Abstract: An improved power vent and associated control system for a heating apparatus such as a furnace. The invention utilizes a vent blower and a flow control orifice device permitting the use of a single size air moving device and motor with different size furnaces. The control is arranged to discontinue delivery of fuel to the furnace in the event of a blockage of the furnace flue or a failure of the air moving structure. In one form of the invention, a pressure condition is sensed downstream of the air moving structure to detect the failure conditions. In another form of the invention, the control utilizes structure to sense the speed of the air moving device. The invention comprehends the use of a motor for driving the air moving device which varies in speed substantially between the unloaded and loaded conditions. The air moving device preferably unloads under high discharge pressure conditions, such as by a blocked flue.

Abstract: A flame rod inserted in a flame created by the secondary air supplied to a burner is used to generate a flame signal voltage. This flame signal voltage fluctuates with the amount of secondary air available and with the fuel supplied. These fluctuations are relied upon by an integrated control system that utilizes a microprocessor or microcomputer to safely control an induced draft-type of furnace.

Abstract: A combined microwave and electric heater oven includes a fan system for cooling a magnetron, and a damper for selectively introducing a forced air flow generated by the fan system into an oven cavity. A damper cam is secured to a drive shaft of a damper motor, and a damper link is disposed between the damper cam and the damper to drive the damper. A microswitch is disposed near the damper cam so that the microswitch develops a first detection signal when the damper is tightly closed. In response to the first detection signal, the rotation of the damper motor is terminated to hold the damper in the tightly closed state. The microswitch develops a second detection signal when the damper is placed in the full-open state. In response to the second detection signal, the rotation of the damper motor is terminated to hold the damper in the full-open state.

Abstract: A draft control system for furnaces comprises an auxiliary channel in communication both with ambient air and the flue of the furnace, a main draft control means for regulating the entrance of ambient, auxiliary draft air into the flue, and auxiliary draft control means mounted in the auxiliary channel for dampening the effect of extreme changes in external conditions on the main draft control means. Thus, uniform draft and efficient combustion is maintained in the furnace under a wide variety of conditions. The main draft control means comprises counter-balanced draft control plates which are initially set in an open position so that they can either open or close in order to efficiently regulate the draft in the flue. The auxiliary draft control means comprises, in one embodiment, an isolation damper plate rotationally mounted in the auxiliary channel, or, in a second embodiment, a set of louvred panels.

Abstract: A furnace stack damper control apparatus has a motor for connection to a stack damper to open the damper upon a call for heat by a space thermostat. The motor is driven in a closed direction by electrical energization and in an open direction by a spring return. A relay having two normally open switches and a normally closed switch is energized when a space thermostat calls for heat. The normally closed switch then opens to allow the damper motor to open the damper by the spring return. The motor has an end switch having a normally open and a normally closed circuit. The normally open circuit is used with one of the normally open switches of the relay to energize a gas valve when the damper is open. The normally closed end switch is used to provide the energization circuit for the relay by the space thermostat and the relay is maintained energized when the damper is open by the other normally open switch of the relay connected in parallel to the normally closed end switch.

Abstract: An improved boiler purge control in which purging air is forced into the boiler only after the damper is substantially in its high fire position.

Abstract: An interior building area containing at least one combustion type heating appliance is equipped with a combustion air inlet having an openable and closable damper operatively associated therewith. The damper is weighted for gravity closing and is suspended from a swinging pivot in a manner to assure a substantially airtight closure for the combustion air inlet. In addition, actuator structure is provided for each combustion-type heating appliance within the interior building area and operatively associated with the damper for moving the latter to an open position responsive to operation of at least one of the heating appliances.

Abstract: An integrated control system for a temperature conditioning apparatus which contains a microprocessor which is connected to the various components of a control system of the temperature conditioning apparatus such as the space thermostat, the fuel valve, the fuel igniter and ignition proving apparatus, the stack temperature sensor, the ambient or vestibule temperature sensor, the plenum temperature sensor, the induced draft blower motor, the refrigeration compressor, and the air circulating fan or blower. With the microprocessor, which has the capability of fast and many types of operations, the interaction of parameters of the temperature conditioning apparatus and operation of the various components of the system can be controlled in an improved manner to add to the overall efficiency of such a temperature conditioning apparatus.

