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Flue Gas Spillage Switch & Combustion Air / Backdrafting Test Procedures
Manufacturers' recommended test steps for flue spillage sensors & for inadequate combustion air
- POST a QUESTION or COMMENT about how to test flue gas spill sensors & how to test for backdrafting or inadequate combustion air in buildings
Test procedures for flue gas spill switches and for combustion air adequacy or backdrafting at gas or oil fired heating equipment.
Adapting information from flue gas spillage sensor manufacturers we expand on that advice with practical warnings to give first a Flue Gas Spillage 6-Step Safety Interlock Test and next a 6-Step Combustion Air Test or Backdrafting Test for Oil or Gas Fired Heating Equipment.
Adjustments and opinions are offered about more or less aggressive test procedures and at the article's references section we include authoritative research on flue gas spillage devices, their designs and operations, and on NFPA, ANSI, ASHRAE and other standards for heating appliance combustion air requirements.
In this article series we explain the installation, function, & troubleshooting Flue Gas Spill Switches and we provide a Guide to inspecting Furnace or Boiler Flue Gas Spill Switches on gas fired equipment such as heating boilers, warm air furnaces, water heaters.
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Safety Tests for a Flue Gas Spillage Switch Detector & for Inadequate Combustion Air in Buildings
[Click to enlarge any image]
Watch out: the tests described in this section are adapted from advice from equipment manufacturers, may not fit your equipment or building, and in any event are intended for performance by a trained heating or chimney service technician. These are not tests that we recommend for performance by a homeowner nor by a home inspector.
Watch out: messing with or testing this or any safety device may involve serious life safety hazards, and flue gas spill switch test procedures that we have reviewed (mostly the same procedure copied among websites) is dangerous as we will elaborate below. Check with the installation and testing specifications provided by the manufacturer of the particular flue gas spillage safety switch that you have installed.
Flue Gas Spillage 6-Step Safety Interlock Test
The following flue gas spill switch safety interlock test is adapted, illustrated, and expanded (with comments) from a procedure described by Tjernlund and is one we've seen replicated at various websites. This procedure is found in 24SP200 Safety Interlock System (P/N 950-2420) [Installation & Operating Instructions] retrieved 25 Jan 2015, original source given atReferences or Citations
- Turn on the fuel supply (gas or oil) to the heating appliance
- Remove the flue vent connector from the vent breeching at the joint immediately above the flue gas spillage sensor devices.
Note that this will normally be the flue vent connector joint immediately above the draft hood on gas fired appliances that use a flue-vent draft hood or on the small draft hood found on gas fired water heaters.
This procedure does not apply to gas fired appliances such as some furnaces that incorporate a draft opening into the body of the furnace. - Block the flue vent connector with sheet metal or other non-combustible material.
We have used a piece of fiber cement shingle siding which had the advantage of a little weight to keep it in place. You do not have to block or seal 100% of the opening, the flat sheet metal or FC siding will close the opening adequately to cause plenty of flue gas spillage. - Set the thermostat to cause the heating appliance burner to ignite. This may mean setting the room thermostat for a furnace or boiler to well above room temperature or for a gas fired water heater, either setting up the thermostat or simply running enough hot water to cause the water heater to fire. As Tjernlund points out,
Flue gas spillage will emit around the draft hood, draft diverter, or on oil fired heating equipment, around the flapper opening of the draft regulator or barometric damper.
Successful fuel gas spillage sensor switch test result: in less than two minutes (for most equipment) hot flue gases spilling at the draft hood/diverter will cause the flue gas spill sensor to open, shutting off the heating appliance.
Different types of flue gas sensor switches may take different approaches to shutting down the heating appliance such as opening the thermostat circuit (stopping the call for heat) or closing a gas supply valve (stopping fuel supply to the burner).
Watch Out: Failure of the flue gas spillage sensor test result if the flue gas sensor switches do not "open" to turn off the heating appliance check for flue vent pipe leaks and seal them if necessary.
It should be sufficient to trip the sensor switch if you feel hot flue gases spilling out at the draft hood or draft diverter or barometric damper for two minutes or longer.
