Abstract: This invention provides a water heater including a water storage tank, a flue, a jacket around the tank and the flue and having a top end, a top cover which extends over the tank and the flue and which closes the jacket top end, and a flue collector within the top cover and having an exhaust opening within the top cover and in communication with the flue. The water heater further includes a flue damper mechanism comprising a damper disk pivotally mounted within the flue collector exhaust opening so that the disk can pivot between a closed position closing the exhaust opening and an open position opening the exhaust opening, and drive means for pivoting the damper disk. The drive means comprises a damper actuator exterior of the top cover, a mounting tube secured to the flue collector and secured to the damper actuator, and a damper shaft within the mounting tube and extending between the damper actuator and the damper disk.

Abstract: A method for controlling combustion air in a boiler plant, where combustion air is supplied into a boiler located in a boiler building, comprises the steps of determining a ratio of air flow inside the building to air flow outside the building on the basis of at least the temperature of the outside air and of a load of the boiler; taking a first air flow from inside of the building in accordance with the ratio; taking a second air flow from outside the building in accordance with the ratio; the second air flow being at a certain temperature; and supplying a combined combustion air flow including the first and second air flows, in accordance with the ratio, to the boiler. Also an apparatus is provided for controlling combustion in boiler building permitting it to achieve the above steps.

Abstract: A thermally activated vent damper assembly for occluding passage of gases in a passageway such as a flue. The assembly includes first and second damper members which are pivotable about a common axis. Coaxial first and second support members which are spaced apart along the common axis support thermally activated biasing members which are attached to the damper members to thereby suspend the damper members within the flue. When heated, the biasing members pivot the first and second damper members about their common axis from a flue closing orientation to a flue opening orientation. The assembly may include a housing mountable to the flue and to which the first and second support members are attached.

Abstract: A chimney safety and control system includes a control panel which indicates the position of the chimney damper and the operational status of a chimney fan unit, and allows the operator to electro-mechanically open and close the damper and set the fan. When the safety control system senses that a predetermined condition (e.g., high temperature) exists in the chimney firebox while the damper is closed, it automatically opens the damper and activates the fan. The system may also be used in conjunction with one or more smoke detectors, in which case the system automatically opens the damper and activates the fan when a smoke detector is activated.

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.

Abstract: An actuator employing a unidirectional electric motor driving a first rotating member connected to a second rotating member through a pivotable link of which a first end is connected to the first rotating member at a smaller distance from its axis of rotation than the distance between the point at which the second end is connected to the second rotating member and its axis of rotation. An enegerization circuit includes first and second limit switches through which the motor is alternately energized to rotate the second men%her in opposite directions to first and second limiting positions respectively.

Abstract: A device for use in improving the heating efficiency of a water heater comprises a housing mounted over the heat collecting pieces of the water heater and provided with at least a set of ventilating ports, each of which is composed of a predetermined number of ventilation holes arranged in a geometric pattern. Pivoted to each of the ventilation holes is a damper, which can be triggered by a heat sensing element to turn so as to open or close automatically the ventiation holes. The heat sensing element is caused by heat to deform in order to bring about a displacement of the damper. The extent of the opening of the ventilation holes depends on the extent of the displacement of the damper.

Abstract: A stack damper control apparatus for positioning a stack damper and controlling a fuel source in response to closing of a temperature sensitive switch. Limit switches comprising drop cams are coupled to the drive shaft of the damper. In response to a call for heat, a motor turns the damper, coupling a source of energy to a fuel source when the damper is open and the limit switches transfer. A relay coil is energized to hold open a switch providing a parallel energization path for the motor. When the call for heat has been met and the temperature sensitive switch opens, the relay de-energizes closing the parallel energizing path and allowing the motor to close the damper. Provision is made for a safety interlock to ensure the fuel source is not activated when the damper is closed. Provision is also made for interface to a blocked vent shutoff system.

Abstract: A thermally activated vent damper assembly for a flue is adapted to be situated in relation to the flue for occluding the passage of gas through the flue. A support member traverses the flue and suspends the damper member across the flue for movement between an open and a closed position. A thermally activated biasing member is operatively coupled between the support member and the damper member to bias the damper member in the open position in the presence of heat and to bias the damper member in the closed position in the absence of heat. The coupling of the biasing member between the support member and the damper member is such that potential sites for frictional inhibition of damper member movement are eliminated. Upon breakage or other failure of the biasing member to apply bias, the damper member defaults to or remains in an open position under the force of gravity, providing for a unique fail-safe feature.

