Apparatus and method for controlling a damper in a gas-fired appliance

Abstract

A gas-fired appliance is provided having a burner which is configured to receive and burn pressurized gas, such as natural gas, during operation. A control comprises a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a motor operatively connected to the battery and the pressure switch which is operated in response to the application of pressurized gas at the inlet. A damper assembly is connected to the motor. The damper assembly comprises a damper movable between an open position and a closed position in response to operation of the motor.

Description

TECHNICAL FIELD

The present invention relates generally to gas-fired appliances, and, more particularly, to a damper control mechanism for a water heater or other gas-fired appliance.

BACKGROUND OF THE INVENTION

Many gas-fired appliances, such as boilers or water heaters, include burners that fire to raise the temperature of materials, such as water, contained within a tank. In many such appliances, the burners periodically cycle on and off. When the contents of the tank fall below a desired minimum temperature, a call for heat is triggered, which initiates the firing of a main gas burner assembly. The resulting heat generated by the burner acts to raise the tank temperature. When the tank temperature reaches a desired maximum threshold, the main burner is deactivated, until such time as the tank cools and again falls below the minimum desired temperature. A small pilot burner can be provided to maintain a small flame under normal operation, which flame is used to ignite the main burner when desired.

To increase the energy efficiency of such gas-fired appliances, many systems include one or more dampers. For example, a flue damper can be provided within an exhaust flue near the top of a gas fired appliance. The flue damper is opened during operation of the main burner, to permit the venting of heat and exhaust gases generated during operation of the main burner; However, once the main burner is shut off, the flue damper closes the flue, thereby reducing heat loss out the flue and retaining heat within the appliance to improve the overall energy efficiency of the appliance.

Conventionally, dampers can be operated using an electric motor supplied by 24 volt or 120 volt power sources. However, such designs typically require the routing of a power source to the location of the gas-fired appliance, potentially increasing installation costs. More recently, gas fired appliances have been designed using thermoelectric devices such as one or more 750 millivolt thermopiles, operating using heat from the pilot flame, to power a low-power motor. The low-power motor in turn operates the flue damper.

However, many gas-fired appliances, particularly residential water heaters, do not include power sources having sufficient voltage to reliably operate a damper motor. As a result, many residential water heaters are primarily mechanically operated. While some such water heaters may utilize a thermocouple to operate a magnetic pilot safety switch, such thermocouples typically generate only 10 to 30 millivolts, and do not supply sufficient power to drive a damper motor. Because of such control limitations, flue dampers are often not provided on residential water heaters, thereby sacrificing potential improvements in energy efficiency.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a gas-fired appliance is provided having a burner which is configured to receive and burn pressurized gas, such as natural gas, during operation. A control comprises a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a motor operatively connected to the battery and the pressure switch which is operated in response to the application of pressurized gas at the inlet. A damper assembly is connected to the motor. The damper assembly comprises a damper movable between an open position and a closed position in response to operation of the motor.

In accordance with some embodiments, the gas-fired appliance further includes a pilot burner, and a thermoelectric device, such as a thermocouple or thermopile, positioned near the pilot burner, such that the thermoelectric device generates an electrical voltage differential when exposed to heat from the pilot burner. A magnetic pilot valve controls gas flow to the pilot burner, and features an electrical input. The magnetic pilot valve is maintained in an open position in response to the maintenance of the voltage generated by the pilot flame. A switch circuit is interposed in an electrical conduction path between the thermoelectric device and the magnetic pilot valve electrical input, whereby it can operate to control the transmission of the electrical voltage differential generated by the thermoelectric device to the magnetic pilot valve electrical input. The switch circuit is movable between an open state and a closed state in response to movement of the damper.

It is a feature of the invention the motor operates a cam, and the switch circuit is comprised of a first switch which is closed by the cam when the damper is in a first position, and a second switch, connected electrically in parallel with the first switch, which is closed by the cam when the damper is in a second position. A resistor and a capacitor may be operably interconnected, the capacitor being connected between a signal path leading to the pilot valve electrical input and a ground reference voltage. The capacitor charges when the switch circuit is in the closed state, and discharges when the switch circuit is in the open state.

It is another feature of the invention that the switch circuit further comprises a third switch connected in series with the pressure switch to stop the motor after the damper is moved from the first position to the second position or from the second position to the first position.

