Drain down freeze prevention control system for a solar collector

摘要

A control device for preventing freeze damage to a solar hot water heater collector and auxiliary conduits, while insuring system operation for absorbing energy whenever sufficient useable solar energy is available, thereby increasing the overall efficiency of the system. The control device includes a drain valve that may be opened as a function of ambient temperature and a drain down override circuit that insures closure of the drain down system whenever a predetermined temperature differential exists between the water in the collector and the heated water in the storage tank. The drain down will be thereby overridden in favor of increasing system energy at a predetermined temperature differential.