Abstract: A thermally activated vent damper assembly for a flue is adapted to be situated in relation to the flue for occluding the passage of gas through the flue. A support member transverses the flue and suspends the damper member across the flue for movement between an open and a closed position. A thermally activated biasing member is operatively coupled between the support member and the damper member to bias the damper member in the open position in the presence of heat and to bias the damper member in the closed position in the absence of heat. The coupling of the biasing member between the support member and the damper member is such that potential sites for frictional inhibition of damper member movement are eliminated. Upon breakage or other failure of the biasing member to apply bias, the damper member defaults to or remains in an open position under the force of gravity, providing for a unique fail-safe feature.

Abstract: A pivotal electrical connector for connecting a shape memory alloy element in the form of a coil spring to a fixed member, the connector including a strip of electrically conductive material having a clip or a pair of legs for securing the connector to one of the coils of the element. A pair of holes may be provided in the strip through which the coil is threaded. A rotational connector is provided in the strip for engaging the fixed member.

Abstract: A furnace comprises a housing, a fan or blower for moving air through housing, a burner in the housing, fuel supply means operatively connected to the burner, a heat exchanger in the housing a combustion chamber, the burner cooperating with said combustion chamber, an enclosure enclosing the heat exchanger and burner, said enclosure having an opening therein, and a damper operable to control the flow of air through said opening to the heat exchanger. The damper comprises a plate member pivotally mounted in the housing for opening and closing said opening. Preferably a drive motor opens the plate member and a spring biases the plate member closed. The damper is closed when the burner is off and is open when the burner is on. There is a circuit associated with the fuel supply means which is responsive to a predetermined open position of the plate member for permitting the flow of fuel through the fuel supply means when the plate member is open to said predetermined open position.

Abstract: A forced air heating system having a dedicated supply duct for delivering heated air to the heated portions of the building and having an open air return system which uses the rooms, hallways, door openings, etc. of the building for returning air back to the furnace for reheating and recirculating. The elimination of a dedicated return air duct significantly improves the distribution airflow volume and thereby the efficiency and comfort of the central heating and air conditioning. The system includes a flue draft controller which monitors the flue draft at all heating applicances, such as furnaces, hot water heaters, etc., and servos a damper in a single main flue serving all appliances to optimize the flue draft for all appliances. If the flue draft becomes inadequate in any appliance, the controller shuts down heating appliances, as well as all heating system circulation fans, power fans and building exhaust fans which can affect the flue draft.

Abstract: A shape memory actuator for controlling the position of a control member, such as a damper plate in a duct, the actuator including first and second shape memory elements each having an austenite phase transition temperature above which each element assumes a predetermined memory shape and a lower phase which forms when said element is stretched from the predetermined memory shape, the first and second elements being connected to move the control member in different directions when one or the other of the elements are heated to a temperature above its austenite phase transition temperature and an electrical circuit for selectively raising the temperature of one or the other of the elements. The control member may be held in a position between full open and full closed by holding mechanisms which connect the actuator to the control member.

Abstract: A self-contained electronic air register controller can easily be mounted directly onto the outside of an air register. When so mounted, the controller engages the register's actuating lever and permits automatic opening and closing of the air register by way of simple programming instructions and/or by way of a temperature sensor. The controller comprises a small battery, a miniature electric motor with a gear/linkage mechanism operable to engage with and to move the register's actuating lever between its OPEN and SHUT positions, and a quartz-clock-based programming means.

Abstract: A damper has a frame with a cross bar and a reciprocal blade. A bimetallic element which moves in response to temperature is coupled to the blade and is hingedly coupled to the cross bar so that movement of the bimetallic element in response to temperature causes the blade to move with respect to the frame. The coupling of the bimetallic operator and the frame is accomplished by a biasing hinge which is coupled to the frame and to the bimetallic element to couple the bimetallic element to the frame and control the temperature movement response of the element. The biasing force of the biasing means is adjustable for controlling the temperature movement response of the damper blade. The bimetallic element is a serpentine spring having a plurality of bends and the biasing means is a hinge. The closed position of the blade of the damper, as well as the biased temperature response of the damper, and adjustable by rotation of adjustment screws.

