Gas fired appliance igntion and combustion monitoring system
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     BACKGROUND 
     I. Field of the Invention 
     This invention relates to fuel gas ignition and combustion monitoring systems, and more particularly to a system and method which utilize an electronically monitored ignition and combustion monitoring device for controlling the operation of a gas fired appliance. 
     II. Background Art 
     Fuel gas is used in a wide range of gas fired appliances including ranges, stoves, gas refrigerators, barbecue pits, gas fired fireplaces, clothes dryers and water heaters. A conventional mechanism for igniting the fuel supplied to the gas fired appliances is a high voltage spark created by a spark generator. In spark ignition, two separated conductors have a voltage potential difference therebetween sufficient to induce a spark to jump the gap separating the two conductors. A third rod is engulfed in the flames of combustion and is used by the conductivity thereof to ascertain ongoing combustion. The conductivity of the air and third rod within the combustion envelope verifies that combustion is ongoing. 
     A problem known to spark generation equipment is the large draw of power required to make the spark jump the gap. This is particularly true if, by some happenstance, the gap size is increased between the two conductors. Additionally, the spark causes electromagnetic interference which tends to be a nuisance to radios, television sets, personal computers, and other electronic appliances in the area. In light of such a problem with spark ignition systems, it would be an advance in ignition systems for gas fired appliances to provide an ignition system that meets both conventional and developing telecommunication standards for electromagnetic interference omission. 
     Gas fired appliances are frequently controlled by microprocessors. Such microprocessors can be interfered with by spark generators. Additionally, the high voltages characteristics of spark generation can be deleterious to semiconductors in the control system of the appliance, as such high voltages can lead to the breakdown of semiconductor parts therein. Thus, the reliability of semiconductor components for controlling gas fired appliances may be jeopardized. 
     Another problem known to spark generators for the ignition of gas fired appliances is that the spark that is generated is consistent in both standard magnitude and size for an average environment of relative humidity. Consequently, in very high ambient relative humidity, the spark being generated may be insufficient to cause proper ignition of the fuel gas. Particulates in the air, accumulations of soot, and variations in altitude, in addition to the foregoing, can hinder spark generation and the ignition of the fuel gas. 
     An option to spark ignition for gas fired appliances is circuit ignition using a hot carbide surface, such as silicon carbide. Circuit ignitions are, however, typically more expensive than spark ignition systems. Carbides used for hot surface ignition of combustible fuel gases can withstand very high temperatures, have a high melting point, and are corrosion resistant. A difficulty with such hot surface ignition systems is the necessity of having to bond or otherwise weld the carbide to a metallic system that conducts electricity. This type of welding is necessary to electrically resistance heat the carbide, but is both expensive and difficult in that it requires very high temperatures to accomplish. Further, the carbide providing the hot surface ignition tends to be quite brittle and thus frangible and unreliable in physically non-fragile environments, such as is known to recreational vehicle appliances. 
     From the foregoing, it can be seen that it would be an advance in gas fired appliance ignition art to provide an ignition system that is inexpensive, does not cause electromagnetic interference with controllers of the gas fired appliance, and withstands heavy-duty use without breaking. 
     Gas fired appliances may have an ignition and combustion system that is regulated by a controller that causes the correct order, correct timing, and safety features thereof to be cooperating as subsystems of the appliance. Such modem gas fired appliances consist of a gas supply system, an ignition and combustion verification system, a safety cut-off valve to the gas supply system, and a heat extraction or heat exchange system. It is the goal of such controllers to provide transparent operation of the gas fired appliance to the user. By way of example, such a controller may control the combustion mix of air and fuel gas so that it is neither too lean nor too rich, but rather combusts most efficiently. Such a controller may regulate the operation of an electrically activated solenoid valve which opens and closes the gas flow to the appliance so that the right amount of gas at the right velocity is mixed into the combustion area or mixing space for combustion. 
     In the case of furnaces and other gas fired appliances requiring an air delivery system, a blower fan may also be operated by a controller. Should there ever be an extinguishment of combustion, a blower fan may be operated by the controller so as to purge the combustion area free of combustible fuel gas and thereby prevent a build up of same and a subsequent explosion. When the controller operates the blower fan following extinguishment of a flame, a safety timing period is provided between the receipt of the controller of a request of a thermostat to start opening the gas valve, and the subsequent opening of the gas valve supplying fuel gas to the combustion area. Thus, the controller may control the timing of the actual delivery and purging of the combustible fluid contents of the combustion area. 
     Another important function which may be controlled by a controller, and may also be accomplished by mechanical systems, is that of a sail switch which measures air flow to the combustion area. A sail switch is a mechanical switch that is switched on or off by the flow or non-flow of air. The switch signals the controller to turn off the supply of fuel gas if air flow to the combustion area has been terminated. By way of example, an obstruction in the air intake to the blower fan may cause a rich fuel gas mixture in the combustion area due to an absence of air coming through the air intake. A sail switch would prevent such a problem by giving an indication of air intake malfunctioning, which indication is acted on by the controller to prevent the fuel gas from flowing into the combustion chamber. Thus, gas is not combusted in the case where air is not being provided to the combustion area, or is not being provided so as to remove heat from the combustion chamber. The sail switch helps to indicate that air is flowing to reduce the heat of combustion, and thus prevent the burning up of heat exchanger components of the gas fired appliance. 
     In short, the sail switch is an anemometer to measure the amount of air that is being delivered to the combustion area. The sail switch, by its function of assuring that the appliance will not operate without a proper air flow to the combustion chamber, prevents a typical problem of air flow blockage or redirections of the air which may in turn cause the flames of redirection of the flames of combustion to be redirected to an area that is hazardous to the appliance. 
     While prior art sail switch techniques have been widely used with success, there is still a serious risk of human error when using such systems. The sail switches used on such gas fired furnaces are often prone to mechanical failure due to environmental conditions, and due to corrosion over time as the appliance ages. Thus, improper sail switch operation may occur. Accordingly, there is a need for a gas fired appliance that safely and accurately acknowledges a proper in take of air to the combustion area so as to assure that a flue is not blocked. The system and method of the present invention provide an effective solution to these problems which has not heretofore been fully appreciated or solved. 
     A controller for a gas fired appliance may also be in electrical communication with a limit switch or ECO. The ECO switch cuts off power so as to close the gas supply valve whenever certain critical areas of the appliance reach a maximum tolerable temperature. In the case of furnaces and other gas fired appliances having a blower fan to the combustion chamber, a timing relay is also operated in conjunction with the ECO so that there is a purging of the gas combustion area following the shut off of electrical power to the appliance. 
