US20090191493A1 - Apparatus and method for controlling a damper in a gas-fired appliance - Google Patents
Apparatus and method for controlling a damper in a gas-fired appliance Download PDFInfo
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- US20090191493A1 US20090191493A1 US12/291,805 US29180508A US2009191493A1 US 20090191493 A1 US20090191493 A1 US 20090191493A1 US 29180508 A US29180508 A US 29180508A US 2009191493 A1 US2009191493 A1 US 2009191493A1
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- Prior art keywords
- damper
- gas
- switch
- battery
- motor
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L11/00—Arrangements of valves or dampers after the fire
- F23L11/005—Arrangements of valves or dampers after the fire for closing the flue during interruption of burner function
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
- F23N5/10—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples
- F23N5/102—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples using electronic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
- F23N5/242—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using electronic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2235/00—Valves, nozzles or pumps
- F23N2235/02—Air or combustion gas valves or dampers
- F23N2235/04—Air or combustion gas valves or dampers in stacks
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2235/00—Valves, nozzles or pumps
- F23N2235/02—Air or combustion gas valves or dampers
- F23N2235/10—Air or combustion gas valves or dampers power assisted, e.g. using electric motors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2241/00—Applications
- F23N2241/04—Heating water
Definitions
- 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.
- 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.
- 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.
- 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;
- 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.
- dampers can be operated using an electric motor supplied by 24 volt or 120 volt power sources.
- such designs typically require the routing of a power source to the location of the gas-fired appliance, potentially increasing installation costs.
- 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.
- 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.
- a gas-fired appliance 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.
- 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.
- the motor operates a cam
- 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.
- 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.
- 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.
- 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.
- 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.
- 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).
- 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 ).
- 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 .
- 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.
- burner valve 190 is opened, thereby supplying gas to main burner 112 through burner supply tube 200 .
- burner valve 190 is closed, thereby shutting off the flow of gas to burner 112 .
- 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.
- 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.
- 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.
- 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 .
- 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 .
- 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 .
- damper control activation arm 240 is made with first arm portion 240 a and second arm portion 240 b, 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 260 a and 260 b, which are mounted adjacent to one another.
- Pilot power control switches 260 a and 260 b are further illustrated in FIGS. 4 and 5 .
- Pilot power control switches 260 a and 260 b include switch arms 265 a and 265 b, respectively.
- Switch arm 265 a extends downwards from the point at which it is attached to switch 260 a.
- Switch arm 265 b extends upwards from the point at which it is attached to switch 260 b.
- Damper control activation arm 240 a is aligned to interact with pilot power control switch 260 a, such that switch arm 265 a 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 240 b is aligned to interact with pilot power control switch 260 b, such that switch 265 b 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 .
- 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 .
- link 270 may incorporate a cable structure, such as a metal cable that slides freely within a polymer sheath.
- link 270 may incorporate a cable structure, such as a metal cable that slides freely within a polymer sheath.
- link 270 may incorporate a cable structure, such as a metal cable that slides freely within a polymer sheath.
- 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.
- 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.
- 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 260 a and 260 b 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.
- pilot power control switches 260 a and 260 b 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.
- 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 260 a and 260 b is closed.
- pilot magnet 140 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 260 a, 260 b and thermoelectric device 140 , and flame safety switch 304 , interposed in the connection of thermoelectric device 140 to ground.
- damper control activation arms 240 will inherently move momentarily through an intermediate position, in which neither of switches 260 a and 260 b is closed, when transitioning normally between elevated and lowered states.
- 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.
- a lowpass filter or timer circuit is provided between damper switches 260 a and 260 b, and pilot magnet 140 .
- 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 260 a and 260 b 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 .
- the motor 406 is supported on a mounting plate 408 mounted to a duct 409 .
- 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 .
- 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.
- a combined schematic/block diagram illustrates a control for the gas-fired appliance 400 .
- 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.
- 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.
- the first switch 418 - 1 is closed it completes the circuit between the thermocouple 160 and the magnet 140 , as above.
- 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.
- the motor 406 comprises a DC motor.
- the battery 420 may comprise one or more standard 9 V 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 .
- 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.
- 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.
- 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.
- the cam lobe 410 - 1 causes the first switch 418 - 1 to open.
- the capacitor 320 starts discharging to keep the pilot operating.
- 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 .
- 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 .
- 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.
- 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.
- 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.
- operation of the gas-fired appliance 400 is similar to that of the gas-fired appliance 100 discussed above.
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
- This application is a continuation-in-part of application Ser. No. 12/011,944 filed Jan. 29, 2008.
