Abstract: A water heater having a monitoring mechanism, an appliance burner configured to heat water in a tank of a water heater, a water temperature sensor configured to detect a water temperature in the tank, a pilot device configured to ignite the appliance burner, and a thermopile having a tip and a base, and having an output voltage that represents a temperature difference between the tip and the base. The tip of the thermopile may be heated by the pilot device. The base of the thermopile may receive heat from the appliance burner when the appliance burner is turned on, and thus the voltage output of the thermopile may decrease. If the voltage output does not decrease and the water temperature exceeds a thermal cutout limit, then a warning about the water heater may be issued by the monitoring mechanism.

Abstract: A remotely actuated pilot gas valve includes safe lighting and complete shutoff capabilities in the event that the flame that is heating a thermocouple is extinguished. The invention provides for a heater system that utilizes such a pilot gas valve as well as a method whereby the pilot gas valve used in such a system can be remotely and electronically actuated when required. Remote actuation is accomplished by use of a solenoid that is incorporated within the valve design and which is controlled by a remote operator.

Abstract: The invention provides a system for controlling flame to produce a music-reactive fire display. This system comprises a digital signal analyzer, electronically-controlled burner elements that allow variable control of fuel flow rate, an automatic ignition system, flame detection, and a means of communication between the signal analyzer and the burner elements.

Abstract: One or more techniques and/or systems are disclosed for a portable gas-fired heater comprising a ousing, a burner assembly, and a carbon dioxide detector system. The housing may, at least, partially enclose one or more fuel sources. The burner assembly can be enclosed by, and recessed into, the housing.

Abstract: A catalytic tank heater includes a catalytic heating element supported on an LPG tank by a support structure that holds the element in a position facing the tank. Vapor from the tank is provided as fuel to the heating element, and is regulated to increase heat output as tank pressure drops. The heating element is internally separated into a pilot heater and a main heater, with respective separate fuel inlets. The pilot heater remains in continual operation, but the main heater is operated only while tank pressure is below a threshold. Operation of the pilot heater keeps a portion of the catalyst hot, so that, when tank pressure drops below the threshold, and fuel is supplied to the main heater, catalytic combustion quickly expands from the area surrounding the pilot heater to the remainder of the catalyst.

Abstract: A safety pilot can be used with a gas appliance. The gas appliance can be a single fuel or a dual fuel appliance for use with one of a first fuel type or a second fuel type different than the first. The safety pilot can include a first thermocouple, a second thermocouple, and a nozzle configured to direct combusting fuel towards both the first and second thermocouples.

Abstract: An ignition system and method of igniting the ignition system includes a main catalyst section in a staged relationship with a pilot-catalyst section to stage a decomposition though the pilot-catalyst section which preheats the main catalyst section.

Abstract: A method for flame sensing in a solid, liquid or gaseous fuel burner, the flame generated at an ionization electrode, the flame presence resulting in an ionizing effect on the electrode. The electrode is powered by an alternating voltage signal. The ionization phenomenon generates in the electrode a direct current. The current being sensed by a suitable sensing circuit including a control unit. This signal generator being of relatively low internal impedance to enable the measured generated current to have a high value compared with that normally used and of waveform to tend to limit the value of the direct current flowing through the electrode. The sensing and control circuit being such as to enable the presence of a parasitic current on the flame sensing electrode to be measured. A device for implementing the method is also disclosed.

Abstract: The invention relates to a method and an arrangement for igniting a gas flow by means of remote control. The aim of the invention is to maintain the current consumption so low that an integratable voltage source can be used. To this end, a thermoelectric safety pilot valve (17) is opened and the escaping gas ignited by the actuation of an electronic control unit (5) fed by a voltage source. Said thermoelectric safety pilot valve (17) is maintained open by a safety pilot magnet (18) by means of a holding current from the voltage source until a thermocouple (22) provides the required holding current once the gas flow has been ignited or a defined holding time is exceeded.

Abstract: A micro pilot for a gas hot water heater is provided. The micro pilot provides a flame that is substantially smaller than a typical pilot in a hot water heater during standby operation of the burner. Just prior to allowing gas to flow to the burner upon a call for heat, a pilot flame of sufficient size to ensure ignition of the burner is provided. In one embodiment this larger pilot flame is produced by providing an additional amount of bleed gas to the pilot to increase flame size. In another embodiment, bleed gas is provided to a separate booster pilot, which is ignited by the micro pilot. The flame from the booster pilot is then used to ignite the main burner. This design allows for the micro pilot to be positioned closer to the flame trap of a flammable vapor resistant hot water heater to ensure smooth ignition of any such vapor.

