US20110277706A1

US20110277706A1 - Gas-fired heating device having a thermopile

Info

Publication number: US20110277706A1
Application number: US12/779,078
Authority: US
Inventors: J. Eric Arnold; Michael A. Garrabrant
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 2010-05-13
Filing date: 2010-05-13
Publication date: 2011-11-17
Also published as: CA2739135A1

Abstract

A gas-fired heating device having a burner, a pilot to provide a pilot flame, a thermopile thermally coupled to the pilot flame and configured to generate a power in response to the pilot flame, an electrically controlled gas valve to control the flow of gas to at least one of the pilot and the burner, and a controller electrically coupled to the thermopile and the gas valve. The controller receives and is powered by the power from the thermopile. The controller initiates closing of the gas valve after a monitored component of the power, such as a voltage, traverses a threshold.

Description

BACKGROUND

The present invention relates to heating devices, and particularly, to gas heating devices. More particularly, the invention relates to a controller used for controlling gas heating devices.
An exemplary gas-fired heating device is a gas water heater having a burner. Gas water heaters often include a combustion chamber and an air plenum disposed below a tank, such as a water tank. A gas manifold tube, an ignition source, a thermocouple, and a pilot tube typically extend into the combustion chamber. When the temperature of the water in the tank falls below a set minimum, fuel is introduced into the combustion chamber through the gas manifold tube and a burner element. This fuel is ignited by a pilot burner flame or the ignition source, and the flame is maintained around the burner element. Air is drawn into the plenum via an air inlet, and mixes with the fuel to support combustion within the combustion chamber. The products of combustion typically flow through a flue or heat exchange tube in the water tank to heat the water by conduction.

SUMMARY

In one embodiment, the invention provides a new gas water heater having a burner, a pilot, a gas valve coupled to the pilot, a thermopile thermally coupled to the pilot flame and operable to generate an output voltage, and a controller powered by the thermopile and coupled to the gas valve.
In a more specific embodiment, the controller is operable to control the gas valve based on the output voltage it receives from the thermopile. The controller includes a processor that processes a voltage value received by the controller and communicates a shutdown signal for preventing gas flow to the pilot and/or burner when an insufficient amount of voltage is outputted by the thermopile.
In another embodiment, the invention provides a controller for a gas water heater. The gas water heater includes a burner, a pilot, an igniter, an electrically controlled gas valve, and a thermopile. The thermopile can be positioned in a standing pilot flame provided by the pilot. The standing pilot flame causes the thermopile to generate an output voltage that it used to power the controller and the electrically controlled gas valve. The controller responds to an insufficient amount of output voltage provided by the thermopile by, for example, closing the electrically controlled gas valve. The insufficient amount of output voltage can indicate the presence of a possible flammable vapor event or a possible lint, dust, or oil blockage event. Once the electrically controlled gas valve receives the shutdown signal it closes and prevents gas flow to the pilot and burner.
In another embodiment, the invention provides a method of controlling a gas water heater. The gas water heater includes a burner, a pilot, an igniter, a thermopile, a controller, and a gas valve. The method can include detecting a possible flammable vapor event or a possible lint, dust, or oil blockage event. The thermopile produces an output voltage in response to a standing pilot flame generated by the pilot and igniter. The output voltage generated by the standing pilot flame can be between about 400 and 800 millivolts. When the thermopile outputs an insufficient amount of voltage, a voltage less than 400 millivolts, for example, the controller generates a shutdown signal and closes the gas valve. Alternatively, when the thermopile outputs too much voltage, a voltage greater than 800 millivolts, for example, the controller generates the shutdown signal and closes the gas valve. The closing of the gas valve prevents gas flow to the pilot and burner, thereby preventing any combustion from occurring.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a gas water heater.

FIG. 2 is a sectional view of the bottom portion of the gas water heater.

