Dual Sensor Companion Water Heater

A companion water heater comprising:

• a hot water storage tank;
• a heat exchange coil disposed in the hot water storage tank;
• a lower sensor disposed in thermal contact with a lower portion of the hot water storage tank;
• an upper sensor disposed in thermal contact with an upper portion of the hot water storage tank;
• a circulator pump to urge a flow of a heating fluid to circulate between a boiler and the heat exchange coil;
• and
• a controller configured to control a heat source in response to a sensed temperature at an upper portion of the hot water storage tank and a sensed temperature at a lower portion of the hot water storage tank, wherein the controller is configured to control the heat source to provide a boiler water to the hot water storage tank at a temperature above a predetermined temperature in response to both of the sensed temperature at an upper portion of the hot water storage tank and the sensed temperature at a lower portion of the hot water storage tank being below the predetermined temperature and the controller is configured to control the heat source to provide the boiler water to the hot water storage tank at a temperature at the predetermined temperature in response to the sensed temperature at an upper portion of the hot water storage tank being above the predetermined temperature and the sensed temperature at the lower portion of the hot water storage tank being below the predetermined temperature.