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.
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