If after 2 minutes (or in our opinion 2-4 minutes depending on the sensor switch specifications) of continuous burner firing and gas spillage, if the sensor has not opened to shut down the heating appliance the switch or its wiring is defective and the heating system is unsafe. - Re-set the flue gas spillage switch:
Following a successful flue gas spillage sensor test, turn off the heating system by setting the thermostat to below room temperature, turning off hot water (for a water heater) etc. Then wait 2-3 minutes to allow the flue gas spill sensor switch to cool down, then pus the spill switch re-set button.
The button should "click" in place and should remain depressed. If you press the button too soon and the sensor is still hot the switch may not reset. - Re-connect the flue vent connector to the rest of the venting system and chimney. While you're at it be sure that the connections are properly secured (sheet metal screws may be needed) and are properly connected.
Watch out: you can be burned touching hot flue venting system components
See FLUE VENT CONNECTORS, HEATING EQUIPMENT
When you have restored the system to proper operation don't forget to set your thermostat to its normal position or program.
6-Step Combustion Air Test or Backdrafting Test for Oil or Gas Fired Heating Equipment
Watch out: The following flue gas spill switch safety interlock test is intended to provide a chance of detecting inadequate combustion air supply in buildings that may be affected by ventilation systems, exhaust fans, clothes dryer and similar devices. This is not a comprehensive test for backdrafting hazards as performing the test at any given time cannot possibly represent all building conditions, weather conditions, or building occupancy conditions or activities that can significantly affect the building air pressure and combustion air supply.
This procedure is adapted and expanded (with comments) from a procedure described by Tjernlund and is one we've seen replicated at various websites.
This procedure is found in 24SP200 Safety Interlock System (P/N 950-2420) [Installation & Operating Instructions]
Warning from Tjernlund:
The 24SP200 Flue Gas Spillage Sensing Kit is designed to alert the user to a potentially hazardous condition. It is not designed to and cannot replace regular chimney inspection, appliance servicing, and combustion testing. Do not use the 24SP200 as a substitute for professional appliance maintenance.
- Set up tight or closed building conditions by closing all doors and windows of the building. Close any fireplace dampers in the building. Tjernlund also advises that if the heating appliance is in a utility room or closet you should close the entrance door to this room.
Watch out: OPINION: while closing the utility room door of a small utility room will often so drastically reduce combustion air as to cause improper and unsafe heating equipment operation, if the utility room is quite large, closing a door between this room and the rest of the building may actually reduce the impact of operation of building exhaust fans and vents which otherwise can also cause inadequate combustion air and backdrafting. In this situation you may want to conduct this combustion air test or backdrafting test in both conditions: with the utility room door open and with it shut. - Turn on exhaust fans and appliances that exhaust indoor air to the outdoors. These include bathroom exhaust fans, kitchen exhaust fans and range hoods, whole house exhaust fans, and other one-way fans that blow building air outdoors. Place all of these exhaust fans at their maximum speed.
See VENTILATION, EXHAUST ONLY
Watch out: OPINION: Tjernlund advises that you should not operate an exhaust fan that is used strictly for summer exhausting, such as a whole house vent fan or attic exhaust fan used only in summer. I'm not sure we agree in all cases. For example if you are testing a gas or oil fired heating appliance that in fact does run during summer months, such as a domestic water heater, a tankless water heater, or a gas-fired cooling system, you may indeed want to see what happens when the whole house fan is running.
Also note that the same backdrafting problems that these exhaust fans may cause for heating equipment can also subvert radon mitigation systems if one of those is installed in your building.
See RADON REMOVAL INDOORS, HOW-TO - Set the heating appliance thermostat to cause the appliance to operate continuously.
Watch Out: OPINION: even if you are only testing the flue gas spillage device on one heating appliance, you may want to turn on all of the fuel-fired heating appliances in the building. Having all of the appliances running at once maximizes the venting of indoor air caused by those devices and may detect interference among heating devices when they run simultaneously. - Wait 5 minutes, allowing all of the exhaust fans and heating appliances to run continuously during this test interval.