     An ignition control board or other appliance controller device, incorporates the foregoing functions of monitoring the ignition, combustion, and ongoing operation of a gas fired appliance. It would be an advance in art to provide a safe and reliable integrated ignition and combustion control system that overcomes foregoing problems while intercoordinating typical functions provided by a gas fired appliance. 
     BRIEF SUMMARY AND OBJECTS OF THE INVENTION 
     The system and method of the present invention have been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art not heretofore fully or completely solved by ignition and combustion systems for gas fired appliances. It is not intended, however, that the system and method of the present invention will necessarily be limited solely to ignition and combustion control, since they will also find useful application with potentially many kinds of gas fired appliances which require the control of various operational aspects, including temperature regulation, burn efficiency, and operational communications. Thus, it is an overall object of the present invention to provide a system and method which provide for the safe and efficient operation of a gas fired appliance. 
     Another important object of the present invention is to provide a system and method whereby state of the art electronic technology can be utilized to assist the safe and efficient operation of a gas fired appliance. 
     Another important object of the present invention is to provide a gas ignitor system and method of electronic monitoring fuel gas ignition which increases the convenience and safe utilization of gas fired appliances in general. 
     These and other objects and features of the present invention will become more fully apparent from the following more detailed description taken in conjunction with the drawings and claims, or may be learned by the practice of the invention. 
     Briefly summarized, the foregoing and other objects are achieved in an electronically monitored ignition system and method for combustible gases used in gas fired appliances. By way of example, such appliances include ranges, stoves, gas refrigerators, or gas appliances in general. The novel ignition and combustion control system and method is capable of igniting combustible gases as well as detecting a flame resulting from such ignition. 
     The ignition and flame sensing system is used in a heat exchange system that employs a fuel-to-air mixing mechanism. The gas mixture is fed to an electrically heated solid material providing a hot surface ignition for the mixture. The hot surface ignition on the electrically heated solid material produces a flame by combustion of the fuel. Energy of the flame from the combustion heats a solid material that emits radiation when heated. The flame heated solid material may be the same as, or different from, the electrically heated solid material. 
     Radiation from the solid material is detected by an infrared sensor and is monitored by associated circuitry. The infrared sensor may be focused to detect radiation from either or both of the electrical and flame heated solid material. As mentioned, the electrical and flame heated solid materials may also be one and the same. Alternately, multiple infrared sensors with associated circuitry may also be provided to focus on a separate one of the electric or flame heated solid materials. 
     Radiation emitted from the electric or flame heated solid materials is indicative of the temperature of the solid material. The temperature of the solid material is effected by the degree of its electrical or flame heating. As such, circuitry associated with the infrared sensor can verify that the electrically heated solid material is both operational and hot enough to function in hot surface ignition. Additionally, the infrared sensor and associated circuitry can prove that combustion was successfully achieved by the electrically heated solid material serving as a point of hot surface ignition. 
     The temperature of the electrically heated solid material can be lowered by the degree to which an air flow engulfs the same so as to lower its temperature by a cooling off effect. As such, the infrared sensor and associated circuitry can verify that a blower fan associated with the gas fired appliance is being properly operated so as to cause a proper air flow into a combustion chamber in which the electrically heated solid material is also situated. 
     The temperature of the flame heated solid material can be affected by the existence and efficiency of the flame that heats the solid material. The degree of infrared radiation being emitted by the flame heated solid material is indicative of how efficient the burning of the flame is, as well as being indicative of the temperature of the combustion area. Such efficiency of radiation emission may be effected by a poor air-to-fuel mixture due to a blockage in air intake, contaminated fuel gas, and atmospheric conditions including air borne particulates and high relative humidity, any one on combination of which may lower the efficiency of the combustion and thus the emission of radiation that is detected and verified by the infrared sensor and it associated circuitry. 
     A further capability of the one or more infrared sensors in the inventive method and system is the ability to detect excessive infrared emission characteristic of weakening or failing structural material of the gas fired appliance, such as a broken seam or a hole in a combustion chamber of a gas fired furnace. Weakened materials that are heated, such as sheet metal, give off excessive infrared energy during failure. 
     In general summary, the inventive method and system coordinates on-going combustion by the detection of infrared emissions emanating from a solid material engulfed within and being heated by a flame of combustible gas, where an infrared sensor is focused by line of sight upon the solid material that is emitting infrared radiation in proportion to the temperature of the solid material, the solid material being heated by a flame in a combustion area, the flame heated solid material being constant in surface area and composition, and upon which an infrared sensor is focused for the purpose of evaluating the presence and efficiency of the combustion of combustible fuel, the circuitry associated with the infrared sensor receiving a signal from the infrared sensor and using such signal for verifying the presence and continuity of a flame in a combustion area, which radiation is monitored by the infrared sensor as a means of deriving therefrom the presence and efficiency of the combustion of a combustible gas that is used to heat the infrared radiating solid material, where the monitored efficiency of combustion is used by the circuitry associated with the one or more infrared sensor(s) to control operational parameters including the input of fuel and air to the combustion chamber. 
     The circuitry associated with one or more infrared sensors of the inventive system may be characterized as an electronic circuit means or a controller. The controller is responsive to a control signal produced by the infrared sensor for controlling a valving means which supplies fuel to the combustion chamber. 
     Aspects of the inventive method and system relating to the ignition of combustible fuel may be considered as separate functional aspects relating to on-going combustion of the combustible fuel. 
     Structurally, in a preferred embodiment, the inventive ignition and combustion control system consists of two rods which are connected together by a first filament material. Preferably, although optionally, the first filament material is made from KANTHAL™. This material is basically an aluminum and nickel alloy that has a high melting point. Alternatively, the material may be stainless-steel with an aluminum silicone additive such that its melting point is high (i.e. above 1,200 degrees Fahrenheit). 
     The first filament material is wrapped with four or five turns around each of the two rods, and is then welded using spot welds to the two rods. The proper electrical resistance for hot surface ignition of combustible gas in the system is determined as a function of the number of turns in the first filament material between the two rods. In this way, the hot surface ignition area on the first filament material can be optimized for the combustible gas having contact therewith as an electrical current resistance heats the first filament material between the two rods. Preferably, the first filament material is within the line of sight of the infrared sensor. 
     Preferably, one of the two rods is longer than the other and may have welded at or near an end thereof a second filament material that is coiled or wrapped there around. When so wrapped, the larger rod act as a heat sink for the second filament material. Alternatively, the longer rod can be either straight or bent at an angle without a second filament material wrapped there around, yet still extend beyond the length of the shorter rod. Regardless of the form of the larger rod, it is intended that the end extending past the end of the shorter rod be within the line of sight of the infrared sensor and also be heated by a flame in the combustion area of the appliance which is the product of the combustion of the fuel gas. 
