Abstract: A furnace control system for controlling a gas-fired induced-draft furnace having a variable speed inducer blower. A control apparatus, responsive to a signal corresponding to the magnitude of a pressure difference between an inlet and outlet of the combustion chamber, controls blower motor speed to maintain the pressure difference at a predetermined magnitude corresponding to a selected gas flow rate. Inducer blower motor speed is varied directly and precisely to maintain an optimal pressure drop across the combustion chamber. The control system can be used in multi-stage and modulating furnace systems and in furnace systems utilizing pressure- assist modulating gas values.

Abstract: A controller for a two-stage heat source is provide, which may be connected to either a single stage or a two-stage thermostat to provide low stage heating for a variable time period before switching to high stage heating. The controller includes at least a first terminal for receiving a signal requesting heating from a single-stage thermostat or a two-stage thermostat connected to the first terminal. A microcontroller in communication with the first terminal determines a duty cycle value for a heating cycle based on the duration in which a signal at the first terminal is present relative to the duration of the heating cycle. The microcontroller determines a low stage time limit from the duty cycle, and provides low stage heating when a signal is present at the first terminal for a time period not more than the time limit, and switches to high stage heating after the time limit.

Abstract: Methods and systems for operating a fuel fired appliance that may include an optional hardware component such as a damper are disclosed. In some cases, the presence of the optional hardware component is detected, and it is determined whether the optional hardware component is required for future operation of the fuel fired appliance. The fuel fired appliance may be operated normally if the optional hardware component is present and required, or, in some cases, if the optional hardware component is determined to be not required. If the optional hardware component is absent but required, normal operation of the fuel fired appliance may be stopped.

Abstract: A universal controller for coordinating activity of an appliance room including a configurable air control portion, and a configurable appliance control portion. The configurable air control portion controls at least one air flow condition of the appliance room and includes an air control interface adapted to be operatively coupled with at least one of an influent combustion air system and a venting system. The configurable appliance control portion controls operation of a plurality of appliances and includes at least one appliance interface adapted to be operatively coupled with the plurality of appliances. The appliance control portion is adapted to selectively coordinate operation of individual appliances such that a selected at least one of the plurality of appliances can be operated according to a dynamically adjustable sequence.

Abstract: A controller and method for operating an HVAC system including an air conditioning unit, such as a gas furnace, having three stages of heat output and responsive to signals from a single stage or two stage thermostat. The W1, W2, and W3 inputs to the controller may be configured for receipt of a single stage control signal simultaneously or paired as W1, W2 or W2, W3. The system controller is configured to determine which input connection arrangement is in existence and operates the system in mock one stage or mock two stage modes depending on the signals received from a single or two stage thermostat, respectively.

Abstract: Systems, methods, and controllers for controlling gas-fired appliances such as warm air furnaces are disclosed. An illustrative furnace system can include a burner unit in communication with a combustion air flow conduit and heat exchanger, a variable speed inducer fan or blower adapted to provide a flow of combustion air to the burner unit, a furnace controller and motor speed control unit adapted to regulate the speed of the inducer fan or blower, and a pneumatically modulated gas valve adapted to variably output gas pressure to the burner unit based at least in part on the combustion air flow.

Abstract: A hot-water supply apparatus is an apparatus which has a primary heat exchanger absorbing sensible heat of combustion exhaust and a secondary heat exchanger absorbing latent heat of the combustion exhaust, and improves a freezing prevention function of the hot-water supply apparatus at a cold period. Further, this apparatus has a temperature detection means (temperature sensors) which detects a freezing prevention temperature, a combustion means (a burner group) which supplies combustion exhaust generated by combustion to the primary and secondary heat exchangers, an air supply means which supplies air to the combustion means, and a control means (a control unit) which makes the combustion means burn and drives the air supply means based on a detected temperature of the temperature detection means.

