Patent ID: 6467288
Filing Date: 2002-10-22
Classification: F25B,Y02B

Abstract:
A heat-pump water heater for heating water, comprising:a tank for storing water; a heat pump cycle for heating water, used as a heating source; and a control unit for controlling operation of the heat pump cycle, wherein: the heat pump cycle includes a compressor which compresses sucked refrigerant and discharges compressed refrigerant, a water heat exchanger which is disposed to perform a heat exchange between refrigerant from the compressor and water supplied from the tank, in such a manner that a flow direction of refrigerant is opposite to a flow direction of water in the water heat exchanger, an expansion valve decompressing refrigerant flowing from the water heat exchanger, an air heat exchanger disposed to perform a heat exchange between refrigerant decompressed in the expansion valve and outside air, an accumulator disposed between the air heat exchanger and the compressor, for separating refrigerant from the air heat exchanger into gas refrigerant and liquid refrigerant so that only gas refrigerant is introduced into the compressor, a bypass passage through which refrigerant from the water heat exchanger bypasses the expansion valve and the air heat exchanger, and an adjustment valve for adjusting a flow amount of refrigerant flowing through the bypass passage; the control unit controls the operation of the heat pump cycle to set one of a general cycle operation where refrigerant flowing from the water heat exchanger is supplied to the air heat exchanger after being decompressed in the expansion valve, and a bypass operation where refrigerant from the water heat exchanger flows through the bypass passage while bypassing the expansion valve and the air heat exchanger; the control unit has a water temperature sensor for detecting a water temperature flowing into the water heat exchanger, and a heat-radiation determining member which determines whether or not a heat radiation from refrigerant to outside air will occur in the air heat exchanger based on the water temperature; the heat-radiation determining member determines that there is a possibility of the heat radiation from refrigerant to outside air in the air heat changer when the water temperature detected by the water temperature sensor is higher than a predetermined temperature; and the control unit performs the bypass operation when it is determined that the heat radiation will occur by the heat-radiation determining member.