     Both the first filament material between the two rods and the second filament material at an end of the longer rod are preferably of low thermal mass and have a rapid response to heating such that infrared emissions can be detected by a relatively inexpensive infrared sensor. The longer of the two rods, when lacking a second filament material, may be composed of materials having a rapid response to emit infrared radiation through heating, such as KANTHAL™. The geometry of end of the longer rod may also be thinned to have a low thermal mass so as to give a rapid infrared radiation emission upon heating of the sallie. 
     The first filament material extending between the two rods, referred to herein as the first radiator, is initially heated with an electrical current passed therebetween. The electrical current passing through the first radiator causes the first radiator to be raised to an ignition temperature for the combustible gas. The elevated temperature of the first radiator, acting as a hot surface ignitor, ignites the combustible gas. The inventive ignition system is capable of verifying that the first radiator is hot enough to ignite the combustible gas by detecting emissions of infrared radiation emanating from the first radiator material due to the resistance heating thereof. 
     In an alternative embodiment, the next step following resistance heating of the first radiator is to actuate a blower fan to direct a stream of air into a combustion area where the resistance heated first radiator is located. The stream of air causes a slight cooling of the first radiator. This cooling is detected by a decrease in infrared radiation being emitted by the first radiator, which decrease is detected by the infrared sensor and associated circuitry. Such a decrease in the emission of infrared radiation is an indication that the blower fan is properly delivering air into the combustion area. Such a embodiment is preferred in confined areas of combustion for the fuel gas, such as is found in gas fired furnaces. 
     Upon verification of achieving the ignition temperature by the first radiator, the current between the rods is cut off, the first radiator cools down, and the appliance is controlled to supply additional combustible gas to the flame. In some preferred embodiments of the inventive system and method, the flow of combustible gas tends to shift and extend the length of the flame to engulf the length of the longer rod extending beyond the shorter rod, which length may have the second filament material thereon. The extended flame causes the extended length of the second rod, and/or second filament material thereon, to heat up. 
     Upon heating by the combustion flames, the extended length of the second rod, and/or second filament material, these being referred to herein as the second radiator, begins to emit infrared energy which is then detected by the infrared sensor and it associated circuitry. Once the flame is shifted in position and elongated by a supply of gas and air mixture that is under greater pressure that the initial ignition pressure, the first radiator is no longer resistance heated or within the times of the combustible gas. Thus, the infrared sensor substantially detects only infrared energy being emitted by the second radiator, as the first radiator is no longer resistance heated or within the heating zone of ongoing combustion. 
     Henceforth, the infrared sensor witnesses the on-going combustion of combustible gases as evidenced by the emission of infrared energy from the second radiator. As such, the second radiator serves as the solid material object upon which the infrared sensor focuses so that its associated circuitry can verify the presence of a flame of combustible gas or the absence thereof. The infrared sensor and circuitry also verifies, by the intensity of infrared radiation, a measure of bum efficiency of the combustible fuel as well as ascertaining potential material failure and weakening of the structural elements of the combustion area. 
     It is contemplated that the invention involves microprocessor control of the gas fired appliance for the purposes of controlling the flow of gas to the appliance, controlling the temperature of the first radiator for the purpose of ignition of the combustible gas, as well as other microprocessor controls which monitor and automatically adjust the general operation of the gas fired appliance. 
     As an example of the type of control that the inventive ignition and combustion control system and method is capable of, should the flame of combustible gas extinguish or otherwise perform substandardly, then a supply valve for the flow of gas to the appliance can be modulated closed by microprocessor control when a substandard signal from the infrared sensor is detected based upon the quantity of emitted radiation from the second radiator. After the flow of gas has been cut off, the microprocessor can then control the ignition system to attempt one or more retries to ignite the combustible gas by signals derived from the first radiator after the extinguishment of the flames of the combustible gas is verified by signals to the microprocessor derived from the second radiator. 
     A further concept of the type of control capable with the inventive system and method is the ability to sense the effect of a flow of air upon the first radiator. To do so, the general principle is observed that the infrared energy emitted by a heated solid material is inversely proportional to the cooling effect of air upon the heated solid material. The amount of cooling air to which the heated solid material is exposed is proportional to the infrared energy emitted. As such, infrared energy emitted by a heated radiator, with the infrared sensor and associated circuitry, function as a form of anemometer to measure air velocity. 
     In further application, the efficiency of the combustion in the appliance is also effected by air flow and is indicated by the degree of infrared radiation emitted from the heated solid material, which infrared radiation is detected by the infrared sensor and circuitry associated therewith. By way of example, should the air flow into the gas combustion chamber become blocked during ongoing combustion, then the diminished air flow will cause a decreased efficiency in the combustion of combustible gas. This efficiency decrease will cause the second radiator, which is engulfed in flames, to emit less infrared radiation due to the decrease of gas combustion. The infrared sensor will detect the decrease in the emission of infrared energy from the second radiator and the appliance operational parameter, such as the flow of combustible gas thereto, is then adjusted using software control via a microprocessor associated with the inventive system. Thus, the infrared sensor, associated circuitry, and the second radiator are used in the inventive system and method to monitor obstructions of air flow to the combustion chamber. 
     The monitoring of air flow performs the function of a conventional sail switch, and is also used to maximize the efficiency of the combustion of the combustible gas. By controlling both air and fuel feeding to the combustion area, a comprehensive gas fired appliance control and efficiency system is achieved. 
     As a further extension and safety feature of the invention, the infrared sensor can be used to detect abnormal infrared emissions which may signal that the materials from which the appliance is constructed have reached a critical temperature that is near the point of fatigue or cracking. Upon such abnormal emissions of radiation which are detected by the infrared sensor and circuitry, microprocessor control of the appliance initiates a process to decrease or otherwise turn-off the feed of combustible gas to the appliance via a gas valve modulation system. 
     While it is preferable, the infrared sensor need not be physically situated in direct view of either the first or second radiators. Rather, optical fibers having an end directed toward such radiators can be used to direct the infrared radiation to an infrared sensor that is located remotely from the source of the infrared radiation. By way of example, an infrared sensor on a gas fired stove can be focused upon an end of one or more optical fibers having an opposite end directed at solid material engulfed within a flame so as to assist therethrough infrared radiation therefrom. 
     The inventive ignition system has the versatility of being able to detect a variety of combustible gases including propane, natural gas, or liquid petroleum gas. Once the type of combustible gas is known, the appropriate range of infrared radiation from the first and second radiators that is applicable to the ignition and combustion of such gas can then be set as a process variable in the microprocessor control for the corresponding gas fired appliance. 