Abstract: A heater having first and second oxygen depletion sensors and a main burner injector and configurable for the delivery of at least first and second types of fuels.

Abstract: In certain embodiments, an apparatus can comprise a dual fuel pilot assembly. The pilot assembly can comprise a first fuel dispenser, a second fuel dispenser, an igniter and at least one of a thermocouple, and a thermopile. The pilot assembly can be configured to direct heat from combustion of one of either a first fuel or a second fuel to the at least one of the thermocouple and the thermopile.

Abstract: A device for controlling a gas supply to a burner includes a main duct, which is provided with at least one main valve including a valve seat and associated shutter with a control for opening the seat in opposition to a resilient recall member. A pilot duct leads from the main duct to supply a pilot burner, the main duct includes a magnetic thermoelectric safety unit which is manually or automatically armed, acting on the pilot duct to enable gas to flow to the pilot burner when armed. The pilot duct includes a pressure regulator having a shutter with a membrane control, the membrane subject to pressure regulated by the regulator and to a calibration pressure determined in a calibration chamber of the regulator. The device includes a fluid connector between the calibration chamber and the main valve to provide a pressure signal correlated with the gas supply pressure.

Abstract: An automatic system and method to provide the ignition and monitoring of a pilot flame for gas burners. The circuit includes a microcontroller that acts on at least one gas valve, a flame igniter, and a flame detector circuits. The valve driver is a switching circuit able to open the valve and keep it open with power saving. The flame detection uses the ionization principle with full use of the rectification property of a flame. Furthermore the flame detection is activated for reduced times to save power. The microcontroller governs the system according to the signals that it receives from points of the circuit. The system provides a circuit realizing advanced power saving techniques to provide also a long term operation on battery powered systems. In addition the automatic control can save gas resources versus traditional thermocouple based systems by applying the intermittent pilot ignition.

Abstract: A flame sensor apparatus for use with a flame heated thermal abatement reactor is provided, including a flame sensor adapted to sense a flame within the thermal abatement reactor; and a shutter adapted to selectively block the transmission of radiation from the flame to the flame sensor.

Abstract: A pilot ignition system for an outdoor gas appliance provides a pilot igniter that is isolated from the ambient wind around the burner by physically distancing the pilot igniter from the burners. The distance is overcome by providing a jet of gas to a nozzle slightly upstream of the pilot, the jet of gas being directed toward the burner. The jet of gas is ignited by the pilot resulting in a torch or jet of flame extending from the pilot igniter through the downstream length of an enclosure to the burner. The jet of flame bridges the distance between the pilot igniter and the burner, while the distance itself isolates the pilot light from wind in the vicinity of the burner.

Abstract: A redundant ignition control system and method for gas burning appliances is provided. The system utilizes a main processor and a supervisory processor to provide the redundant, fail safe operation of both the pilot valve and the main gas valve of the appliance. Three switching elements under the control of the two processors, as well as the use of high pass filters to block DC from the gas control valves provide redundant, fail safe operation. The use of variable duty cycle or frequency pulse width modulated signals enables use in low power applications and ensures system safety. Inclusion of a gas valve verification sequence, ignition sequence, burner monitoring sequence, and heat shutdown and standby sequences ensures safe, low power operation during normal control, and fail safe operation upon the failure of any component of the system.

Abstract: In a fuel reforming system (32) of a fuel cell system (1), which includes a reformer (7) generating hydrogen-containing gas to be an electromotive fuel and a combustor (6) generating combustion gas, the combustor (6) has two combustion parts including a main combustion part (20) and a sub-combustion part (18), a fuel pre-vaporization part (19) between the two combustion parts and a main fuel injection valve (16) and a sub-fuel injection valve (15) which supply the fuel to the respective combustion parts.

Abstract: A reactant supply and control system supplies a regenerative burner assembly with streams of pilot fuel and pilot air. The system can maintain a pilot flame throughout regenerative cycles in which a main flame is turned on and off, and supplies either or both of the pilot streams with an increased flow rate for shifting from a regenerative exhaust condition to a regenerative firing condition.

