US20120052454A1

US20120052454A1 - Multi-Port Ignition System for a Sectional Furnace

Info

Publication number: US20120052454A1
Application number: US13/216,908
Authority: US
Inventors: William J. Roy; Kevin D. Thompson; Gary D. Wedlake
Original assignee: Carrier Corp
Current assignee: Carrier Corp; Taylor Commercial FoodService LLC
Priority date: 2010-08-24
Filing date: 2011-08-24
Publication date: 2012-03-01

Abstract

An ignition system for a gas furnace being controlled by a main controller and having at least one burner is provided. The ignition system may include at least one flame sensor and an interface module. The flame sensor may be disposed in close proximity to the burner and configured to output a flame check signal indicative of a status of a flame at the burner. The interface module may be configured to receive the flame check signal and generate a fault check signal based on the flame check signal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a non-provisional U.S. patent application, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/376,560 filed on Aug. 24, 2010, the entirety of which is incorporated by reference herein.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to ignition systems, and more particularly, to multi-port ignition arrangements for sectional gas furnaces.

BACKGROUND OF THE DISCLOSURE

Sectional gas furnaces are well known in the art and are commonly used in residential applications to supply heat. These furnaces typically employ a multiple heat exchanger configuration in which the inlet of each heat exchanger is provided with its own individual burner. In such an arrangement, only the endmost burner is provided with an igniter and the remaining burners are lit using a flame carryover mechanism. As illustrated in the prior art embodiment of FIG. 1, the flame carryover mechanism 2 employs a small channel 4 that interconnects each of the burners 6-8. Once the endmost burner 6 is ignited, the small channel 4 serves to transfer hot gases to the remaining burners 7, 8 so as to ignite all of the burners 6-8 in succession. Currently existing systems also employ one flame sensing mechanism to monitor the general status of the flames and to promote efficient combustion of gases. While these sectional gas furnaces perform with a degree of efficiency and robustness, there is still room for improvement.
Sectional gas furnaces rely upon one igniter and a flame sensing mechanism to monitor the status of the multiple flames. Flame sensing technologies may be implemented using a single infrared (IR) sensor, an IR emitter/sensor pair, a flame rectification configuration, or the like. Although a single flame sensor may adequately determine a general joint status of the flames, present technologies lack the resolution to accurately and quickly discern the status of each and every flame. For example, a single flame sensor may be unable to detect a fault condition in which only one of the burners is missing a flame. Even if it can detect such a fault condition, the single flame sensor may be unable to determine the faulty burner that is missing a flame. Such failures can result in inefficient combustion of the gases.
Furthermore, as with any combustion device, the combustion of gases within sectional gas furnaces results in unwanted emissions. Of particular concern are nitric oxide (NO) and nitrogen dioxide (NO2) emissions because of their roles in forming ground level smog and acid rain as well as depleting the stratospheric ozone. For simplicity, NO and NO2 are often grouped together as NOx. With the increase in concerns to minimize atmospheric pollution, many jurisdictions have stringent NOx emissions regulations. For example, the state of California limits NOx emissions from gas furnaces to a maximum of 40 ng/J. It is expected that over the coming years, the regulations will become increasingly more stringent and more widely accepted.