- 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.
- 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.
- 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.
-
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. - 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 firedappliance 100 receives combustible gas, such as natural gas, viasupply 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 intocontrol body 120 and throughpilot valve 130, which supplies gas to a pilot burner 132 (shown schematically). Oncepilot burner 132 is ignited,pilot valve 130 is maintained in an open position bypilot valve magnet 140, which is energized by voltage received atthermoelectric device connection 150.Thermoelectric device connection 150 is energized by thermoelectric device 160 (illustrated inFIG. 2 ). In exemplary embodiments,thermoelectric device 160 may include a thermocouple or a thermopile.Thermoelectric device 160 is positionedadjacent 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 forpilot valve magnet 140 to maintainpilot valve 130 in an open position, thereby stopping the flow of gas to pilotburner 132 viasupply tube 170 and preventing unintentional flooding of unburned gas. -
Control body 120 further includesgas pressure regulator 180, which operates to regulate the gas pressure withincontrol body 120. Temperature controlledburner valve 190 operates to limit the conditions under which gas is supplied toprimary appliance burners 112 viaburner supply tube 200. For example, in an embodiment in which gas firedappliance 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 tomain burner 112 throughburner supply tube 200. Whenburner 112 acts to raise the monitored temperature above a desired maximum level,burner valve 190 is closed, thereby shutting off the flow of gas toburner 112. - In addition to providing gas feeds to pilot
burner supply tube 170 and mainburner supply tube 200,control body 120 further includes a gaspressure tap port 210. Gaspressure tap port 210 is connected to adiaphragm device 220 viatube 230 to communicate pressure withincontrol body 120 therethrough. Thus, whenpilot valve 130 andmain burner valve 190 are both open, the resulting flow of gas pressurizes a chamber to which gaspressure tap port 210 is connected. Whenmain burner valve 190 is closed, gaspressure tap port 210 and thusdiaphragm device 220 are exposed to ambient pressure conditions. -
Diaphragm device 220 is a mechanism having aninlet 231, which is alternatively exposed to pressure of the gas or ambient pressure conditions, depending upon the state ofmain burner valve 190.Diaphragm device 220 also includes amovable 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 afirst 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 withindiaphragm device 220 is operably interconnected withintermediate shaft 235 and dampercontrol activation arm 240, forming a portion of an operable linkage withdevice 220. When gas pressure is applied to the inlet side ofdiaphragm device 220,intermediate shaft 235 moves upwards, causing dampercontrol activation arm 240 to pivot aboutpivot point 250 in the direction of the illustratedarrow 251. When gas pressure is released fromdiaphragm device 220,intermediate shaft 235 returns to a lowered position andactivation arm 240 pivots oppositely to the direction indicated byarrow 251. - Damper
control activation arm 240 is illustrated in perspective view inFIG. 3 . In the illustrated embodiment, dampercontrol activation arm 240 is made withfirst arm portion 240 a andsecond arm portion 240 b, which are mechanically connected. Oneend 252 of dampercontrol activation arm 240 interacts with aswitch circuit 260 that includes pilot power control switches 260 a and 260 b, which are mounted adjacent to one another. - Pilot power control switches 260 a and 260 b are further illustrated in
FIGS. 4 and 5 . Pilot power control switches 260 a and 260 b include switcharms Switch arm 265 a extends downwards from the point at which it is attached to switch 260 a.Switch arm 265 b extends upwards from the point at which it is attached to switch 260 b. Dampercontrol activation arm 240 a is aligned to interact with pilotpower control switch 260 a, such thatswitch arm 265 a is depressed whenactivation arm 240 is moved to a first position, as shown inFIG. 4 , and released whenactivation arm 240 is moved to a second position, as shown inFIG. 5 . Dampercontrol activation arm 240 b is aligned to interact with pilotpower control switch 260 b, such thatswitch 265 b is depressed whenactivation arm 240 is in the second position, shown inFIG. 5 , and released whenactivation arm 240 is in the first position ofFIG. 4 . In the exemplary embodiment ofFIGS. 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 ofactivation 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 ofactivation 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 offlue damper 280, illustrated inFIG. 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 oflink 270 opposite dampercontrol activation arm 240 is attached tolever arm 290, which is secured todamper control shaft 300.Damper 280 is mounted oncontrol shaft 300. Accordingly, movement oflink 270 results in pivoting ofcontrol shaft 300 anddamper 280 between open and closed positions. - In operation, when
