Patent ID: 8117859

Claim:
An air conditioning system having a cooling mode and a free-cooling mode, comprising: a refrigeration circuit having a compressor and a pump; a suction pressure sensor for measuring a suction pressure of said compressor; a discharge pressure sensor for measuring a discharge pressure of said compressor; a controller for selectively operating in the cooling mode by circulating and compressing a refrigerant through said refrigeration circuit via said compressor or operating in the free-cooling mode by circulating said refrigerant through said refrigeration circuit via said pump; and a recover-refrigerant sequence resident on said controller, said recover-refrigerant sequence being configured to pump the refrigerant in a portion of said refrigeration circuit not used in the free-cooling mode to remaining portions of said refrigeration circuit used in the free-cooling mode when said controller switches from the cooling mode to the free-cooling mode; wherein said refrigeration circuit further comprises an controllable expansion device, said recover-refrigerant sequence being configured to maintain said expansion device in a predetermined open position until a pressure differential across said compressor reaches a threshold pressure differential, the controllable expansion device being restricted when the pressure differential across said compressor reaches the threshold pressure differential.