liquid pressure amplification with bypass is used in an air - conditioning or refrigeration system which includes a compressor , a condenser , a pump , an expansion valve , and an evaporator , interconnected by conduits in a closed refrigerant loop . a first conduit coupling an outlet of the compressor to an inlet to the condenser . a centrifugal pump is coupled to the condenser outlet for boosting the pressure of the condensed liquid refrigerant by a substantially constant increment . a second conduit transmits a first portion of the condensed liquid refrigerant from outlet of the pump through the expansion valve into the evaporator to effect cooling . a third conduit transmits a second portion of the condensed liquid refrigerant from the pump outlet into the condenser inlet , which cools the superheated vapor refrigerant entering the condenser , reducing head pressure . a bypass having a valve around is provided to direct refrigerant around the pump in the event the pump is idled while the compressor remains in operation .