through the hear recovery coil flows along conduit 26 to the remote condenser in order to maximize the efficiency of the heat recovery coil the pressure within the coil should be maintained at a fairly high level thereby maintaining the high temperature of the gaseous refrigerant for this purpose pressure regulator 28 is included along conduit 26 for regulating the pressure in coil 20 during certain milder seasons of the year although extraction of heat from heat recovery coil 20 is desirable only a lower level of heat is needed accordingly a bypass solenoid 30 can be provided for enabling the refrigerant to circumvent regulator 28 when solenoid 30 is open a portion for example one third of the heat of rejection will be recovered to the store this effectively causes a drop in the pressure and hence temperature of the gaseous refrigerant in heat recovery coil 20 during the normal refrigeration operation liquid refrigerant flows through liquid manifold 40 into evaporator 48 the evaporated refrigerant then flows through three way valve 50 into suction manifold 52 the evaporated refrigerant from suction manifold 52 is then returned to the compressors through suction conduit 56 during the defrost cycle of operation however the flow of liquid refrigerant is terminated temporarily and gaseous refrigerant is supplied to evaporator coil 48 thus gaseous refrigerant is supplied along conduit 58 to gas defrost manifold 54 from which it is then fed through defrost gas conduit 55 into three way valve 50 three way valve 50 then directs the defrost gas into evaporator 48 after the defrost gas has been supplied to evaporator 48 for a first period of time the flow is terminated by a solenoid 82.