The present disclosure generally relates to ignition systems, and more particularly, to multi-port ignition arrangements for sectional gas furnaces.
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
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.
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.
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.
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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.
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.
Number | Date | Country | |
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61376560 | Aug 2010 | US |