Survey of Failure Modes from 122 Residential Solar Water Heaters

This report describes the results of a survey on the operation of active solar heating and cooling systems and their components. Questionaires were sent to homeowners and installers, covering 122 systems. Results were categorized according to problem severity, location, system type, length of system operation, and time of the year. Approximately 47% of the systems had at least one reliabilityproblem over a two-year period. Flat-plate collector and storage systems were highly reliable. Improper operation of these components was attributed to installation problems. Drainback designs also had the greatest reliability; drain down systems were the least reliable, largely because of the failure of drain down valves. Differential controllers caused the largest number of failures thatresulted in a repair cost in excess of $50 to the homeowner.