     In summary, the device may be characterized in main preferred embodiments thereof as a system and method having an electronic ignition control board for the purpose of igniting and monitoring a gas fired appliance operation by infrared sensing of a solid infrared emitting material as a mean of gauging the presence, absence, ignition potential for, and efficiency of a flame of combustible gas. 
     The inventive system is easy to manufacture while at the same time providing improved overall safety in the ignition and accurate determination of the existence and the quality of on-going combustion of fuel gas in a gas fired appliance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The presently preferred embodiments and the presently understood best mode of the invention will be described with additional detail through use of the accompanying drawings, wherein corresponding structural parts are designated by the same reference numerals throughout, and in which: 
     FIG. 1A is a preferred embodiment of the inventive hot surface ignition and combustion monitoring device; 
     FIG. 1B shows an alternative preferred embodiment of the inventive hot surface ignition and combustion monitoring device positioned above and adjacent to a burner tube with the ignition coil thereof protruding from an end of the burner tube; 
     FIG. 1C shows the alternative preferred embodiment of the inventive hot surface ignition and combustion monitoring device positioned above and adjacent to a burner tube, wherein the ignition coil thereof is positioned above and adjacent to an ignition hole providing an inlet for ambient air to the inside of the burner tube; 
     FIG. 2 is a preferred embodiment of an inventive gas fired furnace incorporating the inventive ignition and combustion monitoring device; 
     FIG. 3 is preferred embodiment of an inventive gas fired water heater incorporating the inventive ignition and combustion monitoring device; 
     FIG. 4 is a functional block diagram which schematically illustrates the primary components of one presently preferred electronic circuit used in connection with the electronic controller incorporated into the inventive ignition and combustion monitoring system; 
     FIGS. 5A-5D taken together constitute a detailed electrical schematic diagram which illustrate, as an example, a presently preferred embodiment and one presently understood best mode for implementing the electronics of the system and method of the present invention in a gas fired furnace; 
     FIGS. 6-14, 15a-15h, and 16-19 taken together illustrate flow charts showing one presently preferred method for programming the digital processor of the inventive ignition and combustion monitoring system in accordance with the method of the present invention for controlling a gas fired furnace. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     III. The System 
     A. The Presently Preferred Inventive Ignitor and Combustion Monitor within Gas Fired Appliances: (FIGS. 1A-3). 
     FIG. 1A depicts a preferred embodiment of the inventive device referred to hereinafter as an ignitor, generally indicated at 10. Ignitor 10 has a first electrically conductive rod 12 and a second electrically conductive rod 14 with an electrically conductive ignition coil 16 therebetween. A voltage potential between first conductive rod 12 and second conductive rod 14 causes ignition coil 16 to undergo electrical resistance heating. When ignition coil 16 is heated, it begins to glow and emit infrared radiation. The temperature to which ignition coil 16 is heated is sufficient for hot-surface ignition of a combustible gas that comes in contact with ignition coil 16. 
     While ignition coil 16 is being electrically heated, an IR detector 18 detects infrared radiation being emitted by ignition coil 16. During the time that ignition coil 16 is being electrically heated, IR detector 18 detects the emission of infrared radiation therefrom. Preferably, IR detection 18 has ignition coil 16 within its line of sight. 
     After a predetermined period of time, electrical current supplied to ignition coil 16 by first and second conductive rods 12, 14 is terminated. This predetermined period of time is equal to or greater than the period of time necessary for ignition coil 16 to ignite the combustible gaseous fuel coming in contact therewith. When electrical current ceases to flow through ignition coil 16, ignition coil 16 will no longer emit a high degree of infrared radiation as it begins to cool. The cooling and emission of a lesser amount of radiation by ignition coil 16 will be detected by IR detector 18 as ignition coil 16 cools. 
     After ignition coil 16 has ignited by a hot surface thereon the combustible gaseous fuel, the flames of combustion will be directed towards combustion and emission region 20 seen in phantom in FIG. 1A. 
     The physical arrangement and placement of combustion and emission region 20 is such that the flames from the combustion of gaseous fuel will essentially heat only combustion and emission region 20 and will not substantially heat ignition coil 16. The gradation in temperature between ignition coil 16 and combustion and emission region 20 is preferable due to the physical arrangement of the fuel being fed to combustion and emission region 20. Alternatively, a blower fan may direct air so as to shift the flames of combustion. The net effect of this physical arrangement or flame shifting is that infrared radiation will be emitted from combustion and emission region 20 to a substantially larger degree than that which is emitted from ignition coil 16. 
     As combustion and emission region 20 is heated by the flames produced through the combustion of gaseous fuel, solid materials that are within combustion and emission region 20 will begin to heat up. Preferably, the solid material that is within combustion and emission region 20 will be of the type that emits a high degree of infrared radiation when heated. As seen in FIG. 1A, an emission coil 22 is wrapped around and upon an emission element 24, both of which are within combustion and emission region 20. Emission coil 22 is preferably a relatively thin coil that withstands heating for an extended period of time without failure. Emission element 24 is similarly able to withstand heating over a lengthy period of time without disintegration or otherwise failing. 
     While the materials within combustion and emission region 20 are being heated to the point of emitting infrared radiation, IR detector 18 detects infrared radiation being emitted from combustion and emission region 20. By the detection of infrared radiation coming from combustion and emission region 20, IR detector 18 can determine whether a successful combustion has taken place and is ongoing. Preferably, combustion and emission region 20 and, specifically, emission coil and elements 22, 24, are within the line of sight of IR detector 18. 
     In order to preserve the integrity of the detection of infrared radiation detected by IR detector 18, a cloaking tube 26 may be placed around IR detector 18 at one end thereof, while the other end of cloaking tube 26 opens near ignition coil 16. Preferably, cloaking tube 26 defines a line of sight of IR detector 18 directly toward emission coil and element 22. By limiting the peripheral view of IR detector 18 using cloaking tube 26, or a similarly functioning structure, IR detector 18 will be limited in its detection of infrared radiation from a limited number of sources, which will preferably be ignition coil 16 and combustion and emission region 20. 
     The solid materials to receive heating from the combustion of the gaseous fuel, which solid materials are found within combustion and emission region 20, must be carefully chosen to withstand extended periods of being heated within a combustible gas. Preferably, this material is an aluminum-nickel alloy or a stainless-steel material with an aluminum-silicon additive such that its melting point is high (e.g. above 1200° F.). 
     With respect to emission coil 22, it is preferably wrapped around emission element 24 several times and is spot-welded thereon. Preferably, emission coil 22 and emission element 24 are both made from KANTHAL™, supplied as 8-gauge rod. This rod is between 4 and 5% aluminum, about 22% chromium, and substantially comprises iron. The size of the rod is between 0.6 inches and 0.12 inches diameter. While the foregoing represents a preferred material for emitting infrared radiation from within combustion and emission region 20, those of skill in the art will understand that other materials are capable of emitting infrared radiation adequately for the present inventive system. 
