Heat pump type water heater

A heat pump type hot water supply apparatus, comprising:

• a hot water storage tank;
• a circulating path coupled to said hot water storage tank;
• a heat exchanging path inserted in said circulating path;
• said heat pump type hot water supply apparatus being operable to perform an operation in which said heat exchanging path is so heated by a heat pump heating source as to boil low-temperature water let out from a lower part of said hot water storage tank for forwarding to an upper part of said hot water storage tank;
• a refrigerant circulating circuit of said heat pump heating source being formed by a sequential connection of a compressor, a water heat exchanger for heating said low-temperature water, a pressure reducing mechanism, and an air heat exchanger;
• said refrigerant circulating circuit further comprising a defrost circuit for supplying hot gas from said compressor, to said air heat exchanger;
• wherein said heat pump type hot water supply apparatus is operable to perform a defrost operation for providing a supply of hot gas to said air heat exchanger, with a water circulation pump of said circulating path held in abeyance;
• wherein defrost control means is provided which activates said water circulation pump if said defrost operation has been continued for not less than a predetermined time period since the start thereof.