A heat pump system using a non-azeotropic refrigerant mixture comprising a main refrigeration circuit, an engine coolant circuit, and a refrigerant rectifier circuit interfacing with main refrigeration circuit, and the engine coolant circuit. The refrigerant rectifier circuit comprises in order of decreasing relative elevation a condenser, a storage vessel in communication with a condenser, a rectifier in communication with a storage tank and a condenser, a receiver vessel in communication with a rectifier, and a boiler in communication with the rectifier and the receiver vessel. The refrigerant rectifier circuit is used to adjust the relative concentrations of lower boiling point refrigerant, and higher boiling point refrigerant in the non-azeotropic refrigerant mixture thereby changing the cooling or heating capacity of the heat pump system.