Abstract: In a bimetal-actuated damper a loop-shaped bimetal element engages a damper element. One end of the loop is fixedly fastened while the other end of the loop is movably connected with the damper element. This improves temperature-dependent response and sensitivity of the damper and prevents damage from overheating or permanent change of operating characteristics.

Abstract: A device is provided for controlling the position of a damper within a flue or stack of a forced air heating or cooling system or a commercial or industrial boiler. The device comprises a damper plate and means to control rotation of the plate within a flue under force supplied by the movement within the flue of air or gases.

Abstract: A housing supporting a signal-controlled, power operating unit for a damper is mounted internally within a duct by a tubular supporting sleeve in an angularly and axially adjusted position projecting from an open end of the duct. A shield fixed to the external end of the sleeve backs an annular sealing flange engaged by the damper element, which is enclosed by a flow deflecting hood slidably assembled on the shield.

Abstract: A heating appliance such as a hot-air circulating microwave oven using a shape memory alloy as the damper spring for driving the damper unit. The damper lid a capable of switching the direction of air to be supplied into the heating chamber and the damper spring, made of shape memory alloy drives the damper lid in the air path inside a duct, delivering air cooled by a cooling fan to both the heating chamber and a magnetron.

Abstract: An oil and gas fueled hot water heater system having improved efficiency and performance embodies air and fuel regulator valves, water and air supply jackets, cold and hot water insulating check valves, and flow directors and restrictors for the hot combustion gas generated by the heater burner which gas passes through a central flue in a water storage tank and is then exhausted through an exhaust vent to atmosphere. The air and fuel regulator valves are non-electrically controlled and are responsive to water demand requirements for improved heater efficiency and performance. The water supply jacket closely surrounds the central flue and receives supply water at the top thereof and discharges same to the bottom of the storage tank thereby increasing the heat transfer characteristics of the heater. The air supply jacket surrounds the exhaust vent and air is drawn in through the top of the jacket along the exhaust vent for preheating and then is directed to the burner to support combustion.

Abstract: The present invention is an electronically controlled, automatically operated flue damper mechanism which is totally fail safe in operation. The mechanism is to be fitted within the draft hood of a thermostatically controlled heating device such as a gas or oil fired furnace. The electronic control circuitry of the damper being integrated with that of the heating device to which it is fitted. The action of the damper being to close the flue a sufficient time after combustion has stopped, to allow all noxious gases from combustion to have left the flue, and to open the flue before combustion can begin.

Abstract: A thermally responsive damper assembly for mounting into a duct which is to be regulated by the damper assembly comprises a damper plate having oppositely disposed notch portions and arm portions one piece with said damper plate projecting outwardly in said notch portions and thermally responsive convoluted coil elements having convolutions surrounding said arm portions, bracket means affixed to the outermost convolution of each of said coil elements for attachment to said duct, and each of said coil elements having innermost convolutions keyed for attachment in only one orientation to an arm projecting outwardly in a notch portion of said damper plate.

Abstract: A control system is provided for controlling a flue damper in a furnace flue. The control system includes a voltage source, a thermostat, a gas valve, and means for moving the flue damper between a closed position and an open position. The moving means includes a timer driven by a motor with a specially wound coil assembly including a first winding and a second winding. The coil assembly further includes a first terminal, a second terminal and a center tap terminal. The control system manipulates the flue damper and heating system during three stages of operation. The flue damper is closed and the furnace is off at the beginning of stage one. The control system opens the flue and turns on the furnace during stage one. The flue damper remains open during stage two. The control system turns off the furnace and closes the flue damper during stage three.

Abstract: A flue damper is rotated 360.degree. in a predetermined direction in 90.degree. increments to be selectively opened and closed in 90.degree. increments. The incremental rotation is accomplished by a motor driven timing mechanism with power to the motor being controlled by the timing mechanism and a single pole double throw relay.