One way to substantially reduce NOx emissions is to fully premix the fuel and air before combustion. This requires the majority of the air that is used for combustion to be supplied with gas flow, and further, requires the secondary air to be minimized. However, the flame carryover mechanism in currently existing sectional gas furnaces makes it extremely difficult to implement in such premix configurations. More specifically, the considerable amount of space between each premix burner in sectional applications makes it difficult to maintain proper ignition of the flames in the burner-to-burner configuration, and the space occupied by the flame carryover mechanism itself makes it difficult to effectively manage any secondary air.
It is therefore an object of the present disclosure to provide an ignition apparatus and method that optimizes premix combustion and minimizes NOx emissions. Moreover, there is a need for an ignition system that provides individualized and improved management of flame control to ensure proper combustion at each individual burner. There is also a need for an ignition system that overcomes the deficiencies of premix flame carryover mechanisms and allows for a significant reduction in space between each burner and its associated heat exchanger.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, an ignition system for a gas furnace being controlled by a main controller and having at least one burner is provided. The ignition system may comprise at least one flame sensor and an interface module. The flame sensor may be disposed in close proximity to the burner and configured to output a flame check signal indicative of a status of a flame at the burner. The interface module may be configured to receive the flame check signal and generate a fault check signal based on the flame check signal. The interface module may further be configured to output the fault check signal.
In accordance with another aspect of the disclosure, another ignition system for a gas furnace being controlled by a main controller and having a plurality of burners is provided. The ignition system may comprise a plurality of flame sensors and an interface module. Each flame sensor may be disposed in close proximity to its corresponding burner and configured to output a flame check signal indicative of a status of a flame at its corresponding burner. The interface module may be configured to receive the flame check signals provided by the flame sensors and output a fault check signal. The interface module may further comprise a multiplexer configured to generate the fault check signal based on the flame check signals.
In accordance with yet another aspect of the disclosure, a method for providing a multi-port ignition system to a gas furnace having a plurality of burners and corresponding igniters is provided. The method may comprise the steps of: providing a flame sensor in close proximity to each burner, wherein each flame sensor may be configured to output a flame check signal indicative of a status of a flame at each burner; determining if flames are expected in the burners; monitoring the flame check signals; indicating a normal condition if flames are expected and if all flame check signals indicate presence of a flame; indicating a normal condition if flames are not expected and if none of the flame check signals indicate presence of a flame; indicating an abnormal condition if flames are expected but not all flame check signals indicate presence of a flame; and indicating an abnormal condition if flames are not expected but at least one flame check signal indicates presence of a flame.
These and other aspects of this disclosure will become more readily apparent upon reading the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art ignition system for a gas furnace having a flame carryover mechanism;

