A control valve according to one embodiment includes a shaft that transmits the solenoidal force to a valve element. The control valve, in one example, ensures high pressure resistance at a mounting part where a control valve is mounted in a variable displacement compressor. A solenoid includes a bottomed sleeve into which the pressure of refrigerant is introduced, a core secured coaxially to the sleeve, a plunger, contained in the sleeve on its bottom side, which is displaceable integrally with the shaft in a direction of axis line, a first spring that applies the biasing force in a valve opening direction to the shaft, a second spring that applies the biasing force in a valve closing direction to the plunger, and a shaft support member, which is press-fitted such that the shaft support member is secured to an inner wall of the sleeve near its bottom portion. The second spring is set between the shaft support member and the plunger.

A heat source unit includes a controller configured to control the subcooling-side decompression valve according to a degree of subcooling of a refrigerant flowing out of the first flow path of the subcooling heat exchanger. Under a condition that the opening degree of a subcooling-side decompression valve is equal to or greater than a predetermined opening degree, the controller determines that there is a shortage of a refrigerant in the refrigerant circuit.

A heat source unit constitutes a refrigeration apparatus by being connected to a utilization-side unit. The heat source unit includes a low-stage compression element, a high-stage compression element, and a heat exchanger. The low-stage compression element has a discharge pipe provided with a pressure switchgear. The high-stage compression element compresses a refrigerant discharged from the low-stage compression element. When the low-stage compression element is paused in response to activation of the pressure switchgear, the high-stage compression element operates while the low-stage compression element is kept paused.

A refrigeration system is described having a circuit around which a refrigerant circulates. The circuit includes a compressor, a metering device, a first heat exchanger for exchanging heat between the refrigerant and a medium, and a second heat exchanger for exchanging heat between the refrigerant and a thermal store. The refrigeration system is operable in a first mode and a second mode. In the first mode, the metering device has a first restriction such that the medium is cooled at the first heat exchanger and the thermal store is heated at the second heat exchanger. In the second mode, the metering device has a second, less restrictive restriction or is bypassed such that the medium is heated at the first heat exchanger and the thermal store is cooled at the second heat exchanger.