Air-conditioning apparatus including unit for increasing heating capacity

An air-conditioning apparatus, comprising:

• an outdoor unit including a compressor that compresses and discharges a refrigerant, a discharge port that discharges the refrigerant that has been discharged from the compressor to an outer portion, a first flow switching device that is connected to a passage branching off from a passage between the compressor and the discharge port and that switches a passage of the refrigerant discharged from the compressor, an outdoor heat exchanger that is connected by piping to the first flow switching device and is used to evaporate or condense the refrigerant, an on-off device that opens and closes the branched off passage between the compressor and the first flow switching device, an outdoor expansion valve that is provided on an upstream side of the outdoor heat exchanger during heating operation, a receiver that retains the refrigerant, and an intermediate-pressure port provided in a passage branching off from the passage between the outdoor heat exchanger and the receiver;
• an indoor unit including an indoor heat exchanger that functions as a condenser condensing the refrigerant discharged from the compressor during a heating operation and an indoor expansion valve that controls a flow rate of the refrigerant leaving the indoor heat exchanger during the heating operation;
• a gas extension piping constituting a passage communicating the discharge port of the outdoor unit to the indoor heat exchanger of the indoor unit;
• a liquid extension piping constituting a passage communicating the indoor expansion valve of the indoor unit to the receiver of the outdoor unit;
• a refrigerant circuit of a refrigeration cycle being formed by the outdoor unit and the indoor unit connected through the gas extension piping and the liquid extension piping;
• a second flow switching device provided in the gas extension piping between the discharge port of the outdoor unit and the indoor heat exchanger of the indoor unit, the second flow switching device communicating the indoor heat exchanger to a discharge side of the compressor during the heating operation and communicating the indoor heat exchanger to a suction side of the compressor during a cooling operation;
• an additional unit having a first bypass and a second bypass, the first bypass and the second bypass each having one end in communication with the intermediate-pressure port of the outdoor unit and the other end in communication with a passage between the first flow switching device and the suction side of the compressor;
• the first bypass having a first bypass expansion valve that is capable of controlling a throughput of the refrigerant and an auxiliary heat exchanger with a heat source different from the outdoor heat exchanger, the auxiliary heat exchanger functioning as an evaporator that heats the refrigerant flowing in the first bypass during the heating operation;
• and
• the second bypass having a second bypass expansion valve that is capable of controlling a throughput of the refrigerant.