FIG. 2 is partial perspective view of a sectional gas furnace having an exemplary multi-port ignition system;

FIG. 3 is an exemplary schematic of the ignition system of FIG. 2;

FIG. 4 is an exemplary schematic of the interface module of FIG. 3; and

FIG. 5 is an exemplary algorithm for managing a gas furnace having the ignition system FIG. 2.

While the present disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to be limited to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling with the spirit and scope of the present disclosure.

DETAILED DESCRIPTION

Referring to the drawings and with particular reference to FIG. 2, an exemplary ignition system for a gas furnace is provided and referred to as reference number 16. It is understood that the teachings of the disclosure may be used to construct ignition systems above and beyond those specifically disclosed below. One of ordinary skill in the art will readily understand that the following are only exemplary embodiments.
Turning to FIG. 2, a typical sectional gas furnace 10 is provided having one or more burners 12 each corresponding to one or more heat exchangers (not shown) that may be disposed within the gas furnace 10. Each of the burners 12 may be individually provided with a corresponding igniter 14, or alternatively, the burners 12 may share a single igniter 14. Each igniter 14 may be positioned in close proximity to an inlet of its corresponding burner 12 and adapted to ignite a flame using a spark gap, or the like. The gas furnace 10 may also be provided with an ignition system 16, as partially shown in FIG. 2. The ignition system 16 may include a plurality of flame sensors 18. Each flame sensor 18 may be positioned in close proximity to an interior of its corresponding burner 12 and configured to detect the presence of a flame therein. The flame sensors 18 may employ an ultraviolet (UV) sensor, an infrared sensor (IR), a combination UV/IR sensor, a combination IR/IR sensor, a combination IR/IR/IR sensor, a bi-metallic strip, an optical sensor, a flame rectification configuration or any other suitable sensing mechanism configured to output a signal indicative of the status of a flame in the respective burner 12. In alternative embodiments, the ignition system 16 may provide one flame sensor 18 for use with a gas furnace 10 having several burners 12, or the ignition system 16 may provide several redundant flame sensors 18 for use with a gas furnace 10 having only one burner 12.
Still referring to FIG. 2, each of the burners 12 may be provided with one igniter 14 so as to eliminate the need for a flame carryover mechanism. By eliminating flame carryover, the ignition system 16 may ensure proper and consistent ignition of flames within each burner 12 and significantly reduce the size of the secondary air gap, or the space between a burner 12 and the inlet of its corresponding heat exchanger. Moving the burners 12 closer to the heat exchangers may further serve to direct more combustion products into the heat exchangers, and thus, promote more efficient thermal management thereof. Additionally, by providing a flame sensor 18 to each individual burner 12, the ignition system 16 may enable quicker and more accurate detection of flames in each burner 12 or the lack thereof. In such a way, the ignition system 16 may significantly increase furnace efficiency and effectively reduce NOx emissions.
Turning now to FIG. 3, an exemplary interface module 20 of the ignition system 16 is provided. As shown, the interface module 20 may serve to communicate information between a main controller 22 of the gas furnace 10 and the flame sensors 18 of the ignition system 16. In alternative embodiments, the interface module 20 may also be configured to communicate directly with the igniters 14 and/or to communicate information between the main controller 22 and the igniters 14. Each igniter 14 may be controlled by an optional remote 24 for selectively igniting a flame in its respective burner 12. Depending on the desired application, each remote 24 may be operated by the main controller 22 and/or by the interface module 20 of the ignition system 16. Furthermore, each flame sensor 18 may be configured to output a flame check signal A1-A4 to the interface module 20 that is indicative of a status of a flame at its corresponding burner 12. The flame check signal A1-A4 may be an electrical voltage and/or current signal of a predefined magnitude and/or frequency that is responsive to light and/or heat emitted from an existing flame. Based on the flame check signals A1-A4, an interface circuit 26 of the interface module 20 may generate and transmit a fault check signal A5, A6 to the main controller 22 for further processing. In response to the fault check signal A5, A6, the main controller 22 may be configured to continue normal furnace operation, attempt re-ignition of one or more burners 12, indicate a furnace failure alert, turn off gas flow to the burners 12, turn off all furnace operations, or the like. The interface circuit 26 may optionally provide a multiplexer 27 configured to receive one or more flame check signals A1-A4 and to generate one or more fault check signals A5, A6 based on the combination of the flame check signals A1-A4 received. For example, the multiplexer 27 may be configured such that it outputs a fault check signal A5, A6 enabling the main controller 22 to continue normal furnace operation if and only if all flame check signals A1-A4 indicate that a flame is present. If any flame check signal A1-A4 indicates that a flame is not present at its respective burner 12, the multiplexer 27 may output a fault check signal A5, A6 which turns off gas flow to the burners 12, halts all furnace operations, or the like.