Abstract: A normally energized motor maintains a counterbalanced damper closed to block air inflow in a non-combustion condition of an appliance. Deenergization of the motor by thermostat control releases a rotor for displacement through a limited angular stroke. Through a lost-motion linkage connection the damper is displaced, in lagging relation to the rotor to the open position. The open position of the damper is detected by a sensor to open a fuel valve in the appliance.

Abstract: A heat generating system using solid fuel in a water jacketed combustion chamber for supplying hot water to units for space heaters and hot water storage units, and in which control means is provided for operating the fuel combustion mode to obtain recovery of the products of combustion during low rates of combustion, and to greatly reduce emissions during increased rates of combustion, the control means including thermostatic units having selected points of active and inactive responses.

Abstract: A thermally operated vent damper wherein a flue pipe (12) mounts an eliptical damper plate (38) for rotation about a hollow rod (30). A slot (42) is formed in the damper plate (38) by bending a flange (44) perpendicular to the plane of the damper plate (38) and providing an opening for a coil (52) of bimetallic material. The coil (52) controls the movement of the damper plate between closed and opened positions responsive to temperature in the flue pipe (12). An opening (19) in the flue pipe adjacent to the coil (52) provides a means for maintaining the coil (52) temperature lower than the flue gas temperature and for controlling the opening of the damper plate in the flue pipe in inverse proportion to the draft therein. A second bimetallic coil (60) is mounted outside the flue pipe to relieve stresses on the first bimetallic coil during prolonged high temperature excursions within the flue pipe.

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 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: A mechanical draft controller integrated in the draft hood of a furnace and coupled to a flue damper is responsive to the draft in the flue for controlling exhaust stack heat loss and eliminating heated room air loss via the draft hood under normal operating conditions. The pressure-sensitive controller is variably positioned as a face damper on a surface of the draft hood and is coupled to the flue damper by means of mechanical linkage. Increasing pressure in the draft hood caused by a reduction in the draft value due to partial flue blockage, large down draft, etc., displaces the pivoted controller resulting in a corresponding opening of the flue damper to re-establish the desired draft value. Similarly, excessive draft causes the displacement of the controller in an opposite direction resulting in flue damper displacement so as to reduce the draft value and exhaust stack heat loss.

Abstract: A barbecue grill unit which includes thermally actuated dampers and insulated walls to conserve heat during its operation. The dampers are of the laminated bimetallic type which progressively open in direct proportion to the heat generated by burner. This limits the amount of air entering the grill which must be heated yet affords efficient combustion. A vent in the back wall of the cover also maximizes heat usage before the heated air is expelled from the grill unit. Preferably, the barbecue grill unit is of the gas-burning type.

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 automatic vent damper control mechanism for use on furnaces or the like having a spring loaded open position and an electric motor which drives it to a closed position, against the spring bias, via a gear train. A unique over-travel mechanism is provided which prevents damage to the gear train from occurring when the damper reaches the end of its travel towards its open condition.

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: An fuel-fired hot water furnace includes the use of an improved combustion chamber, heat exchanger and breaching damper, and further includes utilizing the water heated in the furnace as the means of heating a separate domestic supply of water directed through a side car hot water heater in fluid communication with the furnace. The improved combustion chamber includes a primary combustion cylinder which is orthogonally attached to a secondary combustion cylinder, and the secondary combustion cylinder is provided with a necked-down discharge so as to facilitate a thorough burning of a fuel and air mixture. The heat exchanger includes a primary rise and fall arrangement for the combustion gases so as to provide for maximum heating of the water within the heat exchanger prior to the gases being emitted outwardly from the furnace through a breaching tube, and the breaching damper is provided within the breaching tube so as to regulate the rate of combustion gas flow.

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: The present invention relates to a self-checking safety switch control circuit for a power combustion system. The circuit comprises a safety switch, a combustion blower relay, a thermal pilot switch, and a fuel supply system. The safety switch operates to detect flow through the combustion system. The safety switch either operates the pilot switch directly or operates the fuel supply system directly to shut down the system if no flow through the combustion system is detected. The circuit has a self-checking feature because combustion cannot be initiated in a subsequent cycle of the system if the safety switch remains in the proven condition from the previous combustion cycle.

