Abstract: A system includes a compressor and an expansion valve. The exit side of the compressor and the inlet side of the expansion valve are connected by a high pressure conduit, and the exit side of the expansion valve and the inlet side of the compressor are connected by a low pressure conduit. A bypass conduit is connected to the high pressure conduit and the low pressure conduit and a flow rate regulating valve is mounted on the bypass conduit. A control unit controls the expansion valve and the flow rate regulating valve to perform two starting operations in such a way that the flow rate regulating valve is open and the expansion valve is closed in a first starting operation, and the flow rate regulating valve is closed and the electronic expansion valve is open to a predetermined extent in a second starting operation. The compressor is controlled by a duty control signal having a period shorter than a period during a normal operation for starting operations.