| 摘要 |
In a heat-pump water heater, an ECU sets a target temperature difference between water flowing into a water heat exchanger and refrigerant flowing out from the water heat exchanger, and controls a valve opening degree of an expansion valve so that the target temperature difference is obtained. When a refrigerant temperature discharged from a compressor is higher than a predetermined value, the target temperature difference is increased until the refrigerant temperature discharged from the compressor becomes lower than the predetermined value. Further, when water-heating capacity is decreased due to the increase of the target temperature difference, a rotation speed of the compressor is increased.
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