Abstract: A gas valve includes a gas inlet in fluid communication with a first chamber, a second chamber in selective fluid communication with the first chamber, a gas outlet in selective fluid communication with the second chamber, a pilot light outlet in fluid communication with the second chamber, and a bypass channel in fluid communication with the second chamber and in fluid communication with the first chamber. The bypass channel limits bypass gas flow to an amount that is insufficient to ignite a pilot flame at the pilot light outlet when the second channel is in fluid communication with the gas outlet.

Abstract: The method and apparatus provides a controller (which might comprise a microprocessor) that can control gas flow to a pilot burner in fluid communication with a manual pilot valve and an automatic pilot valve. The exemplary embodiments can comprise a selectable input device that can open the manual pilot valve to allow gas flow to the pilot burner. A pilot flame can then heat one or more thermal detection devices in thermal communication with the pilot burner, wherein the one or more thermal detection devices can output a variable voltage potential to the controller. The controller can then open the automatic pilot valve to maintain gas flow to the pilot burner after the manual pilot valve has been closed. In an exemplary embodiment, the only voltage potential used to power the controller is supplied by the one or more thermal detection devices.

Abstract: A self-sustaining control for a heating system, having conventional operational modes and pilot burner assembly, is disclosed. A controller directs operation in accordance with a need-based protocol and monitors the condition of a storage device, which provides system power during the stand-by or off mode under normal conditions. A thermo-electric device is in thermal communication with the pilot burner assembly and powers the system whenever the pilot is lit. Regardless of heat need, the controller directs operation in a pilot-on mode, in lieu of an off mode, whenever the storage device is compromised.

Abstract: A fault-tolerant multi-point flame sense circuit utilizes a single electronic switch to signal the presence or absence of flame to an electronic controller. Multiple flame sense electrodes may be input to this circuit. By configuring these electrodes in accordance with the present invention, cross-contamination of a single failed flame sense electrode will not affect the other flame sense electrodes' ability to sense a flame at their associated burner. The circuit provides inputs for a number of flame sense electrodes via input channels that are capacitively coupled to the line voltage and resistively coupled to an RC network that controls the state of an electronic switch. When a flame is present at any one of the electrodes, the resulting unbalance current flow through the RC network turns the switch off to indicate the presence of flame. This operation is not affected by a short on any other electrode in the circuit.

Abstract: An automatic flame-out detector and reignition system for a fuel burning apparatus comprises at least one spark generator. The spark generator comprises a spark gap and a transformer. The transformer has a primary winding and a secondary winding. The spark gap is connected across the secondary winding of the transformer. A switch is in electrical communication with the primary winding such that when the switch is in a first state, electrical current may flow through the primary winding and when the switch is in a second state, electrical current may not flow through the primary winding. The system comprises at least one flame detector having an output indicating the presence of a flame. A programmable circuit having an input for receiving the output of the flame detector and an output for triggering the spark generator is provided. A method of ignition is also provided.

Abstract: An automatic flame-out detector and reignition system for a fuel burning apparatus comprises at least one spark generator. The spark generator comprises a spark gap and a transformer. The transformer has a primary winding and a secondary winding. The spark gap is connected across the secondary winding of the transformer. A switch is in electrical communication with the primary winding such that when the switch is in a first state, electrical current may flow through the primary winding and when the switch is in a second state, electrical current may not flow through the primary winding. The system comprises at least one flame detector having an output indicating the presence of a flame. A programmable circuit having an input for receiving the output of the flame detector and an output for triggering the spark generator is provided. A method of ignition is also provided.

Abstract: In a burner for operating a combustor, the former consists essentially of a rotation generator (100), a transition piece following the rotation generator, and a mixing pipe following this transition piece. Transition piece and mixing pipe form the mixing section (220) of the burner and are located upstream from a combustion chamber (30). In the lower part of the mixing pipe is located a pilot burner system (300) which creates, among other things, a stabilization of the flame front, in particular in the transient load ranges, while minimizing pollutant emissions. A sensor (400) installed in the burner detects a flashback of the flame (80), whereupon the fuel quantity of this flame is at least temporarily reduced and at the same time the fuel quantity for the pilot burner is increased in such a way that the total fuel quantity and thus the turbine output remains constant. This measure prevents a destruction of the burner.