- Watch OutFailure of the Combustion Air & Backdrafting Test: if the spillage sensing device trips off, shutting down the appliance that it is intended to protect during this 5 minute interval not only is the spill detector switch working as it should, you have detected an unsafe building condition that can cause improper heating appliance operation and the production of potentially dangerous, even fatal carbon monoxide as well as other indoor air contaminants. In this case you should leave the unsafe heating appliance(s) off pending thorough diagnosis and repair by a trained professional.
Successful (no problem found) Completion of the Combustion Air & Backdrafting Test: interestingly the Tjernlund instructions do not describe a "successful" backdrafting or combustion air test.
OPINION: this omission may be because the company (and we) warn that this test and these safety devices cannot possibly detect all possible unsafe conditions. There are numerous possible chimney defects, for example, that are unsafe but that may not show up just by the test procedure described here. Additional chimney safety inspection procedures are described by articles in the ARTICLE INDEX.
One should argue the old saw that absence of evidence (of a safety hazard for example) is not evidence of absence (of the safety hazard). - Restore normal operation if no trouble was detected. Return all windows, doors, fans and heating appliances to their previous conditions of use.
...
Continue reading at CARBON MONOXIDE INSPECTION or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
Or see these
Recommended Articles
- BACKDRAFTING HEATING EQUIPMENT
- COMBUSTION AIR DEFECTS
- COMBUSTION AIR REQUIREMENTS
- CARBON MONOXIDE - CO
- CARBON MONOXIDE WARNINGS: HOME HEATERS
- GAS DETECTOR WARNINGS
- FLUE GAS SWITCH INSTALLATION & WIRING
- FLUE GAS SPILL SWITCH SOURCES & SELECTION
- FLUE GAS SPILL SWITCH TRIPPING & RESET
- FLUE SPILL SWITCH & COMBUSTION AIR TESTS
- THERMOCOUPLE REPAIR / REPLACEMENT
Suggested citation for this web page
SPILL SWITCH & COMBUSTION AIR TESTS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
Or see this
INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING SYSTEMS
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Citations & References
In addition to any citations in the article above, a full list is available on request.
- Field Controls, Gas Spillage Sensing Kit, Model: GSK-3, GSK-4, GSK-250M, [Installation & Operation Instructions], [PDF] Field Controls, 2630 Airport Road, Kingston NC 28504, USA, GEl: 252-522-3031, Website: www.fieldcontrols.com
- Tjernlund's Products, Inc., 24SP200 Safety Interlock System (P/N 950-2420) [Installation & Operating Instructions], [PDF] Tjernlund's Products, Inc., 1601 Ninth Street • White Bear Lake, MN 55110-6794 Tel: (800) 255-4208 Website: www.tjernlund.com.
- NFPA 54: National Fuel Gas Code (2015), addresses heating appliance combustion air ventilation specifications. NFPA 54, ANSI Z223.1 provides minimum safety requirements for the design and installation of fuel gas piping systems in homes and other buildings.
- NFPA 85: Boiler and Combustion Systems Hazards Code: NFPA 85 contributes to operating safety and prevents explosions and implosions in boilers with greater than 12.5 MMBTUH, pulverized fuel systems, and heat recovery steam generators.
- NFPA 87: Recommended Practice for Fluid Heaters, This recommended practice provides safety guidance for fluid heaters and related equipment to minimize fire and explosion hazards that can endanger the fluid heater, the building, or personnel
-
Research on Flue Gas Spillage Sensors
- Andersson, Mike, Ruth Pearce, and Anita Lloyd Spetz. "New generation SiC based field effect transistor gas sensors." Sensors and Actuators B: Chemical 179 (2013): 95-106.
Abstract: With the advances in SiC processing and high temperature packaging technology over the past few years as well as the accumulation of knowledge regarding the sensing characteristics of different gate metal/insulator material combinations for different gaseous substances SiC based field effect high temperature sensors are moving towards commercial maturity. The route towards commercialization has, however, also led to the necessity of making new considerations regarding the basic transducer design and operation. The focus of this paper is thus the investigation of some basic transducer related parameters’ influence on sensor device performance, e.g. sensitivity and long-term stability, and characteristics to exemplify the importance of taking design, processing and operation parameters into account when developing field effect sensor devices for commercial applications.
