An outdoor unit being part of a refrigeration cycle apparatus in which refrigerant circulates and having a maintenance opening port includes an open-close panel configured to cover the maintenance opening port by being attached openably and closably to the outdoor unit, a heat source side heat exchanger disposed above the maintenance opening port and provided at least with an open-close panel-facing heat exchange unit facing a plane containing the open-close panel, a drainage channel located at least below the open-close panel-facing heat exchange unit of the heat source side heat exchanger, wherein the heating energy supply unit includes a refrigerant pipe configured to pass refrigerant higher in temperature than a freezing point of water in an upstream direction from a downstream direction of the drainage channel.

An air conditioning system may include an outdoor device disposed in an outdoor space, the outdoor device including a compressor and an outdoor heat exchanger, a plurality of indoor devices disposed in an indoor space, the plurality of indoor devices including an indoor heat exchanger, and a distributor that distributes and introduces a refrigerant into the plurality of indoor devices. The outdoor device may include an outdoor branch branched into a plurality of refrigerant paths, a first outdoor tube that extends from the outdoor branch to guide the refrigerant to a first heat exchanger of the outdoor heat exchanger, a second outdoor tube that extends from the outdoor branch to guide the refrigerant to a second heat exchanger of the outdoor heat exchanger, and a bypass tube that extends from the outdoor branch to allow the refrigerant to bypass the outdoor heat exchanger, thereby guiding the refrigerant to the compressor.

An air-conditioning apparatus includes a main circuit in which a compressor, an indoor heat exchanger, a first flow control device, and a plurality of parallel heat exchangers connected in parallel to each other are sequentially connected via a pipe to allow refrigerant to circulate, a first defrost pipe that branches a part of the refrigerant discharged from the compressor and allows the refrigerant to flow into the parallel heat exchanger to be defrosted among the plurality of parallel heat exchangers, a expansion device provided in the first defrost pipe and configured to depressurize the refrigerant discharged from the compressor, and a connection switching device that allows the refrigerant flowing out of the parallel heat exchanger to be defrosted to flow into the main circuit at a position upstream of the parallel heat exchangers other than the parallel heat exchanger subject to defrosting.

An air conditioner and a method of controlling an air conditioner are provided. The method of controlling an air conditioner may include determining whether a low-load condition is satisfied on the basis of a number of indoor devices or a temperature of external air, performing a low-load operation of a compressor at a predetermined frequency when the low-load condition is satisfied, detecting whether an operation pressure is out of a target pressure value or range while the low-load operation is performed, and bypassing a refrigerant from the compressor to a gas/liquid separator via an injection passage when the operation pressure is out of the target pressure value or range.

A compressor unit for an air conditioner includes a compressor disposed in a first casing, and first and second heat source heat exchanger unit ports configured to connect the compressor unit to a heat source heat exchanger of a heat source heat exchanger unit of the air conditioner, the heat source heat exchanger being disposed in a second casing separate from the first casing and being configured to exchange heat with a heat source, first and second indoor unit ports configured to connect the compressor unit to an indoor heat exchanger of at least one indoor unit of the air conditioner, a first refrigerant piping fluidly connecting the first heat source heat exchanger unit port and the first indoor unit port, and a sub-cooling heat exchanger disposed inside the first casing and fluidly connected to the first refrigerant piping for heat transfer with the refrigerant to be flown through the first refrigerant piping.

A flow rate of circulating water to a water heat exchanger is determined by multiplying, by a rated water flow rate, a ratio of an absolute value of a difference between a total operation capacity of each of indoor side heat exchangers serving as a heating load and a total operation capacity of each of indoor side heat exchangers serving as a cooling load to a total operation capacity of the water heat exchanger.

In a refrigeration apparatus, in a first operation mode, a comparison is made between a first liquid pipe temperature, which is a temperature of a refrigerant on a side of a liquid pipe heat exchanger that is near usage-side heat exchangers, and a second liquid pipe temperature, which is a temperature of the refrigerant on a side of the liquid pipe heat exchanger that is near a plurality of heat-source-side heat exchangers, the liquid pipe heat exchanger performing heat exchange with the refrigerant flowing through liquid sides of the heat-source-side heat exchangers. When an evaporation-switch liquid pipe temperature condition is satisfied, the heat-source-side heat exchanger functioning as a radiator of the refrigerant is switched to an evaporator of the refrigerant, and the first operation mode is switched to a second operation mode in which the plurality of heat-source-side heat exchangers are caused to function as evaporators of the refrigerant.

The air conditioner has a configuration such that, in an air-warming operation: the average refrigerant exit temperature, which is obtained by averaging the temperature of the refrigerant exits of indoor heat exchangers 7 in a plurality of indoor units 10, as detected by heat-exchanger-refrigerant-exit temperature probes 34 in the indoor units 10, is determined; the temperature difference between the average refrigerant exit temperature and the refrigerant exit temperatures of the indoor heat exchangers 7 of each of the indoor units 10 is determined; and the degree to which indoor expansion valves 9 of the indoor units 10 are open is controlled such that the determined temperature difference falls within a predetermined temperature difference range.

A heat pump includes a control device configured to control conduction and shutting-off of electric power to a first compressor heater, and to control whether or not an alarm unit notifies an alarm. The control device causes the alarm unit to notify the alarm when the control device determines that duration of electric conduction to the first compressor heater is a predetermined period or longer. With this, it is possible to provide a heat pump that can control electric conduction to the heater to enable saving of electricity, and that can detect a problem in the controlling of the electric conduction to the heater.

An outdoor heat exchanger includes a fan configured to adjust a heat transfer coefficient ao of the outside of a heat transfer tube through which a refrigerant flows, a bypass passage and flow rate control valve configured to adjust a heat transfer coefficient i of the inside of the heat transfer tube through which the refrigerant flows, and an on-off valve configured to adjust a heat transfer area A where the refrigerant exchanges heat with a heat medium. A controller controls the heat transfer coefficient o of the outside of the heat transfer tube, the heat transfer coefficient i of the inside thereof, and the heat transfer area A to control a heat exchange amount of the outdoor heat exchanger.