There is disclosed in accordance with another aspect of the invention a damper control mechanism for an appliance that operates through combustion of gas having a pressure that is greater than ambient pressure. The damper control mechanism comprises a damper, and a motor operatively connected to the damper to control position of the damper. A cam is operatively connected to the damper. A control comprises a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a switch operated by the cam, to selectively energize and de-energize the motor to control damper position responsive to change of the pressure at the inlet.

There is disclosed in accordance with a further aspect of the invention a method for controlling a damper in a gas-fired appliance, comprising the steps of: applying pressurized gas to a first portion of the gas-fired appliance which includes a main burner; and opening a damper by operatively connecting a battery to a motor connected to the damper using a pressure sensor sensing introduction of pressurized gas into the first portion of the gas-fired appliance.

Further features of the application will be readily apparent from the specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a portion of a gas-fired appliance, having a manually-operated damper and pilot power control switch, in accordance with one embodiment of the invention.

FIG. 2 is a schematic block diagram of a flue damper control circuit.

FIG. 3 is a perspective view of a pilot power control switch.

FIG. 4 is an elevation view of a portion of a pilot power control switch, in a position corresponding to an open damper condition.

FIG. 5 is an elevation view of a portion of a pilot power control switch, in a position corresponding to a closed damper condition.

FIG. 6 is a perspective view of a damper.

FIG. 7 is a diagrammatic view of a portion of a gas-fired appliance included a controlled damper in accordance with a second embodiment of the invention.

FIG. 8 is a perspective view of a motor controlled damper of the second embodiment.

FIG. 9 is a side elevation view of the motor and associated cam switches.

FIG. 10 is a schematic block diagram of a flue damper control circuit of the second embodiment.

DETAILED DESCRIPTION

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail, certain specific embodiments with the understanding that the present disclosure should be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments so illustrated or described.

Referring initially to FIG. 1, a portion of a gas-fired appliance, such as a water heater, is illustrated. Gas fired appliance 100 receives combustible gas, such as natural gas, via supply line 110. The gas is supplied at a pressure greater than the ambient air pressure in which the main appliance burners 112 (shown schematically) operate. Gas is fed into control body 120 and through pilot valve 130, which supplies gas to a pilot burner 132 (shown schematically). Once pilot burner 132 is ignited, pilot valve 130 is maintained in an open position by pilot valve magnet 140, which is energized by voltage received at thermoelectric device connection 150. Thermoelectric device connection 150 is energized by thermoelectric device 160 (illustrated in FIG. 2). In exemplary embodiments, thermoelectric device 160 may include a thermocouple or a thermopile. Thermoelectric device 160 is positioned adjacent pilot burner 132 to generate voltage when exposed to the heat of the pilot flame. If the pilot flame is extinguished, thermoelectric device 160 ceases generation of sufficient voltage for pilot valve magnet 140 to maintain pilot valve 130 in an open position, thereby stopping the flow of gas to pilot burner 132 via supply tube 170 and preventing unintentional flooding of unburned gas.

Control body 120 further includes gas pressure regulator 180, which operates to regulate the gas pressure within control body 120. Temperature controlled burner valve 190 operates to limit the conditions under which gas is supplied to primary appliance burners 112 via burner supply tube 200. For example, in an embodiment in which gas fired appliance 100 is a water heater, a temperature sensor can be provided within the water tank, such that a call for heat is issued when the water temperature falls below a desired level. In response to a call for heat, burner valve 190 is opened, thereby supplying gas to main burner 112 through burner supply tube 200. When burner 112 acts to raise the monitored temperature above a desired maximum level, burner valve 190 is closed, thereby shutting off the flow of gas to burner 112.

In addition to providing gas feeds to pilot burner supply tube 170 and main burner supply tube 200, control body 120 further includes a gas pressure tap port 210. Gas pressure tap port 210 is connected to a diaphragm device 220 via tube 230 to communicate pressure within control body 120 therethrough. Thus, when pilot valve 130 and main burner valve 190 are both open, the resulting flow of gas pressurizes a chamber to which gas pressure tap port 210 is connected. When main burner valve 190 is closed, gas pressure tap port 210 and thus diaphragm device 220 are exposed to ambient pressure conditions.