     While cloaking tube 26 is depicted in FIG. 1A in one embodiment thereof as a shield or tube to block peripheral vision of IR detector 18, tube 26 may also be considered to one or more optical transmission fibers capable of transmitting infrared radiation from either ignition coil 16 or combustion and emission region 20 so as to communicate the same to IR detector 18. In such an alternative embodiment, combustion and emission region 20 and ignition coil 16 may be located at an open gas fuel and air source such as a gas burner of a stove, where tube 26 transmits infrared radiation by optical fiber therein from such location at the burner of a stove to a remote location where IR detector 18 is situated. Such an embodiment of a gas fired stove provides an environment in which IR detector 18 can be safely maintained out of the heating zone of the burner. It should also be understood that IR detector 18 may be further separated from first and second conductive rods 12, 14 in a gas fired stove embodiment of the present inventive ignition and combustion control system and method. Alternatively, a heavy duty IR detector 18 may be maintained closer to the combustion flames, when properly positioned or thermally shielded by a mica shield or other transparent shield, so that IR detector 18 may be positioned directly in between first and second conductive rods 12, 14 and within the line of sight of solid materials to be monitored for infrared radiation. 
     Alternative embodiments oft he inventive ignition and combustion detection system are seen in FIGS. 1B and 1C. A burner tube 33 is disposed below and immediately adjacent to ignitor 10. Burner tube 33 has at one end thereof a gas line 32 feeding a supply of combustible fuel through an orifice 35. Ambient air, due to pressure differentials, is fed to the inside of burner tube 33 through a venturi 21 to be mixed with combustible fuel from fuel inlet 32. Past an opposite end 19 of burner tube 33 is combustion and emission region 20. 
     In the embodiment of ignitor 10 seen in FIG. 1B, ignition coil 16 is positioned outside of and past end 19 of burner tube 33. Thus, ignition of the supply of combustible fuel emitted from orifice 35 of gas line 32 takes place at end 19 of burner tube 33. Upon combustion, the pressure of combustible fuel emitted from orifice 35 of fuel end 32 shifts the flame from the region of ignition coil 16 to combustion and emission region 20. By such flame shifting, ignition coil 16 is not heated by the flames of combustion, and emission element 24 within combustion and emission region 20 is heated by the flames of combustion which have shifted away from end 19 of burner tube 33. 
     As can be seen in FIG. 1B and 1C, emission element 24 is a thin piece of material which, preferably, has a flat surface effaced toward and within the line of sight of IR detector 18. Unlike ignitor 10 seen in FIG. 1A, emission element 24 does not have an emission coil 22 wrapped therearound. As such, emission element 24 of FIGS. 1B and 1C has a relatively small thermal mass, which is conducive to rapid emission of infrared radiation upon heating of the same. 
     The embodiment of ignitor 10 seen in FIG. 1C shows burner tube 33 having an ignition hole 17 proximal of end 19. Immediately adjacent to ignition hole 17 and above burner tube 33 is ignition coil 16 of ignitor 10. In this embodiment, a combustible fuel is fed into fuel inlet 32 and through orifice 35 so as to, by pressure differential, draw ambient air through venturi 21 creating a primary fuel-air mixture. The primary mixture of fuel and air translates to the location of ignition hole 17. Again, by pressure differential, ambient air is received through ignition hole 17 to mix with the primary mixture of fuel and air so as to create a secondary and combustible mixture of fuel and air. As the combustible secondary mixture of fuel and air begins to surround ignition coil 17 from within burner tube 33 at ignition hole 17, ignition coil 16 is heated electrically to a temperature at which the secondary mixture of fuel and air will combust. Upon combustion, the pressure of gaseous fuel from fuel inlet 32 will cause the flames of combustion to shift out of burner tube 33 and extend to combustion and emission region 20. By such flame shifting, ignition coil 16 is outside of the flames of combustion, and emission element 24 within combustion and emission region 20 is engulfed within the flames of combustion. Consequently, IR detector 18 essentially receives infrared radiation solely from combustion and emission region 20 to the exclusion of ignition coil 16 which is no longer electrically resistance heated. 
     The concept of shifting the flames of combustion following ignition away from the hot ignition surface to a solid material exposed to ongoing combustion may be accomplished through increased gas mixture pressure, spatial arrangement of the infrared radiators, forced air pressures, or by other conventional means. 
     An alternative embodiment from ignitor 10 seen in FIGS. 1A, 1B, and 1C is an embodiment in which the flames of combustion, subsequent to ignition, engulf only ignition coil 16. In such an embodiment, ignition coil 16 is electrically resistance heated to the point of igniting the combustible gaseous fuel mixture. Subsequent to ignition, ignition coil 16 is no longer electrically heated, but rather is thermally heated by the flames of combustion. IR detector 18 thus detects infrared radiation emitted from ignition coil 16 as it is electrically and then thermally heated. In such embodiment, the flames of combustion do not heat combustion and emission region 20. This embodiment is not considered the best mode in that ignition coil 16 is exposed for prolonged periods to high temperatures due to the flames of combustion. Additionally, ignition coil 16 has a limited thermal heat sink in communication therewith so as to transfer heat energy therefrom to the heat sink. As a result, ignition coil 16 has a shorter life due to a rigorous environment of constant exposure to high temperatures, both thermally and electrically. In such embodiment, the presence of the extended portion of second conductive rod 14 having at an end thereof emission coil 22 and emission element 24 would not be necessary. Additionally, the thermal mass of ignition coil 16 should be increased to lengthen its service life, should the requisite power be available in the appliance to achieve hot surface ignition temperatures. 
     The inventive ignition and combustion monitoring device can be placed in a variety of gas fired appliances such as furnaces, water heaters, barbecue pits, fire places, stoves, refrigerators, and other appliances where the ignition and subsequent combustion of a gaseous fuel is required. 
     The foregoing is a description of preferred embodiments of the inventive ignition and combustion monitoring device. Components of one such embodiment are more fully described in Table I, below. The artisan will understand that different structural, component, and material designs and arrangements are possible to implement the device seen in FIG. 1A. 
     FIG. 2 depicts an embodiment of an inventive gas fired furnace containing the inventive ignitor. A fire box 30 has therein ignitor 10. Ignitor 10 is supplied with gaseous fuel by a fuel inlet 32. Fuel inlet 32 distributes the gaseous fuel in a spread out or otherwise extended area. Upon ignition, a series of combustion plumes 34 heat combustion and emission region 20 shown in FIG. 2. 
