Method for operating a refrigeration cycle as a heat pump and operable as a heat pump refrigerant circuit

A method of operating a refrigerant circuit (10) as a heat pump, wherein • compressed by a compressor and refrigerant through a refrigerant / heating heat exchange means (14) is pumped, • from the refrigerant / heating heat exchange means (14) coming refrigerant is expanded in at least a first expansion member (23), • via the first expansion member (23) flows relaxed refrigerant through at least one evaporator (24) to a suction inlet (12) of the compressor (11), at a between a refrigerant inlet (21) and a refrigerant output (22) of the refrigerant / heating heat exchanger device (14) situated branch-off point (23a) of the refrigerant / heating heat exchange means (14) is branched off via a second refrigerant expansion device (26) directed toward the suction inlet (12), characterized in that • that the refrigerant circuit (10) via the refrigerant / heating heat exchange means (14) thermally connected to a flow-through of fluid heating circuit (17) is coupled, wherein the refrigerant / a refrigerant is heating heat exchange means (14) / liquid heat exchanger means (14), and • that of the at least one evaporator (24) coming refrigerant via a collector (25) is guided to the suction inlet (12).