FIG. 3 is a block diagram of a portion of the gas water heater.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
FIGS. 1 and 2 illustrate a storage-type, gas-fired water heater 10 that includes a base pan 15. The base pan 15 may be constructed of stamped metal or molded plastic, for example, and includes a generally horizontal bottom wall 20, a vertical rise 25 having an air inlet opening 27, and an elevated step 30. The water heater 10 also includes a water tank 35, insulation 40 surrounding the tank 35, and an outer jacket 45 surrounding the insulation 40 and the water tank 35. A skirt 50 is supported by the base pan's elevated step 30 and in turn supports the water tank 35. The elevated step 30 also supports the insulation 40 and jacket 45.
In addition, the elevated step 30 supports a divider 60 that divides the space between the bottom of the tank 35, skirt 50, and the base pan 15 into a combustion chamber 65 (above the divider 60) and plenum 70 (below the divider 60).
A cold water inlet tube 75 and a hot water outlet tube 80 extend through a top wall of the water tank 35. A flue 85 extends through the tank 35, and water in the tank 35 surrounds the flue 85. The flue 85 includes an inlet end 90 and an outlet end 95.
The combustion chamber 65 and plenum 70 space are substantially air-tightly sealed, except for the air inlet opening 27 and inlet end 90 of the flue 85. Seals 105 between the skirt 50 and the tank 35 and base pan 15 assist in sealing the space. The seals 105 may be, for example and without limitation, fiberglass material or a high-temperature caulk material. A radiation shield 110 sits on the divider 60 within the sealed combustion chamber 65 and reflects radiant heat up toward the tank 35.
A flame arrester 115 is affixed in a sealed condition across an opening 120 in the divider 60 such that all air flowing from the plenum 70 into the combustion chamber 65 should flow through the flame arrester 115. The air inlet 27, air plenum 70, and opening 120 in the divider 60 together define an air intake for the combustion chamber 65, and air flowing into the combustion chamber 65 through the opening (see arrows in FIG. 2) 120 should flow through this air intake and the flame arrester 115. It should also be noted that the position and orientation of the flame arrester 115 are not limited to those shown in the drawings, and that substantially any construction will work provided that the flame arrester 115 acts as the gateway for the air flowing into the combustion chamber 65 from the plenum 70. Sealing members 125 seal the periphery of the flame arrester 115 to the divider 60 to reduce the likelihood of air circumventing the flame arrester 115. In alternative constructions, a single sealing member 125 may be used to seal the flame arrester 115 with respect to the divider 60, or if the flame arrester fits snugly against the divider 60, no sealing members 125 may be needed. The flame arrester 115 prevents flame within the combustion chamber 65 from igniting flammable vapors outside of the combustion chamber 65.
With reference again to FIG. 2, the air inlet 27 is covered by a lint, dust, and oil (“LDO”) filter 130 mounted to the outer surface of the base pan 15. The LDO filter 130 filters air flowing into the plenum 70 and reduces the likelihood that the flame arrester 115 will become occluded by lint or other debris.
A burner 155 in the combustion chamber 65 burns a mixture of fuel and air to create the products of combustion that flow up through the flue 85 to heat the water in the tank 35. The burner 155 receives fuel through a gas manifold 160 that extends in a sealed condition through an access door 165 mounted in a sealed condition over an access opening in the skirt 50.
The construction shown (illustrated in FIGS. 1 and 2), employs a non-powered gas valve/thermostat assembly 170 mounted to the water tank 10. As used herein, the term “non-powered” refers to a device that is not powered from electrical mains. However, it is envisioned that the assembly 170 can be connected to electrical mains. A gas main 175 provides fuel to the input side of the assembly 170. The assembly 170 includes a controller 200 (FIG. 3) and a water temperature probe 180 that is threaded into the tank side wall 35. Connected to the output side of the assembly 170 are the gas manifold 160, a pilot burner 185, a thermopile 190, and an igniter 195. The pilot burner 185, thermopile 190, and igniter 195 extend into the combustion chamber 65 in a sealed condition through a grommet in the access door 165.
The assembly 170 provides a flow of fuel to the pilot 185 to maintain a standing pilot burner flame, and this construction is therefore generally referred to as a “continuous pilot ignition” system. The igniter 195 is used to initiate the flame on the pilot 185 without having to reach into the combustion chamber with a match. A spark is generated by the igniter 195 in response to pushing a button on the assembly 170. The thermopile 190 provides feedback to the assembly 170 and controller 200 as to the presence of flame at the pilot 185. An exemplary thermopile 190 is a model Q313 thermopile generator manufactured by Honeywell.
The assembly 170 permits fuel to flow to the burner 155 in response to a water temperature sensor (e.g., the water temperature probe 180) indicating that the water temperature in the water tank 35 has fallen below a selected temperature. When fuel flows to the burner 155, it is mixed with air and the mixture is ignited when it contacts the pilot burner flame. Once the water temperature sensor indicates that the water has reached the desired temperature, the assembly 170 shuts off fuel flow to the burner 155, and the water heater 10 is in “standby mode” until the water temperature again drops to the point where the assembly 170 should again provide fuel to the burner 155.
