Heat source unit and refrigeration apparatus

Abstract

A heat-source-side circuit of a heat source unit includes a low-stage compressor, a high-stage compressor, a heat-source-side heat exchanger, a receiver, and a venting passage. The venting passage connects an upper portion of the receiver with an inlet of the high-stage compressor. A determination unit of the heat source unit determines that the amount of the refrigerant charged in a refrigerant circuit is excessive based on the pressure and the degree of superheat of the refrigerant sucked into the high-stage compressor.

1 . A heat source unit connected to a utilization-side unit and forming a refrigerant circuit configured to perform a refrigeration cycle, the heat source unit comprising:
 a heat-source-side circuit including a low-stage compressor, a high-stage compressor, a heat-source-side heat exchanger, and a receiver; and   a determination unit configured to determine that an amount of a refrigerant charged in the refrigerant circuit is excessive,   wherein   the heat-source-side circuit includes a venting passage that connects an upper portion of the receiver with an inlet of the high-stage compressor, and   the determination unit determines that the amount of the refrigerant charged in the refrigerant circuit is excessive based on a pressure and a degree of superheat of the refrigerant sucked into the high-stage compressor.   
     
     
         2 . The heat source unit of  claim 1 , wherein
 the determination unit determines that the amount of the refrigerant charged in the refrigerant circuit is excessive if a determination criterion is satisfied, and   the determination criterion is that the pressure of the refrigerant sucked into the high-stage compressor is higher than a reference pressure and that the degree of superheat of the refrigerant sucked into the high-stage compressor is lower than a reference degree of superheat.   
     
     
         3 . The heat source unit of  claim 2 , wherein
 the refrigerant amount determination unit repeatedly determines whether the determination criterion is satisfied, and determines that the amount of the refrigerant charged in the refrigerant circuit is excessive if the determination criterion is satisfied twice or more within a predetermined time.   
     
     
         4 . The heat source unit of  claim 1 , wherein
 the heat-source-side circuit is charged with carbon dioxide as a refrigerant.   
     
     
         5 . A refrigeration apparatus comprising:
 the heat source unit of  claim 1 ; and   a utilization-side unit connected to the heat source unit.