Abstract: A control system for an automatic damper in a heat generation system. The damper is provided with a spring biasing arrangement to open the damper when the plant is generating heat to permit unobstructed discharge of the products of heat generation. A motor maintains the damper closed when no heat is being generated. Provision is made for disabling the control system permitting the damper to be opened by the spring and the heat generator to function normally when a malfunction occurs in a switch which normally performs in a safety capacity. Included in this arrangement is a fuse in a circuit which opens the circuit when the switch fails as the result of a short circuit or welding of the contacts. The circuit includes means for preventing short circuiting during normal operation.

Abstract: A thermally responsive damper for opening the flue of a gas-fired apparatus when gas firing occurs and for otherwise closing the flue to prevent unnecessary energy losses utilizes a low cost, high flexivity, thermostat metal adapted to operate in the corrosive flue environment, the thermostat metal having a high expansion layer of a corrosion-resistant austentic stainless steel which does not transform as it is worked during manufacture of the thermostat metal and a low expansion layer of an alloy of 36 percent nickel and the balance iron. The thermostat metal also has a thin layer of a stabilized, high chromium, ferritic stainless steel on the outer surface of the lower expansion layer for protecting the low expansion layer from corrosion in the flue gasses and for permitting the achievement of high flexivity in the thermostat metal while also permitting economical manufacture of the composite material.

Abstract: An automatic stove damper having a temperature responsive element which activates a damper plate, the temperature responsive element being oriented by a movable adjustment means. The device allows for easy adjustment of the relative amount of damping provided by the device by shifting the adjustment means, but if the damper plate reaches and is stopped at a fully closed position the adjustment means is allowed to shift, preventing further temperature increases from permanently deforming the temperature responsive element. The adjustment means can release the temperature responsive element to quickly shift the damper plate to a fully damped position. In other aspects of the application a metal ring is attached to a stove pipe, with a magnet being positioned thereupon for orienting the temperature responsive element to provide the desired amount of relative damping. A counterweight urges the damper plate to a fully closed position when the magnet releases the temperature responsive element.

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: A thermally controlled damper construction for a gas fired combustion apparatus such as a furnace, water heater or the like, is described. The damper is pivotally mounted within the stack of the combustion apparatus for pivotal movement from a closed position to a full open position. A thermally responsive device is disposed in the stack on the upstream side of the damper for opening and closing the damper in response to predetermined temperatures. The thermally responsive device comprises a shaft mounted in the stack which extends thereacross and which has the damper rotatably mounted thereon. A helical bi-metal element embraces the shaft between the ends thereof and comprises first and second bi-metal members which are secured together in an end-to-end relationship.

Abstract: A heater vent having a temperature responsive damper such as a bimetallic element is disclosed. A shroud-like structure is positioned to cooperate with the temperature responsive element to close the vent at an elevated temperature and thereby reduce loss of residual heat while permitting the combustion gases to be completely purged from the firebox. For safety, movement of the temperature responsive element is uninhibited in all positions with complete vent closure occurring at ambient temperature and with the damper open during heater burner operation.

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: For a damper, an improved damper operator including a bimetallic element connected at one end to the frame of the damper, and at the other end to a pivotal linkage which is also pivotally connected to the blade or blades of the damper.

Abstract: A thermally responsive damper for operation in a rectangular ventilation duct.

Abstract: A draft control arrangement for a heating apparatus. The draft control arrangement includes a vent damper comprised of one element formed of a shape memory material and another element form of a thermostat material with the elements arranged for coacting to provide a rapid rate of flow passage opening during an initial phase of temperature rise followed by a rate of flow area opening substantially proportional to further temperature rise.

Abstract: In the present invention, an automatic flue damper located in the vent stack of a household furnace or other apparatus requiring venting is interfaced with a thermostatic control and a fuel supply valve associated with the apparatus so as to maintain a vent passage to the atmosphere normally open during times when combustion is occurring in the apparatus and to close the vent passage at an appropriate time following the termination of combustion in the apparatus. The normally open vent condition is maintained by a damper positioning spring. Vent closure following combustion is accomplished by means of a direct current solenoid. Further included in the interfacing circuitry are a temperature sensing device effective to disable the solenoid, thus opening the vent, upon the appearance of unsafe stack temperatures and a pressure sensor which also disables the solenoid to open the vent stack upon the occurrence of an inappropriate discharge of fuel to the combustion chamber.

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.