Abstract: A method and apparatus for increasing the circulating airflow of induced-draft, gas-fired multi-stage furnaces without creating conditions that result in cold spot corrosion therein. Control circuitry is provided to selectably increase the circulating airflow of the furnace during low stage operation. The control circuitry is arranged so that increases in the magnitude of the circulating airflow of the furnace are accompanied by predetermined increases in the magnitude of the combustion airflow of the furnace. The magnitudes of the circulating and combustion airflows are so related to one another that the temperature at the output of the heat exchanger is maintained at a value which is approximately constant, and which is high enough to assure that water cannot condense thereon. The control circuitry may include a relay or relay-like device that is connected to prevent the high stage solenoid of the gas valve from becoming actuated during low stage operation.

Abstract: A space heater for heating air from within a room with a heat exchanger connected to a burner and discharging heated air into the room has a room temperature sensor for detecting a room temperature and a controller for controlling the burner with a freeze prevention temperature set to prevent indoor facilities from being frozen. When the detected room temperature drops to or below the freeze prevention temperature, the controller operates the burner and controls the burner with a lower limit for an amount of heat in the burner with which no moisture condensation occurs in the heat exchanger.

Abstract: A fuel/air mixture control for an induction heater having a tube-type burner includes a side-venting fuel nozzle for introducing fuel into an induction air stream entering the burner. A multi-speed blower draws combustion air into the burner and an air flow constrictor disposed proximate the fuel nozzle increases the velocity of the induction air stream proximate the fuel nozzle, increasing the volume of fuel introduced into the burner conduit. The fuel/air mixture depends upon the speed of the blower, which can be thermostatically controlled to increase speed upon sensing higher temperature combustion products, thereby maintaining a steady mass air flow and air/fuel mixture.

Abstract: A modulated burner combustion system that prevents the use of components that were originally not commissioned for use in the system. The present invention uses actuators that contain unique stored identification numbers. When the system is initially configured or commissioned, the unique identification numbers of the actuators are stored in nonvolatile memory in a fuel/air controller. When the system is brought on line, the fuel/air controller microprocessor initially sends false IDs to the actuator together with test control signals to determine if the actuator operates in response to the false identification numbers. If the actuator does operate in response to the false identification numbers, that is an indication that the system has been tampered with and the system is, consequently, shut down. Subsequently, the true identification numbers are transmitted to the actuators with test control signals.

Abstract: An automatic safety system for a fluid fuel air heating furnace. The safety system utilizes a double-sided carbon monoxide sensor for detecting unsafe levels of carbon monoxide interiorly and exteriorly of the furnace's heated air duct and a single-sided carbon monoxide sensor for detecting unsafe levels of carbon monoxide interiorly of the furnace's flue pipe. The sensors employ carbon monoxide detector chips which are electrically conductive in normal conditions, but become non-conductive when exposed to levels of carbon monoxide that are deemed unsafe for humans. The sensors are incorporated in an electrical circuit for energizing a solenoid valve which valve, when energized, opens to permit fuel flow to the furnace. Detection of unsafe levels of carbon monoxide will result in the sensors becoming non-conductive, thereby causing the solenoid valve to become de-energized and to close thereby preventing fuel flow to the furnace.

Abstract: A combustion air regulating apparatus which is adapted for use with two stage induced draft furnaces and which allows such furnaces to be used with low cost AC inducer motors of the type having one or a small number of nominally fixed operating speeds. A flow restrictor assembly is disposed in fluidic series with the air intake and the exhaust vent to controllably restrict the flow of air through the burner box when the inducer motor operates at its low speed. A pressure sensing assembly is connected to sense a pressure approximately equal to that across the heat exchanger, and to control the flow resistance of the flow restrictor assembly to maintain a sufficient level of excess air when the furnace operates in its low stage. A solenoid valve responsive to the establishment of high stage furnace operation causes the flow restrictor assembly to establish and maintain its minimum flow resistance during operation in that stage.