An electrically controlled gas valve 205 (FIG. 3), or more specifically, an electronically controlled gas valve is biased in the closed position with respect to the gas manifold 160 and the pilot 185. The controller 200 stores some energy in a storage device 200 that allows for the gas valve 205 to be opened while igniting the pilot flame. The start up requires a user to actuate the push button of the assembly 170 which in turn opens the gas valve 205 and triggers the igniter 195. The igniter 195 provides a spark to the pilot 185 while gas is flowing and establishes the pilot flame. The thermopile 190 is positioned near or within the pilot flame and produces an output voltage in response to the pilot flame. The output voltage is used as a power source by the controller 200, which keeps the electrically controlled gas valve 205 open for the pilot flame 190. An exemplary electrically controlled gas valve 205 that can be used with the invention is a model WV8840B gas valve, manufactured by Honeywell. Before proceeding further, the gas valve 205 is shown in FIG. 3 as a single device providing fuel to both the burner 185 and the pilot 190. It should be understood, however, that the gas valve 205 can include multiple valves that are individually controlled.
The assembly 170 is shown in FIG. 3 as including the controller 200. The controller 200 receives a power from the thermopile 190, the power having a plurality of components (e.g., a voltage, a current). In one construction, the thermopile 190 provides a normal operation (or nominal) voltage of 400 to 800 millivolts to operate and control the assembly 170. The output voltage is recognized as being in an insufficient output voltage (state) by the controller 200 if the output voltage is not within this range. For example, if the voltage is greater than 800 millivolts, then the pilot flame may be burning too hot indicating a first potential issue. Similarly, if the voltage is less than 400 millivolts, the pilot flame may be burning too cool indicating a second potential issue.
In a more specific construction, the controller 200 issues a flag or signal after the output voltage traverses a first threshold voltage (e.g., about 400 millivolts). The signal can be provided to an output device (e.g., a light emitting diode, a display, an audible alarm, etc.) of the assembly 170. The controller 200 can close the gas valve 205, thereby deactivating the gas water heater 10, after the output voltage provided by the thermopile 190 traverses a second threshold voltage (e.g., about 300 millivolts). The gas valve 205 closes in response to a signal (e.g., the application or removal of a voltage, an instruction, etc.) being sent from the controller 200 to the gas valve 205.
In the construction shown in FIG. 3, the controller 200 includes a processor 220 and memory 225. The processor 220 executes instructions from the memory 225 to control the assembly 17, and consequently the gas water heater 10. The memory can also store diagnostic and trending data, which can be helpful to diagnose a potential issue before it occurs and provide more detailed information if a potential fault condition occurs. The controller 200 also includes signal conditioning circuitry 230 that can condition signals to and from the controller 200. For example, the temperature sensor 185 can be conditioned to a voltage within a recognizable range for the processor 220. As discussed above, the controller 200 can include a storage device 210, such as a super capacitor, that can provide additional or supplemental power when necessary to operate the assembly 170. The assembly 170 also includes an input/output interface 240 for an operator to interact with the gas water heater 10. For example, an operator can interact with the assembly to establish a set point temperature for the water heater 10, ignite the pilot flame 180, and similar function normally associated with a gas water heater 10. Further, the assembly 170 can provide information to the operator, including errors or faults determined by the controller 200. It should also be understood that the controller 200, and more broadly the assembly 170, can operate other elements of the water heater 10 not shown. For example, the water heater 10 can include dampers and/or blowers to promote operation of the gas water heater 10.
Once the gas valve 205 closes due to a possible error condition, the gas water heater 10 will not reignite until it is serviced by the user or a serviceperson. The user or serviceperson can read the diagnostics from the controller 200 and appropriately address the condition causing the possible error condition.
As discussed above, the controller 200 can monitor a component (e.g., voltage) of the power supplied by the thermopile 190. For example, the controller 200 can monitor the voltage to determine the status of the pilot flame. For example, the controller 200 can monitor the voltage to determine whether the pilot flame indicates a normal flame burn (or normal state) or an abnormal flame burn (or fault state). The fault state can result from an improper burn by the pilot flame. Example events that may cause an improper burn can include a possible lint, dust, or oil (LDO) filter blockage event, a possible flammable vapor event, a possible improper ventilation event (e.g., the blower or exhaust system not properly discharging the exhaust), and a possible overheating event. For a specific example, a substantial blockage of the LDO filter results in an improper burn by the pilot flame, to which the voltage value provided by the thermopile 190 is reduced. When the voltage value traverses the threshold indicating a possible LDO filter blockage event, the controller 200 will take an action. The action may be providing an error output with the user interface 240 or may be providing a signal to the gas valve 205 to restrict gas to the burner 155 and/or pilot 185. Other thresholds can be used to determine other abnormal flame states. It is envisioned that the various thresholds can be determined by empirical testing and that a single threshold may be used for one or more fault states. In one construction, a nominal voltage range for the thermopile 190 is 400-800 millivolts, and consequently a range for a threshold indicating abnormal operation is between about 275 and 450 millivolts, with a preferred range of 330 and 400 millivolts. It is also envisioned that multiple thresholds can be used for a particular state—a first threshold for providing a warning and a second threshold for closing the gas valve 205.
Thus, the invention provides, among other things, a new and useful gas-fired heating device having a thermopile. Various features and advantages of the invention are set forth in the following claims.

