Refrigeration cycle system

A refrigeration cycle system comprising:

• a first circuit, in which a first refrigerant circulates, includes a first compressor, a cascade heat exchanger, and a first heat exchanger;
• a second circuit, in which a second refrigerant circulates, includes a second compressor, the cascade heat exchanger, and a second heat exchanger;
• and
• a processor, wherein
• the first circuit includes a first flow path connecting the cascade heat exchanger and the first heat exchanger, a suction flow path of the first compressor, a bypass circuit connecting the first flow path and the suction flow path, and a controlling valve provided in the bypass circuit, and
• the processor is further configured to,
• when the cascade heat exchanger functions as a radiator for the first refrigerant and functions as an evaporator for the second refrigerant, open the controlling valve in the event an index on a degree of subcooling of the first refrigerant at an outlet of the cascade heat exchanger satisfies a predetermined first condition.