Abstract: In a heating system, when a high limit opens a predetermined number of times in a single call for heat by the thermostat, the system provides for operating the circulator blower at the cool speed rather than at the heat speed.

Abstract: An electric control is shown adapted for use with gas furnaces which controls fan motors, ignition controls and a gas valve based on inputs from a room thermostat, limit switches, a flame probe, a flame roll-out probe, and a condensate sensor. A roll-out detection circuit utilizing flame rectification includes a multidirectional roll-out probe 16 coupled to a microcontroller (U2) through an inverter (U3) to provide both fault both protection and fault identification. A condensate sensor (20) in the form of a conductive condensate sensor member is also coupled to the microcontroller (U2) through an inverter (U3) to detect the presence of condensate build-up.

Abstract: An apparatus senses the pressure changes in a collector box or relief box of a furnace due to changing wind conditions, and adjusts the gas flow accordingly. The apparatus controls the main gas valve of the furnace through a regulator loop. The regulator loop has a first port that communicates with a chamber below the main diaphragm of the valve, and a second port that communicates with a chamber above the main diaphragm. The regulator includes two diaphragms linked rigidly. A feedback pressure channel is connected to the collector box or the relief box, at one end, and to a feedback pressure tap at the other end. An increase in wind at the furnace vent causes changes in pressure in the collector box and the relief box. This change in pressure is delivered to the feedback pressure tap. When the pressure at the feedback pressure tap increases, the top diaphragm and the bottom diaphragm both move upward.

Abstract: A gas-fired air heating furnace has a modulatable supply air blower and a modulatable gas valve operatively connected to the combustion air heat exchanger burner. A calibration sequence of a microprocessor-based control system is utilized to automatically determine the precise relationship between the gas valve setting and the actual heat transferred by the heat exchanger to air flowing through the furnace by measuring the actual air temperature rise across the heat exchanger obtained using initial calibration settings of the blower and gas valve.

Abstract: A furnace control apparatus is described wherein a flow of gas into a burner assembly is directly dependent on an indicia of burner combustion air airflow, such as heat exchanger pressure drop. According to one embodiment of the invention, a first communication fluid line is interposed between a gas valve regulator and a heat exchanger at a first point, and a second communication fluid line is interposed between a gas valve regulator a heat exchanger at a second point. The main valve of the gas valve is responsive to the pressure differential between the first and second points so that a flow of gas into a furnace burner assembly is commensurate with a present flow level of combustion air.

Abstract: A control system for regulating a flow rate of a heat transfer fluid in a heat transfer system, the heat transfer system having a heat transfer fluid flow path, flow control device for creating flow along the path, a fuel source for providing a combustible fuel to the path, an air source for providing combustion air to the path, and an assembly for combusting the fuel and air, the control system comprising a sensor for sensing a measured flow value at the air source, a controller for storing an optimum flow value at the air source and for storing a range of operating control values for the flow control device, the operating control values corresponding to the optimum flow value, a system for calculating a deviation between the measured flow value and the optimum flow value, and a system for varying the operation of the flow control means in accordance with the deviation.

Abstract: The present invention is a method and apparatus for controlling the flow of combustion air and/or combustion products through a furnace which may experience changing flow restrictions. The method provides constant flow through an induced-draft furnace by determining torque values applied to an inducer motor of the furnace from a lookup table, which is established by operating a test furnace under changing flow restrictions, typically by measuring furnace flue gas carbon monoxide concentration. A lookup table according to the invention may include motor operating performance plots for controlling inducer speed under operating conditions, and threshold plots, which may be employed for determining activation of furnace events such as ignition, gas valve energizing, and shutdown. In an adaptive method of the invention, an adaptive lookup table is provided by averaging torque values from each of several lookup tables.

