An air-conditioning apparatus has different two modes including a response detection diagnosis in which a control unit diagnoses a trouble of a component device during the trouble diagnosis operation based on presence or absence of a response from the operational state sensor when the mode has forcibly changed the device operation, and a performance detection diagnosis in which a trouble is detected by a detection value of the operational state sensor at a time when the operational state of the trouble diagnosis operation is stable, and the performance detection diagnosis is executed after the response detection diagnosis is executed.

An air-conditioning apparatus includes a refrigerant circuit formed by connecting, with pipes, a compressor, a first refrigerant flow switching device, a heat-source-side heat exchanger, an expansion device, and a plurality of intermediate heat exchangers. A heat medium circuit is formed by connecting, with pipes, a plurality of pumps configured to pressurize and circulate the heat medium subjected to heat exchange in the plurality of intermediate heat exchangers, a plurality of use-side heat exchangers each configured to exchange heat between the heat medium and air in an air-conditioned space, and a heat-medium flow switching/control device configured to switch which of the heat medium is to be allowed to flow into and out of each of the use-side heat exchangers; and a controller configured to perform processing for controlling the switching performed by the heat-medium flow switching/control device, in accordance with a capacity of each of the use-side heat exchangers.

An air conditioning apparatus uses R32 as a refrigerant, and includes a compressor, a condenser, an expansion mechanism, an evaporator, an intermediate injection channel, a suction injection channel, a switching mechanism, a branch flow channel, first and second injection opening adjustable valves, an injection heat exchanger, a refrigerant storage tank, a bypass channel, and a control part. The switching mechanism switches between an intermediate injection condition in which refrigerant flows in the intermediate injection channel, and a suction injection condition in which refrigerant flows in the suction injection channel. The branch flow channel branches from a main refrigerant channel which joins the condenser and the evaporator, and guides the refrigerant to the intermediate injection channel and the suction injection channel. The bypass channel guides a gas component of the refrigerant accumulated inside the refrigerant storage tank to the intermediate injection channel and the suction injection channel.

A refrigeration cycle apparatus including a heat source side heat exchanger including a first heat exchanger and a second heat exchanger connected in parallel; an air-sending device that supplies air, which is an object to be heat exchanged in the first heat exchanger and the second heat exchanger, in a variable manner; solenoid valves that each opens and closes a refrigerant passage of the first heat exchanger and the second heat exchanger; a third refrigerant circuit that is parallelly connected to the first heat exchanger and the second heat exchanger; and a flow control valve that controls the flow rate of the refrigerant flowing in the third refrigerant circuit. The refrigeration cycle apparatus can improve continuity of control of a heat exchange capacity of a heat source side heat exchanger.

In a refrigeration cycle system, switching is allowed between a parallel operation mode and a series operation mode. In the parallel operation mode, a refrigerant, upon leaving a load side heat exchanger, parallelly flows through a high-pressure side passage of each of a first internal heat exchanger and a second internal heat exchanger and then flows into an expansion valve. In the series operation mode, the refrigerant, upon leaving the load side heat exchanger, flows through the high-pressure side passage of the first internal heat exchanger, further flows through the high-pressure side passage of the second internal heat exchanger, and then flows through a high-pressure side bypass pipe into the expansion valve.

Disclosed is an air conditioner and control method thereof. The air conditioner and control method thereof is to improve rapid heating performance without using a large-capacity compressor. The air conditioner includes an indoor unit having a first heat exchanger, an outdoor unit having a compressor and a second heat exchanger, a refrigerant cycle configured to form a refrigerant circulation path between the indoor unit and the outdoor unit, a flow path switch configured to switch a flow of a refrigerant in the refrigerant cycle, and a controller configured to control the flow path switch to allow one part of the refrigerant discharged from the compressor to flow into an inlet of the compressor and the other part of the refrigerant discharged from the compressor to flow into at least one of the first heat exchanger and the second heat exchanger.

A refrigeration cycle apparatus includes a refrigerant circuit that is formed by connecting a compressor, a flow passage switching device, an outdoor heat exchanger, an expansion unit, and an indoor heat exchanger via pipes, and through which refrigerant flows, an outdoor air-sending device configured to blow outdoor air to the outdoor heat exchanger, an outdoor air temperature detector configured to detect a temperature of the outdoor air, and a controller configured to control an operation of the outdoor air-sending device.

In an air-conditioning apparatus, a heat source side heat exchanger, intermediate heat exchangers, and use side heat exchangers are formed in separate bodies respectively and adapted to be disposed at separate locations one another. In a heat medium circulation circuit where the intermediate heat exchanger and the use side heat exchanger are connected, temperature sensors are installed. An anti-freezing operation mode is provided in which, when the detection temperatures of the temperature sensors become equal to or lower than a set temperature Ts while a compressor or pumps are stopped, the heat medium is circulated to perform anti-freezing of the heat medium.

An air-conditioning apparatus includes a suction-injection pipe that introduces a refrigerant in a liquid or two-phase state into a suction side of a compressor, an expansion device that is arranged at the suction-injection pipe, and a controller that regulates the suction-injection flow rate of a refrigerant introduced into the suction side of the compressor through the suction-injection pipe by controlling the opening degree of the expansion device.

An air-conditioning apparatus includes a compressor, a four-way valve, expansion means, and an indoor heat exchanger, and further includes a check valve disposed between a discharge side of the compressor and the four-way valve, a first solenoid valve disposed between the expansion means and the indoor heat exchanger, and a controller. Opening and closing of the first solenoid valve are controllable. The controller switches the four-way valve and switches the first solenoid valve between open and closed states. When a heating operation is stopped, the controller switches the four-way valve from connection for the heating operation to connection for a cooling operation, closes the first solenoid valve, and then stops the compressor.