Heat pump type water heater

摘要

A hot water storage tank ( 3 ) and a circulating path ( 12 ) coupled to the hot water storage tank ( 3 ) are provided. An operation is possible wherein low-temperature water, let out from a lower part of the hot water storage tank ( 3 ) and entering the circulating path ( 12 ), is heated and boiled up by a heat pump heating source for forwarding to an upper part of the hot water storage tank ( 3 ). A refrigerant circulating circuit of the heat pump heating source is provided with a defrost circuit ( 38 ) for supplying hot gas from a compressor ( 25 ) to an air heat exchanger ( 28 ). It is possible to perform a defrost operation for providing a supply of hot gas to the air heat exchanger ( 28 ), with a water circulation pump ( 13 ) of the circulating path ( 12 ) held in abeyance. The water circulation pump ( 13 ) is made active if the defrost operation has been continued for not less than a predetermined time period since the start thereof.