Abstract: A carbon monoxide detection and automatic deactivation system including a fuel burner having a fuel supply conduit coupled thereto. A pilot igniter is situated adjacent to a pilot supply conduit and is adapted to provide a flame in an interior space of the burner upon the actuation thereof. A thermocouple is positioned adjacent to the pilot igniter for producing an electric current upon the detection of heat. Also included is an electromechanical fuel valve comprising a solenoid adapted to allow the supply of fuel to the burner upon the receipt of current via the thermocouple and further preclude said supply upon the lack thereof. Finally, a switch mechanism is electrically coupled between the thermocouple and the solenoid. The switch mechanism has a first orientation for allowing current to pass therebetween with the absence of carbon monoxide and a second orientation for precluding current to pass therebetween with the presence of carbon monoxide.

Abstract: A mobile or modular home hot air heating and humidifying system including a counter-flow furnace having a base pan and a housing resting on the base pan and containing a heat exchanger and a blower located above the heat exchanger for directing air downwardly within the housing in heat exchange relation to the heat exchanger and to and through an air outlet opening in the base pan. A humidifier unit resting on the floor below the furnace and structurally supporting the furnace defines a passageway communicating with the air outlet and with a feeder duct which extends downwardly through the floor and connects to a heat distribution duct system below the floor. The humidifier operates in response to operation of the blower. A method for installing a humidifier unit in an existing heating system of the aforedescribed general type is also disclosed.

Abstract: An unvented patio fireplace comprises a fireplace housing that has a front panel configured like an in room fireplace, and which fireplace housing is mounted onto a pedestal and base support for movement along a surface. The base support includes wheels and casters as desired for providing mobility. The base also supports a self contained fuel supply for supplying gas to a burner in the fireplace housing. Burner controls include an oxygen depletion sensor so that the unit can be unvented, and tilt sensors that will sense when the fireplace is tilted a selected amount to shut off the gas supply.

Abstract: A modulating, forced draft, fuel-fired air heating furnace is provided with a two-speed draft inducer fan, and a fuel valve which is fully modulatable between a maximum firing rate and a low firing rate of approximately forty percent thereof. Incorporated into the furnace control system are normally closed low and high fire pressure-electric switches which sense and are sequentially closed by increasingly negative pressure in the draft inducer fan. Upon a call for heat from a thermostat located in the conditioned space served by the furnace, the draft inducer fan is energized at its high speed setting, and a signal is sent to the fuel valve to set it at its full firing rate flow when opened by an ignition switch portion of the control system. The control system functions to open the fuel valve at this maximum flow setting, and permit light-off of the burner, only if (1) both of the low and high fire pressure-electric switches are closed, and (2) the draft inducer fan is operating at its high speed setting.

Abstract: Method and apparatus are disclosed for checking the responsiveness of a circuit which senses the presence of a flame produced by a burner within a furnace. A programmed processor associated with the circuit measures the time the circuit takes to indicate the presence of a flame. A warning is generated when the measured time exceeds a predetermined allowable time. The allowable time is determined by taking into account the decreased responsiveness of an electrode that indicates the presence of the burner flame.

Abstract: Systems and methods for controlling a draft inducer for use with a furnace. The draft inducer includes a fan for inducing a draft in the furnace combustion chamber that causes a pressure drop across a heat exchanger assembly for moving exhaust combustion chamber gases. The heat exchanger assembly has a plurality of heat exchanger elements which determine furnace capacity wherein the pressure drop across the heat exchanger assembly is affected by the furnace capacity. A motor drives the fan in response to a motor control signal and a memory stores information defining a relationship between motor speed, motor torque and parameters defining motor operation. A processor determines the speed and torque of the motor and retrieves from the memory the parameters corresponding to the determined motor speed and motor torque. The processor is responsive to the retrieved parameters for defining at least one set of speed/torque curves corresponding to a desired pressure drop across the heat exchanger assembly.

