Abstract: In a two-stage furnace system, including a thermostat, at least one gas burner with a low and high-fire operating capability, an inducer fan having low and high speed operating settings, and a high-fire pressure switch, a method for handling the high-fire pressure switch being in an inappropriately open condition. The method has the steps of: determining whether the thermostat is issuing a call for high heat and, if it is, determining if the high-fire pressure switch is open. If the high-fire pressure switch is open, waiting a predetermined time, determining if the high-fire pressure switch is still open and, if it is, completing a furnace shutdown procedure, then initiating a normal shutdown, then an ignition sequence in high-speed inducer pre-purge mode, determining if the high-fire pressure switch remains open, and if so, running at least one gas burner in low-fire mode. If, while these steps are being performed, the high-fire pressure switch closes, running the system in high-fire mode.

Abstract: The present invention relates to an intelligent transient eliminator which allows a gas ignition system to prevent gas valves from being turned off by a pressure switch in response to a transient pressure wave. The transient eliminator is preferably provided in a HVAC unit or furnace which burns a fuel such as natural gas. An ignition control system employing an intelligent transient eliminator provides a secondary relay across the pressure switch. The secondary relay is controlled by a signal to an ignitor in the furnace. The secondary switch is tested before energizing the inducer blower in the system.

Abstract: Apparatus and method for sensing the operating condition of a burner temperature as the indicating variable. When the operating status is stable, the flue temperature should be nearly identical to that when the system was known to be in proper condition. During a time when the system is known to be in proper operating condition, the flue temperature is recorded during stable operation for a number of different firing rates. When identical or similar firing rates occur at a later time and operation is stable, the operating flue temperature is compared with the current flue temperature, and if substantially different, an operation status signal is set to a state indicating this change in operating condition.

Abstract: A method of controlling the pressure in an incinerator for incinerating municipal refuse, industrial waste, etc. Exhaust gas from an incinerator typically passes through an exhaust gas cooler and an exhaust gas treating device and then discharged into the atmosphere by the action of an induced draft fan. In a method of controlling the pressure in such an incinerator for incinerating municipal refuse, industrial waste, etc. gas, e.g., part of the flow of exhaust gas induced by the induced draft fan or air taken in from the atmosphere, is added to a gas flow path upstream of the inlet of the induced draft fan through an addition gas line provided with an addition gas control damper. The addition gas control damper is controlled on the basis of an output from a furnace pressure controller such that when the furnace pressure is relatively high, the flow rate of the addition gas is reduced, whereas, when the furnace pressure is relatively low, the flow rate of the addition gas is increased.

Abstract: A control assembly in combination with a thermostatically responsive apparatus. In a preferred mode the principles of the present invention are applied to an infra-red heating system of the type including burner assemblies (12, 12') connected in series by a heating pipe (14), the assemblies being further connected by heating pipes (14) to a vacuum pump (40). The pump (40) is driven by a variable-speed electric motor (42) which is responsive to a thermostat (16) which may initiate, through control panel (15), operation of the burner assemblies. The burning rate of the burner assemblies is controlled by varying the speed of the electric motor and this is accomplished by the control assembly (44) which is responsive to indoor and outdoor temperature sensing devices (48, 50). The control assembly is initially programmed with climatic data which is correlated with operational speeds of the pump to give desired thermal operational characteristics of the burners at differing temperature ranges.

Abstract: The present invention involves a two stage furnace and a method of controlling the fans. In the furnace, a high pressure switch indicates whether sufficient air is present to support high combustion. Normally the furnace operates at one of the combustion settings. The circulator fan operates at the high speed setting when the high pressure switch indicates that sufficient air is present for high combustion, and operates at the low speed setting when the high pressure switch indicates that insufficient air is present for high combustion.

Abstract: A forced draft direct vent system is provided for an indoor domestic type gas water heater having an atmospheric burner. The forced draft system permits adaptation of the water heater as a combined water heater and space heater in a compact continuous upright arrangement of components.

Abstract: Disclosed is a heating system having a combustion air blower, a fuel valve for providing fuel to a burner, and an exhaust stack for exhausting combustion products. Also disclosed is flow sensor apparatus operatively associated with the stack for providing control signals to a furnace control, the control signals being related to flow conditions in the stack.

Abstract: Method and apparatus for maintaining excess air control in a gas furnace. A pressure switch is placed across a heat exchanger to indicate when, while accelerating the inducer motor speed during purging operation, the pressure drop reaches a predetermined level. When that occurs, the motor speed is sensed and recorded. When the furnace is subsequently fired, the desired inducer motor speed is obtained by modifying the recorded motor speed on a correction factor derived from empirical data obtained from a gas furnace operating under selective variable conditions.

Abstract: Disclosed is a fuel gas control for controlling the delivery of fuel gas. The present gas control comprises an inlet chamber having an inlet for receiving a supply of gas and an outlet chamber having an outlet for providing a supply of gas. The inlet and outlet chambers are connected by a valve opening. A valve is operatively associated with the opening. The valve has a closed position for preventing the flow of gas through the opening and an open position for permitting the flow of gas through the opening. The present control further comprises control chamber means for moving the valve between its open and closed positions in response to pressure variations within the control chamber means. The present control further comprises apparatus for directly connecting the control chamber means to a pressure signal from a power combustion air blower so that the valve is positioned in response to the pressure signal from the combustion air blower.

