Patent ID: 8813687

Claim:
A fuel-fired water heater comprising: a tank in which water may be stored; heating apparatus operative to heat the stored water to and maintain the heated water at a predetermined original setpoint temperature; and control apparatus for sensing the tank water temperature and responsively controlling said heating apparatus, said control apparatus incorporating therein a control algorithm operative to: monitor the time between heating apparatus energizations in each successive pair of heat demands, activate a setback mode in which said predetermined original setpoint temperature is reduced by a predetermined setback limit magnitude, when the times between heating apparatus energizations in consecutive heat demands are each less than or equal to a predetermined setback time for a predetermined setback limit number of heat demands, and then return the reduced setpoint temperature to the original setpoint temperature in response to the time between heating apparatus energizations in two successive heat demands subsequent to the setpoint temperature reduction being greater than said predetermined setback time.