Two different types of devices, enhancement and depletion type MISFET sensors, with different gate dimensions and two different gate metallisations, Pt and Ir, have been processed. I/V-characteristics have been obtained under exposure to various concentrations of H2, NH3, CO and O2 and different bias conditions and the influence of gate dimensions and bias conditions on the sensitivity and dynamic range investigated. The long-term stability has also been studied and compared between different devices and bias conditions for conceptually different gas compositions. The results show that the type of basic transducer device, its design and mode of operation has a large influence on sensor performance. Depletion type devices offer better possibilities for tuning of sensitivity and dynamic range as well as improved long-term stability properties, whereas enhancement type devices require much less control of the processing to ensure good repeatability and yield. Some results have also been verified for two possible applications of SiC based field effect sensors, ammonia slip monitoring for the control of SCR/SNCR and combustion control in domestic/district heating facilities. - Andersson, Mike, and Anita Lloyd Spetz. "Detecting non-hydrogen containing species with field effect devices." In Sensors, 2008 IEEE, pp. 1320-1323. IEEE, 2008.
- Andersson, Mike, Helena Wingbrant, and A. Lloyd Spetz. "Study of the CO response of SiC based field effect gas sensors." In Sensors, 2005 IEEE, pp. 4-pp. IEEE, 2005.
Abstract: The response characteristics of SiC based field effect gas sensors towards varying CO and O2 concentrations over a wide temperature range and at atmospheric pressure has been studied in detail. Both thin, discontinuous as well as dense, homogeneous Pt films as the catalytic gate material in field effect transistor devices have been investigated and the results compared to CO oxidation characteristics over Pt/SiO2 catalysts as reported in literature. Based on the results a hypothesis regarding the mechanism behind CO sensitivity of field effect devices is put forward, also emphasizing the importance of increased sensitivity to background hydrogen - Carn, K. K., and P. C. Chatwin. "Variability and heavy gas dispersion." Journal of Hazardous Materials 11 (1985): 281-300.
- Eklund, Bart M., W. David Balfour, and Charles E. Schmidt. "Measurement of fugitive volatile organic emission rates." Environmental progress 4, no. 3 (1985): 199-202.
- Fukuchi, Tetsuo, and Tatsuo Shiina, eds. Industrial Applications of Laser Remote Sensing. Bentham Science, 2012.
- Hübner, Michael, Dorota Koziej, Jan-Dierk Grunwaldt, Udo Weimar, and Nicolae Barsan. "An Au clusters related spill-over sensitization mechanism in SnO 2-based gas sensors identified by operando HERFD-XAS, work function changes, DC resistance and catalytic conversion studies." Physical Chemistry Chemical Physics 14, no. 38 (2012): 13249-13254.
- Lundström, Ingemar, Hans Sundgren, Fredrik Winquist, Mats Eriksson, Christina Krantz-Rülcker, and Anita Lloyd-Spetz. "Twenty-five years of field effect gas sensor research in Linköping." Sensors and Actuators B: Chemical 121, no. 1 (2007): 247-262.
- Morgan, J. M., and J. D. Andrews. "Assessment of safety systems using fault tree analysis." (1984).
- Nagda, Niren L., Michael D. Koontz, Irwin H. Billick, Neil P. Leslie, and David W. Behrens. "Causes and consequences of backdrafting of vented gas appliances." Journal of the Air & Waste Management Association 46, no. 9 (1996): 838-846.
Abstract: House depressurization occurs when household equipment such as a kitchen or bathroom fan or a fireplace exhausts air from the house and lowers the pressure indoors with respect to the outside. The operation of air handlers for forced-air heating or cooling systems also can have a depressurization effect. This depressurization can hinder the natural draft from vented combustion appliances and lead to backdrafting, which in turn can result in combustion gases spilling into the indoor airspace. Extensive spillage can cause elevated indoor levels of combustion products such as carbon dioxide (CO2) and water vapor, as well as contaminants such as carbon monoxide (CO) and nitrogen dioxide (NO2).
