Air source heat pump system for heating buildings - has refrigerant charged bulb within air flow passing over outdoor coil for sensing ambient temp.

摘要

Air source heat pump system for heating a building comprises a refrigerant charged bulb within the air flow passing over the outdoor coil of the heat pump system to sense outside ambient air temp. The bulb supplies a variable satd. pressure which acts upon a bellows of a control unit whose opposite side is subjected via a second bellows to satd. suction pressure of the refrigerant returning from the outdoor coil to the inlet of the compressor. An electrical switch responsive to the pressure differential acts first to block unnecessary loading of the compressor and secondly to initiate unloading of the compressor. A further switch prevents excessive unloading of the compressor and ensures subsequent initiation of loading to prevent liq. logging of the evaporator coil. The satd. suction pressure of the compressor is never allowed to fall further than necessary to adequately heat the building and which prevents the satd. condensing pressure from exceeding that necessary to adequately heat the building under steady state conditions.