Heat source unit for refrigeration apparatus

A heat source unit forming, together with a utilization-side unit, a refrigeration apparatus including a refrigerant circuit performing a refrigeration cycle, the heat source unit housing at least a compressor and a heat-source-side heat exchanger, each of which is provided for the refrigerant circuit, wherein

• the heat-source-side heat exchanger is connected to a heat source water circuit in which heat source water circulates so that a refrigerant circulating in the refrigerant circuit exchanges heat with the heat source water, the heat-source-side heat exchanger having a heat exchange region, of a variable size, in which the refrigerant flows and exchanges heat with the heat source water, and
• the heat source unit comprises a controller which adjusts the size of the heat exchange region of the heat-source-side heat exchanger based on a differential pressure index value indicating a difference between high pressure and low pressure of the refrigeration cycle performed by the refrigerant circuit.