Apparatus and method for controlling a heat pump water heater

摘要

A method and apparatus for controlling the operation of an add-on heat pump water heater unit is disclosed. A combination of a thermally conductive tube having a flattened portion and a thermostat mounted thereto is utilized to sense the temperature level of water in a tank to which the heater unit is connected. The tube and thermostat are additionally insulated from the ambient. A circulating pump is provided and connected to the water thermostat such that the pump is energized only when it is necessary to operate the heat energy adding unit.