Defrost control system for a refrigeration heat pump.

摘要

A control system for a refrigeration heat pump (10) having an outdoor coil (14) through which air is blown by a fan for extracting heat from outdoor air with means to defrost the coil periodically has a differential pressure responsive means (23) responding to the differential air pressure across the outdoor coil (14). A time control means periodically operates the heat pump for a time controlled operation for predetermined time period (such as 90 minutes of elapsed operating time) and measures and stores the value (PB) of the differential pressure across the coil at the end of the time period in memory. A control means (32) controls the heat pump (10) for a total elapsedime operation in a pressure controlled operation until the pressure differential (PB) as previously stored occurs at which time a defrost cycle is initiated. Periodical a time controlled operation is initiated to update the pressure stored in the memory.