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.

In the case of a heating operation in which a use side heat exchanger functions as a condenser when the outside air has a predetermined low temperature, a low-outside-air-temperature heating operation start mode is executed in which, while a refrigerant, as discharged from a compressor, flows into the use side heat exchanger, the refrigerant is supplied to the injection port of the compressor via an injection pipe and a part of a refrigerant that is accumulated in an accumulator is supplied to the compressor via a connecting pipe, and thereafter a low-outside-air-temperature heating operation mode is executed in which the refrigerant, as discharged from the compressor, is supplied to the injection port of the compressor via the injection pipe while flowing into the use side heat exchanger.

In an air-conditioning apparatus including a plurality of indoor units connected to a heat medium converter and a plurality of remote controllers respectively provided for the indoor units, the remote controllers each include a temperature sensor that detect a temperature of a corresponding space to be air-conditioned, and are each configured to communicate with a heat medium converter controller of the heat medium converter and an indoor unit controller of the corresponding indoor unit, transmit an instruction to start and stop an operation and data related to rotation speed of an indoor air-sending device to the corresponding indoor unit controller, and transmit the instruction to start and stop the operation, and a target temperature and a temperature detected by the temperature sensor or a difference therebetween, to the heat medium converter controller.

A heat pump system adjusts a degree of subcooling of an indoor-side heat exchanger in a heating priority mode, and adjusts any one of a degree of subcooling of a hot-water supply-side heat exchanger (water-side heat exchanger) and a discharge temperature of a compressor in a hot-water supply priority mode.

An air-conditioning apparatus is capable of completing heat medium freeze prevention control more quickly by performing heat medium temperature rise control for raising the temperature of a cooled heat medium and includes a controller that adjusts a current opening degree of a bypass device at a bypass pipe to an opening degree, and that makes an adjustment such that the flow passage resistance in the case of the opening degree becomes equal to the flow passage resistance in the case of an opening degree before an expansion device is adjusted to a minimum opening degree.

An air-conditioning apparatus includes a temperature sensor for detecting a temperature of the heat medium sent from each of the intermediate heat exchangers to each of the use-side heat exchangers, and a temperature of the heat medium that has exited each of the use-side heat exchangers, an opening degree controller for regulating a flow rate of the heat medium through each of the heat medium flow control devices, and a computing unit for computing a usage capacity of each of the indoor units from a rotation speed of the pump, an opening degree of each of the heat medium flow control devices, temperatures detected by the temperature sensors, and power consumption of each of the indoor units, and proportionally dividing the power consumption for a common portion among each of the indoor units based on the computed usage capacity and the power consumption of the common portion.

An air conditioner includes an outdoor unit, a plurality of mode change devices including at least one mode changer including a branch duct and a changing valve, and configured to receive a control signal from the outdoor unit to control an operation of the at least one mode changer. A plurality of indoor units are connected to the outdoor unit or the plurality of mode change devices. The outdoor unit may determine an operation mode to operate the plurality of mode change devices a plurality of times. Each of the plurality of indoor units may detect a temperature change of an indoor heat exchanger in response to the operation of the mode change devices, to determine the number of connected mode changers and a connectable mode changer candidate group based on the temperature change of the indoor heat exchanger.

A method for defrosting a heat exchanger of a refrigeration circuit is provided. The method includes monitoring a compressor suction parameter at a suction line to a compressor of the refrigeration circuit. The method also includes determining a compressor suction parameter threshold. Also, the method includes initiating a defrost mode of the refrigeration circuit when the compressor suction parameter is less than or equal to the compressor suction parameter threshold.

An air conditioner may prevent a refrigerant stored in a refrigerant storage from rapidly flowing into a main refrigerant circuit when the type of operation is switched.

The air conditioner may include a refrigerant circuit provided with a compressor, a condenser, an expansion valve and an evaporator; a refrigerant amount detection device configured to determine whether a refrigerant state in an outlet of the compressor is a supercooled state or a gas-liquid two phase state, and configured to calculate a refrigerant amount ratio in the refrigerant circuit, based on a predetermined set value according to at least one of a temperature and a pressure detected in the refrigerant circuit, and the refrigerant state; and a controller configured to control the refrigerant circuit according to the refrigerant amount ratio calculated by the refrigerant amount detection device.

When the temperatures of outdoor heat exchangers 23a and 23b detected by outdoor heat exchanger temperature sensors 57a and 57b become equal to or higher than 5 degrees C. and the sucking superheating degrees of compressors 21a and 21b become equal to or lower than 0 degrees C. while an air conditioning apparatus 1 is performing the reverse defrosting operation, the reverse defrosting operation is stopped and the heating dominant operation is resumed. At this time, the total operating times of the compressors 21a and 21b are reset. The sucking superheating degrees of the compressors 21a and 21b are obtained by subtracting the low pressure saturation temperatures calculated from the sucking pressures of the compressors 21a and 21b, from the temperatures of the refrigerants sucked into the compressors 21a and 21b which temperatures are detected by the sucking temperature sensors 54a and 54b.