Air-conditioning apparatus

An air-conditioning apparatus comprising:

• a compressor;
• a heat source side heat exchanger;
• an expansion device;
• a heat exchanger related to heat medium;
• a pump;
• and a plurality of use side heat exchangers,
• the compressor, the heat source side heat exchanger, the expansion device, and the heat exchanger related to heat medium being connected with refrigerant pipes to form a refrigerant circuit in which a heat-source-side refrigerant is circulated,
• the pump, the plurality of use side heat exchangers, and the heat exchanger related to heat medium being connected with heat medium pipes to form a heat medium circuit in which a heat medium is circulated,
• the compressor and the heat source side heat exchanger being housed in an outdoor unit,
• the expansion device, the heat exchanger related to heat medium, and the pump being housed in a relay unit,
• each of the plurality of use side heat exchangers being housed in an indoor unit,
• the heat exchanger related to heat medium exchanging heat between the heat-source-side refrigerant and the heat medium, wherein
• the refrigerant pipes are configured such that an inner cross-sectional area of a refrigerant pipe among the refrigerant pipes, which connects between the outdoor unit and the relay unit and through which a high-pressure refrigerant flows, is smaller than an inner cross-sectional area of a refrigerant pipe among the refrigerant pipes, which connects the outdoor unit and the relay unit and through which a low-pressure refrigerant flows,
• a heat medium pipe among the heat medium pipes, which connects the relay unit and the indoor unit, is configured such that each inner cross-sectional area of the heat medium pipe per 1 kW of capacity of the plurality of the indoor units is larger than the inner cross-sectional area per 1 kW of the outdoor unit capacity of the refrigerant pipe through which the low-pressure refrigerant flows.