Abstract: Systems and methods for controlling a draft inducer for use with a furnace. The draft inducer includes a motor for driving a fan for inducing a draft in the furnace that causes a pressure drop across the heat exchanger of the furnace. A memory stores information including a table of predefined speed/torque values for defining a set of speed/torque curves for operating the motor. A pressure switch provides a pressure signal representative of a reference pressure across the heat exchanger and a processor determines the speed and torque of the motor when the pressure drop corresponds to the reference pressure. In response to the determined motor speed and motor torque, the processor retrieves a parameter defining at least one delta value from the memory. The processor adapts the predefined speed/torque values as a function of the delta value thereby to define the speed/torque curves corresponding to a desired pressure drop.

Abstract: The apparatus consists basically of an atmospheric burner, a combustion chamber, and means for creating a vacuum within the combustion chamber. To provide optimum combustion using different gases from one gas family, means for detecting at least one apparatus temperature and means for controlling the primary air flow according to the temperature detected are provided. Various applications are described wherein the temperature is measured at the surface of a burner diffuser and the primary air is controlled to keep the temperature below a critical value and the flame stable. For improved operation at the ignition stage, the flow rate of the primary air is set at a comparatively low predetermined starting value.

Abstract: A control system for regulating a flow rate of a heat transfer fluid in a heat transfer system, the heat transfer system having a heat transfer fluid flow path, flow control device for creating flow along the path, a fuel source for providing a combustible fuel to the path, an air source for providing combustion air to the path, and an assembly for combusting the fuel and air, the control system comprising a sensor for sensing a measured flow value at the air source, a controller for storing an optimum flow value at the air source and for storing a range of operating control values for the flow control device, the operating control values corresponding to the optimum flow value, a system for calculating a deviation between the measured flow value and the optimum flow value, and a system for varying the operation of the flow control means in accordance with deviation.

Abstract: A control system for a fluid-fuel burner, such as a furnace for an HVAC system. The furnace has a variable flow of fuel into the burner. In addition, the circulating air blower is also variable. The furnace heat exchanger plenum is maintained at a substantially constant temperature, as a means for providing substantially constant temperature air to the spaces to be heated.

Abstract: A combination water heating and space heating apparatus includes a water heating unit and a space heating unit releasably coupled with the water heating unit. The water heating unit has a water storage tank and a helically wound tubular heat exchanger inside the tank for exhausting products of combustion from a combustion chamber located in a top part of the tank and for transferring heat from the products of combustion to the surrounding water. The space heating unit is an air handler with an hydronic heat exchanger coil and a blower for blowing air over the coil. Hot water is supplied from the tank to the coil and is returned to the tank by means of a water circulation pump located in the space heating unit. Air blown over the coil is heated by the hot water flowing over the coil.

Abstract: This invention relates to a method and system for controlling a heating/air conditioning unit. More particularly, this invention relates to a control unit which detects the presence of one or more gases (e.g. CO, fuel, refrigerant or radon) produced by the heating/air conditioning unit and disables the heating/air conditioning unit if gases are present in undesired concentrations. In one embodiment of the present invention, the presence of multiple gases are detected and a separate indication for each gas is provided. An alternate embodiment of the present invention provides means for resetting the heating/air conditioning unit a selected number of times after the heating/air conditioning unit has been disabled due to the presence of a gas in undesired levels. An alternative embodiment of the present invention provides means for disabling the central heating/air conditioning unit based upon the activation of one or more smoke alarms.

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: A control or regulating system for an automatic heat furnace is disclosed. This control system simplifies the construction of automatic gas furnaces for heating plants. The control system operates the furnaces with a high degree of efficiency and low pollutant emission, even at partial capacity. The adjusting element or mechanism for air is a blower with adjustable rotational speed which is driven by a motor. The motor is controllable by, preferably, digital pulse-width modulated control signals of a control aggregate acted upon by a regulator. A gas valve regulates the pressure of the gas supplied to the burner as a function of the air pressure in the line leading from the blower to the burner.