     The furnace seen in FIG. 2 has an air-intake flow seen by an arrow 36 which carries a stream of air into fire box 30. A blower fan 35 forces air in the direction of an arrow 36 into fire box 30. The force of blower fan 35 on the air flow through fire box 30 also forces the heated air within fire box 30 to exit at an exhaust vent 38. The air of the air stream is heated within fire box 30 and exits fire box 30 through an exhaust vent 38. Exhaust vent 38 will preferably exhaust heated air into the ambient where the furnace is installed so as to heat an intended area. 
     As seen in FIG. 2, a fuel source 40 deliver fuel gas to a gas valve 42 prior to being delivered to fire box 30. For subsequent combustion, fuel supply 40 feeds gaseous fuel through a gas valve 42 to fire box 3. Outside of firebox 30 is a temperature detection and signaling device 44 which detects ambient temperature within the environment to be heated by the furnace. 
     An appliance control board 46 controls the operation of the furnace. Appliance control board 46 is in electrical communication with a power supply through power supply leads 48. Control board 46 is in electrical communication with the temperature detection and signaling device 44 through thermostat leads 52. Appliance control board 46 is also in electrical communication with blower fan 35 through blower fan leads 42. 
     Ignitor 10 is in electrical communication, through ignitor and IR detector leads 56, with appliance control board 46. Appliance control board 46 also controls a manual gas shut-off valve modulating capability of the furnace through manual shut-off valve leads 58. Additionally, input and output communications to appliance control 46 are made to appliance control board 46 through an I/O communications device 60. 
     An alternative embodiment of the inventive ignitor is shown installed within a water heating system is seen in FIG. 3. As seen in FIG. 3, ignitor 10 heats a water tank 62 by combustion plumes 34. As water tank 62 is heated, cold water following in the direction of an arrow 64 causes water to enter water tank 62, and hot water exits in the direction indicated by an arrow 66 from water tank 62 upon external demand for same. The temperature of water within water tank 62 is detected by temperature and detection signaling device 44 which communicates with control board 46 for the monitoring of the water temperature. A power supply and thermal limit switch 68 also feeds into control board 46 for the purpose of detecting excessive water temperatures which, for instance, might tend to scald a user demanding hot water from water tank 62. 
     Various operational parameters may be set by a user with a mode-selection device 70 which is in electrical communication with appliance control board 46. 
     As an option to gaseous fuel combustion to heat water tank 62, an electrical resistance heating system 72 seen in FIG. 3 can also heat the water within water tank 62. Heating system 72 obviates the need for ignitor 10 and associated circuitry, except where IR detector 18 and associated circuitry monitor for structural failure of combustion area components as discussed above. 
     In the case of a gas fired hot water heater, the infrared sensor detects for both low and high radiation being omitted by the second radiator. It is necessary to so monitor in that forced air is not fed to the combustion area of the hot water heater. The absence of a forced air stream, in combination of a poor combustion, may result in the combustion of carbon and produce a flame from such combustion which emits an excessive amount of infrared radiation. As such, the method implemented for the inventive gas fired water heater must anticipate such circumstances and cause the control of the appliance to respond appropriately. 
     The burning of carbon is visually indicated by an orange color, and may be due to an insufficient air supply available to the combustion area of the gas fired water heater. In the gas fired water heater, a sail switch function would not be incorporated in that no blower fan is used. Thus, the method for using the inventive ignition and combustion control system must anticipate an excessive infrared radiation being detected from the gas combustion area of the gas fired water heater, the explanation for which is a poor air supply as opposed to an excessive temperature. Parameters may be set within the microprocessor and its data storage area so as to discern between excessive temperatures of the water in the water heater, and a deprivation of air to the combustion area of the water heater. 
     FIG. 3 shows a group of the inventive equipment 74 that is needed for most gas fired appliances to operate with the inventive ignition and combustion control system and method. 
     B. The Presently Preferred Electronic Controller: FIGS. 4 through 5D. 
     Appliance control board 46, seen in FIGS. 2-3, incorporates a variety of both hardware and software to accomplish the function of operating a gas fired appliance. In FIG. 4, a microprocessor 92 may have an optional non-volatile memory, such as an EPROM, to store additional software and data to be fed to appliance control board 46, seen in FIGS. 2-3. An external communications module 78 can be used to feed appliance data to peripheral equipment, as well as to receive data to be fed to the appliance. A gas modulator circuit 80 is used to control the flow of gas going through a valve to the appliance. An LED indicator for alarms is seen at 82. Device 82 may include visual LED indicators, sound alarms, or a combination thereof. 
     The controlling of blower fan 35, seen in FIG. 2, may be controlled by a blower fan control module 84 seen in FIG. 4. Power supply and voltage regulation is accomplished by a module seen at 88. The temperature that is achieved by the medium being heated may be controlled by a temperature input 90 which directly measures the medium being heated and communicates a signal with microprocessor 92. 
     All of the foregoing data is communicated with microprocessor 92, seen in FIG. 4, for being processed. Microprocessor 92 has an analog to digital converter 94 which converts the signals from the aforedescribed devices in preparation for processing the data contained in the signals. 
     In the presently preferred embodiment, microprocessor 92 in FIG. 4, and IC1 seen in FIG. 5, is an example of a digital processor means. Such a digital processor means can be a general purpose microprocessor or an equivalent device. Alternatively, it may be desirable to utilize a more powerful microcomputer, such as an IBM personal computer, to devise a microprocessor-based apparatus specifically designed to carry out the data processing functions incidental to this invention. Importantly, the hardware which embodies the processor of the present invention must function to perform the operations essential to the invention and any device capable of performing the necessary operations should be considered an equivalent of the processor means. As will be appreciated, advances in the art of modem electronic devices may allow the processor to carry out internally many of the functions carried out by hardware illustrated in FIGS. 2 though 5 as being independent of the processor. The practical considerations of cost and performance of the system will generally determine the delegation of functions between the processor and the remaining dedicated hardware. However, a low cost processor is desirable. 
     Visual display aspects of I/O device 60 seen in FIGS. 2 and 3, and controlled through LED indicator 82 of FIG. 4, performs the function of a display means. As intended herein, the display means may be any device which enables the operating personnel to observe visually displayed or audibly reported operational parameters calculated by the microprocessor. Thus, the display means may be a device such as a cathode ray tube, an LCD display, a chart recorder, and/or speaker, or any other device performing a similar function. In the preferred mode, the display means may be one or more series of low cost LEDs. 