Turning to FIG. 4, an exemplary schematic for implementing the ignition system 16 is provided. As shown, the ignition system 16 may include one or more flame sensors 18, wherein each flame sensor 18 is provided with a flame rod 28 and a flame sense circuit 29. The flame rods 28 may provide means for detecting a flame and may be disposed in close proximity to the burners 12. The flame sense circuits 29 may generate flame check signals A1-A4 that are responsive to the flames detected at the flame rods 28. The flame check signals A1-A4 may be routed to an interface circuit 26 of the interface module 20 for further processing. Additionally, power supplied to the flame sense circuits 29, for example, 120 VAC, may be selectively enabled or disabled via a switch, relay, or the like, coupled to an input signal A7. Power to the flame sense circuits 29 and thus the flame rods 28 may be temporarily enabled or disabled via input signal A7 by the main controller 22 or the interface module 20 for diagnostic purposes, or the like.
As shown for example in FIG. 4, the interface circuit 26 may include a series of logic gates 30, 31 that are configured to output at least two binary fault check signals A5, A6. In the example shown, each flame sensor 18 and associated flame sense circuit 29 may be configured to output a logical high value when a flame is detected. In such a case, the first signal A5 of the interface circuit 26 may be set to a logical high value only when all four flame sensors 18 indicate a lit flame, and the second signal A6 may be set to a logical high value when any of the four flame sensors 18 indicate a lit flame. Correspondingly, the first signal A5 may indicate a logical low value when any of the flame sensors 18 indicate an unlit flame, and the second signal A6 may indicate a logical low value only when all of the flame sensors 18 indicate an unlit flame. The signals that are output by the interface circuit 26, such as fault check or binary signals A5, A6 of FIG. 4, may be routed to the main controller 22 for further analysis. Based on the conditions these signals indicate, the main controller 22 may be able to determine if there is an error or fault, or if there is a normal or abnormal condition, and respond accordingly.
Referring now to FIG. 5, an exemplary algorithm for managing a gas furnace 10 having an ignition system 16 is illustrated. As shown, the algorithm may begin in a base or first mode B1 wherein the algorithm may determine if flames are expected in the respective burners 12. If no flames are expected, the algorithm may proceed to a second mode B2 to ensure that there are no flames and that all burners 12 are indeed off. For example, the algorithm may scan the flame check signals A1-A4 and/or fault check signals A5, A6 to determine if any flame is lit. If any of the signals A1-A6 indicate that a flame is present, the algorithm may indicate a fault or an abnormal condition and disable all gas flow accordingly. The algorithm may then return to the first mode B1 until the abnormal condition has cleared. However, if all flames are confirmed to be off, the algorithm may indicate a safe or normal condition and return to the first mode B1.
If flames are expected during the first mode B1, the algorithm may proceed to a third mode B3 to determine if all flames in the burners 12 are lit and stable. Specifically, the algorithm may refer to the interface module 20 to determine if the fault check signals A5, A6 indicate that each and every flame is lit. If the fault check signals A5, A6 indicate that at least one flame is not lit, the algorithm may indicate a fault or an abnormal condition and disable all gas flow. The algorithm may then return to the first mode B1 until the abnormal condition has cleared. Alternatively, the algorithm may determine the particular burner 12 that is missing a flame and proceed to re-ignite that burner 12 until a stable flame is detected.
If the fault check signals A5, A6 confirm that all flames are lit, the algorithm may set a timer for a predefined duration and remain in the third mode B3 until the timer ends. Once the timer ends, the algorithm may proceed to a fourth mode B4 to test the functionality of the flame rods 28 and/or flame sense circuits 29. In particular, the algorithm may temporarily disable the flame sense circuits 29 via, for example, the input signal A7, and determine if the fault check signals A5, A6 indicate that all flames are unlit. The flame sense circuits 29 may be configured such that they output fault check signals (A5, A6) that are null, or signals indicating no flames, when powered off. By cutting power to the flame sense circuits 29, the algorithm may be able to determine if the flame sense circuits 29 are operational and indicate no flame at the burners 12, or if they are faulty and indicate otherwise. If the fault check signals A5, A6 indicate any flame after cutting power to the flame sense circuits 29, the algorithm may indicate a fault or abnormal condition and disable all gas flow. The algorithm may then return to the first mode B1 until the abnormal condition has cleared. If, however, the fault check signals A5, A6 are null, the algorithm may indicate a safe or normal condition, re-enable power to the flame sense circuits 29, return to the first mode B1 and continue normal furnace operation.
Based on the foregoing, it can be seen that the present disclosure provides individualized and improved management of flame control to ensure proper combustion at each individual burner of a gas furnace. The present disclosure also eliminates the need for flame carryover mechanisms and allows for a significant reduction in space between each burner and its associated heat exchanger.
While only certain embodiments have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure.