Abstract: This disclosure relates to a flue damper control including an automatic control and a manual override for use in the event of failure of certain parts. The control includes a first lever means connected to the damper for opening and closing the damper. An electric solenoid is connected in circuit with a furnace thermostat, and the solenoid is coupled by spring means to the first lever means. In automatic operation, when the thermostat calls for heat, the solenoid armature moves, and the first lever means is operated by the spring means coupling to move the damper to the open position. A return spring moves the damper to the closed position when the thermostat no longer calls for heat. The control further includes a first switch connected in circuit with a fuel control valve, which is actuated by the first switch means as it opens the damper.

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.

Abstract: In the event of a malfunction of the unit, the damper plate may be moved to and locked in the open position, to permit the furnace to operate. With the plate locked, the motor would normally run continuously, even when the furnace was not operating. This is because the closed position of the plate, necessary to turn off the motor, cannot be reached. A slip clutch, located between the motor shaft and the plate, has parts which slip relative to each other when the motor is running but the plate is locked. The contours and biasing of the parts causes one part to move a limited distance, in a direction opposite to normal. The motor is stopped in response to this oppositely directed movement.A bent portion of the plate positioning shaft is freely received in a recess elongated in and laterally spaced from the motor shaft for self-alignment and to permit the oppositely directed movement necessary to stop the motor.

Abstract: The system includes a damper plate equipped with a draft controller or sensing switch and a motor for positioning the damper plate to control the furnace draft. Upon generation of a call-for-heat signal, an initialization signal drives the damper off its closed position. From then on, draft must be sensed by the draft controller switch to complete the cycle to open the damper plate. When the damper plate is fully opened, a fuel and ignition control circuit is energized to supply fuel to the furnace, and an electronic timer is energized to generate a signal which establishes a trial-for-draft period. When the fuel is ignited, the draft will increase and energize the motor to move the damper plate off the fully open position during the trial-for-draft period, and thereafter, the position of the damper plate is controlled by the draft controller switch to achieve a proper draft within design range.

Abstract: Apparatus is provided for modifying an open draft hood furnace and its control system, to produce an induced draft furnace having increased efficiency. A blower located in the furnace exhaust stack is used to induce movement of air and combustion products into and through the draft hood. A flow-limiting orifice located in the exhaust stack upstream from the blower causes a region of reduced pressure to exist downstream from the orifice. A pressure signal representative of the flow rate of exhaust stack gases is sensed on the downstream side of the orifice and is communicated by a conduit to a pressure switch connected to a gas valve, which together control gas to the burner. No gas is permitted to flow to the burner unless a predetermined reduced pressure level is achieved at the downstream side of the orifice. A small opening in the conduit permits a small flow of flushing air to enter the conduit.

Abstract: A control system for regulating exhaust gas pressure in a furnace smokestack by means of three power cylinder actuated butterfly valves in the smokestack opening. An electronic control circuit provides digital output signals, which operate spool valve devices via which a hydraulic fluid circuit is established to control the power cylinders. In a trim mode control circuit, a first comparator senses a difference between the actual stack pressure and a desired pressure. The comparator output is converted by an analog to digital section to provide the digital output signals for control of a single butterfly valve. A rangefinder mode control circuit includes a second comparator that senses an output from the first comparator in excess of a predetermined value.

Abstract: An induced draft combustion apparatus and its associated control system has a blower located in the exhaust stack or vent which is used to induce the movement of air and combustion products into, through and out of the combustion chamber. A flow-restricting orifice in the exhaust stack near the blower causes a region of higher pressure to exist upstream from the orifice with a region of lower pressure downstream from the orifice. An exhaust gas pressure signal representative of the exhaust gas volume flow rate is sensed on one side of the orifice and is fed back to a modulating gas valve which controls the outlet gas flow from the valve to be proportional to the magnitude of the exhaust gas volume flow rate. By controlling blower speeds and exhaust gas volume flow capacities as related to a selected orifice size, various firing rates for the furnace can be selected, from the design maximum down to various derated levels.

