Heat source unit and refrigeration device

A heat source unit constituting a refrigeration apparatus by being connected to a utilization-side unit, the heat source unit comprising:

• a low-stage compression element;
• a high-stage compression element;
• a heat exchanger;
• and a controller, wherein
• 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,
• the controller is configured to pause an operation of the low-stage compression element in response to activation of the pressure switchgear, and pause an operation of the high-stage compression element once and restart the operation of the high-stage compression element while the operation of the low-stage compression element is kept paused, thereby allowing refrigerant remaining in the discharge pipe of the low-stage compression element to be sucked by the high-stage compression element so as to reduce the pressure at the discharge pipe of the low-stage compressor element before restarting the low-stage compression element.