Abstract: A water heater is disclosed. The water heater includes a water storage tank and a heat source positioned to heat water within the water storage tank. A heat exchanger is positioned within the bottom end portion of the water storage tank. The heat exchanger is configured to contain a fluid medium for heat exchange with water in the bottom end portion of the water storage tank. A temperature sensor is positioned at an elevation above the heat exchanger for sensing a temperature of water within the tank. A control system is configured to selectively activate the heat source as a function of the water temperature sensed by the temperature sensor. The heat source can be either a heating element positioned within the water storage tank, or a burner positioned to deliver products of combustion into a flue positioned within the tank for heating water within the water storage tank.

Abstract: A water heater including a tank having a wall defining an interior for holding water is provided. A heat exchange assembly is positioned at least partially within the interior of the tank. The heat exchange assembly has an outer tube extending within the interior of the tank. The outer tube has a wall with an inner surface. An inner tube extends within the outer tube. The inner tube has a wall with an outer surface. A gap is defined between the outer surface of the inner tube and the inner surface of the outer tube. Heat conducting fluid is contained within the gap. The fluid facilitates the transfer of heat between the inner tube and the outer tube.

Abstract: A water heater including a tank having a wall defining an interior for holding water is provided. A heat exchange assembly is positioned at least partially within the interior of the tank. The heat exchange assembly includes a metallic outer tube positioned within the interior of the tank. The outer tube has a wall with an inner surface and end portions positioned within the interior of the tank. The heat exchange assembly further includes a metallic inner tube extending within the outer tube and having end portions extending through the wall of the tank. A portion of the outer surface of the inner tube contacts a portion of the inner surface of the outer tube. An elongated passageway is defined between a portion of the outer surface of the inner tube and a portion of the inner surface of the outer tube to facilitate a flow of fluid.