Abstract: A heating system of the type having a combustion chamber with a fuel burner, an inlet for combustion air and an exhaust stack is improved by adding a variable-speed induced draft blower, a flow-restricting stack orifice and a fuel valve sensitive to the exhaust gas flow rate through the stack orifice. The fuel valve turns on at a first predetermined exhaust gas flow rate and turns off at a second predetermined exhaust gas flow rate, which is lower than the first predetermined rate. The fuel valve also supplies fuel at a rate proportional to the exhaust gas flow rate. Sensing of the differential pressure across the stack orifice is used to determine the exhaust gas flow rate.

Abstract: A microprocessor based controller for regulating the position of a stack damper in a combustion furnace by feedback control adjusting damper position in view of an operator input target value of excess oxygen and an actual monitored excess oxygen value. A feedforward control overrides the feedback control for a time period initiated by the feedforward control responding to process variables indicating increase in combustion demand.

Abstract: A control circuit for a fuel supply and ignition control system controls the operation of pilot and main valves of the system and of a motor which controls the positioning of a vent stack damper plate to normally close the vent stack and to open the vent stack at the start of each ignition cycle. At the start of each ignition cycle, a start relay is operated to energize the pilot valve and a spark generator for a trial for ignition interval defined by the excursion time of the damper plate as it is driven to the open position. When the pilot fuel is ignited, a flame sensing circuit operates a flame relay which completes a holding path for the pilot valve and when the damper plate reaches the fully open position, limit switches connect the main valve to the holding path and deenergize the drive motor and the start relay.

Abstract: An automatic vent damper and fuel valve control for a fluid fuel-fired furnace including an electrically-operated valve in the fuel line, a normally-open damper in the furnace vent having electrically-operated means for closing the damper, and a thermostat for sensing the temperature in the space being heated. A Hall-effect generator is employed for sensing the positions of the damper and for respectively providing signals in response thereto. A gas detector is provided for sensing the presence of hydrocarbon-containing gas in the region of the draft hood and vent of the furnace and for providing a gas-present signal in response thereto. A control is provided for the valve responsive to both the damper-open signal and the thermostat calling for heat to energize the valve to open the same, the valve control de-energizing the valve to close the same in response to the thermostat calling for termination of heating, or the damper-closed signal, or the gas-present signal.

Abstract: A control circuit for gas fired burners and the like such as are employed in commercial laundry fabric ironers requiring the energization of a blower motor and the resulting opening of a gas valve and ignition of a gas burner only after an air pressure sensitive switch is actuated through the operation of the blower motor for purging the system of combustible gases.

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.

Abstract: This device provides a means of automatically detecting smoke in a room, through an ionization chamber, prior to it being noticed by humans. It consists primarily of an automatic control unit, which through a small servomotor will open the fireplace damper in step fashion, or close it to conserve heat. It further includes a manual over-ride switch for use when desired.

Abstract: An automatic damper control comprising: damper means for use in a flue or the like; diaphragm means adapted to expand and contract in response to pressure variations in the flue; and sensor means for sensing the pressure in the flue. The sensor means is connected to the diaphragm means and comprises means for generating a plurality of beams of light. The sensor means further comprises collimating means adapted to collimate each of the beams of light onto a photoreceptor. The damper control also comprises blocking means for blocking at least one of the beams of light. The blocking means is operatively associated with the diaphragm means and is adapted to be displaced relative to the beams of light in response to movement by the diaphragm means. Drive means are additionally provided for moving the damper means in response to pressure variations in the flue.

