Continuous Duty Current (Amps)-Wires in Bundles, Groups, Harnesses, or Conduits (See Note #1) h t i w , r e g r a l d n a 8 e z i s r o f s e r i w 9 d n a , 0 1 h g u o r h t 4 2 s e z i s r o f e l d n u b e h t n i s e r i w e r o m r o 3 , t n e i b m a C ° 0 7 r o f s i g n i t a R : 1 e t o N  no more than 20 percent of harness current carrying capacity being used, at an operating altitude of 60,000 feet.  Note 2: For resistance of silver or nickel-plated conductors, see wire specifications. Wire Size 105 °C 150 °C 200 °C 24 22 20 18 16 14 12 10 8 6 4 2 1 0 00 000 0000 2.5 3 4 6 7 10 13 17 38 50 68 95 113 128 147 172 204 4 5 7 9 11 14 19 26 57 76 103 141 166 192 222 262 310 5 6 9 12 14 18 25 32 71 97 133 179 210 243 285 335 395 28.40 16.20 9.88 6.23 4.81 3.06 2.02 1.26 0.70 0.44 0.28 0.18 0.15 0.12 0.09 0.07 0.06 475 755 1,216 1,900 2,426 3,831 5,874 9,354 16,983 26,818 42,615 66,500 81,700 104,500 133,000 166,500 210,900 Wire Conductor Temperature Rating Max. Resistance ohms/1,000 ft@20 °C Tin Plated Conductor (See Note #2) Nominal Conductor Area (circ.mils) Figure 4-76.  Current-carrying capacity and resistance of copper wire.  Allowable Voltage Drop Continuous Operation Intermittent Operation Nominal System Voltage 1 2 8 14 0.5 1 4 7 14 28 115 200 Copper Aluminum Characteristic 25,000 40,000 48 160 17 55,000 55,000 100 100 10.6 Tensile strength (lb/in 2 ) Tensile strength for same conductivity (lb) Weight for same conductivity (lb) Cross section for same conductivity (CM) Specific resistance (Ω/mil ft) Figure 4-78.  Recommended voltage drop in load circuits. Figure 4-77.  Characteristics of copper and aluminum. at a constant value. structure is always considered negligible. However, this is  based on the assumption that adequate bonding of the structure  or a special electric current return path has been provided  that is capable of carrying the required electric current with  a negligible voltage drop. A resistance measurement of 0.005  ohms from ground point of the generator or battery to ground  terminal of any electrical device is considered satisfactory.  The graph in  Figure 4-79  applies to copper conductors  carrying direct current. To select the correct size of conductor,  two major requirements must be met. First, the size must  be sufficient to prevent an excessive voltage drop while  carrying the required current over the required distance.  Second, the size must be sufficient to prevent overheating  of the cable while carrying the required current. The graphs  in  Figures 4-79  and  4-80  can simplify these determinations.  To use this graph to select the proper size of conductor, the  following must be known:  Another satisfactory method of determining circuit resistance  is to check the voltage drop across the circuit. If the voltage  drop does not exceed the limit established by the aircraft or  product manufacturer, the resistance value for the circuit is  considered satisfactory. When using the voltage drop method  of checking a circuit, the input voltage must be maintained  1. The conductor length in feet 4-48