To provide a heat pump hydronic heater that improves usability, without erroneously detecting leakage of refrigerant.
A heat pump hydronic heater includes: a refrigeration cycle formed of at least a compressor 1, a water refrigerant heat exchanger 3, a decompression unit 4, and an outdoor heat exchanger 5; a discharge pressure detecting means 1b for detecting a discharge pressure of the compressor 1; a discharge superheat degree detecting means for detecting a superheat degree of a discharge refrigerant of the compressor 1; and a control unit 11a. In the heat pump hydronic heater, the control device stops operation of the compressor 1 if the discharge pressure detected by the discharge pressure detecting means 1b is lower than a first set pressure and the discharge superheat degree detected by the discharge superheat degree detecting means is equal to or higher than a predetermined value when a predetermined time is elapsed after the compressor 1 is started, or if the discharge pressure detected by the discharge pressure detecting means 1b is lower than a second set pressure which is set lower than the first set pressure.
NISHIMURA HIDEJI
Daisuke Nagano
Kentaro Fujii