The focus of this paper is to review studies on depressurization- induced backdrafting and spillage from gas-fired, drafthood equipped furnaces and domestic hot water heaters. Qualitative and quantitative techniques that were used in depressurization and backdrafting studies conducted in Canada, Europe, and the United States are analyzed. These studies have shown that exhaust fans operated simultaneously with fireplaces depressurize houses by 3 to 8 Pa on average. The CO indoor concentrations due to spillage, as reported in these studies, generally have been lower than 5 ppm. However, such low CO concentrations do not necessarily imply that a potential problem associated with backdrafting does not exist. Other combustion products, such as NO2, rarely have been measured in prior backdrafting studies.
It can be concluded from the literature review that causes of house depressurization are well understood. However, more comprehensive research is needed to better understand the frequency, duration, and severity of depressurization-induced spillage in a broad cross section of houses. Efforts in this direction have begun recently in the United States through a workshop to define research issues, pilot studies to develop comprehensive measurement protocols, and consensus standard development activities to prepare standardized methods and protocols. - Tooley, J. J., and Neil Moyer. "Mechanical air distribution and interacting relationships." In Symposium on Improving Building Systems in Hot and Humid Climates. Dallas, TX. 1989.
- Andersson, Mike, Ruth Pearce, and Anita Lloyd Spetz. "New generation SiC based field effect transistor gas sensors." Sensors and Actuators B: Chemical 179 (2013): 95-106.
Flue Gas Spill Detector Patent Research
- Barth, James T. "Damper construction for a gas fired combustion apparatus." U.S. Patent 4,289,271, issued September 15, 1981.
Abstract: A thermally controlled damper construction for a gas fired combustion apparatus such as a furnace or the like is described. A damper is pivotally mounted within the stack or flue of the combustion apparatus for pivotal movement from a closed position, wherein the damper is located at an acute angle with respect to the axis of the stack, to a full open position. One edge of the damper is recessed to provide a vent opening between the damper and the stack to permit the venting of gases generated by operation of the pilot light during periods when the furnace is not operating. The damper is pivotally moved between its closed and open positions by a bi-metallic thermally responsive element which is located upstream of the damper and which is connected to the damper by means of a linkage. The linkage includes means for permitting the unrestrained rotational movement of the bi-metallic element after the damper is in its position thereby preventing stressing of the thermally responsive element at high temperatures. An opening is formed in the stack upstream of the damper and substantially immediately below the recessed portion. A temperature responsive safety switch is positioned at the outside surface of the stack outwardly of the opening formed therein and is operably connected to the gas supply of the furnace. In the event the damper does not open when the furnace is operated or an improper draft is present, the products of combustion spill outwardly through the stack opening onto the temperature responsive safety switch thereby activating the same to terminate the gas supply to the furnace. - Berkhof, Hendrikus. "Control system for a gas heated water or air heater." U.S. Patent 4,436,506, issued March 13, 1984.
Abstract: In a control system for a gas heated water or air heater, the use of the supplied fuel gas is to be improved by automatically determining and supplying the amount of air which is required for obtaining complete combustion. A gas control valve feeds a burner with the required amount of gas dependent on the demand of heat. A sensor responding to the content of oxygen or carbon dioxide within the flue gases is located in the stack and the output signal of this sensor is compared with a set point within an electric controller. In case of a control deviation, the output signal of the controller controls an adjustable source of air under pressure formed by a fan with subsequent air control valve in such a manner that the required amount of air for reaching optimum combustion is supplied. - Birtch, Susan Leslie, and Donald Reginald Jamieson. "Draft hood locating device for combustion apparatus." U.S. Patent 5,752,500, issued May 19, 1998.
- Bourke, Brendan Vincent, Zoran Valcic, and Geoffrey Mervyn Whitford. "Ignition inhibiting gas water heater." U.S. Patent 6,138,613, issued October 31, 2000.
- Bourke, Brendan Vincent, Zoran Valcic, and Geoffrey Mervyn Whitford. "Ignition inhibiting gas water heater." U.S. Patent 5,797,355, issued August 25, 1998.