Abstract: A burner control system for gas fired apparatus of the powered blower vent type wherein a diaphagm valve for controlling the supply of gas to the main burner of the apparatus is operated by a gas bleed line which is subject to pressure regulation by a servo regulator valve. The bleed line is also subject to on-off control by pneumatically operated bleed valve means which are responsive to the subatmospheric fluid pressure produced in the exhaust vent of the apparatus by an exhaust blower to permit opening of the diaphragm valve only when the fluid pressure level within the exhaust vent is sufficiently below atmospheric pressure. The control system preferably includes switching circuit means which are effective to energize the exhaust blower only during the existence of a pilot burner flame adequate to ignite the main burner.

Abstract: A recirculation device for recirculating a selected volume of preheated gas exhausted from a heating chamber in a mixture with fresh air back to the heating chamber. The device comprises a first passageway having an entrance and a pair of exits; a second passageway having a pair of inlets and an outlet; and a third passageway connecting one exit and one inlet. The other exit communicates with a preheated gas exhaust, and the other intake communicates with a source of fresh air. A back pressure damper is secured adjacent the other exit. A manual control assembly is connected to the back pressure damper so that the volume of preheated gas flowing into the preheated gas exhaust may be selectively determined. A mixing damper is secured adjacent the other intake. An automatic temperature dependent control assembly is connected to the mixing damper so that the mixture of preheated gas and fresh air entering the heating chamber is dependent upon the temperature in the heating chamber.

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 flow control device is provided for use with a fan to prevent pressure excursions in a furnace or any other hardware equipment to which the fan is connected. The control device is connected in parallel relation with respect to the fan so that a recirculating flow path is formed between an outlet of the fan and an inlet thereof. This recirculating flow path controls the pressure differential produced by the fan. The control device includes duct work and a controlled element, preferably, a damper. In a furnace system, an induced draft fan is connected in series with a furnace and the controlled device is normally in a closed position in parallel with the induced draft fan. Upon the occurrence of one or more predetermined fault conditions, the controlled device modulates open to provide a circulating path through the induced draft fan and rapidly controls the pressure differential between the inlet and outlet of the fan.

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: 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 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: A process for the production of heated aggregate mix, such as bituminous mix, and a reactor for carrying out the process. In one aspect, the process entails the control of gas flow through a tumbler drum, preferably by controlling exhaust from the drum, in dependence upon the continuous monitoring of a parameter, such as gas pressure within the drum. In a second aspect the aggregate contents of the drum are heated by using a burner to preheat the gas flow, a technique which permits admission of the drum feed as a homogenous stabilized mix.

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: The inlet vanes for an induced draft (ID) fan in a power plant boiler are position controlled in accordance with the furnace pressure to limit the potential destructive power developed by the fan. The ID inlet suction temperature is sensed and a control signal is developed as a function of the inlet temperature to limit the opening of the inlet vanes during boiler startup.

Abstract: In a fired furnace system having a convection section, and in which control a furnace draft is vital to both fuel conservation and avoidance of furnace damage, apparatus for monitoring the pressure conditions (draft) inside the furnace comprises a first pressure sensor means positioned at the arch (roof) of the furnace, a second pressure sensor means inside the furnace downstream from the convection section, and differential pressure measuring means connected between the first and second means for constantly measuring the pressure drop through the convection section.

Abstract: Method and apparatus for the heat treatment of volatile containing materials in a rotary hearth type furnace wherein the flue gases emanating from the calciner are employed to create either a positive or negative pressure within the calciner hearth as well as the soaking pit area of the said calciner.

Abstract: A furnace draft control for a fossil fuel fired steam generator wherein the rates of flow of fuel, air and flue gas are adjusted in parallel in accordance with changes in power demand and the forced and induced drafts are adjusted in opposite directions as required to maintain furnace draft at set point.

Abstract: There has been provided a control for regulating the pressure excursions in a furnace having forced draft and induced draft fans. A pressure detector responsive to pressure in the furnace delivers an output indicative thereof. Circuit means, responsive to the pressure detector means and a set point input, delivers a correction signal output. Fan control means coupled to the induced draft fan is responsive to a demand input signal corresponding to a desired flow rate through the furnace and is likewise responsive to the correction signal for delivering a fan control signal for regulating said induced draft fan in accordance with variations in the flow rate and pressure excursions in the furnace. An override circuit is responsive to the pressure detector and an override set point input to produce an override output for controlling the induced draft fan at a rate substantially higher than that of the correction signal.

Abstract: A furnace system having a combustion chamber, and heat transfer surfaces, forced and induced draft fans for moving gas through the burner, chamber, and heattransfer surfaces, first controls for maintaining predetermined gas flows and furnace pressure or draft dependent upon the desired normal operating conditions, and second controls responsive to the flow of the gas exterior to the chamber, e.g., at the inlet or outlet of the induced draft fan and, if desired, at the outlet of the forced draft fan, for controlling a damper or dampers in the gas path or the speed of the fans so as to limit the vacuum which can be developed in the chamber by the induced draft fan to a value less than the chamber vacuum withstanding design value. Also, if desired, the second controls at the outlet of the forced draft fan can limit pressure which can be developed in the chamber by the forced draft fan to a value less than the chamber pressure withstanding design value.