Claims

What is claimed is:

1. An ignition system for a gas furnace being controlled by a main controller and having at least one burner, comprising:

at least one flame sensor disposed in close proximity to the burner, the flame sensor being configured to output a flame check signal indicative of a status of a flame at the burner; and

an interface module configured to receive the flame check signal, the interface module configured to generate a fault check signal based on the flame check signal, the interface module configured to output the fault check signal.

2. The ignition system of claim 1, wherein the interface module is configured to output the fault check signal to the main controller.

3. The ignition system of claim 2, wherein the main controller is in electrical communication with at least one igniter, the main controller being configured to selectively ignite the igniter based on the fault check signal.

4. The ignition system of claim 2, wherein the main controller is configured to selectively turn off gas flow to the burner based on the fault check signal.

5. The ignition system of claim 1, wherein the interface module is in electrical communication with at least one igniter, the interface module being configured to selectively ignite the igniter based on at least one of the fault check and flame check signals.

6. The ignition system of claim 2, wherein the interface module is configured to selectively instruct the main controller to turn off gas flow to the burner based on the fault check signal.

7. The ignition system of claim 1 further comprising one or more additional flame sensors, the additional flame sensors configured to output one or more additional flame check signals.

8. The ignition system of claim 7, wherein the interface module comprises a multiplexer configured to receive the flame check signals and generate the fault check signal based on all of the flame check signals, the fault check signal indicating a normal condition only if all flame check signals indicate presence of a flame, the fault check signal indicating an abnormal condition if at least one flame check signal does not indicate presence of a flame.

9. The ignition system of claim 1, wherein the flame sensor is configured to detect presence of a flame using one or more of flame heat and flame light.

10. The ignition system of claim 1, wherein the flame sensor is configured to detect presence of a flame using flame rectification.

11. An ignition system for a gas furnace being controlled by a main controller and having a plurality of burners, comprising:

a plurality of flame sensors wherein each flame sensor is disposed in close proximity to its corresponding burner, each flame sensor being configured to output a flame check signal indicative of a status of a flame at its corresponding burner; and

an interface module configured to receive the flame check signals provided by the plurality of flame sensors and output a fault check signal, the interface module comprising a multiplexer configured to generate the fault check signal based on the flame check signals.

12. The ignition system of claim 11, wherein the interface module is in electrical communication with at least one igniter, the interface module being configured to selectively ignite the igniter based on at least one of the flame check signals.

13. The ignition system of claim 11, wherein the main controller is in electrical communication with at least one igniter, the main controller being configured to receive the fault check signal and selectively ignite the igniter based on the fault check signal.

14. The ignition system of claim 11, wherein the fault check signal indicates a normal condition only if all flame check signals indicate presence of a flame, the fault check signal indicating an abnormal condition if at least one flame check signal does not indicate presence of a flame.

15. The ignition system of claim 14, wherein, in the abnormal condition, the interface module is configured to determine the burner that does not have a flame and generate signals to re-ignite that burner.

16. The ignition system of claim 14, wherein the interface module is configured to output the fault check signal to the main controller, the main controller being configured to turn off gas flow to the burners if the fault check signal indicates an abnormal condition.

17. The ignition system of claim 11, wherein the flame sensors are configured to detect presence of a flame using flame rectification.

18. A method for providing a multi-port ignition system to a gas furnace having a plurality of burners and corresponding igniters, comprising the steps of:

providing a flame sensor in close proximity to each burner, each flame sensor configured to output a flame check signal indicative of a status of a flame at each burner;

determining if flames are expected in the burners;

monitoring the flame check signals;

indicating a normal condition if flames are expected and if all flame check signals indicate presence of a flame;

indicating a normal condition if flames are not expected and if none of the flame check signals indicate presence of a flame;

indicating an abnormal condition if flames are expected but not all flame check signals indicate presence of a flame; and

indicating an abnormal condition if flames are not expected but at least one flame check signal indicates presence of a flame.

19. The method of claim 18 further comprising the steps of:

continuing furnace operation if a normal condition is indicated; and

shutting off gas flow to the burners if an abnormal condition is indicated.

20. The method of claim 18 further comprising the steps of:

temporarily disabling the flame sensors if a normal condition is indicated;

monitoring the flame check signals;

re-enabling the flame sensors and continuing furnace operation if none of the flame check signals indicate presence of a flame; and

turning off gas flow to the burners if at least one flame check signal indicates presence of a flame.