Cascade unit and refrigeration system

A cascade unit of a refrigeration system including

• a first circuit through which a heat medium carrying heat flows, including a first heat exchanger that exchanges heat between a heat source and the heat medium, the heat medium including a first refrigerant,
• a second circuit including a compressor that compresses a second refrigerant and a second heat exchanger that exchanges heat between the second refrigerant and indoor air, the second refrigerant circulating the second circuit,
• a cascade heat exchanger that exchange heat between the heat medium in the first circuit and the second refrigerant in the second circuit,
• the cascade unit comprising:
• the cascaded heat exchanger;
• the compressor;
• and
• a casing that accommodates the cascade heat exchanger and the compressor, wherein
• the first circuit includes a first connecting portion that connects a first pipe and a second pipe extending from the cascade heat exchanger, the first pipe and the second pipe connecting the first heat exchanger and the cascade heat exchanger, the first pipe and the second pipe extending from the first heat exchanger inside or outside the casing,
• the second circuit includes a second connecting portion that connects a liquid pipe and a gas pipe extending from the cascade heat exchanger, the liquid pipe and the gas pipe connecting the second heat exchanger and the cascade heat exchanger, the liquid pipe and the gas pipe extending from the second heat exchanger inside or outside the casing,
• the first connecting portion and the second connecting portion are disposed close to each other,
• the first refrigerant includes at least one of an HFC refrigerant or an HFO refrigerant,
• the second refrigerant includes carbon dioxide, and
• a distance between the second connecting portion of the liquid pipe and the second connecting portion of the gas pipe is larger than a distance between the first connecting portion of the first pipe and the first connecting portion of the second pipe.