An air-conditioning apparatus includes a refrigerant circuit in which a compressor, an indoor heat exchanger, a first expansion device, an outdoor heat exchanger, and a flow switching device are sequentially connected to each other; a hot gas bypass pipe coupling a discharge port of the compressor and the flow switching device to each other; and a controller. The outdoor heat exchanger includes an upper heat exchanger and a lower heat exchanger having passages in parallel with each other. The outdoor heat exchanger includes a plurality of hairpin pipes, which are part of a heat transfer pipe. When the upper heat exchanger is defrosted, all hairpin pipes that are located at a lowermost step of the upper heat exchanger are used as refrigerant inlets. When the lower heat exchanger is defrosted, all hairpin pipes that are located at an uppermost step of the lower heat exchanger are used as refrigerant inlets.

An outdoor unit of an air-conditioning apparatus includes a housing, a heat exchanger, a bottom plate, a drainage structure, and a heating means. The housing has an opening through a side of the housing. The heat exchanger is disposed in an upper portion of the interior of the housing. The bottom plate is disposed at the bottom of the housing, and has a drainage hole through which to drain out drain water generated at the heat exchanger. The drainage structure is disposed below the heat exchanger and that guides the drain water to the bottom plate. The drainage structure includes a side panel that covers the opening of the housing, and a water guide plate disposed inside the housing and facing the side panel. The water guide plate and the side panel define a drainage path for draining the drain water between the water guide plate and the side panel.

An outdoor unit of an air-conditioning apparatus includes a housing, a heat exchanger, a bottom plate, a drainage structure, and a heating means. The housing has an opening through a side of the housing. The heat exchanger is disposed in an upper portion of the interior of the housing. The bottom plate is disposed at the bottom of the housing, and has a drainage hole through which to drain out drain water generated at the heat exchanger. The drainage structure is disposed below the heat exchanger and that guides the drain water to the bottom plate. The drainage structure includes a side panel that covers the opening of the housing, and a water guide plate disposed inside the housing and facing the side panel. The water guide plate and the side panel define a drainage path for draining the drain water between the water guide plate and the side panel.

A refrigeration cycle apparatus including a refrigerant circuit including a compressor, an indoor heat exchanger, an expansion device, an outdoor heat exchanger, an outside air temperature sensor, and a controller configured to perform a hot gas defrosting operation and a reverse-defrosting operation based on a temperature obtained by the outside air temperature sensor. In the hot gas defrosting operation, hot gas discharged from the compressor without passing through the indoor heat exchanger is supplied to the outdoor heat exchanger. In the reverse-defrosting operation, refrigerant passing through the indoor heat exchanger is supplied from the compressor to the outdoor heat exchanger. The controller has at least a mixed defrosting operation mode in which the hot gas defrosting operation and the reverse-defrosting operation are performed in sequence. The controller is configured to start the mixed defrosting operation mode when the temperature obtained by the outside air temperature sensor satisfies a preset condition.

A method for controlling the balanced frosting of outdoor units in a multi-split air-conditioning system solving the problem in existing multi-split air-conditioning systems of resource waste caused by a low utilization efficiency of the heating capability of outdoor units as a result of some of the outdoor units entering a defrosting state when the heating capability is not fully utilized. According to the control method, by determining whether an outdoor unit set satisfies a frosting unbalance condition, the actual output capability of outdoor units of the outdoor unit set is selectively controlled on the basis of the frosting degrees of all the outdoor units. Thus, the difference between the frosting degrees of different outdoor units in the outdoor unit set at the same time can be reduced, such that the heating capability of all the outdoor units can be fully utilized when the outdoor unit set enters a defrosting state.

A method for controlling the balanced frosting of outdoor units in a multi-split air-conditioning system solving the problem in existing multi-split air-conditioning systems of resource waste caused by a low utilization efficiency of the heating capability of outdoor units as a result of some of the outdoor units entering a defrosting state when the heating capability is not fully utilized. According to the control method, by determining whether an outdoor unit set satisfies a frosting unbalance condition, the actual output capability of outdoor units of the outdoor unit set is selectively controlled on the basis of the frosting degrees of all the outdoor units. Thus, the difference between the frosting degrees of different outdoor units in the outdoor unit set at the same time can be reduced, such that the heating capability of all the outdoor units can be fully utilized when the outdoor unit set enters a defrosting state.

An outdoor unit of an air-conditioning apparatus includes a compressor, a heat exchanger, and a controller. The controller includes a compressor driving circuit configured to drive the compressor, a harmonic suppressing unit configured to suppress harmonics in the compressor driving circuit, and a housing containing the compressor driving circuit and the harmonic suppressing unit. The housing has a first section having ventilation holes that allow communication between the outside and the inside, and a second section constituting a frame outside the first section. The first section contains the harmonic suppressing unit and a fan configured to blow air from inside the first section to the outside through the ventilation holes. The second section contains the compressor driving circuit.

A heat exchange system includes an outdoor unit heat exchange assembly, a first circulation pipeline, a control valve assembly, a heating pipeline and a heating assembly, wherein the outdoor heat exchange assembly includes a coolant heat radiation module and fins; the first circulation pipeline includes an output pipe, a connecting pipe and a return pipe; the output pipe communicates with an air conditioner indoor unit and the coolant heat radiation module; the connecting pipe communicates with the coolant heat radiation module and the fins; the return pipe communicates with the fins and the air conditioner indoor unit; the control valve assembly is connected with the output pipe; the heating pipeline communicates with the output pipe and the fins, communicates with the return pipe, and is also connected with the control valve assembly; and the heating assembly is connected with the heating pipeline.

A refrigerating and air-conditioning apparatus includes multiple refrigeration cycles each including a compressor, a four-way valve, an indoor heat exchanger, a pressure reducing device, and an outdoor heat exchanger which are connected by a pipe, each refrigeration cycle being configured to be capable of performing a cooling operation and a heating operation, an outdoor fan configured to send air for heat exchange with the outdoor heat exchangers of the refrigeration cycles, multiple indoor fans arranged corresponding to the respective indoor heat exchangers of the refrigeration cycles, and a controller configured to defrost the outdoor heat exchanger of the at least one refrigeration cycle, control a rotation speed of the indoor fan corresponding to the refrigeration cycle performing the defrosting operation such that a temperature of air mixed by air-sending through the indoor fans reaches a predetermined temperature.

In a heating main operation mode in which a load to be processed by the heating operation is dominant during cooling and heating mixed operation, an air-conditioning apparatus closes an opening and closing valve, and adjust the opening degree of an expansion device in accordance with the evaporating temperature of a load-side unit requesting cooling.