Abstract: A gas water heater including a water container adapted to be heated by a gas burner; and an enclosure surrounding the burner, the enclosure having at least one entryway adapted to allow air and fumes to enter the enclosure without igniting flammable gases or vapors outside of the enclosure. - Brandt, John H., Randall T. Meyer, and Bradley N. Plank. "Control system for a water heater." U.S. Patent RE37,745, issued June 18, 2002.
- Brandt, John H., Randall T. Meyer, and Bradley N. Plank. "Control system for a water heater." U.S. Patent 5,797,358, issued August 25, 1998.
Abstract: A multi-function controller for a water heater is advanced comprising a control panel and a plurality of sensors that monitor a variety of functions that impact the operation of a water heater. A flammable gas sensor, placed in proximity to the air intake, detects the presence of an unsafe concentration of gas and issues a signal to the control panel, which subsequently discontinues the operation of the burners. Detection of a blocked vent pipe is achieved by a carbon monoxide sensor placed near the draft hood. The control panel is equipped with circuitry which monitors usage of the heater for a specified time period to develop a pattern of use. Subsequent to the monitoring period, the controller will activate the burners a predetermined time prior to an anticipated period of high use. During periods of low use, the controller will decrease the temperature to which the water is to be heated, thereby resulting in a more efficient heater. Non-volatile memory records data from the sensors so that the operation status of the heater may be ascertained subsequent to a power outage. The control panel contains a plurality of visual alarms, each of which corresponds to a sensor. Consequently, repair and maintenance are simplified because the cause of a malfunction is quickly recognized. - Comuzie Jr, Franklin J. "Gas appliance detection apparatus." U.S. Patent 5,280,802, issued January 25, 1994.
Abstract: A first and second sensor and alarm member is mounted relative to a gas appliance, and more particularly to the diverter housing and adjacent a lower portion of the gas appliance for detection of spillage in the form of flue restriction relative to the first sensor or roll-out sensing relative to gas fumes backed up relative to the flame portion of the gas appliance. - DePalma, Thomas M. "Gas log fireplace system." U.S. Patent 5,575,274, issued November 19, 1996.
Abstract: A gas-fired, simulated log fireplace insert incorporating an automatic flue damper for controlling the operational state of a chimney vent (open/closed) in response to gas combustion, an externally mounted carbon monoxide detector for terminating or inhibiting gas combustion in response to an unsafe level of detected carbon monoxide and a temperature actuated switch, disposed within the firebox area of the fireplace proximate the flue, for terminating gas combustion in response to excessive fireplace temperatures caused by a malfunctioning damper. - DePalma, Thomas M. "Gas log fireplace system." U.S. Patent 5,503,550, issued April 2, 1996.
- Dolan, Pat. "Gas fired appliance safety device." (2002),
Abstract: A flammable vapor detector is used to detect flammable vapors in the event of a volatile organic liquid spill near a gas fired appliance, such as a hot water heater. The appliance is mounted at an elevation above the floor while the detector is mounted at or near the floor where the spill may occur. The detector is connected electrically to a safety gas cut-off solenoid valve in the appliance to urge the valve to cut-off the flow of gas to the appliance in the event that the detector detects flammable vapor. Because the detector is below elevation of the appliance, the detector reacts to higher concentrations of flammable vapors than the concentrations of flammable vapors at the higher elevation of the appliance to turn off the gas to the appliance before the combustion air to the appliance reaches a lower flammability limit. The appliance used to describe the invention is a gas fired hot water heater. - Guzorek, Steven E. "Apparatus and method for controlling a damper in a gas-fired appliance." U.S. Patent 8,113,823, issued February 14, 2012.
Abstract: A damper mechanism for a gas-fired appliance is disclosed. The damper mechanism is mechanically operated in response to changes in pressure within a portion of the appliance. Changes in gas pressure operate to displace a diaphragm, thereby moving a linkage attached to a flue damper, such that the damper can be moved between open and closed positions. An interim damper control activation arm can pivot in response to movement of the linkage to actuate electrical switches, which act to close a magnetic pilot valve when the damper is in a partially-opened or partially-closed position. - Guzorek, Steven. "Water heater with mechanical damper." U.S. Patent Application 10/672,401, filed September 26, 2003.