Diaphragm device 220 is a mechanism having an inlet 231, which is alternatively exposed to pressure of the gas or ambient pressure conditions, depending upon the state of main burner valve 190. Diaphragm device 220 also includes a movable member 232, which is a structural component displaced in response to the application of gas pressure to an inlet portion of the device. Moveable member 232 includes a first surface 233 which is exposed to the pressure conditions of the inlet, and a second surface 234 that is exposed to ambient pressure conditions. Accordingly, moveable member 232 is displaced in response to changes in inlet pressure. For example, in some embodiments, moveable member 232 may include a diaphragrm, such as a thin, flexible membrane, spanning inlet and ambient conditions.

Moveable member 232 within diaphragm device 220 is operably interconnected with intermediate shaft 235 and damper control activation arm 240, forming a portion of an operable linkage with device 220. When gas pressure is applied to the inlet side of diaphragm device 220, intermediate shaft 235 moves upwards, causing damper control activation arm 240 to pivot about pivot point 250 in the direction of the illustrated arrow 251. When gas pressure is released from diaphragm device 220, intermediate shaft 235 returns to a lowered position and activation arm 240 pivots oppositely to the direction indicated by arrow 251.

Damper control activation arm 240 is illustrated in perspective view in FIG. 3. In the illustrated embodiment, damper control activation arm 240 is made with first arm portion 240a and second arm portion 240b, which are mechanically connected. One end 252 of damper control activation arm 240 interacts with a switch circuit 260 that includes pilot power control switches 260a and 260b, which are mounted adjacent to one another.

Pilot power control switches 260a and 260b are further illustrated in FIGS. 4 and 5. Pilot power control switches 260a and 260b include switch arms 265a and 265b, respectively. Switch arm 265a extends downwards from the point at which it is attached to switch 260a. Switch arm 265b extends upwards from the point at which it is attached to switch 260b. Damper control activation arm 240a is aligned to interact with pilot power control switch 260a, such that switch arm 265a is depressed when activation arm 240 is moved to a first position, as shown in FIG. 4, and released when activation arm 240 is moved to a second position, as shown in FIG. 5. Damper control activation arm 240b is aligned to interact with pilot power control switch 260b, such that switch 265b is depressed when activation arm 240 is in the second position, shown in FIG. 5, and released when activation arm 240 is in the first position of FIG. 4. In the exemplary embodiment of FIGS. 4 and 5, the first activation arm position (FIG. 4) is maintained over a range from about 80% to about 100% of the normal range of travel of activation arm 240, in which gas is being supplied to the main burner and the flue damper is substantially open. The second activation arm position (FIG. 5) is maintained over a range from about zero to about 20% of the normal range of travel of activation arm 240, in which the supply of gas to the main burner has been shut off and the flue damper is substantially closed.

Damper control activation arm 240 is further connected to link 270, which extends to control the opening and closing of flue damper 280, illustrated in FIG. 6. In an exemplary embodiment, link 270 may incorporate a cable structure, such as a metal cable that slides freely within a polymer sheath. Alternatively, it is understood that other varieties of mechanical links that are known in the art could be implemented, such as a rod or shaft. The end of link 270 opposite damper control activation arm 240 is attached to lever arm 290, which is secured to damper control shaft 300. Damper 280 is mounted on control shaft 300. Accordingly, movement of link 270 results in pivoting of control shaft 300 and damper 280 between open and closed positions.

In operation, when appliance 100 initiates a call for heat, temperature controlled burner valve 190 opens, which permits the flow of pressurized gas to main burner 112, gas pressure tap port 210, tube 230 and diaphragm device 220. The resulting displacement of diaphragm device 220 causes movement of intermediate shaft 235, pivoting of damper control activation arm 240 and movement of link 270, which in turn pivots damper 280 into an open position, so that exhaust is vented while main burner 112 is ignited. When continued activation of main burner 112 is no longer required, temperature controlled burner valve 190 closed, thereby depressurizing gas pressure tap port 210 and diaphragm device 220. Shaft 235 is displaced downwards, which pivots damper control activation arm 240 and moves link 270, which in turn pivots damper 280 into a closed position, so that heat loss from appliance 100 is reduced.

Damper switches 260a and 260b operate to provide added safety measures in the event that damper 280 becomes stuck in a partially-opened position. In such a position, the flue may be opened sufficiently to permit operation of main burner 112 without tripping a flame safety switch in the burner chamber, but it may not provide enough venting of the flue to eliminate the creation of high levels of carbon monoxide. Accordingly, a further safety feature is provided to address partial opening of the damper.

