An outdoor unit of an air-conditioner and two-pipe and three-pipe air-conditioning systems having the same are provided. The outdoor unit includes a compressor defining an outlet and an inlet; a first four-way valve defining a first valve communicated with the outlet, second and third ports communicated with the inlet; a second four-way valve defining second and third ports communicated with the inlet; an outdoor heat exchanger defining a first refrigerant valve Communicated with the fourth port of the first four-way valve; a first gas pipe defining a first end connected with the second and third ports of the first and second four-way valves and, the inlet; a second gas pipe defining a first end connected with the fourth port of the second four-way valve; a third gas pipe defining a first end connected with the outlet and a second end connected with the first port of the second four-way valve.

Even in the case of a large outdoor heat exchanger (24), it is possible to completely remove frost without reducing the defrosting effect. Provided are: a distributor (25) installed between the outdoor heat exchanger (24) and an expansion valve (26); a plurality of distribution pipes (252) of which one end is connected to the distributor (25) and of which the other end is connected to a plurality of heat transfer pipes (241) of the outdoor heat exchanger (24); and a bypass pipe (30) of which one end is connected to a compressor (23) and diverges on the way, and simultaneously of which the respective plurality of other ends are connected to a connection part between the distribution pipe (252) and the heat transfer pipe (241) or in the vicinity thereof.

A refrigerant channel switching unit is disposed between a heat source unit and a utilization unit to switch flow of refrigerant in the refrigerant circuit. The refrigerant channel switching unit includes a first refrigerant pipe connected to a suction gas communicating pipe extending from the heat source unit, a second refrigerant pipe connected to a high-low pressure gas communicating pipe extending from the heat source unit, a third refrigerant pipe connected to a gas pipe extending to the utilization unit, a coupling portion, a first switch valve mounted to the first refrigerant pipe, and a second switch valve mounted to the second refrigerant pipe. The coupling portion is connected to the first, second and third refrigerant pipes. The First second and third are coupled through the coupling portion.

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.

A heat pump apparatus is provided in which refrigerant circulates between an indoor unit and an outdoor unit, wherein the refrigerant is a mixed refrigerant of HFO-1123 and an HFC refrigerant other than HFO-1123, the outdoor unit has a cooling capacity (kW) in the range of 2.2 to 9.5 kW, the outer diameter (mm) of a gas pipe between the indoor unit and the outdoor unit and the cooling capacity (kW) of the outdoor unit satisfy the relation (1.00outer diameter (mm) of gas pipe/cooling capacity (kW) of outdoor unit5.77), and the outer diameter (mm) of a liquid pipe between the indoor unit and the outdoor unit and the cooling capacity (kW) of the outdoor unit satisfy the relation (0.67outer diameter (mm) of liquid pipe/cooling capacity (kW) of outdoor unit5.77).

A refrigeration cycle system is capable of reducing an amount of information required to be specified in advance, reducing a computational processing load, reflecting differences in actual installation conditions, and speeding up stabilization of an operational state in which the total amount of required input energy is reduced. A refrigeration cycle system is provided with a plurality of actuators, including outdoor fan motors, compressors, indoor fan motors, and the like for causing a refrigerant circuit to carry out a refrigeration cycle. A control unit obtains the slope at the current evaporation temperature and/or the current condensing temperature on a graph of the function between the actuators and the evaporation temperature or the condensing temperature, and updates the value of the target evaporation temperature and/or the target condensing temperature so that the sum of the input energy to the actuators is less that the current level.

An air-conditioning apparatus includes a heat medium circuit in which a compressor, a flow switching unit, a flow regulating unit, a gas header, a heat source-side heat exchanger, a distributor, an expansion unit, and a use-side heat exchanger are connected by a pipe, and during a defrosting operation to defrost the heat source-side heat exchanger, heat medium circulates, in order, the compressor, the flow switching unit, the gas header, the heat source-side heat exchanger, the distributor, the expansion unit, and the use-side heat exchanger. The heat source-side heat exchanger includes a first heat exchange unit, and a second heat exchange unit provided lower than the first heat exchange unit. The flow regulating unit is configured to, during the defrosting operation, regulate a flow rate of heat medium flowing through the first heat exchange unit and a flow rate of heat medium flowing through the second heat exchange unit.

An air conditioner is provided that may include at least one compressor that compresses a refrigerant to a high pressure; a plurality of heat exchanger that condenses the refrigerant compressed in the at least one compressor; a plurality of outdoor valves, respectively, provided at an outlet side pipe of the plurality of heat exchangers; a gas liquid separator that separates the refrigerant into gas and liquid refrigerants and supplies the gas refrigerant to the at least one compressor; and one or more bypass devices connected to the outlet side pipe of one or more of the plurality of heat exchangers and an inlet side pipe of the gas liquid separator, the one or more bypass devices controlling a flow of the liquid refrigerant. During a cooling low load operation in which a portion of the plurality of heat exchangers is operating, a liquid refrigerant loaded into a heat exchanger of the plurality of heat exchangers, which is not operated, may flow through the one or more bypass device.

A heating, ventilation, and/or air conditioning (HVAC) system has a first variable refrigerant flow outdoor unit, a first ducted variable speed indoor unit configured to selectively exchange refrigerant with the first variable refrigerant flow outdoor unit, and a second indoor unit configured to selectively exchange refrigerant with the first variable refrigerant flow outdoor unit.

An air-conditioning apparatus includes at least one system including a heat-medium conveying device, a heat-medium flow regulator, and a heat-medium flow control device, as a heat medium system capable of regulating a flow rate of a heat medium supplied to a heat source device-side heat exchanger exchanging heat between refrigerant and the heat medium. The air-conditioning apparatus switches each of a plurality of use-side heat exchangers to a cooling operation or a heating operation in accordance with a control command to perform a cooling and heating simultaneous operation. The refrigerant is caused to flow through the heat source device-side heat exchanger depending on a ratio of a total cooling capacity and a total heating capacity of the plurality of use-side heat exchangers. The heat-medium flow control device controls the flow rate of the heat medium supplied to the heat source device-side heat exchanger based on a difference between the total cooling capacity and the total heating capacity of the plurality of use-side heat exchangers and a total operation capacity of the heat source device-side heat exchanger.