Abstract: A dual mode pilot burner having a control flame mode of operation and a pilot flame mode of operation, which dual mode pilot burner is suitable for controlling the fuel/air ratio of a main burner when operating in the control flame mode of operation. The dual mode pilot burner includes a burner body having a control flame holder and a pilot flame holder disposed downstream of the control flame holder, a mixing chamber having a fuel gas inlet, an oxidant inlet, and a mixed gas outlet, which mixed gas outlet is in fluid communication with the control flame holder and a fuel gas control valve for controlling a fuel gas flow rate through the fuel gas inlet into the mixing chamber.

Abstract: A gas appliance is provided for producing an open flame. The gas appliance includes an elongated gas tube, a gas inlet, a nozzle, a flame sensor, a gas shut-off valve, and a protective member. The gas tube has a proximal end and a distal end. The gas inlet is located near the proximal end, for connection to a source of combustible gas. The nozzle is located at the distal end, for expelling the combustible gas to produce the open flame. The flame sensor detects the open flame and communicates its absence or presence to the gas shut-off valve. The gas shut-off valve has a valve inlet, a valve outlet, a control input, and the over-ride mechanism. The valve inlet is connected to the gas inlet. The valve outlet is connected to the proximal end of the elongated gas tube.

Abstract: A temperature control system for gas operated devices. The system includes a burner (23) that is connected to a gas supply through a regulator (41). A pilot light assembly (26) has a first vane (29) and a second vane (32) which provide a flame for igniting the gas from the burner (23) and for heating a thermocouple (38) to produce a control voltage for operating the regulator (41) and a temperature control (44).

Abstract: In this combustion gas control device, an electromechanical control is provided for automatically controlling the supply of the gas to the pilot burner when it is being ignited and subsequently to the main burner. The device has a main chamber, a pilot chamber and an outlet chamber. A spring-biassed valve is provided between the main chamber and the pilot chamber to close communication between the main chamber and pilot and outlet chambers. The spring-biassed valve is opened when a solenoid is actuated to allow gas from the main chamber to flow into the pilot chamber to the pilot outlet for lighting the pilot light. A diaphragm cover is provided between the pilot chamber and outlet chamber while the pilot is lighted to prevent gas from entering the outlet chamber.

Abstract: A pilot for a gas fuel burner assembly is controlled so that the pilot is extinguished when the burner is ignited and lit when the burner is extinguished.

Abstract: A fuel/air control system for use in controlling the operation of a surface combustion burner includes a photodetector that provides electrical signal equivalents of burner flame emission to a controller. The controller simultaneously receives signals indicative of the fuel/air mixture. The controller fits the emission and fuel air mixture data to a fourth order polynomial. Thereafter, the mathematical inflection point is computed and the corresponding fuel/air mixture is determined. The controller then generates command signals to adjust and maintain the burner at the inflection point fuel/air mixture. Multiple burner control can also be achieved with the present fuel/air control system without the need to sample exhaust gas.

Abstract: A fuel control device, system using the device and method of making the same are provided, the device comprising a housing having an inlet for being interconnected with a fuel source and an outlet for being interconnected to a main burner, the housing having a main valve seat between the inlet and the outlet and a thermostatically operated valve member for opening and closing the main valve seat, the housing having an annular heater pilot valve seat surrounding the main valve seat and being opened and closed by the thermostatically operated valve member at the same time that the thermostatically operated valve member is opening and closing the main valve seat, the housing having an annular auxiliary fuel supply valve seat surrounding the heater pilot valve seat and being adapted to be opened and closed by the thermostatically operated valve member at the same time that the thermostatically operated valve member is opening and closing the main valve seat and the heater pilot valve seat, the housing having a pa

Abstract: A flame powered logic supply circuit (60) responds to a pilot flame (39b) and supplies electrical energy to power electronic logic circuitry (62) for a heater, such as a hot water heater (1), a furnace, or the like. A thermoelectric element (64) responds to the flame and outputs electrical current which is stored in an inductor (70). A pair of parallel circuit branches (78 and 80) are connected to the thermoelectric element (64) and the inductor (70). The first branch (78) has a semiconductor switch (82) with an on state during which current flow supplies energy to the inductor (70) which is stored therein. The second circuit branch (80) has a second energy storage component provided by a battery (90) which receives the stored energy from the inductor (70) during an off state of the semiconductor switch (82) to charge the battery (90) and maintain a given power rating thereof for powering electronic logic circuitry (62) of the heater.

