Patent ID: 7027724

Claim:
A method of heating water stored in a water tank of a storage-type water heater comprising a first electric-resistance heating element comprising a thermal surface disposed within an inner surface of the tank at a first location, a second electric-resistance heating element comprising a thermal surface disposed within the inner surface of the tank at a second location disposed vertically above the first location, and first and second temperature sensors associated with the first and second heating elements, respectively, a third temperature sensor coupled to the tank at a third location disposed vertically between the first and second locations, the method comprising: sensing a first temperature with the first temperature sensor; sensing a second temperature with the second temperature sensor; preventing power to the second heating element and controllably providing power to the first heating element if the first temperature is below a first set point, the second temperature is above a second set point, and zero or more other conditions exist; preventing power to the first heating element and controllably providing power to the second heating element if the second temperature is below a second set point and zero or more other conditions exist; preventing power to the first and second heating elements if the first and second temperatures are above the first and second set points, respectively, and zero or more other conditions exist; and wherein the acts of preventing power to the second heating element and controllably providing power to the first heating element and preventing power to the first heating element and controllably providing power to the second heating element occur during normal operation, and wherein the method further comprises sensing a third temperature with the third temperature sensor; ceasing normal operation if the third temperature is below a third set point and zero or more other conditions exist; and entering boost operation if the third temperature is below a third set point and zero or more other conditions exist.