appliance 100 initiates a call for heat, temperature controlledburner valve 190 opens, which permits the flow of pressurized gas tomain burner 112, gaspressure tap port 210,tube 230 anddiaphragm device 220. The resulting displacement ofdiaphragm device 220 causes movement ofintermediate shaft 235, pivoting of dampercontrol activation arm 240 and movement oflink 270, which in turn pivotsdamper 280 into an open position, so that exhaust is vented whilemain burner 112 is ignited. When continued activation ofmain burner 112 is no longer required, temperature controlledburner valve 190 closed, thereby depressurizing gaspressure tap port 210 anddiaphragm device 220.Shaft 235 is displaced downwards, which pivots dampercontrol activation arm 240 and moves link 270, which in turn pivotsdamper 280 into a closed position, so that heat loss fromappliance 100 is reduced. - Damper switches 260 a and 260 b 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 ofmain 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 260 a and 260 b are wired in parallel, betweenthermoelectric device 160 andpilot magnet 140, such that voltage generated bythermoelectric device 160 is applied topilot magnet 140 whenactivation arm 240 is in a raised or lowered position. However, ifdamper 280 becomes stuck in a partially-opened or partially-closed position,activation arm 240 is likewise placed into an intermediate position, such that neither ofswitches pilot magnet 140 is interrupted, such thatpilot valve 130 is closed and the flow of gas to mainburner supply tube 200 and pilotburner supply tube 170 is interrupted, thereby shutting off themain burner 112 andpilot burner 132 and avoiding misoperation that might otherwise be caused by partial closure ofdamper 280 during firing ofmain burner 112. Further safety measures can be implemented through the operation ofspill switch 302, interposed between damper switches 260 a, 260 b andthermoelectric device 140, andflame safety switch 304, interposed in the connection ofthermoelectric 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 ifdamper 280 sticks in a partially-open or partially-closed position, even during the intended operation, dampercontrol activation arms 240 will inherently move momentarily through an intermediate position, in which neither ofswitches pressure tap port 210 will fully pressurize in about 2 to 3 seconds after opening ofburner valve 190, during which period dampercontrol activation arm 240 andflue damper 280 are moved between open and closed positions. In order to avoid unintentional closure ofpilot valve 130 during this transition period, a lowpass filter or timer circuit is provided between damper switches 260 a and 260 b, andpilot magnet 140. In the embodiment ofFIG. 2 , a series RC circuit withresistor 310 andcapacitor 320 is provided.Resistor 310 andcapacitor 320 operate to temporarily maintain the voltage level present atpilot magnet 140 when both ofswitches -
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 topilot magnet 140 to maintainpilot 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-firedappliance 400, such as a water heater, according to a second embodiment of the invention. The gas-firedappliance 400 includes acontrol body 120 and related components similar to the gas-firedappliance 100 ofFIG. 1 . Such components are identified with similar reference numerals and are not described in detail with respect to this embodiment. Theappliance 400 includes apressure switch 402 connected to the gaspressure tap port 210. Thepressure switch 402 is used for controlling the damper operation as well as serving as a redundant safety control to detect gas pressure leakage from themain gas valve 190. Thepressure switch 402 has an inlet exposed to pressure from the pressurized gas during operation of theburner 112. - The
appliance 400 includes adamper assembly 404 including aDC motor 406. Referring also toFIGS. 8 and 9 , themotor 406 is supported on a mountingplate 408 mounted to aduct 409. Also connected to the mountingplate 408 is acam 410 driven by themotor 406. Themotor 406 also drives arotating connector 412 on the mountingplate 408 for connecting to adamper drive shaft 414 for operating adamper plate 416 in theduct 409. Particularly, themotor 406 rotates thedamper plate 416 between a closed position as shown inFIG. 8 and an open position, as shown with the first embodiment inFIG. 6 . Thecam 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 thecam 410 and operate to control motor and pilot operation, as described below. The specific design of thecam 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-firedappliance 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 thedamper plate 416 is closed. If thedamper 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 thedamper plate 416 is closed and the second switch 418-2 is closed if thedamper plate 416 is open. When the first switch 418-1 is closed it completes the circuit between thethermocouple 160 and themagnet 140, as above. Similarly, when the second switch 418-2 is closed, it also completes the circuit between thethermocouple 160 and themagnet 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 theDC motor 406 and abattery 420. Thepressure switch 402 has a first contact A connected to a second contact B of the third switch 418-3. Thepressure switch 402 has a second contact B connected to a first contact A of the third switch 418-3. Thepressure switch 402 has a common contact C connected to thebattery 420. The third switch 418-3 has a common contact C connected to themotor 406. The other sides of thebattery 420 and themotor 406 are interconnected. Each of thepressure switch 402 and the third switch 418-3 includes a movable contact D. In an illustrated embodiment of the invention, themotor 406 comprises a DC motor. Thebattery 420 may comprise one or more standard 9V batteries or AA batteries, or the like, as necessary for the particular motor used. Thebattery 420 is replaceable and is mounted to the mountingplate 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 thedamper plate 416 is open. Thepressure 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, thepressure switch 402 operates to turn themotor 406 on to move thedamper plate 416 and the third switch 418-3 operates to turn themotor 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 inFIG. 