Abstract: This invention relates to a method and system for controlling a heating/air conditioning unit. More particularly, this invention relates to a control unit which detects the presence of one or more gases (e.g. CO, fuel, refrigerant or rador) produced by the heating/air conditioning unit and disables the heating/air conditioning unit if gases are present in undesired concentrations. In one embodiment of the present invention, the presence of multiple gases are detected and a separate indication for each gas is provided. An alternate embodiment of the present invention provides means for resetting the heating/air conditioning unit a selected number of times after the heating/air conditioning unit has been disabled due to the presence of a gas in undesired levels. An alternative embodiment of the present invention provides means for disabling the central heating/air conditioning unit based upon the activation of one or more smoke alarms.

Abstract: A thermostatic gas heater which permits the user to mechanically select the number of active heating elements, ranging from one to the total number of heating elements. The thermostat mechanically regulates gas flow to all active heating elements. No electricity is necessary for operation because all control components operate mechanically.

Abstract: A gas radiant tube heater and method of operating the heater. The heater has a housing and a radiant tube mounted within the housing. The heater further has a modular control box mounted within the housing in which serviceable parts can be easily removed as a unit and replaced. The housing and control box are sealed against the elements for outdoor as well as indoor use. The control box is divided into two chambers, with the inlet air flowing from a first chamber into a second chamber. The first chamber is subjected to a vacuum pressure, in which the heat sensitive equipment is mounted, and the second chamber is subjected to a positive pressure, in which the combustible gas and air mix prior to combustion. The heater further has a pressure switch to shut off the gas supply if the air flow through the heater is blocked, and a flame sensor to shut off the gas supply if the ignition element fails to ignite the air/gas mixture.

Abstract: An uninterruptible gas-fired forced hot air furnace utilizes a thermoelectric generator in the path of the hot combusted gas to a heat exchanger. The combusted gas (combustion products) flows through the pipes of the heat exchanger to an exhaust which may lead to the chimney,or direct vent, in the building in which the furnace is located. The thermoelectric generator is also in the path of the forced cold air which also goes to the heat exchanger. The cold air thus picks up heat in the process of cooling the cold junctions of the thermoelectric generator and picks up more heat in the heat exchanger from the combustion products before being ducted into the heating system. The thermoelectric generator cold junctions may be air-cooled by fins connected thereto through which the stream of air from the blower passes or the cold junctions may be cooled by liquid which is circulated through a liquid-to-air heat exchanger.

Abstract: A two-stage induced draft furnace is operated at either high heat or low heat with the gas valve switched to high-fire or low-fire. High-fire and low-fire combustion pressure switches sense the collector box flue gas pressure and actuate respective solenoids of the gas valve. Under some conditions the inducer can produce sufficient negative pressure at low fire to prove the high fire pressure switch and cycle the burners on high fire. To prevent this, relay contacts are interposed between the high fire pressure switch and the gas valve solenoid to deny thermostat power to the high-fire solenoid whenever there is a call for low heat.

Abstract: There is disclosed a modification in the control circuitry of a gas furnace having a primary or main limit whereby the primary circuit subsumes the functions of a the secondary or manual reset limit circuit. The control circuit incorporates a microprocessor capable of sensing conditions in the furnace, enabling and disabling the various furnace components.

Abstract: A pilot pressure switch for a furnace detects the fluid pressure within the pilot line for a pilot flame, and upon the fluid pressure in the pilot line exceeding a predetermined value, an electrical signal from a thermostat may be passed to a furnace blower control to operate the furnace main blower and furnace vent blower.

Abstract: A furnace for supplying circulated heated air to a comfort zone, the furnace having a condensing heat exchanger and a blower for moving ambient air over the heat exchanger, wherein a transformer for stepping down line voltage (115 VAC) to control voltage (24 VAC) is secured to the inner surface of an enclosed housing within the furnace wherein the inner wall also supports at least one retaining bracket and one fastenable support bracket. A first flange extending from the transformer engages the retaining bracket to rotatably support the transformer. A second flange extending from the transformer engages the fastenable support bracket to secure and further support the transformer supported within the housing. A threaded member secures the fastenable support bracket to the second flange, thereby preventing disengagement.