Abstract: A housing structure with a single pivoted damper member is provided as a replacement for the draft hood associated respectively with the flue outlet and vent pipe inlet in a gas heater system. The normal flue outlet for the gas system connects to a first passage in the housing and the normal overhead vent inlet connects to a second passage in the housing above the first passage. First ends of the passages adjacent to their connections to the flue outlet and vent pipe inlet are closed off and second ends open out in a common plane. Communicating with the second ends is an ambient atmosphere opening so that under conditions where the second ends of the passages are open, proper exhausting of gases passing up through the flue to the vent takes place. The single damper itself is mounted to swing in a manner to close off both passages simultaneously when in a first position and also isolate these passages from the ambient atmosphere inlet. In this first position, heat is retained in the heater as well as the room.

Abstract: An adapter circuit for retrofitting an oil burner control system with a flue damper includes a source of energy in circuit with the thermostat for energizing the damper motor in response to a call for heat to open the damper. A first relay in the adapter circuit includes a pair of contacts for simulating the operation of the thermostat contacts. When the damper is open, this relay is energized, and its contacts close, simulating the operation of the thermostat after the damper is opened, to energize the burner control circuit, thereby energizing the burner motor and ignition. A second relay in the adapter circuit senses whether the burner motor is energized; and when the burner motor is de-energized, this relay initiates a time delay after which the adapter circuit closes the damper.

Abstract: A device for generating an electric output signal in response to the positioning of a mechanical member. The mechanical member carries an optical fibre, and the optical fibre coacts with one of several, preferably two, phototransistors in response to the setting position of the mechanical member. The phototransistors are connected to an amplifier generating the electric output signal corresponding to the member's position.The device may be used in control equipment for controlling the draught in a boiler, preferably an oil-fired boiler.

Abstract: An apparatus for opening and closing the draft hood discharge opening and vent and fuel line of a fluid fuel-fired heating device such as a domestic water heater. The disclosed apparatus includes a diaphragm-type expansible chamber fluid motor assembly mechanically linked to a damper assembly such that when the heating devices call for heating, the supply of pressurized fuel acts to actuate the motor for opening the damper assembly. The motor assembly also has a pressure output line which operates a fail-safe type of diaphragm valve for controlling flow. This prevents burner operation until after the dampers are open. Additionally, when the supply of fuel is terminated, the motor assembly does not close the damper assembly until after the diaphragm valve stops fuel to the burner.

Abstract: In a flue damper control system, a thermistor 64 responsive to flue temperatures upstream of the damper 12 is incorporated in a trigger circuit for a triac 52 which controls energization and deenergization of the damper motor 17, the damper motor being fully energized only when the flue temperature is below a predetermined value and there is no demand for heat by the thermostat 36.

Abstract: A pivotal vane carrying member secured to the damper for a furnace flue normally maintains the damper by gravity in an open position. An electric motor driven air blower discharges air against the vanes of the pivotal member to pivot the latter and damper to a closed position when no fuel is supplied to the furnace. Otherwise power for the blower motor is shut off and the pivotal member returns by gravity to its normal flue-open position.

Abstract: Apparatus and method for changing the calibrated linkage relationship between two flow control devices of combustion apparatus without impeding the normal operation of the associated process. Means are provided, responsive to remote, manual or automatic control, to calibrate a jackshaft linkage type of control apparatus in order to provide for range changes and zero adjustment.

Abstract: A shut-off device for installation in the waste gas line from combustion spaces. The device includes a flow-through housing, a shut-off plate mounted in this flow-through housing and adjustable, and a positioning motor arranged on the outside of the flow-through housing for the shut-off plate. The shut-off plate is biased by a spring in a direction toward a first terminal position defined by an abutment and is capable of being adjusted by the positioning motor in a direction toward a second terminal position defined by a second abutment. At least one limit switch is provided for actuation by a control element in the open position of the shut-off plate and serving to initiate operation of combustion spaces arranged upstream from the shut-off device. The positioning motor is a rapidly rotating electric motor having a motor shaft connected with the transmission input of a step down transmission for converting the rotary speed of the motor into a slower speed.

Abstract: A method of and apparatus for controlling the feed amount of air for combustion in a natural draft type heating furnace is disclosed, in which the draft pressure, the oxygen concentration in a combustion gas, the opening degree of a damper for controlling the flow rate of the combustion exhaust gas, the flow rate of a fluid to be heated and the temperatures of the fluid to be heated at inlet and outlet portions of the heating furnace are measured, and the feed amount of air for combustion is controlled based on measured values obtained at predetermined time intervals or corrected values thereof.