     The functional block diagram of FIG. 4 can be implemented by the circuitry depicted in FIGS. 5A-5D, the components thereof being more fully described in Table II, below. The artisan will understand that different circuit designs are possible to implement the functional block diagram of FIG. 4. Thus, FIGS. 5A-5D and the component list of Table II are offered only for purposes of illustration and not for purpose of limitation of the inventive method and system. 
     IV. The Method 
     Attention is next turned to a detailed description of the presently preferred method by which the system of the present invention is used to ignite and monitor the combustion of a fuel gas, and to control the operation of a gas fired furnace, with particular reference to FIGS. 6 through 14, 15-A through 15H, and 16 through 19 which illustrate one presently preferred embodiment of the instructions which may be utilized for digital processor control of the gas fired furnace depicted in various aspects in FIGS. 1-2, and 4-5. 
     Both the function block diagram of FIG. 4 and the electrical schematic of FIGS. 5A-5D illustrate a presently preferred embodiment of an inventive gas fired appliance ignition and combustion monitoring system. 
     As will be appreciated by those of ordinary skill in the art, and as noted above, while the system and method as described in reference to the preferred embodiments herein illustrate the system and method as implemented using state of the art digital processing design and corresponding program instructions for controlling the processor, the system and method could also be implemented and carried out using a hardware design which accomplishes the necessary electronic processing, which is thus intended to be embraced within the scope of various of the claims as set forth hereinafter. 
     The method of the present invention is seen in overview in FIGS. 6 and 7 which depict flow charts schematically illustrating the primary routines of one presently preferred method for programming both the initialization mode and the operational mode, which modes are performed essentially by the digital processor means of the fuel gas ignition and combustion monitoring system in accordance with the method of the present invention. As seen in FIGS. 6 and 7, the software programming is essentially divided into two sections: respectively, the initialization loop and the main execution loop. The initialization loop, as seen in FIG. 6, prepares the system hardware for the main execution loop and in part verifies functionality of the hardware. The main execution loop, as seen in FIG. 7, controls all other functions in the operation of the furnace. 
     Microprocessor control of the preferred embodiment of the inventive furnace is detailed in Appendix A hereof by a software source code listing of programs, subprograms, and subroutines, each of which includes documentation descriptive thereof. Each of the programs, subprograms, and subroutines in Appendix A is labeled with a title seen in the top-most labeled step corresponding to a title of a software flow chart seen in FIGS. 6 through 14, 15-A-15H, and 16-19. Each of the FIGS. 6-14, 15-A-5H, and 16-19 graphically sets forth a series of steps for performing a program, subprogram, or subroutine for which a listing appears in Appendix A. A description of each of these steps in the Figures is found in Appendix B, which with the source code listings in Appendix A provides a complete understanding of the method of a preferred embodiment of the invention. A summary of the general functions performed by the flow charts depicted in each of the Figures, however, is set forth below. 
     FIG. 6 depicts steps to prepare the microprocessor for the ongoing execution of the software by initializing the data storage addresses and registers, as well as assignment of addresses for subsequent storage of data. Miscellaneous maintenance and initialization routines are carded out. 
     The steps depicted in FIG. 7 will now be generally described. At the start of the steps, the blower fan motor is initiated into directing an air stream into the furnace combustion chamber. The ignitor receives a current developing a voltage potential between the two electrically conductive rods so as to resistance heat a first radiator extending there between. The voltage applied to the first radiator is monitored by the microprocessor. 
     Infrared radiation is detected as it is emitted by the resistance heated first radiator, and particularly as the stream of air from the blower fan engulfs and cools the first radiator so as to reduce the infrared radiation emitted therefrom. A verification routine, similar to the sail switch function described above, acknowledges that the blower fan is operating properly, or alternatively that a malfunction has occurred. A gas valve is opened, under the control of the microprocessor, as the blower fan increases its air flow into the combustion chamber. The first radiator is heated for a period of two seconds, which is the desired amount of time to cause a hot surface ignition of the combustible gas mixture that is entering the combustion chamber. Another period of four seconds passes during which flames from the now ignited combustible gas heat the second radiator which is situated at the end of the longer of the two rods on the ignitor. 
     After a six second period has passed, infrared radiation is detected by the infrared sensor, where the infrared radiation is radiating from the second radiator. In the event that infrared radiation is insufficient, the microprocessor is signaled that an ignition has failed. In such case, the supply of gas to the combustion chamber will be shut off, and the blower fan will cause a purge of the combustion chamber for a period of 45 seconds. 
     The foregoing routine of blower fan operation, resistance heating of the first radiator, and attempt to detect infrared radiation coming from the second radiator will continue for a total of three cycles as the system repeats attempts to ignite the combustible fuel. Once combustion within a six second period is verified by IR detection from the second radiator, then a period of 45-50 seconds passes during which a proper infrared radiation level must be detected by the infrared sensor, or else the system will shut down the gas flow to the combustion chamber and will begin the foregoing retry attempts to ignite the combustible fuel. 
     Once ongoing combustion is established by sufficient detection of radiation by the infrared sensor, the thermostat is monitored to determine if a request for heat has been signaled. In the event that the thermostat is not requesting to heat, then the flow of gas to the combustion chamber will cease, combustion will cease, and the fire pot of the furnace will be purged by the blower fan for a period of 45 to 50 seconds. 
     In the event that the furnace becomes too hot, then an ECO switch in communication with the furnace will send a signal to the microprocessor to shut the power down to most of the system. Particularly, the gas valve is no longer electrically modulated and the flow of gas to the combustion chamber ceases. Upon such cessation of flow of gas to the combustion chamber, combustion also ceases. Upon such a thermal failure, a period of two and one-half minutes passes during which electrical power to the gas valve is monitored to determine if a cooling of the furnace has occurred which is signified by power being applied to the gas valve. In the event that a cooling has transpired, then the ignition routine described above will take place. 
     FIG. 7 shows at step 17 a routine titled &#34;IGNITION&#34;. This routine includes most basic operations of the inventive ignition and combustion control system for the method of controlling the gas fired furnace. This routine is further expanded in FIGS. 15a-15h. FIGS. 15a-15h reveal that step 17 seen in FIGS. 7 calls for a variety of other routines for the purpose of accomplishing the basic functions of the ignition and combustion and control method for the gas fired furnace. 
     The remains of FIGS. 8 through 19 will now be briefly discussed in perspective to the overall operation of the furnace. 
     The flow chart seen in FIG. 8 essentially monitors infrared radiation detected by the infrared sensor by reading the voltage therefrom. 
     In FIG. 9, a maintenance routine performs a series of steps necessary for the modulation of a valve controlling the flow of fuel gas to the furnace combustion area. 
     In FIG. 10, a routine performs a series of steps necessary for controlling the blower fan to the furnace. 
