Patent ID: 7103272

Claim:
A storage-type water heater comprising: a water tank comprising an inner surface and a vertical axis; and a control system comprising a first electric-resistance heating element coupled to the tank, the first heating element comprising a thermal surface disposed within the inner surface at a first location, a second electric-resistance heating element coupled to the tank, the second heating element comprising a thermal surface disposed within the inner surface at a second location disposed vertically from the first location, a first temperature sensor coupled to the tank and associated with the first heating element, a second temperature sensor coupled to the tank and associated with the second heating element, and a third temperature sensor coupled to the tank at a third location disposed vertically between the first and second locations wherein the first and second temperature sensors sense first and second temperatures, respectively, having a relation to the water temperature, and wherein the control system comprises a controller operable to receive the first and second temperatures and control the first and second heating elements based on the first and second temperatures, wherein the third temperature sensor senses a third temperature having a relation to the water temperature, and wherein the controller is further operable to determine a boost state based on the third temperature sensor.