Apparatus and method for controlling a heat pump water heater

A water heating system including a tank wherein heated water may be stored and a refrigeration circuit having a compressor, condenser and evaporator wherein the condenser includes a water passageway and a refrigerant passageway in heat exchange relation to transfer heat energy from the refrigerant to the water to be heated which comprises:

• a thermally conductive tubular member extending from a bottom portion of the tank;
• a first conduit connecting the tubular member to the water passageway of the condenser;
• a second conduit connecting the water passageway of the condenser to the tank at a position spaced from the tubular member;
• a pump for circulating water through the first conduit, the water passageway, condenser and second conduit;
• thermal sensing means mounted to sense the temperature of the tubular member, said thermal sensing means being connected to energize the pump to circulate water, to energize the compressor of the refrigeration circuit when the temperature sensed is below a first threshhold temperature and to de-energize the pump and the compressor when the temperature sensed exceeds a second threshhold temperature;
• and
• insulation mounted about the thermal sensing means and the thermally conductive tubular member to reduce the heat transfer from the tubular member to the ambient air such that the temperature sensed by thermal sensing means is an accurate reflection of the temperature of the water in the tank, said insulation comprising an elastomeric foam sheet, said sheet being wrapped about said tubular member and said thermal sensing means, and further including a securing means for securing said sheet in position, and said sheet further defining an opening leading to said thermal sensing means for allowing said thermal sensing means to be adjusted without removal of said insulation.