Abstract: An interactive system for controlling the operation of an HVAC system is provide that comprises a thermostat for initiating the operation of the HVAC system in either a full capacity mode of operation or at least one reduced capacity mode of operation, and a controller for an outside condenser unit having a condenser fan motor and a compressor motor, the controller being capable of operating the compressor in a full capacity mode and at least one reduced capacity mode. The system also comprises a controller for an indoor blower unit having a blower fan motor, the controller being capable of operating the blower fan motor in a full capacity mode an at least one reduced capacity mode. The system further includes a communication means for transmitting information between the outside condenser unit controller and at least the indoor blower controller, where the information relates to the operation of the indoor blower and the outdoor condenser unit.

Abstract: A heating or cooling system, such as an HVAC system, of variable output has a number of control elements and may include a variable speed compressor, a variable speed combustion (induced or forced draft) blower motor; a variable speed circulator blower motor; a variable output gas valve or gas/air premix unit; and a controller specifically developed for variable output applications. The system may utilize a pressure sensor to determine the actual flow of combustion airflow in response to actual space conditions, vary the speed of the inducer blower, and subsequently vary the gas valve output to supply the correct amount of gas to the burner system. A temperature sensor may be located in the discharge air stream of the conditioned air to provide an input signal for the circulator blower.

Abstract: An air handler operates alternately in (a) a heating state at times when air in a space in a building is at an actual temperature that is insufficient relative to a set temperature and (b) a non-heating state at times when the air in the space is at an actual temperature that is sufficient relative to a set temperature, and at least sometimes during the non-heating state, delivering heated air to the space.

Abstract: A fan motor speed control system for controlling the fan motor speed of an air conditioning system includes a power output circuit including a power triac which is turned on and off by an opto-isolator connected to a pulse generator circuit for varying an AC voltage waveform imposed on the fan motor. The pulse generator circuit is connected to heating and cooling ramp circuits and a minimum speed circuit to provide a variable voltage signal imposed on the pulse generator circuit corresponding to the temperature difference sensed by a return air sensor and a heating or cooling sensor or by separate heating and cooling sensors disposed adjacent respective heating and cooling heat exchangers of the air conditioning system. An adjustable minimum speed circuit and a cutoff circuit are provided to control motor minimum speed or motor shutoff when a predetermined minimum speed is reached to prevent motor bearing failure or overheating.

Abstract: A method of determining the amount of air flowing through an outside air damper of a recirculating air heater includes the steps of sensing an amount of airflow flowing through the damper, recording the amount of airflow and a damper position value at a plurality of damper positions, and interpolating a curve relating the amount of airflow to the damper position for all damper positions between a minimum damper position and a maximum damper position. Once the amount of air flowing through the outside air damper is determined from a position on the curve, the concentration of carbon dioxide (CO2) within a building space can be calculated and/or determined to be within acceptable limits.

Abstract: An apparatus is provided for controlling a fuel fired heating appliance, the apparatus comprising a first processor for controlling the ignition operation of the furnace and a second processor for controlling the operation of a variable speed blower motor, wherein the first processor sends communication signals to the second processor requesting a desired speed of the blower motor to provide air flow for combustion. The second processor responsively sends a signal to the first processor indicating the receipt of the requested speed for the blower motor. The apparatus further comprises at least one pressure switch, where the first processor senses an opening of the pressure switch and responds by successively sending incrementally higher speed request signals to the second processor until the first processor detects the closing of the at least one pressure switch.

Abstract: Control apparatus for an environmental control system comprises input circuitry receiving environmental information and output circuitry for controlling an HVAC system. Processing circuitry in the controller configures the output circuitry based at least in part on the signals received on the input circuitry. Information about the status of the HVAC system may be transferred to system administrators using a wireless link.

Abstract: A multistage furnace for heating residential or commercial spaces is operated by a single stage thermostat and a return air temperature sensor providing sensed temperature information to a controller. The furnace is started at a first, low firing rate and after a predetermined time is increased to a second firing rate if the rate of change of temperature of air returning to the furnace from the space is less than a predetermined amount. The method of operation is carried further to increase the firing rate to second and third rates based on predetermined rates of temperature change of return air from the enclosed space as sensed by the return air sensor.