Claims

1. A gas water heater comprising:

a burner;

a pilot to provide a pilot flame;

a thermopile thermally coupled to the pilot flame and configured to generate a power in response to the pilot flame;

an electrically controlled gas valve to control the flow of gas to at least one of the pilot and the burner;

a controller electrically coupled to the thermopile and the gas valve, the controller to receive and be powered by the power from the thermopile, and to initiate closing of the gas valve after a monitored component of the power traverses a threshold.

2. The gas water heater of claim 1 wherein the threshold indicates an abnormal flame state for the pilot flame.

3. The gas water heater of claim 1 wherein the threshold indicates the detection of a possible flammable vapor event.

4. The gas water heater of claim 1 wherein the threshold indicates the detection of a possible lint, dust, and oil (LDO) filter blockage event.

5. The gas water heater of claim 1 wherein the threshold indicates the gas water heater has a possible improper ventilation event.

6. The gas water heater of claim 1 wherein the threshold indicates the gas water heater has a possible overheating event.

7. The gas water heater of claim 1 wherein the controller includes a processor and memory.

8. The gas water heater of claim 1 wherein the power from the thermopile includes a voltage, and wherein the monitored component includes the voltage.

9. The gas water heater of claim 8 wherein the threshold for the monitored component is between about 275 and 450 millivolts.

10. The gas water heater of claim 1 wherein the controller includes an electronic device and the gas valve includes an electronically controlled gas valve.

11. The gas water heater of claim 10 wherein the power for opening the electronically controlled gas valve originates from the power from the thermopile.

12. A safety system for use in a gas water heater including a burner, a pilot, and a gas valve, the safety circuit comprising:

a thermopile to be thermally coupled to a pilot flame of the pilot and configured to generate a power having a voltage in response to the pilot flame thermally interacting with the thermopile;

a controller electrically coupled to the thermopile and for connecting to the electronically controlled gas valve, the controller to be powered by the power from the thermopile, to monitor the voltage to determine a pilot flame status, and to control the gas valve based on the pilot flame status.

13. The safety system of claim 12 wherein the pilot flame status includes a status indicating a normal flame burn.

14. The safety system of claim 12 wherein the pilot flame status includes a status indicating a possible abnormal flame burn.

15. The safety system of claim 14 wherein the controller initiates the closing of the gas valve after the pilot flame indicates the possible abnormal flame burn.

16. The safety system of claim 14 wherein the controller determines a possible abnormal pilot flame burn when the voltage is between about 275 and 450 millivolts.

17. The safety system of claim 12 wherein the controller includes a processor and memory and wherein the memory includes diagnostic thresholds for indicating the possible abnormal flame burn.

18. The safety system of claim 12 wherein the safety circuit further includes the gas valve, and wherein the gas valve includes an electronically controlled gas valve.

19. The safety system of claim 18 wherein the power for opening the electronically controlled gas valve originates from the power from the thermopile.

20. A method for controlling a gas water heater including a burner, a pilot, a thermopile, a controller, and an electronically controlled gas valve, the method comprising:

establishing a pilot flame with the pilot;

powering the controller with a power generated by the thermopile thermally interacting with the pilot flame, the power having a voltage;

monitoring the voltage with the controller;

detecting a possible LDO filter blockage event or a possible flammable vapor event with the monitored voltage;

generating a shutdown signal with the controller in response to detecting the possible LDO filter blockage event or the possible flammable vapor event; and

closing the electronically controlled gas valve in response to the shutdown signal.

21. The method of claim 20 and further comprising opening the electronically controlled gas valve with power originating from the thermopile.