HEAT PUMP TYPE HOT WATER SUPPLY MACHINE

PROBLEM TO BE SOLVED: To suppress discharge lift shortage of a water pump which forcibly feeds supplied hot water and to suppress inflow of low temperature supplied hot water into a hot water storage tank, in a heat pump type hot water supply machine for heating the supplied hot water in a plurality of heat pump cycles.SOLUTION: Minimum water forcible feeding capacity determination means for determining minimum rotational frequency Npmin of a plurality of water pumps 28a to 28d determines the minimum rotational frequency Npmin within a range where the water pumps which are in the minimum rotational frequency Npmin do not become discharge lift shortage, and also, decreases the minimum rotational frequency Npmin according to the decrease of an average value Npave of the rotational frequency of the plurality of water pumps 28a to 28d. Thereby, inflow of low temperature supplied hot water into a hot water storage tank 20 is suppressed while suppressing the discharge lift shortage of the water pumps. 【課題】複数のヒートポンプサイクルにて給湯水を加熱するヒートポンプ式給湯機において、給湯水を圧送する水ポンプの吐出揚程不足を抑制しつつ、貯湯タンク内に低温の給湯水が流入してしまうことの抑制を図る。【解決手段】複数の水ポンプ２８ａ〜２８ｄの最低回転数Ｎｐｍｉｎを決定する最低水圧送能力決定手段が、最低回転数Ｎｐｍｉｎとなっている水ポンプが吐出揚程不足とならない範囲で最低回転数Ｎｐｍｉｎを決定するとともに、複数の水ポンプ２８ａ〜２８ｄの回転数の平均値Ｎｐａｖｅの低下に伴って、最低回転数Ｎｐｍｉｎを低下させる。これにより、水ポンプの吐出揚程不足を抑制しつつ、貯湯タンク２０内に低温の給湯水が流入してしまうことを抑制する。【選択図】図３