Abstract: A hot water heater comprises a valve control unit having a gas inlet, a pilot burner, a main burner and a damper assembly. The damper assembly has a pressure diaphragm, a gearing mechanism and a movable damper. The control unit being coupled to operatively supply gas to the pilot burner, the main burner and the damper assembly whereby when gas is supplied to the damper assembly, the pressure diaphragm is moved to thereby cause the gearing mechanism to move the damper from a first position to a second position. - Habegger, Millard A. "Method and apparatus for regulating flue draft." U.S. Patent 4,406,396, issued September 27, 1983.
Abstract: Method and apparatus for regulating the flue draft in heating systems including a combustion volume, a flue communicating with the combustion volume, and a vent opening between heated ambient air and the flue, the regulation being accomplished by sensing the flow of air through the vent into the flue, and modulating the setting of a downstream damper to maintain such flow at a predetermined, positive but minimal value. A particularly preferred embodiment includes a temperature sensor positioned at the flue side of the vent and connected to a control system to maintain the damper at such a position that the temperature at such location is at a predetermined value above that of the ambient air temperature, and thus indicative of flow of ambient air into the flue at minimal values approaching incipient spillage of combustion gases at the vent. - Hu, Ke Ren. "Automatic security gas holding device fitted in an igniter." U.S. Patent 6,135,762, issued October 24, 2000.
- Joumas, George E., and Edward R. Kmetz. "Safety control for furnace burner." U.S. Patent 4,204,833, issued May 27, 1980.
Abstract: A burner cut-out safety control for a combustion heating device having an automatic exhaust flue damper. The safety controls act to discontinue burner operation in the event the damper actuator device or controls fail, or other flue blockage causes products of combustion to be exhausted through the draft diverter inlet opening. The control is integrated with an existing burner pilot safety circuit and pilot valve to cause the pilot valve to be closed in the event combustion gases begin to pass out of the flue through the draft diverter inlet opening, this condition being detected by a lineal temperature sensor extending about the draft diverter inlet opening, which senses combustion gas spillage by the resultant heating of any portion of the lineal temperature sensor. The lineal temperature sensor is placed in series with the pilot burner ignition temperature sensor to cause closing of the pilot valve, located ahead of the main gas valve activated by the burner controls during normal automatic operation of the burner. The fuel supply is thus cut off even if the main gas valve fails. A second temperature sensor is located in the plenum of the warm air ducting as a secondary safety control feature also acting to cause the pilot valve to close in the event of an excessive temperature being sensed in the warm air plenum. - Meeker, John. "Atmospheric gas burner and control system." U.S. Patent 5,391,074, issued February 21, 1995.
Abstract: A gas and solid fuel burning chamber is provided with a control system for the safe and efficient operation of a gas burner. The simple control system uses multiple thermocouples in series to permit the safe operation of the gas burner in a vented device without the need for a draft hood. A combination of gas and solid fuel is demonstrated where gas can be used to start the solid or as an independent source of heat. The control system comprises generally of thermocouples for measuring the flame temperature, the combusted gas temperature and the overall chamber internal temperature and producing signals to regulate the flow of fuel to the gas burner in response thereto. - Monette, Michael. "Detection of exhaust gas spillage from naturally aspirated gas furnaces and naturally aspirated gas hot water heaters." U.S. Patent 4,751,912, issued June 21, 1988.
Abstract: A device for detecting the diversion of gas furnace or gas hot water heater exhaust into a dwelling due to chimney backdrafting detects a sustained rise in the temperature of the gases passing through the draft-diverter orifice. A significant rise in temperature indicates that the above condition has occurred. This temperature rise is recorded only after the condition has persisted for a sufficiently long period of time, thereby avoiding the recording of temporary backdrafting conditions which are not required to be recorded. The device consists of a high temperature resistant plastic strip or other material with similar conductivity and specific heat qualities with a temperature sensitive color-change material mounted on the surface of the plastic strip at one end of the strip. This strip is attached to the furnace or gas hot water heater in a preferred location with the color-change material facing away from the normal flow of backdrafting exhaust gases. Heat from the backdrafting flow causes the color-change material to change color once the heat in the gas flow has penetrated through the underlying plastic strip. An aerodynamic stagnation zone on the front face of the plastic strip during a backdraft condition prevents the color-change material from changing color prematurely. - Penrose, William R., Joseph R. Stetter, and Solomon Zaromb. "Sensor array for toxic gas detection." U.S. Patent 4,670,405, issued June 2, 1987.
