Abstract: To provide a water heat exchanger, a manufacturing method of the water heat exchanger, and a refrigeration cycle apparatus capable of preventing corrosion of a brazing material and deterioration of a refrigerant. The water heat exchanger according to the present embodiment includes a plurality of stacked heat-exchange plates, a joint (9) provided on at least one cover plate (14) of a pair of cover plates sandwiching the plurality of heat exchange plates, a first refrigerant pipe (10) brazed to the joint (9) by a brazing material (11), and a protector (12) provided to prevent contact between the brazing material (11) and the refrigerant circulating to the plurality of heat exchange plates through the first refrigerant pipe (10) and the joint (9).

Abstract: 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.

Abstract: According to one embodiment, a cascade refrigeration cycle apparatus according to the present embodiment includes a high-temperature-side and a low-temperature-side refrigeration circuits, an inverter and a control section. The high-temperature-side refrigeration circuit includes a first compressor and a cascade heat exchanger. The low-temperature-side refrigeration circuit includes a second compressor and the cascade heat exchanger. The inverter connected to at least one of the compressors. The control section controls the inverter so that a set operating frequency for the first compressor is higher than a set operating frequency for the second compressor when an operation of the apparatus is started.

Abstract: According to one embodiment, an apparatus includes a housing, two high-temperature-side refrigeration circuits and two low-temperature-side refrigeration circuits. Each of the high-temperature-side refrigeration circuits is configured to exchange heat with both of the two low-temperature-side refrigeration circuits by cascade heat exchangers. A hot-water pipe letting water or hot water through water-refrigerant heat exchangers of the high-temperature-side refrigeration circuits is provided. When the low-temperature-side refrigeration circuit conducts a defrosting operation of the evaporator, the low-temperature-side refrigeration circuits are controlled in such a way that the low-temperature-side refrigerant circuit releases heat in the cascade heat exchanger.

Abstract: According to one embodiment, an apparatus includes a housing, two high-temperature-side refrigeration circuits and two low-temperature-side refrigeration circuits. Each of the high-temperature-side refrigeration circuits is configured to exchange heat with both of the two low-temperature-side refrigeration circuits by cascade heat exchangers. A hot-water pipe letting water or hot water through water-refrigerant heat exchangers of the high-temperature-side refrigeration circuits is provided. When the low-temperature-side refrigeration circuit conducts a defrosting operation of the evaporator, the low-temperature-side refrigeration circuits are controlled in such a way that the low-temperature-side refrigerant circuit releases heat in the cascade heat exchanger.

Abstract: According to one embodiment, a cascade refrigeration cycle apparatus according to the present embodiment includes a high-temperature-side and a low-temperature-side refrigeration circuits, an inverter and a control section. The high-temperature-side refrigeration circuit includes a first compressor and a cascade heat exchanger. The low-temperature-side refrigeration circuit includes a second compressor and the cascade heat exchanger. The inverter connected to at least one of the compressors. The control section controls the inverter so that a set operating frequency for the first compressor is higher than a set operating frequency for the second compressor when an operation of the apparatus is started.