Combined heating and cooling system

Combined refrigerant heating and cooling system, comprising a compressor, an outside heat exchanger, an inside heat exchanger, a refrigerant-to-engine coolant heat exchanger, at least one refrigerant expansion device and at least one redirection device, wherein the arrangement being such that said compressor is switchable between a heat pump loop defining a heat pump mode and a cooling loop defining a cooling mode by means of said redirection device, said heat pump loop comprising said inside heat exchanger, said refrigerant expansion device and said refrigerant-to-engine coolant heat exchanger, and said coolant loop comprising said outside heat exchanger and said inside heat exchanger, characterized in that an outlet of said outside heat exchanger is connected to a connection point which when in said heat pump mode said connection point lies downstream of said refrigerant expansion device and further including a non-return valve arranged between said outlet of said outside heat exchanger and said connection point for allowing fluid to flow through said outlet from said outside heat exchanger toward said connection point and for preventing fluid to flow from said connection point into said outside heat exchanger when in both said heat pump and cooling modes thereby improving the operation of said system when in said heat pump mode.