Abstract: An external circuit that works in conjunction with the existing tank thermostatic controls to control both a heat pump and existing resistance elements in compliance with existing governmental codes. At the same time, this circuit disables the resistive heating elements in the hot water tank and enables the heat pump connected thereto so that the heat pump heats the water in the hot water tank. The control of the operation of the heat pump is provided through the thermostat(s) in the existing tank circuitry in the hot water tank which normally controls the resistive heating elements. At the same time, the electric resistive heating elements remain available for standby use. Further, the circuitry of the invention precludes the simultaneous operation of the electric resistive heating elements in the hot water tank and the heat pump heating unit.

Abstract: A heat exchanger including a first piece of heat conductive tubing wound in helical configuration defining a plurality of first helical flights having an outboard portion thereon and a second piece of heat conductive tubing wound in a helical configuration defining a plurality of second helical flights having an inboard portion thereon where the first and second helical flights are arranged so that the outboard portions of the first helical flights are in heat conducting contact with the inboard portions of the second helical flights and where the first and second helical flights have been formed by forcing the outboard portions of the first helical flights and the inboard portions of the second helical flights together so that the portions are forced into heat conducting contact with each other. The disclosure also describes the method of manufacturing the heat exchanger and the method of operating the heat exchanger.

Abstract: A connection assembly for connecting an external heating unit to a heater water tank comprising a mounting assembly connected to a tank opening with a passage opening interiorly of the water tank and connected to the heating unit exteriorly of the water tank, a tube assembly extending through the mounting assembly into the interior of the water tank and thermostatic control means for controlling the operation of the heating unit with a temperature sensing element mounted on the tube assembly within the water tank so that the temperature sensing element is exposed to the temperature of the water in the water tank. The tube assembly may be provided with a tube passage connected to the heating unit exteriorly of the water tank and opening interiorly of the water tank so that water can be withdrawn from the water tank through one of the passages to be supplied to the heating unit and returned from the heating unit to the heater water tank through the other of the passages.

Abstract: A heat exchanger including a first piece of heat conductive tubing wound in a helical configuration defining a plurality of first helical flights having an outboard portion thereon and a second piece of heat conductive tubing wound in a helical configuration defining a plurality of second helical flights having an inboard portion thereon where the first and second helical flights are arranged so that the outboard portions of the first helical flights are in heat conducting contact with the inboard portions of the second helical flights and where the first and second helical flights have been formed by forcing the outboard portions of the first helical flights and the inboard portions of the second helical flights together so that the portions are forced into heat conducting contact with each other. The disclosure also describes the method of manufacturing the heat exchanger and the method of operating the heat exchanger.