an improved change of phase refrigeration system utilizing low compressor head pressures to maximize compressor efficiency , employing a relatively low temperature cooling medium to cool refrigerant gases , using a metering device which is operable at a relatively low pressure differential to feed condensate to the evaporator coil and providing additional controls to temporarily increase head pressure and thus condensate temperature when such increased temperature is needed for heat recovery or gas defrost . because the proposed refrigeration system employs condensate at a relatively low temperature it may be necessary to enlarge the supply line for liquid refrigerant running from the condenser to the metering device to minimize evaporation of the condensate in the supply line . further , it may be preferable to insulate the liquid refrigerant line so as to minimize premature evaporation of condensate in that line .