductors from the duct DC but block AC. The ideal 12-volt source is pure alternator (or generator) case and from the DC. Noise, on the other hand, is AC, either generated cases of the affected equipment to boat by the alternator or generator, or picked up by power ground. leads acting like antennas. To reduce the amount of AC 2. Install a 10,000 F, 50 VDC electrolytic capac- in a DC supply, we place capacitors across the + and – itor across the alternator + output and ground µ leads and inductors in series with the leads. terminals. Capacitors for 12-volt DC applications should be 3. Install a 1 F, 50 VDC capacitor from the volt- rated at 50 working volts (50 WVDC) minimum. Large age regulator battery terminal to ground. µ capacitors are generally polarized electrolytics, so make 4. Install 1 F, 50 VDC capacitors across the + sure you observe proper polarity. and – power input leads of all motors, fluores- µ Inductors are rated by the maximum continuous cent fixtures, and the depth sounder. DC current they can carry, as well as the value of induc- 5. Install an alternator filter across the alternator tance. For electronic navigation equipment, a 5-amp + output and ground terminals. The filter rat- rating is generally sufficient. For DC motors (pumps ing must exceed the output ampere rating of and autopilots), a 10-amp rating is common. Alterna- the alternator. tors and generators require ratings that match or 6. Install commercial 10-amp filters across the + exceed their peak output ratings. Inductors with 50-, and – power input leads of all motors and 10- 70-, and 100-amp ratings are common. amp filters across the + and – power input leads In the case of noise on power leads, the unprotected of fluorescent fixtures and the depth sounder. length of lead serves as an antenna, picking up the 7. Install 1 F, 50 VDC capacitors across the + noise. Thus, it is important to install the filter as closely and – power input leads of all affected elec- µ as possible to the noise generator or the receiver. tronics. Sometimes a single capacitor or inductor will 8. Install 1 F, 50 VDC nonpolarized capacitors reduce the noise to an acceptable level. More powerful from the + power lead to chassis ground and µ solutions are provided by a variety of special commer- the – power lead to chassis ground. cially available filters, combining capacitors and induc- 9. Install commercial 5-amp line filters across the tors, as shown in Figure 13.12. + and – power input leads of each piece of affected electronics. Fig. 13.12 A Typical RFI Filter 10. Enclose affected electronic equipment in screened-metal enclosures, or wrap in foil tape + + and connect the enclosure, or tape, to boat ground. In case all of the above grounding, shielding, and Input Output filtering prove insufficient, the only remaining option is relocation of the antenna, cables, or the equipment itself. Remove both antenna and equipment chassis from their mounts and connect temporary power and – – antenna leads. Experiment with the location of the antenna and chassis and the routing of supply and antenna cables until the best results are obtained. Electrical Filters 235
Electrical Filters Fig. 13.13 Incremental Attack on Electronic Noise (see text) STEP 1. Ground All Cases STEP 6. Filter on Accessory Supply Motor, 10-amp + fathometer, filter + fluorescent + + + F GND IN OUT F GND – – – – STEP 2. Capacitor across Alternator Output STEP 7. Capacitor on Equipment Supply + + + + 10,000µF 1µF F GND F GND – STEP 3. Capacitor on Regulator Input STEP 8. Capacitors from Supply to Gnd + Batt 1µF Voltage 1µF regulator 1µF – F STEP 4. Capacitor on Accessory Supply STEP 9. Filter on Equipment Supply + + 1µF + + – IN OUT – – – 5-amp filter STEP 5. Alternator Filter STEP 10. Grounded Equipment Screen + + + + IN OUT F GND F GND – – – 236 Installing Electronics
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14 CHAPTER Do-It-Yourself Projects PROJECT 6: Expanded-Scale Analog Battery Monitor (11.7–12.7V) R OPT 3V M V – + VIN VOUT 317T Battery 11.7V Adjust R TO3 TO-220 Bottom View VOUT ADJ VIN CASE IS OUT ADJ VIN 238 Copyright © 1993, 2006 by Charlie Wing. Click here for terms of use.
T his chapter describes thirteen do-it-yourself proj- ects that are fun and can be completed in an afternoon. By doing these projects, you can increase your understanding of electricity and electron- ics, upgrade your boat's electrical system, and save money—all at the same time. Each project can be completed in a Sunday afternoon and typically costs less than $10. Most of the compo- nents are available at RadioShack stores, of which there are more than 7,000 nationwide. As an aid I have listed the RadioShack part numbers of each component next to the circuit diagram. Those parts that cannot be found at a RadioShack can be found at Internet mail-order stores such as www.surplussales.com. 239
Passive Circuit Components Projects are always more fun and generally more suc- two end terminals. By connecting to the wiper terminal cessful when you understand how they work. To under- and the appropriate end terminal, we can have a resis- stand the behavior of a circuit, you first have to under- tance that increases or decreases with clockwise rota- stand how each of its components works. A few of the tion of the screw. Using all three terminals, you have, integrated circuits listed are actually complex circuits in effect, two resistors, which form a voltage divider. containing, in a single small package, hundreds of com- Low-power variable resistors are known as trim- ponents. For these we will have to settle for an action/ mers or trimpots; medium-power variable resistors are reaction, or input/output understanding. Each of the potentiometers; and high-power variable resistors are discrete components is described in a thumbnail sketch rheostats. below. Thermistor. In reality a semiconductor, the thermistor (T) is a component whose resis- T Conductors tance changes with temperature. Thermis- No connection. A conductor is shown as a tors are specified by their resistance at 25°C, solid line. Where conductors simply cross for example 10 kW (10,000 ohms) at 25°C. in a circuit diagram, there is no connection. If the variation of resistance with temperature were linear, measuring temperature with an ohmmeter Connected conductors. When two or more would be a simple matter. Thermistors are more often conductors are electrically connected, the used to control temperature, however, using the devia- co