Heat pump-type hot-water heating device

A heat pump-type hot-water heating device comprising:

• a refrigerant circuit where a compressor, a flow path switching device, a water-refrigerant heat exchanger configured to exchange heat between water and a refrigerant, and an outdoor heat exchanger are connected by a pipe;
• a hot-water circulation circuit where the water-refrigerant heat exchanger, a water pump, a low-temperature heating terminal, and a high-temperature heating terminal are connected by a pipe and by an action of the water pump configured to supply hot water from the water-refrigerant heat exchanger to the low-temperature heating terminal and the high-temperature heating terminal in parallel and reflux a condensate from each heating terminal to the water-refrigerant heat exchanger;
• a hot-water outflow temperature detecting device configured to detect a hot-water outflow temperature of hot water that has passed through the water-refrigerant heat exchanger;
• a hot-water outflow-temperature control device configured to control the flow path switching device such that the water-refrigerant heat exchanger functions as a condenser and to drive the compressor such that, when heating operation is performed with at least one of the high-temperature heating terminal and the low-temperature heating terminal, the hot-water outflow temperature reaches a target hot-water outflow temperature set according to a load of the heating operation;
• and
• a defrosting operation control device configured to control the flow path switching device such that the outdoor heat exchanger functions as a condenser and to drive the compressor to perform defrosting operation of the outdoor heat exchanger, wherein
• the defrosting operation control device is configured to start the defrosting operation in a state in which the hot-water outflow temperature is higher than the target hot-water outflow temperature when a decrease amount per unit time of the target hot-water outflow temperature has become equal to or more than a decrease amount threshold.