A refrigerant flow path switching unit, disposed between a heat source unit and a utilization unit and that switches a refrigerant flow in the utilization unit, includes: a flow path switching valve; a case that houses the flow path switching valve; and an electric component box that houses an electric component that controls the flow path switching valve. At least two surfaces of the case include a box attachment part that is configured to attach the electric component box to the case.

A refrigerant flow path switching device includes: a first header pipe that is connected to a high-and-low-pressure gas connection pipe of a heat source unit in an air conditioner; a second header pipe that is connected to a sucked-gas connection pipe of the heat source unit; a third header pipe that is connected to a liquid connection pipe of the heat source unit; switching units that each correspond respectively to utilization units in the air conditioner and include valves that control refrigerant flows; and a casing accommodating the first header pipe, the second header pipe, the third header pipe, and switching units. The refrigerant flow path switching device switches among refrigerant flow paths, each of which is between the heat source unit and one of the utilization units.

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.

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.

A three-pipe, multi-split system and a control method thereof. The three-pipe multi-split system includes an outdoor unit, a multi-split indoor unit, and a hydraulic module. By optimizing a refrigerant system, the phenomenon that a refrigerant is throttled before flowing through a refrigerant heat dissipation module or supercooled when passing through a plate heat exchanger which causes a relatively low temperature of the refrigerant entering the refrigerant heat dissipation module and consequent condensation on the refrigerant heat dissipation module to produce condensate water and then causes a damage to a compressor frequency conversion module can be avoided. In addition, more refrigerant is caused to flow through the refrigerant heat dissipation module to reduce the temperature of the module.

An air conditioner and a fluid filling method for an air conditioner are provided. The method may include operating, by the air conditioner, in a fluid supply mode, to fill a group of pipes with a fluid, such as water, determining whether an amount of the fluid in the group of pipes is appropriate while continuously filling the group of pipes with the fluid, and outputting, by an output device, information indicating that filling of the fluid has been completed when it is determined that the amount of the fluid is appropriate. The fluid supply mode may include a first fluid supply mode in which fluid is supplied while the outdoor unit is stopped, and a second fluid supply mode in which the fluid is supplied while the outdoor unit is operated.

An air conditioning system, including a compressor, two outdoor heat exchange units, a liquid pipe used for communicating with indoor units, a high-pressure gas tube and a low-pressure gas tube; the air conditioning system further includes a valve assembly. One outdoor heat exchange unit has a first state in which one end thereof communicates with the high-pressure gas tube and another end thereof communicates with the liquid pipe, and has a second state in which one end thereof communicates with the low-pressure gas tube and the other end thereof communicates with the liquid pipe. Further disclosed is a control method for the air conditioning system.

An air conditioning apparatus includes an outdoor device that is configured to circulate refrigerant and that includes a compressor and an outdoor heat exchanger, a plurality of indoor devices configured to circulate water, and a heat exchange device connecting the outdoor device with the indoor device. The heat exchange device includes a heat exchanger configured to exchange heat between the refrigerant and the water, and a switch device configured to control flow of refrigerant between the indoor devices and the heat exchanger.

A heat transport system includes: a refrigerant circuit that seals therein a fluid including HFC-32 and/or HFO refrigerant as a refrigerant and that includes a refrigerant booster that boosts the refrigerant, an outdoor air heat exchanger that exchanges heat between the refrigerant and outdoor air, a medium heat exchanger that exchanges heat between the refrigerant and a heat transfer medium, and a refrigerant flow path switch that switches between a refrigerant radiation state and a refrigerant evaporation state; and a medium circuit that seals carbon dioxide therein as the heat transfer medium.