10 . Thecapacitor 320 begins charging. The initial charge takes about 5 minutes. When there is a call for heat, theburner valve 190 is opened in the normal fashion and the gas pressurizes themain burner 112 and thepressure switch 402. This causes thepressure switch 402 movable contact D to move to provide electrical connection between contacts C and B to provide a complete circuit to themotor 406, via the third switch 418-3 moveable contact D being in contact with its first contact A. Themotor 406 rotates thedamper plate 416 to the open position. As thedamper plate 416 rotates, the cam lobe 410-1 causes the first switch 418-1 to open. Thecapacitor 320 starts discharging to keep the pilot operating. As themotor 406 rotates to the full open position of thedamper 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 themotor 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 thecapacitor 320. - When the call for heat is satisfied, the
main valve 190 closes in the conventional fashion causing thepressure 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 thebattery 420 and themotor 406, owing to the third switch 418-3 moveable contact D being connected between the contacts B and C. Themotor 406 begins rotation to move thedamper plate 416 to the closed position. This rotation opens the second switch 418-2. Thecapacitor 320 starts discharging to keep the pilot operating. As themotor 406 rotates thedamper 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 themotor 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-firedappliance 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 (20)
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; and
a 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; and
a 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; 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.
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; and
whereby 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; and
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 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; and
where 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; 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.
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; and
the 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; and
removing 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.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US12/291,805 US20090191493A1 (en) | 2008-01-29 | 2008-11-12 | Apparatus and method for controlling a damper in a gas-fired appliance |
CA 2666236 CA2666236A1 (en) | 2008-11-12 | 2009-05-20 | Apparatus and method for controlling a damper in a gas-fired appliance |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US12/011,944 US8113823B2 (en) | 2008-01-29 | 2008-01-29 | Apparatus and method for controlling a damper in a gas-fired appliance |
US12/291,805 US20090191493A1 (en) | 2008-01-29 | 2008-11-12 | Apparatus and method for controlling a damper in a gas-fired appliance |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US12/011,944 Continuation-In-Part US8113823B2 (en) | 2008-01-29 | 2008-01-29 | Apparatus and method for controlling a damper in a gas-fired appliance |
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US20090191493A1 true US20090191493A1 (en) | 2009-07-30 |
Family
ID=40899586
Family Applications (1)
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US12/291,805 Abandoned US20090191493A1 (en) | 2008-01-29 | 2008-11-12 | Apparatus and method for controlling a damper in a gas-fired appliance |
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US20100058997A1 (en) * | 2008-09-09 | 2010-03-11 | Bradford White Corporation | Thermal switch for energy sustaining water heater |
CN102705994A (en) * | 2012-02-09 | 2012-10-03 | 李茂本 | Anti-freezing device of gas water heater |
US20120282853A1 (en) * | 2011-05-03 | 2012-11-08 | Sinur Richard R | Make-up air system and method |
US9464805B2 (en) | 2013-01-16 | 2016-10-11 | Lochinvar, Llc | Modulating burner |
USD771233S1 (en) * | 2015-08-07 | 2016-11-08 | A. O. Smith Corporation | Air inlet damper |
USD771234S1 (en) * | 2015-08-07 | 2016-11-08 | A. O. Smith Corporation | Air inlet damper |
USD771790S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
USD771791S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
USD771792S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
USD771789S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
USD771793S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
USD779650S1 (en) * | 2015-08-07 | 2017-02-21 | A. O. Smith Corporation | Air inlet damper |
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USD771234S1 (en) * | 2015-08-07 | 2016-11-08 | A. O. Smith Corporation | Air inlet damper |
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USD771791S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
USD771792S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
USD771789S1 (en) * | 2015-08-07 | 2016-11-15 | A. O. Smith Corporation | Air inlet damper |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: FIELD CONTROLS LLC, NORTH CAROLINA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GUZOREK, STEVEN E.;REEL/FRAME:022189/0849 Effective date: 20090115 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |