Heat pump type hot-water supply system capable of performing defrosting operation

A heat pump type hot-water supply system comprising:

• a heat pump cycle including a compressor, a first heat exchanger, a pressure-reducing device, and a second heat exchanger which are annularly connected to each other;
• a defrosting control unit for defrosting the second heat exchanger in a defrosting operation by controlling an opening degree of the pressure-reducing device;
• a reservoir for storing liquid that is to be heated in an ordinary operation;
• a circulation pipe passing through the first heat exchanger so that the liquid in the reservoir circulates in the circulation pipe while passing through the first heat exchanger;
• and
• a pump for circulating the liquid in the circulation pipe, wherein:
• the opening degree of the pressure-reducing device in the defrosting operation is controlled by the defrosting control unit to be larger than that in the ordinary operation;
• and
• the liquid heated and stored in the reservoir is supplied into the first heat exchanger in the defrosting operation.

A hot-water supply system comprising:

• a reservoir for storing liquid therein;
• a refrigerant cycle including a compressor for compressing refrigerant, a first heat exchanger for performing heat exchange between refrigerant discharged from the compressor and the liquid from the reservoir to heat the liquid in an ordinary operation, a pressure-reducing device for decompressing refrigerant from the first heat exchanger, and a second that exchanger for performing heat exchange between refrigerant and outside air in the ordinary operation;
• a pump for circulating the liquid between the reservoir and the first heat exchanger;
• and
• a control unit for performing a defrosting operation of the second heat exchanger in a defrosting operation, wherein,
• in the defrosting operation, the control unit controls an opening degree of the pressure-reducing device to be larger than that during the ordinary operation, while the pump operates.