In the embodiment illustrated in the schematic diagram of FIG. 2, pilot power control switches 260a and 260b are wired in parallel, between thermoelectric device 160 and pilot magnet 140, such that voltage generated by thermoelectric device 160 is applied to pilot magnet 140 when activation arm 240 is in a raised or lowered position. However, if damper 280 becomes stuck in a partially-opened or partially-closed position, activation arm 240 is likewise placed into an intermediate position, such that neither of switches 260a and 260b is closed. As a result, power to pilot magnet 140 is interrupted, such that pilot valve 130 is closed and the flow of gas to main burner supply tube 200 and pilot burner supply tube 170 is interrupted, thereby shutting off the main burner 112 and pilot burner 132 and avoiding misoperation that might otherwise be caused by partial closure of damper 280 during firing of main burner 112. Further safety measures can be implemented through the operation of spill switch 302, interposed between damper switches 260a, 260b and thermoelectric device 140, and flame safety switch 304, interposed in the connection of thermoelectric device 140 to ground. These components interrupt burner operation, thereby to avoid excessive heat generation in the combustion chamber, as may be caused by potentially a number of different conditions.

While the above-described termination of power to pilot valve magnet 140 can avoid undesired operating conditions if damper 280 sticks in a partially-open or partially-closed position, even during the intended operation, damper control activation arms 240 will inherently move momentarily through an intermediate position, in which neither of switches 260a and 260b is closed, when transitioning normally between elevated and lowered states. In some embodiments, gas pressure tap port 210 will fully pressurize in about 2 to 3 seconds after opening of burner valve 190, during which period damper control activation arm 240 and flue damper 280 are moved between open and closed positions. In order to avoid unintentional closure of pilot valve 130 during this transition period, a lowpass filter or timer circuit is provided between damper switches 260a and 260b, and pilot magnet 140. In the embodiment of FIG. 2, a series RC circuit with resistor 310 and capacitor 320 is provided. Resistor 310 and capacitor 320 operate to temporarily maintain the voltage level present at pilot magnet 140 when both of switches 260a and 260b are opened.

Capacitor 320 can be sized to accommodate the target switching time, voltage levels and circuit resistance. For example, in an embodiment utilizing a thermocouple having a nominal minimum operating voltage of 10 millivolts and a circuit resistance of 0.017 Ohms, and requiring at least 5 millivolts applied to pilot magnet 140 to maintain pilot valve 130 in an open position, it can be determined that a 220 Farad capacitor would maintain the required voltage level for around 2.6 seconds. In embodiments utilizing a thermopile in place of a thermocouple, the higher operating voltages would allow for a smaller capacitor to maintain the required pilot magnet voltage for a given period of time.

FIG. 7 illustrates a portion of a gas-fired appliance 400, such as a water heater, according to a second embodiment of the invention. The gas-fired appliance 400 includes a control body 120 and related components similar to the gas-fired appliance 100 of FIG. 1. Such components are identified with similar reference numerals and are not described in detail with respect to this embodiment. The appliance 400 includes a pressure switch 402 connected to the gas pressure tap port 210. The pressure switch 402 is used for controlling the damper operation as well as serving as a redundant safety control to detect gas pressure leakage from the main gas valve 190. The pressure switch 402 has an inlet exposed to pressure from the pressurized gas during operation of the burner 112.

The appliance 400 includes a damper assembly 404 including a DC motor 406. Referring also to FIGS. 8 and 9, the motor 406 is supported on a mounting plate 408 mounted to a duct 409. Also connected to the mounting plate 408 is a cam 410 driven by the motor 406. The motor 406 also drives a rotating connector 412 on the mounting plate 408 for connecting to a damper drive shaft 414 for operating a damper plate 416 in the duct 409. Particularly, the motor 406 rotates the damper plate 416 between a closed position as shown in FIG. 8 and an open position, as shown with the first embodiment in FIG. 6. The cam 410 independently operates each of a first switch 418-1, a second switch 418-2 and a third switch 418-3. Particularly, the switches 418 are controlled by lobes 410-1, 410-2 and 410-3 on the cam 410 and operate to control motor and pilot operation, as described below. The specific design of the cam 410 will be apparent to those skilled in the art to satisfy the required operating sequence.

