Abstract: An air conditioner includes a refrigerant circuit that includes a heat source heat exchanger configured such that refrigerant flows in from below and flows out from above when the heat source heat exchanger functions as an evaporator of the refrigerant and a plurality of utilization heat exchangers. When the heat source heat exchanger is caused to function as an evaporator, the refrigerant discharged from a compression mechanism is bypassed to an intake side of the compression mechanism via a first bypass circuit, the heat source heat exchanger is caused to function as a condenser, and an expansion valve is closed, whereby refrigerating machine oil accumulating inside the heat source heat exchanger is returned to the intake side of the compression mechanism from a lower portion of the heat source heat exchanger via an oil returning circuit.

Abstract: An air conditioner (1) including a heat source side heat exchanger (23) constructed such that, when it functions as the evaporator for a refrigerant, the refrigerant flows in from the lower side and flows out from the upper side and having a refrigerant circuit (12) capable of switching to cause the heat source side heat exchanger (23) and use side heat exchangers (32, 42, 52) to function individually as the evaporator or the condenser for the refrigerant. The range of control when evaporation ability of the heat source side heat exchanger (23) is controlled by a heat source side expansion valve (24) is expanded.