Abstract: A method and system are disclosed for providing fuel and air to a furnace. The furnace includes a plurality of burner assemblies, each with its own air valve for controlling the flow of combustion air therethrough. A sensing instrument for each burner assembly senses a condition reflecting the individual performance of that particular, separate burner assembly. A controller is coupled with the sensing instruments and with the air valves of the burner assemblies for controlling each individual air valve in response to the performance reflecting condition sensed by each sensing instrument. This results in individual control of the performance of each burner assembly of the set of burner assemblies feeding fuel and air to the furnace.

Abstract: This invention discloses a heating and cooling system for buildings, such as poultry buildings, that provides clean, filtered gas fuel, efficiently burns gas fuel by providing adjustable airflow profile plates that blocks cold air from reaching the inside of the building and creates an air mixture control for the burning flame on the burner, that provides rain gutter means that prevent rain moisture from being drawn into the air stream of the unit and that has an actuating means coupled to the pilot light that assure safe operation by shutting off the gas fuel valves in the event of loss of flame in the pilot.

Abstract: A fuel control device, system using the device and method of making the same are provided, the device comprising a housing having an inlet for being interconnected with a fuel source and an outlet for being interconnected to a main burner, the housing having a main valve seat between the inlet and the outlet and a thermostatically operated valve member for opening and closing the main valve seat, the housing having an annular heater pilot valve seat surrounding the main valve seat and being opened and closed by the thermostatically operated valve member at the same time that the thermostatically operated valve member is opening and closing the main valve seat, the housing having an annular auxiliary fuel supply valve seat surrounding the heater pilot valve seat and being adapted to be opened and closed by the thermostatically operated valve member at the same time that the thermostatically operated valve member is opening and closing the main valve seat and the heater pilot valve seat, the housing having a pa

Abstract: A plurality of burners, e.g., steam boiler burners, are provided with air and fuel through separate conduits. A separate air volume regulator is provided for each burner, but only a single fuel volume regulator is provided for all burners. After one burner has been ignited, a signal representative of the air volume associated therewith is supplied to an additional burner, whereby substantially the same volume of air is supplied to the additional burner. To ignite the additional burner, it is then only necessary to double the volume of fuel being supplied, and divide that fuel volume equally among the burners.

Abstract: A self-energizing burner control system for a fuel burner is accomplished by heat from a pilot flame energizing a thermoelectric generator. The thermoelectric generator supplies power to an oscillator. The oscillator has an output that is stepped up in voltage level and is converted to a regulated direct current potential. The regulated direct current potential in turn is used to operate a solid state temperature control or controller. This controller has a sampling rate that is visually indicated by a light emitting diode when a proper voltage is present. The system further insures that a temperature sensor is in place, and is functioning properly.

Abstract: An electronic ignition system for a gas burner is battery operated. The battery voltage is applied through a DC-DC chopper to a step-up transformer to charge a capacitor which provides the ignition spark. The step-up transformer has a significant leakage reactance in order to limit current flow from the battery during initial charging of the capacitor. A tank circuit at the input of the transformer returns magnetizing current resulting from the leakage reactance to the primary in succeeding cycles. An SCR in the output circuit is gated through a voltage divider which senses current flow through a flame. Once the flame is sensed, further sparks are precluded. The same flame sensor enables a thermopile driven main valve actuating circuit. A safety valve in series with the main gas valve responds to a control pressure thermostatically applied through a diaphragm. The valve closes after a predetermined delay determined by a time delay orifice if the pilot gas is not ignited.

Abstract: A self-energizing burner control system for a fuel burner is accomplished by heat from a standing pilot energizing a thermoelectric generator. The thermoelectric generator supplies power to an oscillator. The oscillator has an output that is stepped up in voltage level and converted to a regulated direct current potential. The regulated direct current potential in turn is then used to operate a solid state temperature control or controller. The controller in turn responds to a temperature at a thermistor to control a field effect transistor and series connected solenoid of a fuel valve.

Abstract: A gas heating system for a natural gas dehydration or the like comprising a burner housing means, a main gas burner unit and a pilot light gas burner unit mounted in the housing means, and separate air-gas supply means for each of the main gas burner unit and the pilot light gas burner unit.