Referring to FIG. 10, a combined schematic/block diagram illustrates a control for the gas-fired appliance 400. As above, elements which correspond to the first embodiment, are identified using similar reference numerals. The first and second switches 418-1 and 418-2 are configured as single pole switches. The first switch 418-1 is operated by the cam lobe 410-1 so that the switch is closed if the damper plate 416 is closed. If the damper plate 416 is open, then the first switch 418-1 is open. Conversely, the second switch 418-2 is operated by the cam lobe 410-2 so that the switch is open if the damper plate 416 is closed and the second switch 418-2 is closed if the damper plate 416 is open. When the first switch 418-1 is closed it completes the circuit between the thermocouple 160 and the magnet 140, as above. Similarly, when the second switch 418-2 is closed, it also completes the circuit between the thermocouple 160 and the magnet 140.

The third switch 418-3 and the pressure switch 402 comprise three-way switches, such as used with a light control operated by two separate switches, connected in series between the DC motor 406 and a battery 420. The pressure switch 402 has a first contact A connected to a second contact B of the third switch 418-3. The pressure switch 402 has a second contact B connected to a first contact A of the third switch 418-3. The pressure switch 402 has a common contact C connected to the battery 420. The third switch 418-3 has a common contact C connected to the motor 406. The other sides of the battery 420 and the motor 406 are interconnected. Each of the pressure switch 402 and the third switch 418-3 includes a movable contact D. In an illustrated embodiment of the invention, the motor 406 comprises a DC motor. The battery 420 may comprise one or more standard 9V batteries or AA batteries, or the like, as necessary for the particular motor used. The battery 420 is replaceable and is mounted to the mounting plate 408. Alternatively, an AC motor may be used with the battery connected to the motor via a DC/AC transformer.

The third switch 418-3 is operated by the cam lobe 410-3 so that the movable contact D contacts the first contact A if the damper plate 416 is closed and contacts the second contact B when the damper plate 416 is open. The pressure switch 402 movable contact D contacts the first contact A in the absence of gas pressure and contacts the second contact B when the main burner fires. In operation, the pressure switch 402 operates to turn the motor 406 on to move the damper plate 416 and the third switch 418-3 operates to turn the motor 406 off during each damper operation, as described below.

During normal operation, the pilot burner 132 is manually lit and remains on provided that the first switch 418-1 is closed as shown in FIG. 10. The capacitor 320 begins charging. The initial charge takes about 5 minutes. When there is a call for heat, the burner valve 190 is opened in the normal fashion and the gas pressurizes the main burner 112 and the pressure switch 402. This causes the pressure switch 402 movable contact D to move to provide electrical connection between contacts C and B to provide a complete circuit to the motor 406, via the third switch 418-3 moveable contact D being in contact with its first contact A. The motor 406 rotates the damper plate 416 to the open position. As the damper plate 416 rotates, the cam lobe 410-1 causes the first switch 418-1 to open. The capacitor 320 starts discharging to keep the pilot operating. As the motor 406 rotates to the full open position of the damper plate 416, the second switch 418-2 closes and the third switch 418-3 switches so that the movable contact D contacts the second contact B to open the circuit to the motor 406. This stops the motor rotation. Also, the cam lobe 410-2 operates the second switch 418-2 to close the circuit to the pilot allowing the pilot to remain lit and again charges the capacitor 320.

When the call for heat is satisfied, the main valve 190 closes in the conventional fashion causing the pressure switch 402 to return the movable contact D to the normally position in contact with the first contact A. This again completes the circuit between the battery 420 and the motor 406, owing to the third switch 418-3 moveable contact D being connected between the contacts B and C. The motor 406 begins rotation to move the damper plate 416 to the closed position. This rotation opens the second switch 418-2. The capacitor 320 starts discharging to keep the pilot operating. As the motor 406 rotates the damper plate 416 to the closed position, the first switch 418-1 closes and the third switch 418-3 returns the movable contact D to the first contact A. This stops rotation of the motor 406 and again the first switch 418-1 closes the circuit to the pilot allowing the pilot to remain lit and start charging the capacitor. Thereafter, the cycle repeats to satisfy the heat requirements, as will be apparent.

In other respects, operation of the gas-fired appliance 400 is similar to that of the gas-fired appliance 100 discussed above.

