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Reliability and design guidelines for combined solar-space-heating and domestic hot-water systems

Concepts of combined solar space-heating and domestic hot water (DHW) systems, and techniques for development of such systems are summarized for engineers and designers. Minimum instrumentation requirements for determining whether such system are operating properly are discussed, as are start-up and trouble shooting. However, detailed information on design, sizing, and installation are not included. Flat plate and tubular collector modules and generic drain-back systems that use them are analyzed by means of block-type reliability diagrams. System reliability results, based on a 6 h/d duty cycle, are given for five collector array sizes, in terms of mean time between failures. The duty-cycle analysis approach can be similarly applied to other operating cycles.