Abstract: An integrated, closed loop system for controlling the fuel to air ratio in an induced draft combustion chamber which has a control pilot through which a draft is induced so that the fuel to air ratio in the control pilot chamber has a predetermined ratio to the fuel to air ratio in the primary combustion chamber.

Abstract: A water heater is disclosed having a main burner for heating a heat exchanger and a standing burner, and is also provided with an electromagnetic safety valve which is opened by a manual operation member and which is kept in its valve open condition by the electric current from a thermocouple element exposed to the standing burner and a water pressure sensitive member such that it opens in response to a supply of water to the heat exchanger (that is, the water flow is turned on). Both the electromagnetic safety valve and the water pressure sensitive valve are interposed in a fuel passage connected to the main burner. A standing burner fuel passage is connected on one end to the standing burner and is connected at its other end to a point located in between the two valves.

Abstract: Upon a call for heat, gas flows to a pilot burner, a spark generating circuit is energized to ignite the pilot burner, and an oscillator is energized. When flame appears, the output signal of the oscillator is effective, through flame responsive means including capacitor means and solid-state switch means, to enable energizing of the primary winding of a coupling transformer at the frequency of the oscillator signal. When so energized, sufficient power transfer occurs between the primary and secondary windings of the coupling transformer to enable energizing of a relay winding, which energizing terminates energizing of the spark generating circuit and allows gas to flow to the main burner.

Abstract: There is disclosed a control system for a gas burner appliance having an interrupted pilot burner operation. The system employs serially-connected first and second (main) electromagnetic operated valves. The first valve has a dual coil construction with a hold coil which can retain the pilot valve open and a pick coil which, acting in concert with the hold coil, can move the first valve to its open position. The control system utilizes one double pole, double throw relay in circuit with a lockout switch, the voltage source, the thermostat switch, and the cold switch contact of the flame switch. The igniter and pick coil are in circuit to the normally open contact of the relay thus being deenergized after a flame is detected at the pilot burner. The coil of the main gas valve is in circuit with the voltage source, the thermostat switch, the normally closed contact of the relay and the hot contact of the flame switch.

Abstract: A fuel burner safe starting system which utilizes a pilot valve and a main valve is disclosed. A flame detection system operates in conjunction with a relay which properly ignites and operates the fuel burner system. In the event of a failure which improperly energizes the relay, the safe starting system prevents the fuel valves from opening.

Abstract: Safety ignition means for burner installations having a first solenoid operated valve for a pilot burner, a second solenoid operated valve for a main burner, and an electric heater for igniting the pilot burner. The first valve has a hold solenoid connected to a power source through a normally closed bimetal switch. The first valve also has a make solenoid connected parallel to the hold solenoid through a flame switch and a second electric heater for the bimetal switch. The second valve has a solenoid connected parallel to the hold solenoid of the first valve through the flame switch. The flame switch is operative in response to flame of the pilot burner to deenergize the second electric heater for the bimetal switch and the make solenoid of the first valve and energize the solenoid of the second valve.

Abstract: An improved combustion detection apparatus is disclosed that can be employed in a fail-safe control circuit for a combustion apparatus to operate a shut-off valve in the fuel supply in response to the presence or absence of combustion. The improved combustion detector is an electrode assembly of a solid metal oxide member and electrodes in the form of electrical conducting coatings on opposite sides of the metal oxide member. The metal oxide has the characteristic of generating an electromotive force by transfer of oxygen ions therethrough. The combustion detector is placed in the vicinity of a flame from a pilot or main burner of the combustion apparatus. The oxygen gradient established by the burner flame and the resultant high temperature of the metal oxide member provides an instantaneous response to ignition or extinguishment of the burner flame.

Abstract: There is disclosed a thermally responsive switch that is ideally suited for responding to the ignition and extinguishment of a flame. The switch is provided with two switch poles, one that is biased normally open and the other that is biased normally closed. The response of the switch to the presence of a flame is very sensitive and precise to open the normally closed contact within a few seconds after ignition of a flame and, shortly thereafter within another controlled time period, to close the normally open contact. Upon extinguishment of the flame, the switch reverses its movement, opening the normally open contact within a short time interval, and, thereafter, closing the normally closed contact. The switch mechanism employs a thermally responsive, tube-in-tube member with the inner tube connected to a push rod which resiliently carries a switch lever.