A controller is configured to decide whether liquid refrigerant is unevenly distributed among a plurality of outdoor units and then adjust an outlet subcooling degree of an outdoor heat exchanger or an outlet sub cooling degree at a high-pressure outlet of a high-low pressure heat exchanger, and a discharge superheating degree of a compressor in a low capacity-side outdoor unit to match lower heat exchange capacity of the outdoor heat exchanger in the low capacity-side outdoor unit with higher heat exchange capacity of an outdoor heat exchanger in a high capacity-side outdoor unit, the low capacity-side outdoor unit being one of the plurality of outdoor units in which the outdoor heat exchanger has the lower heat exchange capacity, the high capacity-side outdoor unit being another of the plurality of outdoor units in which the outdoor heat exchanger has the higher heat exchange capacity.

A notifier notifies a user of a warning when a ratio of first refrigerant is different from a suitable value, the ratio being determined from a first difference between a first temperature and a second temperature and from a second difference between a third temperature and a fourth temperature. The first temperature is a temperature of non-azeotropic refrigerant mixture between first heat exchanger and a second heat exchanger. The second temperature is a temperature of the non-azeotropic refrigerant mixture between the second heat exchanger and first expansion valve. The third temperature is a temperature of the non-azeotropic refrigerant mixture between a first decompressor and first connecting point. The fourth temperature is a temperature of the non-azeotropic refrigerant mixture between a second decompressor and the first connecting point.

An air-conditioning apparatus includes: a first bypass pipe connected to an inlet-side passage of an accumulator through a second expansion device, a second passage of a subcooling heat exchanger for exchanging heat between refrigerant flowing through the second passage of the subcooling heat exchanger and refrigerant flowing through a first passage of the subcooling heat exchanger, and a first opening and closing device; a second bypass pipe branched from the first bypass pipe between the subcooling heat exchanger and the first opening and closing device and connected to an injection port of a compressor through a second opening and closing device; and a third bypass pipe branched from a refrigerant pipe between a heat source-side heat exchanger and a use-side heat exchanger and connected to a refrigerant pipe between an inlet side of the compressor and an outlet side of the accumulator through a third expansion device.

A refrigerating system includes a bypass channel, a second temperature sensor and a controller, the bypass channel communicates a first channel with a second channel and is provided with a throttling portion, which is located between an inlet and an outlet of the bypass channel; a sensing head of the second temperature sensor is arranged in the bypass channel, and is between the throttling portion and the outlet of the bypass channel and close to the outlet; when the system is in operation, a working medium in the bypass channel where the sensing head of the second temperature sensor is located is in a saturated state, and the controller obtains sensing results of a first temperature sensor and the second temperature sensor, determines the difference between the sensing results, and determines the degree of superheat at an inlet of a compressor according to the difference.

An air conditioner and a control method for an air conditioner are provided. The air conditioner may include a compressor, a flow switch installed at an outlet side of the compressor, a first guide pipe extending from the flow switch to an outdoor heat exchanger, a second guide pipe extending from the flow switch to an indoor unit, a third guide pipe extending from the outdoor heat exchanger to the indoor unit, a bypass passage extending from the second guide pipe to the third guide pipe to allow at least a portion of the refrigerant in the second guide pipe to be bypassed to the third guide pipe or to allow at least a portion of the refrigerant in the third guide pipe to be bypassed to the second guide pipe, and a bypass valve installed on the bypass passage.

An air-conditioning apparatus includes: a first bypass pipe connected to an inlet-side passage of an accumulator through a second expansion device, a second passage of a subcooling heat exchanger for exchanging heat between refrigerant flowing through the second passage of the subcooling heat exchanger and refrigerant flowing through a first passage of the subcooling heat exchanger, and a first opening and closing device; a second bypass pipe branched from the first bypass pipe between the subcooling heat exchanger and the first opening and closing device and connected to an injection port of a compressor through a second opening and closing device; and a third bypass pipe branched from a refrigerant pipe between a heat source-side heat exchanger and a use-side heat exchanger and connected to a refrigerant pipe between an inlet side of the compressor and an outlet side of the accumulator through a third expansion device.

Disclosed herein is an air-conditioning apparatus using a heat pipe, wherein the heat exchange and mixed supply of outside air and ventilation air are effectively performed by comparing the state (e.g., temperature, humidity or wet-bulb temperature) of the outside air with the set state (e.g., temperature or humidity) of supply air, and supplying the supply air in a set state (temperature, humidity) through a change in the flow passage of ventilation air and outside air by the selective opening/shutting of dampers, cooling the outside air through latent heat by spraying mist, and cooling and humidifying the supply air. The energy of the air-conditioning apparatus can be reduced because energy efficiency can be improved using the evaporation latent heat of water. The cooling temperature and humidity of the supply air is controlled at a ratio of the ventilation air passing through a cooling coil and the ventilation air passing through a bypass passage. Using a bypass passage, ventilation air can directly move to an air supply block without the intervention of the cooling coil within a heat exchange block through which a ventilation air passes. Operation costs can be reduced and financial gains can be made because an efficient operation is performed.

A method for controlling an economizer circuit is provided. The economizer circuit includes a valve to regulate refrigerant flow between the economizer and the compressor. The valve can be opened to engage the economizer circuit or closed to disengage the economizer circuit based on the output frequency provided to the compressor motor by a variable speed drive and an operating condition of the economizer.

A return air superheat degree test method for a multi-split system. A multi-split system comprises a re-cooling loop composed of a first heat exchanger (100) and a second heat exchanger (200), a first temperature sensor (11), a second temperature sensor (12) and a third temperature sensor (13). The return air superheat degree test method comprises the following steps: acquiring a first temperature value (T.sub.1) detected by the first temperature sensor (11), a second temperature value (T.sub.intermediate) detected by the second temperature sensor (12) and a third temperature value (T.sub.2) detected by the third temperature sensor (13); acquiring a minimum value between the first temperature value (T.sub.1) and the second temperature value (T.sub.intermediate), and acquiring a maximum value between the third temperature value (T.sub.2) and the second temperature value (T.sub.intermediate); and calculating a superheat degree according to the minimum value and the maximum value.

An air-conditioning apparatus includes: a first bypass pipe connected to an inlet-side passage of an accumulator through a second expansion device, a second passage of a subcooling heat exchanger, and a first opening and closing device; a second bypass pipe branched from the first bypass pipe between the subcooling heat exchanger and the first opening and closing device and connected to an injection port of a compressor through a second opening and closing device; and a third bypass pipe branched from a refrigerant pipe between a heat source-side heat exchanger and a use-side heat exchanger and connected to the second bypass pipe between the second opening and closing device and the injection port of the compressor through a third expansion device.