The foregoing description and drawings merely explain and illustrate the invention and the invention is not limited thereto, inasmuch as those skilled in the art, having the present disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

Claims

1. A gas-fired appliance comprising: a burner, configured to receive and burn pressurized gas during operation;a control comprising a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a motor operatively connected to the battery and the pressure switch which is operated in response to the application of pressurized gas at the inlet; anda damper assembly connected to the motor, the damper assembly comprising a damper movable between an open position and a closed position in response to operation of the motor.

2. The gas-fired appliance of claim 1, further comprising: a pilot burner;a thermoelectric device positioned near the pilot burner which generates electrical voltage when exposed to heat from the pilot burner;a magnetic pilot valve having an electrical input, which valve is maintained in an open position in response to maintenance of the electrical voltage at the pilot valve electrical input; anda switch circuit interposed into an electrical conduction path between the thermoelectric device and the magnetic pilot valve electrical input, the switch circuit being movable between an open state and a closed state in response to movement of the damper.

3. The gas-fired appliance of claim 2, in which the motor operates a cam; andthe switch circuit is comprised of:a first switch which is closed by the cam when the damper is in a first position; anda second switch, connected electrically in parallel with the first switch, which is closed by the cam when the damper is in a second position.

4. The gas-fired appliance of claim 3, further comprising: a resistor and a capacitor operably interconnected, the capacitor being connected between a signal path leading to the pilot valve electrical input and a ground reference voltage; andwhereby the capacitor charges when the switch circuit is in the closed state, and discharges when the switch circuit is in the open state.

5. The gas-fired appliance of claim 3, in which the switch circuit further comprises a third switch connected in series with the pressure switch to stop the motor after the damper is moved from the first position to the second position or from the second position to the first position.

6. The gas-fired appliance of claim 5, in which the motor and the battery are connected in series with the third switch and the pressure switch.

7. The gas-fired appliance of claim 1, in which the battery comprises a 9V battery.

8. The gas-fired appliance of claim 1, in which the battery comprises a AA battery.

9. The gas-fired appliance of claim 5, in which the pressure switch and third switch comprise three way switches.

10. A damper control mechanism for an appliance that operates through combustion of gas having a pressure that is greater than ambient pressure, the damper control mechanism comprising: a damper;a motor operatively connected to the damper to control position of the damper;a cam operatively connected to the damper; anda control comprising a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a switch operated by the cam, to selectively energize and de-energize the motor to control damper position responsive to change of the pressure at the inlet.

11. The damper control mechanism of claim 10, in which in which the battery comprises a 9V battery.

12. The damper control mechanism of claim 10, in which the battery comprises a AA battery.

13. The damper control mechanism of claim 10, further comprising: a thermoelectric device having an output capable of generating an electrical voltage differential;a circuit comprising one or more electrical switches, which circuit electrically connects the thermoelectric device and a magnet pilot valve; andwhere the cam operates the one or more electrical switches to disconnect the thermoelectric device from the magnetic pilot valve when the movable diaphragm is not within either the first or the second position.

14. The control mechanism of claim 13, in which the circuit further comprises a capacitor having a first terminal operably connected with the thermoelectric device and the magnetic pilot valve, and a second terminal connected to a ground reference voltage, whereby the capacitor can temporarily provide electrical energy to the magnetic pilot valve when the circuit opens the connection between the magnetic pilot valve and the thermoelectric device.

15. The control mechanism of claim 10, in which the pressure switch and the cam operated switch comprise three way switches.

16. A method for controlling a damper in a gas-fired appliance, comprising the steps of: applying pressurized gas to a first portion of the gas-fired appliance which includes a main burner; andopening a damper by operatively connecting a battery to a motor connected to the damper using a pressure sensor sensing introduction of pressurized gas into the first portion of the gas-fired appliance.

17. The method of claim 16 in which: the step of applying pressurized gas to a first portion of the gas-fired appliance comprises the step of applying pressurized gas to a pressure switch; andthe step of opening a damper comprises the step of electrically connecting the battery to the motor via the pressure switch.

18. The method of claim 16, in which the step of opening a damper comprises the steps of: providing a magnetic pilot valve which maintains an open position in response to the maintenance of an electrical signal at an input terminal;applying the electrical signal to the magnetic pilot valve input terminal when the damper is in an open or closed position; andremoving the electrical signal from the magnetic pilot valve input terminal when the damper occupies a partially-opened position for at least a predetermined period of time.

19. The method of claim 18, in which the predetermined period of time is at least about 2 seconds.

20. The method of claim 18, in which the predetermined period of time is between about two seconds to about three seconds.