Patent ID: 8082749

Claim:
An air conditioner equipped with a heat-source side unit that is disposed outdoors and comprises a compressor having a refrigerant discharge pipe and a refrigerant suction pipe and a heat-source side heat exchanger, plural use-side units each having a use-side heat exchanger and an inter-unit pipe that comprises a high-pressure gas pipe branched and connected to the refrigerant discharge pipe, a low-pressure gas pipe branched and connected to the refrigerant suction pipe and a liquid pipe connected to the heat-source side heat exchanger and through which the heat-source side unit is connected to the plural use-side units, the heat-source side heat exchanger being branched and connected to the refrigerant discharge pipe and the refrigerant suction pipe of the compressor through a change-over valve, each of the use-side heat exchangers being branched and connected to the high-pressure gas pipe and the low-pressure gas pipe through a change-over valve and an expansion valve being connected to the liquid pipe, thereby forming a refrigerant circuit, further comprising: an auxiliary heat source unit that is disposed indoors and has a water-refrigerant heat exchanger that heat-exchanges refrigerant wherein the water heating the liquid refrigerant, one end of a refrigerant side of the water-refrigerant heat exchanger being selectively connectable to one of the high-pressure gas refrigerant pipe and the low-pressure gas refrigerant pipe through one of a first change-over valve and a second change-over valve, and also the other end of the refrigerant side being connected to the liquid refrigerant pipe through an expansion valve; and a controller that controls the auxiliary heat source unit so that the water-refrigerant heat exchanger of the auxiliary heat source unit functions as an evaporator with a water side thereof serving as a heat source when some of the user-side units are under heating operation, wherein the auxiliary heat source unit contains a boiler at the water side of the water-refrigerant heat exchanger thereof.