Abstract: In a fixed-firing rate induced draft furnace, having a heat exchanger and an integrated control inducer motor, an improved method of controlling excess air comprising the steps of: providing at least one pressure switch that is responsive to a preselected pressure drop level in the heat exchanger, the pressure drop level being selected so as to be commensurate with a theoretically desired excess air level under firing operating conditions; accelerating the integrated control inducer motor until the pressure switch closes and thereupon recording a first motor speed and a first current level; calculating a first torque value based on the first motor speed and the first current level; and regulating torque applied to the integrated control inducer motor in accordance with the first torque value.

Abstract: A front access door suitable for accessing and enclosing a housing within a multipoise furnace functions in conjunction with a safety shutoff switch to provide greater access and safety when assembling and servicing the furnace. The front access door is hingably supported upon the bottom wall of the housing for removal from the furnace and rotation between a closed position and an opened position. The shutoff switch is mounted outside the housing on the top housing wall. When the access door moves into a closed position, a switch activator, mounted to the access door, passes over the top housing wall and closes the switch, thereby allowing power to flow to a blower within the housing. When the access door is moved into an open position, the switch activator opens the switch, thereby terminating power to the blower.

Abstract: A forced air furnace control system for preventing the buildup of dangerous concentrations of CO gas within a building airspace. A CO sensor is mounted in the air exit plenum of the furnace and connected in a circuit which produces an output signal when the concentration of CO gas in the plenum reaches a predetermined unsafe level. A disable control signal is then triggered through the circuit for switching the furnace to its nonoperating mode. A latch circuit is provided for latching the furnace control in the nonoperating mode independent of the disable control signal. A reset circuit is provided to manually override operation of the latch circuit and re-enable the furnace control for switching to the operating mode.

Abstract: A gas-fired construction heater which meets the applicable ANSI Standard and operates to supply heated air separately from products of combustion. The products of combustion are permitted to contain no more than a specified percent of carbon monoxide when uncontrolled heater operating conditions are within predetermined ranges. The uncontrolled operating conditions include variations in input rate and supply voltage. A combustion chamber produces the products of combustion and has primary and secondary combustion zones. A heat exchanger receives the products of combustion and transfers heat therefrom to fresh air to be heated. The chamber and the heat exchanger define a tertiary combustion zone. Inlets supply a separate natural combustion draft to each of the primary and tertiary combustion zones. The inlets include a first and a third fixed-area inlet for respectively supplying the separate natural drafts to the primary and tertiary combustion zones.

Abstract: The present invention is a furnace control system responsive to a circulator fan motor fault condition. Upon detection of the fault, the control determines a first time period which is required to activate the temperature limit switch of the furnace by continuous operation of the gas burner and a second time period which is required for the plenum to dissipate sufficient heat to deactivate the temperature limit switch. After determining the first and second time periods, the furnace control operates the burners for a fraction of the first time period and then allows the heat exchangers to cool for the second time period until the circulator fan motor fault is corrected or the demand for heat ceases.

Abstract: A heat exchanger control system, an electrically operated control valve device therefor and methods of making the same are provided, the heat exchanger control system comprising an electrically operated control valve device having a housing and a differential pressure operated electrical switch unit being operatively interconnected to structure of the system for supplying combustion air to a burner unit of the system and being adapted to be operated thereby to permit the electrically operated control valve device to be operating only when the pressure value of the air being supplied to the burner unit is at or above a predetermined value so that sufficient combustion air will be supplied to the burner unit before the electrically operated control valve device causes fuel to issue from the burner unit, the differential pressure operated switch unit being carried by the housing so as to be self-contained with the electrically operated control valve device.

