In an air-conditioning apparatus, when a plurality of pumps are all operating and a heat exchange amount in use-side heat exchangers is equal to or lower than a lower limit of a thermal capacity that can be conveyed in a heat medium circuit B, before at least one of the plurality of pumps is stopped, a refrigerant flow path in the intermediate heat exchanger connected to the pump that is to be stopped is closed. Then, the at least one of the plurality of pumps is stopped, and the thermal capacity required in at least one of the use-side heat exchangers in the rest of the plurality of pumps is conveyed.

In an air-conditioning apparatus, a controller controls an amount of refrigerant injection into a compressor by controlling an opening area of an expansion device such that the electric power consumption of the compressor becomes smaller, or such that a heating capacity or a cooling capacity of an intermediate heat exchanger becomes larger.

Obtained is a heat medium relay unit capable of having improved serviceability and an air-conditioning apparatus equipped with the heat medium relay unit. Heat medium flow control devices are each disposed below a corresponding one of the first heat medium flow switching devices. The heat medium flow control devices are similarly disposed in a zigzag manner along with the zigzag arrangement of the first heat medium flow switching devices.

The controller controls a bypass solenoid valve and hot-water supply expansion unit in a defrosting operation based on a refrigerant temperature detected by a first temperature sensor and a heat medium temperature detected by a second temperature sensor.

An air-conditioning apparatus controls that a discharge temperature does not become too high with a refrigerant whose compressor discharge temperature readily rises, and thus suppress degradation of the refrigerant and a refrigerating machine oil. An injection pipe that injects a heat source side refrigerant into a compressor is installed, connected a pipe between a backflow prevention device and an opening and closing device installed on a branching pipe, and an aperture unit in the compressor.

An air-conditioning apparatus includes at least one system including a heat-medium conveying device, a heat-medium flow regulator, and a heat-medium flow control device, as a heat medium system capable of regulating a flow rate of a heat medium supplied to a heat source device-side heat exchanger exchanging heat between refrigerant and the heat medium. The air-conditioning apparatus switches each of a plurality of use-side heat exchangers to a cooling operation or a heating operation in accordance with a control command to perform a cooling and heating simultaneous operation. The refrigerant is caused to flow through the heat source device-side heat exchanger depending on a ratio of a total cooling capacity and a total heating capacity of the plurality of use-side heat exchangers. The heat-medium flow control device controls the flow rate of the heat medium supplied to the heat source device-side heat exchanger based on a difference between the total cooling capacity and the total heating capacity of the plurality of use-side heat exchangers and a total operation capacity of the heat source device-side heat exchanger.

A refrigeration cycle is filled with a single component refrigerant of a substance having a property of undergoing disproportionation reaction or a mixed refrigerant containing a substance having a property of undergoing disproportionation reaction and a refrigerating machine oil miscible with the refrigerant.

A heat pump hot-water supply apparatus controls a second expansion device during a heating operation so as to adjust the amount of refrigerant flowing through an injection pipe, and controls a third expansion device during a cooling operation so as to adjust the amount of refrigerant flowing through the injection pipe.

A refrigeration cycle is configured by connecting a compressor, a four-way valve, a heat source side heat exchanger, expansion valves, and intermediate heat exchangers by piping. A heat medium circulation circuit is configured by connecting intermediate heat exchangers, pumps, and use side heat exchangers by piping. The outdoor unit accommodates the compressor, the four-way valve, and the heat source side heat exchanger, and the relay unit that is installed in a non-subject space which is different from an indoor space and is on an installation floor separated by two or more floors and accommodates the expansion valves, the pump, and intermediate heat exchangers are connected by two pipelines. The relay unit and an indoor unit that accommodates use side heat exchangers and is installed at a position where an indoor space can be air-conditioned are connected by two pipelines.

In an air-conditioning apparatus, an expansion device, a second refrigerant flow switching device, and heat exchangers related to heat medium, connected between the expansion device and the second refrigerant flow switching device such that a heat source side refrigerant flows in parallel, are connected in a part of refrigerant passages, and an expansion device, a second refrigerant flow switching device, and heat exchangers related to heat medium, connected between the expansion device and the second refrigerant flow switching device such that the heat source side refrigerant flows in series, are connected in the rest of the refrigerant passages.