Abstract: A heating or cooling system, such as an HVAC system, of variable output has a number of control elements and may include a variable speed compressor, a variable speed combustion (induced or forced draft) blower motor; a variable speed circulator blower motor; a variable output gas valve or gas/air premix unit; and a controller specifically developed for variable output applications. The system may utilize a pressure sensor to determine the actual flow of combustion airflow in response to actual space conditions, vary the speed of the inducer blower, and subsequently vary the gas valve output to supply the correct amount of gas to the burner system. A temperature sensor may be located in the discharge air stream of the conditioned air to provide an input signal for the circulator blower.

Abstract: An air handler operates alternately in (a) a heating state at times when air in a space in a building is at an actual temperature that is insufficient relative to a set temperature and (b) a non-heating state at times when the air in the space is at an actual temperature that is sufficient relative to a set temperature, and at least sometimes during the non-heating state, delivering heated air to the space.

Abstract: The present invention provides a system and single controller for receiving constant and individualized information from a plurality of air control systems. A single controller is capable of controlling and interacting with at least two separate air control systems to control an environmental characteristic, and in the process, reduces the costs associated with the manufacturing and every day operation of the individual systems. In addition, the controller is capable of intelligently communicating with the input and output devices of the system, and particularly with each individually interfaced appliance, such that the controller can adaptively control the system through the use of stored historical data.

Abstract: A compact, highly flexible and efficient, multi-positionable, multi-dimensional and multi-stage gas-fired heat exchanger system as described. The system is connectable in a forced air duct regardless of the angular position and size of the duct. The heat exchanger comprises one or more heat transfer tubes which are shaped and dimensioned as dictated by the customized use of the heat exchanger. The tubes are secured to a support panel as well as the gas burner associated with each of the inlet openings of the tubes. A position orientable gas valve is secured to a gas distribution manifold. A turbulator may be associated with at least some of the tubes to cause turbulence in the hot combustion flow in each of the tubes to modify the efficiency in heat transfer along one or more sections of the tubes by directing hot combustion gas along an inner circumferential wall of the tubes.

Abstract: The present invention provides a system and single controller for receiving constant and individualized information from a plurality of air control systems. A single controller is capable of controlling and interacting with at least two separate air control systems to control an environmental characteristic, and in the process, reduces the costs associated with the manufacturing and every day operation of the individual systems. In addition, the controller is capable of intelligently communicating with the input and output devices of the system, and particularly with each individually interfaced appliance, such that the controller can adaptively control the system through the use of stored historical data.

Abstract: An air comfort control device is disclosed, which has a furnace with a furnace fan, an air conditioner with an air conditioner fan positioned remote from the furnace fan, and a temperature controller responsive to temperature changes in air in a partially enclosed environment, wherein the temperature controller sends a fan output signal to both the furnace fan and the air conditioner fan to run together to circulate air through the partially enclosed environment. The thermostat controller may also provide for multiple operation settings, including both automatic and manual options. The air comfort control device may also have a motor controller capable of sending more than one voltage to a blower motor to set a furnace fan at more than one speed. The motor controller can be produced separate from an ignition controller where the ignition controller sets the gas valve to a high position or a low position.

Abstract: A fan motor speed control system for controlling the fan motor speed of an air conditioning system includes a power output circuit including a power triac which is turned on and off by an opto-isolator connected to a pulse generator circuit for varying an AC voltage waveform imposed on the fan motor. The pulse generator circuit is connected to heating and cooling ramp circuits and a minimum speed circuit to provide a variable voltage signal imposed on the pulse generator circuit corresponding to the temperature difference sensed by a return air sensor and a heating or cooling sensor or by separate heating and cooling sensors disposed adjacent respective heating and cooling heat exchangers of the air conditioning system. An adjustable minimum speed circuit and a cutoff circuit are provided to control motor minimum speed or motor shutoff when a predetermined minimum speed is reached to prevent motor bearing failure or overheating.

Abstract: A forced air heating and/or cooling system utilizing an induction type fan motor is controlled by a controller circuit which is operable to continuously vary the speed of the fan motor during a start-up phase and a shut-down phase of the heating and/or cooling cycle. The controller circuit includes terminals for connection to the source of electrical energy for the heating and/or cooling system and for connection to the system controls without altering the control function or circuitry thereof. The controller circuit includes temperature sensors which are operable to control start-up and shutdown of the fan motor over continuously variable speed operating cycles in response to sensed temperature of the air being circulated by the fan.