Abstract: The humidity of a heated space is regulated by varying the amount of moisture transferred from the combustion gases of the furnace used to heat the space. A porous heat sink element is arranged to move through the path of the combustion gases and one or more reclaim-air paths. The heat sink member can take any of a variety of forms; it can reciprocate back and forth along a track, or it can be configured as a rotating wheel ("heat wheel"). The amount of moisture transferred from the combustion gases to the reclaim air is governed by a humidity signal. If the humidity signal calls for a change in humidity, one of several parameters is varied to provide for a greater or lesser transfer of moisture from the combustion gases to the reclaim air.

Abstract: A control system for a gas fired, direct ignition, induced draft furnace includes a radiant heat sensing switch responsive to a hot surface igniter and burner flame, a single-pole, double-throw pressure switch responsive to fluid flow effected by the inducer, and a plurality of relays responsive to the radiant heat sensing switch, the pressure switch, and various other connected switching means.

Abstract: A flue gas closure system for a furnace which includes a burner and a heat exchanger through which flue gas flows. The system includes a closure member which in an open position permits the flow of flue gas through the heat exchanger and in a closed position prevents the flow of air through the heat exchanger and means for causing said closure member to be in an open position when the burners are on and to be in a closed position when the burners are off. The closure member includes a closure plate which is slidably connected to the heat exchanger. An actuator is connected to said closure member for moving said closure member to at least one of the open and closed positions.

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: An easily portable ventilating heater to supply either ambient fresh air or warm fresh air to utility workers while working in an underground utility installation. The ventilating heater comprises a blower unit and a heater unit. The blower unit can be used and operated without the heater being in operation. On the other hand, the heater cannot operate unless the blower unit is in operation. The ventilating heater has seveal safety features so that the heater automatically shuts down if the heater exceeds a pre-set temperature of about 200.degree. F., the inlet air flow is interrupted or the power or gas supply is interrupted. The ventilating heater automatically restarts once the heater temperature goes below the pre-set temperature and there is no interruption of air or gas flow or power. The heater uses liquid propane gas and the electrical system can be A.C. or D.C.

Abstract: The present invention is a direct fired unit heater which includes a lower combustion chamber which communicates with an upper fan assembly which mixes combustion products with ambient air and discharges this laterally from the unit. The fan assembly has two cylindrical fans each with different critical speeds. One motor drives both cylindrical fans and is adjustable so that at a first higher speed it is within the operating range of both fans. At a lower operating speed, it is only within the operating range of the upper cylindrical fan. The upper cylindrical fan acts to pull in room air and discharge this. Thus, the blower operates continuously thereby destratifying the room air. When the burner operates, the motor speed is increased to act within the operating speed of the lower fan assembly. This lower fan assembly thereby pulls in the combustion products and discharges these along with the ambient air. The size of the cylindrical fans are designed to provide appropriate mixing for a direct fired unit.

Abstract: A heating which comprises a housing containing a water conduit, a fire compartment for heating the water in the water conduit, a heating chamber containing a plurality of heat emitting fin coil members disposed therein, a water storage tank disposed on the housing, and four turbo fans for blowing hot air around the plurality of heat emitting fin coil member and circulating the heated air into the room, whereby the heating apparatus produces hot air with a controlled humidity while at the same time reducing fire danger and pollution due to dust, smoke, and ash.

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 burner control for a condensing furnace having a flame proving circuit that incorporates the flame at the burner to be closed and that opens upon absence of a flame to cause a gas valve to close and block the flow of gas to the burner. A short circuit shunting the flame proving circuit includes a probe that projects into the outlet manifold of the condensing furnace. If liquid level in the outlet manifold reaches the probe, a short circuit is closed between the probe and a ground on the manifold. The control to the valve is energized to close the valve in the same manner as if the flame had extinguished at the burner. Upon closing the gas valve, the burner is extinguished.