Control for a fuel-fired water heating appliance having variable heating rates

• US 20080011245A1
• Filed: 07/12/2006
• Published: 01/17/2008
• Est. Priority Date: 07/12/2006
• Status: Active Grant

• Current Assignee: Emerson Electric Company
• Original Assignee: Emerson Electric Company
• Inventors: Donnelly, Donald E.
• Granted Patent: US 7,380,523 B2
• Time in Patent Office: Days
• US Class Current: 122/14.2
• CPC Class Codes: F24H 1/205 with furnace tubes
• CPC Class Codes: F24H 15/174 Supplying heated water with desired temperature or desired range of temperature
• CPC Class Codes: F24H 15/225 at different heights of the tank
• CPC Class Codes: F24H 15/238 Flow rate
• CPC Class Codes: F24H 15/31 of valves having only one inlet port and one outlet port, e.g. flow rate regulating valves
• CPC Class Codes: F24H 15/36 of burners
• CPC Class Codes: F24H 15/414 using electronic processing, e.g. computer-based
• CPC Class Codes: F24H 9/2035 using fluid fuel

Abstract

A control system for a fuel-fired water heater appliance is provided that includes a control for the appliance that is in communicating with a sensor for sensing a water flow rate through the water heater. The control system is capable of controlling a gas valve to supply fuel to a burner at a maximum rate of fuel flow when the water flow rate is determined to be above a predetermined threshold. The control system is capable of controlling the gas valve to supply fuel to a burner at a reduced rate of fuel flow when the water flow rate is below a predetermined threshold, whereby the control 128 establishes the lower rate of heating operation as long as the temperature of the heated water is below the predetermined maximum temperature.

Claims

1. A fuel-fired water heater control in communication with a water temperature sensor, and flow sensor for sensing a water flow rate through the water heater, the control being capable of controlling a gas valve to supply fuel to a burner at a maximum rate of fuel flow when the water flow rate is above a predetermined threshold and the sensed water temperature is below a predetermined maximum temperature but above the minimum desired temperature at which the gas valve is normally turned on.

2. The fuel-fired water heater control of claim 1 wherein the control is capable of controlling the gas valve to supply fuel to a burner at a reduced rate of fuel flow when the water flow rate is below a predetermined threshold and the sensed water temperature is above the desired minimum temperature.

3. The fuel-fired water heater control of claim 1 wherein the sensor for sensing water flow is capable of monitoring the water flow rate through the water heater and providing an output that is used to determine when the water flow rate through the water heater is above a predetermined threshold rate.

4. The fuel-fired water heater control of claim 3 wherein the sensor provides an analog output that varies with the rate of water flow through the water heater.

5. The fuel-fired water heater control of claim 3 wherein the sensor comprises a switching device that switches when the flow rate of water through the water heater exceeds a predetermined threshold.

6. The fuel-fired water heater control of claim 3 wherein the sensor monitors the flow rate of water being supplied to the water heater.

7. The fuel-fired water heater control of claim 3 wherein the predetermined threshold is a rate of at least 3.0 gallons per hour.

8. The fuel-fired water heater control of claim 2 wherein the control controls the gas valve to supply fuel to the burner only when the sensed temperature of the heated water is less than a predetermined maximum temperature.

9. The fuel-fired water heater control of claim 1 wherein the water temperature sensor is a thermistor having a resistance that changes in value as the temperature of the heated water changes.

10. The fuel-fired water heater control of claim 8 wherein the water temperature sensor is a thermal switch that switches when the temperature of the heated water exceeds the predetermined maximum temperature.

11. The fuel-fired water heater control of claim 8 wherein the predetermined maximum temperature is at least 135 degrees Fahrenheit.

12. A control system for controlling the operation of a fuel fired water heating appliance having a burner, the control system comprising:

a flow sensor capable of monitoring the rate of water flow through the water heater and providing an output that is used to determine when the water flow rate is above a predetermined threshold;

a temperature sensor capable of providing an output indicative of the temperature of the heated water;

a gas valve capable of controlling the supply of fuel to the burner at a maximum rate of fuel flow and at least one reduced rate of fuel flow; and

a controller in communication with the flow sensor, the temperature sensor, and the gas valve, the controller being configured to control the gas valve to establish a maximum rate of fuel flow to the burner in response to receiving an output from the temperature sensor indicative of a heated water temperature that is below a maximum predetermined value when the water flow rate is above the predetermined threshold, and being configured to control the gas valve to establish at least one reduced rate of fuel flow to the burner in response to receiving an output from the temperature sensor when the water flow rate is below the predetermined threshold.

13. The control system of claim 12 wherein the flow sensor provides an analog output that varies with the rate of water flow through the water heater.

14. The control system of claim 12 wherein the sensor comprises a switching device that switches when the flow rate of water through the water heater exceeds a predetermined threshold.

15. The control system of claim 12 wherein the sensor monitors the flow rate of water being supplied to the water heater.

16. The control system of claim 15 wherein the predetermined threshold is a rate of at least 3.0 gallons per hour.

17. The control system of claim 12 wherein the temperature sensor is a thermistor having a resistance that changes in value as the temperature of the heated water changes.

18. The control system of claim 12 wherein the temperature sensor is a thermal switch that switches when the temperature of the heated water exceeds the predetermined maximum temperature.

19. The control system of claim 12 wherein the controller configured to control the gas valve to supply fuel to the burner at a maximum rate of fuel flow when the water flow rate is above a predetermined threshold for more than a minimum time period.

20. A control system for controlling the operation of a fuel fired water heating appliance having a burner, the control system comprising:

a flow sensor for monitoring the rate of water flow through the water heater and providing an output for determining when the water flow rate is above a predetermined threshold;

a temperature sensor for providing an output for determining when the temperature of the water being heated exceeds a predetermined maximum temperature;

a gas valve capable of supplying fuel to the burner at a maximum rate of fuel flow and at least one reduced rate of fuel flow; and

a microprocessor in communication with the flow sensor, the temperature sensor, and the gas valve, the microprocessor being configured to control the gas valve to supply fuel to the burner at a maximum rate of fuel flow when the water flow rate is above a predetermined threshold for more than a minimum time period, and to supply fuel to the burner at a reduced rate of fuel flow when the water flow rate falls below the predetermined threshold and the sensed water temperature is below the predetermined maximum temperature.