Abstract: A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas from a pattern of electrical responses, a source of standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display. The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components. - Silverton, Ernest G. "Safety control for gas stoves." U.S. Patent 2,563,944, issued August 14, 1951.
Abstract:
The object of the invention is to provide electrically operated means operable in response to failure of any gas burner or pilot light for such burner to shut off the main supply valve to the gas stove to which the device is fitted.
In gas stoves where pilot lights are'provided, it has occurred that a liquid from a pan has been spilled or has boiled over the pan onto the burner immediately below and said liquid has plugged many' of the gas burner' jets within the range of the pilot, preventing said pilot from igniting the burner with the result that gas continues to flow from the orifices unaiiected by the-over, flowing liquid and a dangerous explosion has followed, being set off by the pilot light or another lighted burner. With the device as now proposed, the gas is shut off almost immediately after the spilling had taken place and continued gas flow is prevented. - Smith, Donald L. "Venting system for oil or gas-fired appliances." U.S. Patent 4,373,510, issued February 15, 1983.
Abstract: A venting system for the combustion chamber of an oil or gas-fired heating appliance has an elongate diverter box arranged vertically exteriorly of the heating appliance. Such diverter box has an upper end tightly closed off by an insulated imperforate cover and a relief open lower end closed for safety by a perforate grill in which a safety spill switch is mounted. The interior of the diverter box houses a vertically disposed centrally arranged insulated baffle having an upper end in fume tight engagement with cover and a lower free end terminating substantially above the grill. The baffle divides the box into a flue gas inlet section that is connected at the upper portion of the box to the appliance and a vent gas outlet section that is connected at the upper portion of the box to the chimney flue. The inlet section has a turning vane provided on the end wall just below the lower free end of the center baffle. During the burn cycle, the flue gases from the flue outlet of the appliance enter into the upper end portion of the inlet section on one side of the center baffle and travel downward to the lower free end of the baffle before entering the vent outlet section to travel on out the chimney flue. - Smith, Donald Leon. "Venting system for a gas-fired heating plant." U.S. Patent 4,079,727, issued March 21, 1978. Abstract: A venting system for the combustion chamber of a gas-fired heating plant has an elongate diverter box arranged vertically of the heating plant exteriorly thereof and having an upper portion and a lower portion with the latter having a bottom provided with a substantial opening disposed well above the base of the heating plant for the free admission of atmospheric air surrounding the heating plant into the diverter box and with the upper portion having selected openings for the reception of horizontally disposed pipings from the flue outlet for the combustion chamber and for the chimney flue with a vertical baffle depending from the closed top of the upper portion a substantial vertical extent into the diverter box and dividing it into a flue outlet section and a chimney flue section with said sections having thermostat means to indicate exteriorly of the sections the temperature of the gases therein and with a safety limit switch housed in the flue outlet section below the lower free end of the baffle and being protected by a barrier plate from cold down drafts from the chimney flue.
- Smith, Donald L. "Venting system for a gas-fired heating plant." U.S. Patent 4,009,705, issued March 1, 1977.
- Barth, James T. "Damper construction for a gas fired combustion apparatus." U.S. Patent 4,289,271, issued September 15, 1981.
- Field Controls provides instructions for the installation of LP and Natural Gas spill sensor switches, for example for their Gas Spillage Sensing Kit Model GSK-3, GSK-4, GSK-250M switches. Contact your heating service technician directly, or contact Field controls at fieldcontrols.com for more information. These switch models include a manual reset switch. Field Controls, Kingston NC 28504 - Tel 252-522-3031.
- Tjernlund Products provides instructions for the installation and use of their controls, including the WHKE Millivolt Interlock Kit for use with their UC1 Universal Control, MAC1E or MAC4E auxiliary controls for gas fired equipment. Contact Tjernlund Products at tjernlund.com or at 800-255-4208.
- National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
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