Abstract: A heat source unit includes a compressor, a heat-source-side heat exchanger, an outdoor blower, and a controller for electric devices. A hydrothermal exchange unit accommodates water heat exchangers, water pipes, pumps and a controller, and is connected to the heat source unit via refrigerating pipes and electric wiring. A tank unit has tanks for storing hot water obtained as a result of heat exchange by the water heat exchangers. The hydrothermal exchange unit has a housing. The front, rear, upper, left and right sides of the housing are covered with panels. A bottom plate for the housing is disposed a predetermined distance above the lower end of the housing. The housing accommodates the hydrothermal exchange unit, and a space below the bottom plate of the housing accommodates connectors for the water pipes and refrigerant pipes. This completely prevents freezing of the water pipes, makes use-side units compact, and improves operation efficiency.

Abstract: Defrosting operation is possible by causing refrigerant discharged from a compressor to flow to an outdoor heat exchanger, and returning the refrigerant passed through the outdoor heat exchanger to the compressor through a water-heat exchanger, while operating a pump. Quick defrosting operation is possible by causing refrigerant discharged from a compressor to flow to an outdoor heat exchanger, and returning the refrigerant passed through the outdoor heat exchanger directly to the compressor, while stopping a pump. The temperature of water that has flowed into a water-heat exchanger is detected. According to the detected temperature, the defrosting operation using hot water and quick defrosting operation are selectively executed.

Abstract: A heat source unit includes a compressor, a heat-source-side heat exchanger, an outdoor blower, and a controller for electric devices. A hydrothermal exchange unit accommodates water heat exchangers, water pipes, pumps and a controller, and is connected to the heat source unit via refrigerating pipes and electric wiring. A tank unit has tanks for storing hot water obtained as a result of heat exchange by the water heat exchangers. The hydrothermal exchange unit has a housing. The front, rear, upper, left and right sides of the housing are covered with panels. A bottom plate for the housing is disposed predetermined distance above the lower end of the housing. The housing accommodates the hydrothermal exchange unit, and a space below the bottom plate of the housing accommodates connectors for the water pipes and refrigerant pipes. This completely prevents freezing of the water pipes, makes use-side units compact, and improves operation efficiency.

Abstract: Defrosting operation is possible by causing refrigerant discharged from a compressor to flow to an outdoor heat exchanger, and returning the refrigerant passed through the outdoor heat exchanger to the compressor through a water-heat exchanger, while operating a pump. Quick defrosting operation is possible by causing refrigerant discharged from a compressor to flow to an outdoor heat exchanger, and returning the refrigerant passed through the outdoor heat exchanger directly to the compressor, while stopping a pump. The temperature of water that has flowed into a water-heat exchanger is detected. According to the detected temperature, the defrosting operation using hot water and quick defrosting operation are selectively executed.