Patent ID: 8839640

Claim:
An air-conditioning apparatus, comprising: a compressor, a heat source side heat exchanger, a plurality of expansion devices, a plurality of heat exchangers related to heat medium, a plurality of pumps, and a plurality of use side heat exchangers, wherein a refrigerant circuit circulating a refrigerant that contains a refrigerating machine oil therein is formed by connecting the compressor, the heat source side heat exchanger, the expansion devices, and the heat exchangers related to heat medium with a refrigerant piping, a plurality of heat medium circuits circulating a heat medium are formed by connecting the pumps, the use side heat exchangers, and the heat exchangers related to heat medium, the air-conditioning apparatus is capable of executing: a heating only operation mode that heats the heat medium by making high-temperature high-pressure refrigerant flow into all of the heat exchangers related to heat medium; a cooling only operation mode that cools the heat medium by making low-temperature low-pressure refrigerant flow into all of the heat exchangers related to heat medium; a cooling and heating mixed operation mode that heats the heat medium by making high-temperature high-pressure refrigerant flow into one or some of the heat exchangers related to heat medium and cools the heat medium by making low-temperature low-pressure refrigerant flow into one or some of the remaining heat exchangers related to heat medium; and an oil collection mode that collects the refrigerating machine oil stagnating in the heat exchangers related to heat medium into the compressor by changing a flow velocity or a flow direction of the refrigerant flowing in the heat exchangers related to heat medium depending on each operation mode, wherein the air-conditioning apparatus further includes: a first refrigerant flow switching device that switches passages of the refrigerant that is discharged or sucked into the compressor, and a plurality of second refrigerant flow switching devices respectively disposed for the heat exchangers related to heat medium, the second refrigerant flow switching devices each switching passages of the refrigerant that flows into or flows out of the corresponding heat exchanger related to heat medium, and wherein in the oil collection mode, while the switching state of the first refrigerant flow switching device is maintained as it is, the switching state of the second refrigerant flow switching devices is switched such that at least one heat exchanger related to heat medium operates as an evaporator, in which the low-temperature low-pressure refrigerant flow operates as a condenser or a gas cooler by sending the high-temperature high-pressure refrigerant therein.