Abstract: A de-superheater is positioned between the compressor and the condenser of a refrigeration circuit and a pump circulates heat-transfer fluid past the de-superheater to heat it to a temperature higher than fluid heated by the condenser. The de-superheater is by-passed by a refrigerant line and a valve controls the amount of refrigerant passing through the de-superheater in accordance with the demand for the heated fluid as sensed by a temperature sensor at the heated fluid outlet of the de-superheater. The pressure of the refrigerant entering the condenser is measured to determine the amount of heat being taken therefrom. If this is insufficient to allow condensation of refrigerant to be completed in the condenser, a heat exchanger and a variable speed fan provide additional cooling of the refrigerant to ensure its complete condensation.