An air conditioner of an embodiment includes a plurality of outdoor units, one or more indoor units, and a control unit. The outdoor unit includes a compressor, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve and an outdoor blower, and the outdoor units exchange heat between the outside air and a refrigerant. The indoor unit is an indoor unit connected to the plurality of outdoor units by a refrigerant pipe, includes an indoor heat exchanger, an indoor expansion valve, and an indoor blower, and exchanges heat between the indoor air and the refrigerant. The control unit controls the plurality of outdoor units and the one or more indoor units. The control unit controls the condensation pressure of the outdoor unit in a heating operation or the suction pressure of the outdoor unit in a defrosting operation to be equal to or smaller than an upper limit pressure, which is 1/1.5 times the rated maximum pressure during the heating operation when any of the outdoor units is in the defrosting operation.

A multi-air conditioner for heating and cooling may include at least one indoor unit for both cooling and heating including an indoor heat exchanger; an outdoor unit for both cooling and heating including a compressor, a plurality of outdoor heat exchangers, and a switching unit disposed on a discharge side of the compressor to switch a flow of refrigerant; and a distributor disposed between the outdoor unit and the at least one indoor unit, that distributes the refrigerant. The plurality of outdoor heat exchangers in the outdoor unit may include a first heat exchanger, a first end of which is connected to the switching unit, and a second end of which is connected to the distributor; a second heat exchanger disposed under the first heat exchanger, a first end of which is configured to be coupled to or decoupled from the second end of the first heat exchanger, and a second end of which is connected to the distributor; and a third heat exchanger disposed under the second heat exchanger, a first end of which is connected to the discharge side of the compressor, and a second end of which is connected to the indoor unit.

An air-conditioning apparatus includes a refrigerant circuit, an air-conditioning load state detection unit, an operation-state detection unit, and a controller. The refrigerant circuit includes a main circuit and a bypass circuit. The air-conditioning apparatus has a simultaneous heating and defrosting operation mode. In the simultaneous heating and defrosting operation mode, the controller controls a compressor, a pressure reducing device, and a defrosting refrigerant pressure-reducing device such that control amounts of the compressor, the pressure reducing device, and the defrosting refrigerant pressure-reducing device reach respective normal-time control target values that are set based on an air-conditioning load state and an operation state.

A refrigeration cycle apparatus includes: a compressor; an indoor heat exchanger; an outdoor heat exchanger including first and second outdoor heat exchangers; a bypass flow passage causing a discharge side of the compressor to communicate with the first or second outdoor heat exchanger; a flow control valve at the bypass flow passage; and a controller performing a heating operation in which the first and second outdoor heat exchangers operate as an evaporator and the indoor heat exchanger operates as a condenser and a simultaneous heating and defrosting operation in which part of refrigerant the compressor discharges is supplied to one of the first and second outdoor heat exchangers through the bypass flow passage, the other of the outdoor heat exchangers operates as an evaporator, the indoor heat exchanger operates as a condenser, and an upper limit frequency of the compressor changes to a value higher than in the heating operation.

A refrigeration cycle apparatus includes a first flow switch valve including first to fourth ports, a second flow switch valve and a third flow switch valve each including fifth to seventh ports, a compressor, a discharge pipe connecting a discharge port of the compressor and the first port, a first high pressure pipe connecting between the discharge pipe and the fifth ports, a bypass expansion valve provided at a part of the first high pressure pipe, the part extending, a first outdoor heat exchanger connected to the seventh port of the second flow switch valve, a second outdoor heat exchanger connected to the seventh port of the third flow switch valve, and a controller. The controller is configured to perform a differential pressure ensuring process, when switching the second flow switch valve or the third flow switch valve. In the differential pressure ensuring process, the controller is configured to set operation frequency of the compressor to a first frequency and set opening degree of the bypass expansion valve to a first degree if a first condition is not met, and set the operation frequency of the compressor to a second frequency which is higher than the first frequency or set the opening degree of the bypass expansion valve to a second degree which is larger than the first degree if the first condition is met.

An air-conditioning apparatus includes heat-source-side units each including a compressor and a heat-source-side heat exchanger, a load-side heat exchanger and a load-side expansion device, a first header, a second header, bypass expansion devices, circuit switching units, discharge pressure sensors, bypass pressure sensors, and a controller configured to control, in a heat-source-side unit in defrosting mode, the circuit switching unit in such a manner that a portion of refrigerant discharged from the compressor flows into the heat-source-side heat exchanger and configured to control, in the heat-source-side unit in defrosting mode, an opening degree of the bypass expansion device in the heat-source-side unit in such a manner that a value representing a difference between a value obtained by the discharge pressure sensor and a value obtained by the bypass pressure sensor is equal to or greater than a predetermined value.

An air conditioner includes an outdoor heat exchanger in which N heat exchange units are spaced apart from one another sequentially in a vertical direction N expansion valves respectively connected to the N heat exchange units; N hot gas pipes respectively connected to the N heat exchange units; N hot gas valves respectively installed in the N hot gas pipes; and a controller configured to control the N expansion valves and the N hot gas valves to defrost the N heat exchange units, wherein the controller is configured to defrost a bottom heat exchange unit first, then defrost a top heat exchange unit, and defrost the heat exchange units located under the top heat exchange unit sequentially from a second highest heat exchange unit to the bottom heat exchange unit after defrosting the top heat exchange unit.

The refrigeration cycle apparatus includes a refrigerant circuit, a controller to control the refrigerant circuit, a bypass flow path, and a flow control valve. The bypass flow path communicates between the discharge side of the compressor and the first outdoor heat exchanger or between the discharge side of the compressor and the second outdoor heat exchanger. The flow control valve is provided to the bypass flow path. The refrigerant circuit is configured to be able to perform a heating defrosting simultaneous operation. The heating defrosting simultaneous operation is an operation of supplying part of the refrigerant discharged from the compressor to one of the first outdoor heat exchanger and the second outdoor heat exchanger via the bypass flow path, causing the other of the first outdoor heat exchanger and the second outdoor heat exchanger to serve as an evaporator, and causing the indoor heat exchanger to serve as a condenser.

An air conditioner includes a switching valve, a flow rate restricting portion and an on-off valve. The switching valve provided in a flow path between a compressor and an outdoor heat exchanger. The outdoor heat exchanger includes a heat exchange portion and a heat exchange portion. During heating operation, the switching valve causes a second connection port, a third connection port and a first connection port to communicate with one another. The flow rate restricting portion and the on-off valve are connected in series between an outlet and an inlet of the compressor during the heating operation, to bypass a part of refrigerant. During defrosting operation of the heat exchange portion, the switching valve is configured such that a fourth connection port and the second connection port communicate with each other, and the third connection port and the first connection port communicate with each other.

A refrigeration cycle apparatus includes: a first four-way valve having first to fourth ports; a second four-way valve and a third four-way valve each having fifth to eighth ports; a compressor; a discharge pipe connecting a discharge port of the compressor and the first port; a suction pipe connecting a suction port of the compressor and the second port; a first high pressure pipe connecting the discharge pipe and the fifth ports; a second high pressure pipe connecting the third port and the first high pressure pipe; a first valve provided at the first high pressure pipe; a second valve provided at the second high pressure pipe; a low pressure pipe connecting the suction pipe and the sixth ports; a first outdoor heat exchanger connected with the seventh port of the second four-way valve; a second outdoor heat exchanger connected with the seventh port of the third four-way valve; and an indoor heat exchanger connected with the fourth port.