Abstract: Control apparatus for an environmental control system comprises input circuitry receiving environmental information and output circuitry for controlling an HVAC system. Processing circuitry in the controller configures the output circuitry based at least in part on the signals received on the input circuitry. Information about the status of the HVAC system may be transferred to system administrators using a wireless link.

Abstract: An air comfort control device is disclosed, which has a furnace with a furnace fan, an air conditioner with an air conditioner fan positioned remote from the furnace fan, and a temperature controller responsive to temperature changes in air in a partially enclosed environment, wherein the temperature controller sends a fan output signal to both the furnace fan and the air conditioner fan to run together to circulate air through the partially enclosed environment. The thermostat controller may also provide for multiple operation settings, including both automatic and manual options. The air comfort control device may also have a motor controller capable of sending more than one voltage to a blower motor to set a furnace fan at more than one speed. The motor controller can be produced separate from an ignition controller where the ignition controller sets the gas valve to a high position or a low position.

Abstract: Heating of a house and the like is performed by sensing a need for heat by a thermostat; supplying gas into a furnace in response to a signal from the thermostat and burning the gas in the furnace; directing the burning gas to heat exchanging means so as to heat the heat exchanging means; blowing cool air by a fan past the heat exchanging means so as to heat the air; directing the heated air through heat ducts; operating the fan so that it always runs prior, during and after supplying the gas into the furnace for burning; and means for controlling the burning of gas electronically so as to limit a burning cycle to only substantially a few minutes with timed harvest cycles between the burning cycles during which harvest cycles the air is blown by the fan over the hot heat exchanging means and distributed through the heat ducts.

Abstract: A climate control system includes an air evacuation and ventilation system thereof operable to withdraw air from an outflow air duct system and ventilate the withdrawn air to the outside prior to the system treating air withdrawn from an interior space of a building through an inflow air duct system. The air evacuation and ventilation system includes a ventilation duct having a first end in communication with an air outlet junction box and a second end having an opening located outside the building, an exhaust fan, supportably mounted within the junction box, for drawing air out of the outflow air duct system and into the ventilation duct, and a damper, supportably mounted within the junction box and pivotable between a closed position in which the damper prevents air from flowing into the ventilation duct and an open position in which air is drawn into the ventilation duct.

Abstract: A heater control system is operable to modulate a heater of a building or warehouse or the like, in order to maintain the temperature rise of air passing through the heater at or below a maximum allowable temperature rise value. The maximum allowable temperature rise value is determined by a percentage or proportion of outside air being inducted into the heater and the type of heater, in order to limit the accumulation of carbon dioxide within the building. The control system is operable to modulate the heater in response to an outside air temperature, an inside or return air temperature, and the proportion of outside air to return air being inducted into the heater. Preferably, the proportion of outside air is determined by a position of a damper, which is operable to vary the relative flows of outdoor air and return air which are inducted into the heater.

Abstract: An improved, induced-draft, gas-fired furnace which is adapted to operate at any of a high, medium and low firing rate. A pressure sensing assembly generates differential pressure signals that vary in accordance with the pressure across a heat exchanger assembly. A gas flow control assembly is responsive to the differential pressure signals, and to signals received from the furnace control circuit, to supply gas to the furnace at any of its three different firing rates, the lowest of those said firing rates corresponding to a gas-air mixture which cannot be ignited. The furnace control circuit applies to the circulating air blower, and to the inducer blower, speed controls signals that are so related to one another that the fuel utilization efficiency of the furnace is at least as great during steady state operation at its low firing rate as during steady state operation at its medium firing rate.

Abstract: A compact high efficient air heater providing improved comfort regulation. The air heater includes a cross-flow type heat exchanger formed from a plurality of stacked corrugated plates which define a plurality of alternating flue gas passages and air passages, and which include a plurality of modified air passages which provide increased air flow through the heat exchanger along the flue gas inlet side whereby increased heat transfer along the flue gas inlet side is accomplished. The air heater also includes a plurality of bypass channels which direct air flow across at least one surface of the combustion chamber to remove heat from the combustion chamber housing, to lower the temperature of the flue gases entering the heat exchanger, and to reduce the temperature gradient at the air outlet side of the heat exchanger.

