Control Algorithm for Water Heater
AssigneeRheem Manufacturing Company
InventorRaheel A. Chaudhry
Life of this patent
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Abstract
A storage type water heater, which may have either fuel or electric-based heating apparatus, is provided with a control system incorporating a control algorithm that monitors the time between heat demands and then sets the tank water setpoint temperature accordingly to lower the effects of water stratification due to periodic heat demands, and also save energy. When the time between consecutive heat demands is less than a predetermined setback time, for a number of heat demands equal to a predetermined setback limit, a setback mode is activated and responsively operates to reduce the setpoint temperature by a predetermined setback offset at the next cycle. The original control setpoint temperature is restored once the time between two successive heat demands is more than the setback time.
Claims15
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 set point 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.
Control apparatus for controlling a water heater having a tank for storing water, and heating apparatus operative to heat the stored water to and maintain the heated water at a setpoint temperature, said control apparatus being operative to:
- sense the tank water temperature and initiate a heating demand, which energizes said heating apparatus, in response to detecting a tank water temperature below said setpoint temperature;
- monitor the time between each successive pair of heating demands;
- reduce the setpoint temperature by a predetermined magnitude when the times between 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 two successive heat demands subsequent to the setpoint temperature reduction is greater than said predetermined setback time.
A method of controlling a water heater having a tank for storing water, and heating apparatus operative to heat the stored water to and maintain the heated water at a predetermined original setpoint temperature, said method comprising the steps of:
- sensing the tank water temperature and initiating a heating demand, which energizes said heating apparatus, in response to detecting a tank water temperature below said original setpoint temperature;
- monitoring the time between each successive pair of heating demands;
- reducing said original setpoint temperature by a predetermined magnitude when the times between 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
- returning the reduced setpoint temperature to said original setpoint temperature in response to the time between two successive heat demands subsequent to the setpoint temperature reduction being greater than said predetermined setback time.
Dependencies are inferred from the claim text.