According to one embodiment, an air conditioner carries out a heating operation, a cooling operation, a cooling/heating mixed operation in which a higher priority is given to cooling, and a cooling/heating mixed operation in which a higher priority is given to heating.

A defrosting control method of a multi-functional multi-split system with double four-way valves. The multi-functional multi-split system includes an outdoor unit, at least one set of hydraulic modules, and at least one set of indoor modules. When the multi-split system is switched from a normal operation mode to a defrosting mode, a first four-way valve and a second four-way valve are powered down, and operation modes of each set of indoor modules and each set of hydraulic modules, the on/off state of fans of an indoor heat exchanger and a hydraulic heat exchanger, opening degrees of a first electromagnetic valve of the indoor heat exchanger and a second electromagnetic valve of the hydraulic heat exchanger, and the on/off state of the first electromagnetic valve and the second electromagnetic valve are correspondingly adjusted based on the previous operation modes of each set of indoor modules and each set of hydraulic modules.

A refrigeration apparatus includes a gas-liquid separator on a downstream side of a radiator, and a refrigerant circuit in which a high pressure of a refrigeration cycle is equal to or higher than a critical pressure. The refrigeration apparatus includes a gas passage that communicates with the gas-liquid separator and at least one of a plurality of heat exchangers provided in the refrigerant circuit, and an opening and closing device that opens and closes the gas passage. There is provided a controller that opens the opening and closing device when a pressure in the gas-liquid separator is equal to or higher than a predetermined value in a state where a compression unit of the refrigerant circuit is stopped to suppress occurrence of pressure abnormality inside the gas-liquid separator in a state where a compressor is stopped.

An oil return control method of a multi-functional multi-split system with double four-way valves. The multi-functional multi-split system includes an outdoor unit, at least one set of hydraulic modules and at least one set of indoor modules. When the multi-split system is switched from a normal operation mode to an oil return mode, a first four-way valve and a second four-way valve are powered down, and operation modes of each set of indoor modules and each set of hydraulic modules, the on/off state of fans of an indoor heat exchanger and a hydraulic heat exchanger, opening degrees of a first electronic expansion valve of the indoor heat exchanger and a first electronic expansion valve of the hydraulic heat exchanger, and the on/off state of a first electromagnetic valve and a second electromagnetic valve are correspondingly adjusted based on the previous operation modes.

An air-conditioning apparatus that includes a compressor, a flow switching device, an outdoor heat exchange unit, an expansion section and an indoor heat exchanger, which are connected by pipes, in which the outdoor heat exchange unit includes a first outdoor heat exchanger, a first flow rate control device, a second outdoor heat exchanger, a second flow rate control device, a bypass pipe, the second outdoor heat exchanger, the second flow rate control device, a third flow rate control device, and a flow control device.

A refrigeration cycle apparatus includes: an outdoor unit; a branch unit connected to the outdoor unit via a first pipe and a second pipe; a first indoor unit connected to the branch unit via a third pipe and a fourth pipe; and a second indoor unit connected to the branch unit via a fifth pipe and a sixth pipe. A refrigerant circuit includes a compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, and a six-way valve. The six-way valve switches between a first state in which the first heat exchanger acts as a condenser and at least the second heat exchanger acts as an evaporator and a second state in which the first heat exchanger acts as an evaporator and at least the second heat exchanger acts as a condenser.

A refrigeration apparatus includes a heat source-side unit and a utilization-side unit that are connected to each other, and performs a refrigeration cycle in which a high pressure of a refrigerant reaches or exceeds a critical pressure. The refrigeration apparatus also includes a control unit configured to perform a first action of returning the refrigerant to the heat source-side unit when a stop condition of the utilization-side unit is satisfied, and a second action of prohibiting the first action when a pressure at the heat source-side unit is equal to or more than the critical pressure of the refrigerant. This configuration suppresses damage to a refrigerant storage reservoir and the like in returning the refrigerant to the heat source-side unit.

A refrigeration cycle apparatus includes a refrigeration cycle circuit connecting a compressor, a refrigerant flow switching device, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, a first junction portion provided between the outdoor heat exchanger and the expansion valve and configured to divide refrigerant, a second junction portion provided between the indoor heat exchanger and the refrigerant flow switching device and configured to divide the refrigerant, a bypass pipe connecting the first junction portion and the second junction portion and configured to cause the refrigerant to flow through the bypass pipe, a first valve provided between the second junction portion and the refrigerant flow switching device, a second valve provided to the bypass pipe, a first temperature sensor configured to measure a temperature in a room to which air passing through the indoor heat exchanger is provided, and a second temperature sensor configured to measure a temperature of refrigerant at a liquid portion of the indoor heat exchanger. In an operation status in which the compressor operates, the expansion valve is fully closed, the first valve is opened, and the second valve is closed, when a temperature measured by the first temperature sensor and a temperature measured by the second temperature sensor are different from each other, the refrigeration cycle apparatus is configured to detect an abnormality at at least one of the expansion valve and the second valve.

An air conditioning apparatus and a method for controlling an air conditioning apparatus are provided. The air conditioning apparatus may include a controller that performs an abnormal operation diagnosis of the air conditioning apparatus based on an output signal of a pump, thereby directly checking introduction of air into pipes or clogging of valves.

A hybrid multi-air conditioning system with no receiver is provided for optimal valve control. The hybrid multi-air conditioning system includes: a hot-water unit for exchanging heat between refrigerant and water; at least one indoor unit installed indoors and comprising an indoor heat exchanger and an indoor unit expansion valve; and an outdoor unit connected to the indoor unit and the hot-water unit via a refrigerant pipeline and comprising an outdoor heat exchanger, a compressor, and an outdoor unit expansion valve, wherein, when an abnormal refrigerant enters either the at least one indoor unit or the outdoor unit according to an operation mode, the abnormal refrigerant is shut off from the hot-water unit and the at least one indoor unit or the outdoor unit which operates as a condenser. Accordingly, the hybrid multi-air conditioning system improves heat exchange efficiency via direct heat transfer between refrigerant and water by having a coil wound on the water tank to transfer heat between refrigerant and water.