Abstract: Control apparatus for an environmental control system comprises input circuitry receiving environmental information and output circuitry for controlling an HVAC system. Processing circuitry in the controller configures the output circuitry based at least in part on the signals received on the input circuitry. Information about the status of the HVAC system may be transferred to system administrators using a wireless link.

Abstract: An improved, induced-draft, gas-fired furnace which is adapted to operate at any of a high, medium and low firing rate. A pressure sensing assembly generates differential pressure signals that vary in accordance with the pressure across a heat exchanger assembly. A gas flow control assembly is responsive to the differential pressure signals, and to signals received from the furnace control circuit, to supply gas to the furnace at any of its three different firing rates, the lowest of those firing rates corresponding to a gas-air mixture which cannot be ignited. The furnace control circuit applies to the circulating air blower, and to the inducer blower, speed control signals that are so related to one another that the lowest primary wall temperature in the heat exchanger is maintained above the condensation temperature of water during steady state operation of the furnace at its low firing rate.

Abstract: A gas furnace control for two stage gas furnaces which can be used with either a single stage or a two stage room thermostat monitors the length of time the first, low combustion, stage is energized and upon exceeding a selected period of time, e.g., 10 minutes, energizes the second, high combustion stage. Energization of the second stage signal (W2) also energizes the second stage without regard to timing of the first stage.

Abstract: A controller for a two-stage heat source that can be used with a single stage or a two stage thermostat. The controller includes a second stage delay timer that initiates second stage heating when the timer is decremented to zero. The timer is reset when there is no longer a call for first stage heat, when there is a call for second stage heat, or if there is no call for second stage heat and the controller determines that it is connected to a two-stage thermostat. The controller can include an indicator such as a contact bar and jumper or a switch for indicating the type of thermostat connected to the controller. Alternatively, the controller can be programmed to “learn” whether it is attached to a single stage or two-stage thermostat, assuming that it is connected to a single stage thermostat, unless and until a call for second stage heating is received.

Abstract: A circuit arrangement for actuating an air-conditioning system or an automatic air conditioner in a vehicle, in which it is possible to switch the air-conditioning system or automatic air conditioner on and off when the engine is operating. Here, the air-conditioning system or automatic air conditioner is switched off, if the air-conditioning system or automatic air conditioner is operating while the engine is operating and the engine is switched off. Further, the air-conditioning system or automatic air conditioner continues to possess a function with which, when the engine of the vehicle is stationary, the residual heat of the engine is utilizable. Additionally, at least one function of the air-conditioning system or automatic air conditioner, which is switchable manually when the engine is operating, is switchable via the same control element used to activate and deactivate the function in which the residual heat is utilized when the engine is stationary.

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 forced air heating and/or cooling system utilizing a permanent split capacitor (PSC) or shaded pole AC induction motor and including an actuator for energizing a source of heating and/or cooling effect may be controlled by a controller circuit which is operable to continuously vary the speed of the fan motor during a start-up phase and a shut-down phase of the heating and/or cooling cycle. The controller circuit includes terminals for connection to the source of electrical energy for the heating and/or cooling system and for connection to the system controls without altering the control function or circuitry thereof.

Abstract: A method of controlling an HVAC system includes measuring environmental and/or physical parameters associated with the controlled space, and making operational decisions based on those parameters. Control apparatus is also provided comprising input circuitry receiving environmental information and output circuitry for controlling an HVAC system. Processing circuitry in the controller configures the output circuitry based at least in part on the signals received on the input circuitry.

Abstract: A forced air furnace circulation fan controller adjusts the speed of the circulation fan according to the incidence of air delivery restrictions. Upon detecting insufficient air delivery as a function of the temperature of the furnace heat exchanger, the control system increases the circulation fan speed to increase the air delivery within the heating system. The controller utilizes fuzzy logic techniques to determine a speed adjustment for the furnace fan motor, based on the value of the furnace heat exchanger temperature. The use of fuzzy logic control allows the circulation fan controller to provide a highly adaptive response to changes in air delivery. The resulting balanced air delivery provides for efficient furnace operation and superior occupant comfort.