     In FIG. 11, high and low speeds of the blower fan are controlled given a variety of operation conditions. 
     In FIG. 12, verification of the presence of the flame is determined as well as a utility performed for determining if the furnace is overheating. 
     FIG. 13 monitors the overall system to determine if a malfunction has occurred and will initiate visual alarms in the event of an operational malfunction. 
     FIG. 14 shows steps to perform the sail switch function, as described above, in which a decrease in infrared radiation is detected from the first radiator as a flow of air engulfs the first radiator during the electrical resistance heating thereof to determine that an adequate flow of air is entering the furnace combustion chamber. Appropriate flags are set in the event that insufficient air supply is reaching the combustion chamber as determined by the detection of infrared radiation and predetermined standards for proper infrared radiation in application specific circumstances. 
     FIGS. 15A-15H graphically depict steps performed by the inventive method controlling most basic functions of the furnace. Particularly, monitoring of infrared radiation between predetermined low and high levels form the basic routine enacted by the depicted program steps titled &#34;IGNITION&#34;. 
     In FIG. 16, a routine is graphically depicted for reading the voltage applied to the first radiator, which is the ignition coil for igniting the combustible gas in the combustion chamber of the furnace. By monitoring the voltage applied to the ignition coil, it may be determined whether the ignition coil is inoperable due to structural failure, or whether it is being heated properly to a temperature necessary for hot surface ignition of the combustible fuel in the combustion area of the furnace. 
     FIG. 17 graphically depicts a routine for reading the voltage applied to the motor of the blower fan so as to monitor the operation thereof. 
     FIG. 18 is a routine for modulation of the voltage of the ignition coil to determine and to verify, in addition to other routines set forth elsewhere, whether the ignition coil is of sufficient temperature for hot surface ignition of the combustible fuel. 
     FIG. 19 is a routine for modulating the infrared level detected by the infrared sensor, and for regulating the voltage applied to the ignition coil, while also comparing the detected infrared radiation from the first radiator to a predetermined standard for such radiation maintained in a data memory storage area associated with the microprocessor. 
     The figures depicting flowcharts may be further understood by referencing their calling routines, by the source code routines of like-title in Appendix A, by the flow chart step descriptions in Appendix B, or by the general descriptions for the system and method of the present invention set forth herein. 
     It will be appreciated that the microprocessor 92 of FIG. 4, or the digital processor IC1 of FIG. 5 which is identified as a 16C71 microprocessor, could be programmed so as to implement the above-described method using any one of a variety of different programming languages and programming techniques. 
     The method of the present invention is carried out under the control of a program resident in the 16C71 microcomputer and associated circuitry. Those skilled in the art, using the information given herein, will readily be able to assemble the necessary hardware, either by purchasing it off-the-shelf or by fabricating it and properly programming the microprocessor in either a low level or a high level programming language. While it is desirable to utilize clock rates that are as high as possible, and as many bits as possible in the incorporated A/D converters, the application of the embodiment and economic considerations will allow one skilled in the art to choose appropriate hardware for interfacing the microprocessor with the remainder of the embodiment. Also, it should be understood that for reasons of simplifying the diagrams, power supply connections, as well as other necessary structures, are not explicitly shown in the figures, but are provided in actuality using conventional techniques and apparatus. 
     
                       TABLE I                                                     
______________________________________                                    
IGNITOR PARTS LIST                                                        
______________________________________                                    
DESCRIPTION   DEVICE          QUANTITY                                    
______________________________________                                    
SHOULDER      KEYSTONE PART   1                                           
WASHER                                                                    
SPACER        KEYSTONE PART   1                                           
LOCK RING     AU-VE-CO PART   1                                           
METAL BRACKET                 1                                           
MICA INSULATOR                                                            
              KEYSTONE PART   1                                           
SPADE LUG SMALL                                                           
              KEYSTONE PART   1                                           
SPADE LUG     KEYSTONE PART   2                                           
CIRCUIT BOARD                 1                                           
PIN DIODE IR  SHARP PD410P1   1                                           
NUT           6-32            4                                           
KANTHAL ROD   GA.127          2                                           
KANTHAL WIRE  GA.0142         2                                           
LOCK WASHER   ARDEN FASTENER  2                                           
______________________________________                                    
 
    
     
                       TABLE II                                                    
______________________________________                                    
FURNACE CONTROLLER PARTS LIST                                             
DESCRIPTION    DEVICE      QUANTITY                                       
______________________________________                                    
POWER MOSFET   1RFZ40      1                                              
POWER DIODE    MUR1520     1                                              
VOLTAGE        7805CT      1                                              
REGULATOR +5                                                              
DARLINGTON     TIP117      2                                              
TRANSISTOR                                                                
P-MOSFET       IRF9Z30     1                                              
N-MOSFET       IRF530      1                                              
FET            IRF020      1                                              
HIGH SIDE      MIC5014     1                                              
DRIVER                                                                    
N-FET          2N7000      2                                              
N-TRANSISTOR   2N4401      6                                              
P-TRANSISTOR   2N4403      1                                              
MICROPROCESSOR PIC16C71    1                                              
CAPACITOR      330 uF 25 V 3                                              
LOW IMPEDANCE                                                             
CAPACITOR      10 uF 50 V  1                                              
CAPACITOR      1 uF 50 V   3                                              
CAPACITOR      .1 uF       6                                              
RESONATOR      KBR4.00MKST 1                                              
DIODE          1N4002      12                                             
ZENER DIODE    IN5226      1                                              
RESISTOR       10M OHM     1                                              
RESISTOR       200K OHM    2                                              
RESISTOR       100K OHM    1                                              
RESISTOR       91K OHM     1                                              
RESISTOR       51K OHM     2                                              
RESISTOR       10K OHM     19                                             
RESISTOR       5.1K OHM    3                                              
RESISTOR       2K OHM      1                                              
RESISTOR       1K OHM      1                                              
RESISTOR       510 OHM     1                                              
LED            MAA3368S    1                                              
MINI-FIT       39-29-1188  1                                              
CONNECTOR                                                                 
MINI-FIT       39-01-2180  1                                              
CONNECTOR                                                                 
MINI-FIT       39-00-0060  18                                             
CONNECTOR PINS                                                            
CIRCUIT BOARD              1                                              
STAND OFF                  4                                              
CONFORMAL                  1                                              
COATING                                                                   
ALUMINUM                   1                                              
BRACKET                                                                   
BOLT #4-40     F581M       4                                              
NUT #4-40      F557M       3                                              
MICA-INSULATOR 242-4672    3                                              
SHOULDER                   3                                              
WASHER                                                                    
______________________________________                                    
 ##SPC1##