Compressor heat pump system with maximum and minimum evaporator DELTA T control

摘要

An air source heat pump system incorporating a refrigerant charged bulb within the air flow passing over the outdoor coil of the heat pump system to sense outside ambient air temperature. The refrigerant charged bulb supplies a variable saturated pressure which acts upon a bellows of a control unit whose opposite side is subjected via a second bellows to saturated suction pressure (corresponding to refrigerant evaporating temperature) of the refrigerant returning from the outdoor coil to the inlet of the compressor. The bellows provides a spring load. An electrical switching device responsive to this pressure differential acts to first block unnecessary loading of the compressor and secondly to initiate unloading of the compressor. Additional switching means prevents excessive unloading of the compressor and insures subsequent initiation of loading to prevent liquid logging of the evaporator coil.