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: A method and apparatus of regulating cycles of a burner in a forced air heating system. A control unit uses a sensor at an output of a heat exchanger to make measurements of a temperature of air output from the heat exchanger. The control unit observes temperature measurements, after the burner has turned on. It initializes a confirmation interval when two consecutive temperature measurements are the same. If the temperature is the same at an end of the confirmation interval. The invention interrupts firing of the burner for an interrupt interval. The interrupt interval is insufficient to allow the heat exchanger to cool below a temperature useful for heating below which the circulation fan would shut off.

Abstract: A climate control system having a control means for receiving cool call signals and heat call signals from a plurality of thermostats. The control means blocking action by conflicting calls when the system is in a heat mode or cool mode. The system also preventing a single zone from dominating the mode of the control system and allow a conflicting call to be received after the control system has been in a particular mode for a maximum period or the conflicting call has been waiting for longer than a maximum period. The control system also properly adjusting the dampers to allow purging of ducts after heating and cooling mode and to allow zone or system ventilation upon request.

Abstract: A driving arrangement for air refrigeration appliances, of the type comprising a fan (F), a compressor (C), a thermostat (T) and first and second selecting devices (10, 20), which are manually displaceable for activating the fan (F) and compressor (C) and for adjusting the thermostat (T). According to the invention, the first selecting device (10) is displaced along a first portion (1), at the end of which the fan (F) is turned on, a second portion (2), in which only the fan (F) is kept turned on and a third portion (3), in which beginning the compressor (C) is turned on and along which the thermostat (T) is adjusted between a minimum cold condition and a maximum cold condition. The second selecting device (20) has two operative positions, each defining a ventilation regimen for the fan (F).

Abstract: A temperature control method and apparatus therefor controls an air temperature in a room by determining an error temperature between a set temperature and an actual room temperature. An auxiliary reference calorie is initially set as a previous state calorie value, an error calorie associated with the detected error temperature is determined by PID operation and a current calorie value in determined by adding or subtracting the previous state calorie value to/from error calorie, and the room temperature is brought to the set temperature using the current calorie value.

Abstract: An electronic two stage furnace controller may be used interchangeably, without modification thereof, with either a single or two stage thermostat to regulate the heating and cooling operation of a two stage heating/cooling furnace to which the controller is connected. The controller is operative to monitor the input it receives from the thermostat, automatically deduce whether the input is from a single stage thermostat or a two stage thermostat, and responsively regulate the operation of the furnace under a corresponding single stage thermostat heating or cooling mode, or a corresponding two stage thermostat heating or cooling mode.

Abstract: A supplementary thermal system controller for assisting a main system controller in retaining a desired temperature rise by monitoring the temperature in the return duct, wherein the supplemental controller comprises a microcontroller for reading and processing return duct temperature measurements, a signal conditioner circuit for preparing temperature related signals for processing by the microcontroller, processor readable medium of program code for determining the rate of temperature change in the return duct and providing control signals based on the rate of temperature change, and a supplemental thermal source driver for controlling a supplemental thermal source, such as electrical resistance heating elements, to cause the assisting temperature source to increase or decrease its thermal output.

Abstract: An attachment unit (28) to an existing central air conditioning thermostat controller (24) like the ones found in most homes and offices; which provides two independent modes of saving energy, first by turning on a light to indicate when to change the filter and secondly by extending the fan operation for a few minutes without disruption. Uniquely conceived, smaller than the typical thermostat controller, automatic, maintenance free, no batteries or auxiliary power of any kind. Has one button (32) to reset the light (30) after changing the filter and one switch (34) to select the optional extended fan operation.

Abstract: A high efficiency gas furnace utilizes a unique pre-mixed design in combination with a pressurized/high velocity combustion process. The combustion process occurs in a combustion chamber and the high temperature high velocity products of combustion follow a circuitous route from the combustion chamber through finned tubular conduits to an exhaust. Heat from the high temperature high velocity products is transferred to the finned tubular conduits. An air blower assembly forces air across the finned tubular conduits and the combustion chamber to remove the heat from the finned tubular conduits and transfers this heat to a building or an enclosed portion thereof.

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.