Abstract: This invention relates to a furnace equipped with a fuel optimizer for more effectively controlling fuel consumption in the furnace and a method for using the furnace fuel optimizer. In particular, the invention relates to a furnace fuel optimizer which controls combustion air by maximizing radiant section heat transfer with respect to convective section heat transfer while monitoring CO emissions in the flue gas and monitoring the draft below the convective section in order to obtain an optimum control value. The furnace fuel optimizer then regulates the furnace to correspond to the optimum control value by adjusting the air input to the furnace so that continuous furnace operation is possible at maximum efficiency.

Abstract: A venting system for a fuel-burning heating plant, such as a conventional gas-fired furnace. The venting system includes an open-bottomed diverter situated well above the base of the heating plant having vertically disposed inlet and outlet ducts attached to the diverter top. The inlet duct is also attached to the flue outlet of the furnace, while the outlet duct is attached to a chimney flue for expulsion of combustion gases. A heat retention means, such as a damper or a heat-absorbing cone, is located within the inlet duct to permit absorption of heat from passing combustion gases during the combustion cycle and maintain heat in the inlet duct during cessation of the combustion cycle in order to establish a heat lock within the inlet duct and the diverter to prevent the flow of relatively cooler air through the furnace combustion chamber and up the chimney during cessation of the combustion cycle. A similar heat retention means may also be located within the outlet duct.

Abstract: An automatic damper means and controls, which provide an exceedingly safe automatic damper for the exhaust duct-work of an associated gas furnace or the like, by automatic control of the damper, and automatic control of the gas supply, with redundancy features for providing exceedingly safe operation.

Abstract: This invention relates to an automatic damper device for use in exhaust flues, such as flues of combustion devices such as furnaces and water heaters, devices such as air conditioners, and the like, to prevent undesirable loss of hot air or cold air out the flues during periods when no combustion is taking place. The damper has a rotatable damper plate held in normal open position which provides a desired fail safe in the open position assurance. The damper is also adapted to remain in the open position during periods of combustion in the furnace or water heater but otherwise be retained in the closed position to avoid the unnecessary loss of heated air or cooled air.

Abstract: A conventional forced air furnace is provided with a source of outside air for use in combustion. The amount of outside air admitted to the furnace and the amount of heated air lost through the chimney are regulated by simultaneously operable dampers synchronized with the operation of the furnace. Alternate power circuits and an alarm system for the dampers are provided.

Abstract: A gas-fueled oven having energy saving capabilities provided by a thermostatically controlled gas supply valve which supplies fuel to the gas burner at cycled intervals, and a flue restricter which is operatively connected with the thermostat to move into closing relation to the oven exhaust flue when the burner is cycled off, thereby retaining within the oven cavity an amount of heat which would normally be allowed to escape through the flue if the flue restricter was not utilized.

Abstract: A furnace ignition and draft control system includes a damper plate movable under control between a closed and an open position. When a call for heat signal is generated, a holding relay is actuated to energize a damper motor to open the damper provided the damper plate was closed when the signal was generated, otherwise the system will not operate. After the damper is run to the full open position and this is proved, a fuel control circuit is actuated to supply fuel to the furnace, and a trial-for-draft period is initiated. A draft controller energizes the damper motor to open the damper if draft is less than a first predetermined value and to close the damper if draft is greater than a second predetermined value. The predetermined draft values define a desired draft range in which the damper is not operated.

Abstract: A flue throttle to control the amount of flue gas or heated air going out the flue from a heating system, by throttling the flue to the minimum amount required while the heat source is on and to change to a further reduced or a complete throttling of the flue when the burner or heat source is off. The heat source referred to throughout this application is from the combustion of fuel through an electric motor driven burner.

Abstract: A thermal damper assembly mounted to substantially close a flue at room temperature is equipped with thermally responsive coils to move the damper to an open position in response to heat generated by combustion. To allow commencement of combustion the damper assembly is equipped with latch means to position the damper open in preparation for combustion, said latch means responding automatically to an adequate advance of said damper toward its fully open position to disable its own latching capability whereby said coils are permitted to substantially fully close the damper assembly without further attention to the latch means, which serves only to releasably position the damper assembly for commencement of combustion. Also illustrated in this application are various position control members for predetermining fully open and substantially fully closed damper positions. Also illustrated in this application are inboard and outboard mountings for the thermally responsive coils.

Abstract: A thermally controlled damper construction for a gas fired combustion apparatus, such as a furnace. The damper has a generally eliptical shape and is mounted on a shaft in the stack or flue for pivotal movement from a closed position, where the damper is located at an angle of approximately 45.degree. 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 and permit venting of gases generated by operation of the pilot light during periods when the furnace is not operating. The damper is moved between the closed and open positions by a bi-metallic element which is located upstream of the damper and connected to the damper by a linkage. When the furnace is operated, the increase in flue temperature will operate the bi-metallic element to move the damper to the open position.

Abstract: For a vent or flue damper of the type in which the damper is closed by an electrically energized actuator when the furnace is off and the actuator has first biasing means to open the damper when the actuator is deenergized, a second biasing means such as a torsion spring, independent of the first biasing means, is associated directly with the damper shaft and is adapted to always move the damper to an open position in the absence of the actuator.

Abstract: A gas burner device having a gas supply and a primary air supply and secondary air supply to the burner and a flue gas vent means leading from the burner for venting flue gases to a place of disposal. The device has a power driven fan in the flue gas vent for providing simultaneously a forced flow of flue gases away from the burner flame and of primary and secondary air to the flame, a temperature responsive variable speed control for controlling the power supply to the fan motor and thereby the speed of the fan and the rate of movement of the exhaust gas from the burner and flame and primary and secondary air to the flame in direct proportion to the temperature of the flue gases.

Abstract: An automatic flue damper positioned respectively to open and closed positions by means of motive apparatus, such as a solenoid motor, is provided with mechanical means for automatically latching the damper in its open position.

Abstract: Device for automatic draft control of a furnace having an oil burner, a smoke flue, and an exhaust valve located in the smoke flue, part of said smoke flue comprising a metal tube which is connected with the wall of a chimney, said device comprising a first sensoring device provided on said metal tube and subjected to the influence of the temperature prevailing in said tube, and a second sensoring device provided in said chimney wall, said first and second sensoring devices being connected with the exhaust valve in such a manner that their combined registration is transmitted to the exhaust valve.

Abstract: A control system for use with gas-fired appliance installations, such as a furnace, includes a switch responsive to normal draft levels in the vent stack. At the start of a heating cycle, and in the absence of draft, the switch permits a pre-draft enabling circuit to tentatively enable the furnace controller for a predetermined time. The controller opens a stack damper plate and actuates the ignition system and gas valves of the furnace. If draft is not established within the predetermined time, the pre-draft enabling circuit times out and the gas is shut off. If normal draft is sensed within the predetermined time, the draft responsive switch permits the furnace controller to be operated as long as the thermostat calls for heat. If, for any reason, draft subsequently stops, the control system re-cycles itself; and if draft is not re-established before the pre-draft enabling circuit times out, the system deactivates the furnace controller.

Abstract: A combustion chamber-heat exchanger apparatus, wherein air is forced into the combustion chamber and combustion gases are forced out of the heat exchange, is operated at optimum efficiency by detecting in the combustion gases parameter corresponding to the composition and/or temperature thereof and modifying the fluid flow through the fluid flow circuit in response to the detected parameter until the volume of air forced into the combustion chamber corresponds to the volume of air necessary for obtaining the maximum efficiency of the apparatus under the detected condition of operation.

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.

Abstract: An automatic damper means and controls, which provide an exceedingly safe automatic damper for the exhaust duct-work of an associated gas furnace or the like, by automatic control of the damper, and automatic control of the gas supply, with redundancy features for providing exceedingly safe operation.