Abstract: A system includes a two stage heat exchanger and a processor. The processor is configured to receive a call from a thermostat and execute, in response to the call, an adaptive staging algorithm. The adaptive staging algorithm is configured to determine, in response to a recent cycle of the two stage heat exchanger being a first stage cycle, a first stage up time of the two stage heat exchanger as a first function of a first value, the first value corresponding to the recent cycle being the first stage cycle. The adaptive staging algorithm is also configured to determine, in response to the recent cycle of the two stage heat exchanger being a second stage cycle, a second stage up time of the two stage heat exchanger as a second function of a second value, the second value corresponding to the recent cycle being the second stage cycle, where the first and second values are different.

Abstract: A remote control for an air-conditioning apparatus includes: an outer button to be operated by a user for changing an operating condition of an air-conditioning apparatus body; an inner button to be operated by the user for changing the operating condition; a cover that is openable and closable and is configured to cover the inner button; a cover opening/closing detection unit configured to detect opening/closing of the cover; a display unit configured to display an enlarged display screen displaying at least one of an operation mode, a set temperature and a set humidity, and a detail display screen displaying a function of the inner button; and a display switching unit configured to, when the cover opening/closing detection unit detects that the cover is closed, make the display unit display the enlarged display screen, and when the cover opening/closing detection unit detects that the cover is open, make the display unit display the detail display screen.

Abstract: A control device, such as a smart thermostat, employs solid state relays as switches to activate and deactivate systems controlled by the device. By measuring the current flow through the power buses to one or more of the solid state relays of the control device, potentially damaging over current conditions can be distinguished from permissible transient over-current conditions and the control device can deactivate any solid state relays which would be damaged while allowing solid state relays which are experiencing allowable transients to remain operating. In the case of a severe over current condition, a current monitoring device can issue a fault signal, triggering an interrupt condition which will cause a processor in the controller to shut down the affected solid state relays very quickly.

Abstract: A control system method is disclosed for air-conditioning a vehicle by a heat pump system, wherein one of multiple operating modes is automatically set, depending on the air-conditioning requirement. The passenger space is cooled by an air-conditioning evaporator and/or is heated by a heating heat exchanger. The heating heat exchanger is arranged in a heating branch of a coolant circuit and is provided with heat via a heat pump. If cooling is required, the heating branch is opened and the heating pump is deactivated. If heating is required, the heating branch is closed and heat is fed to the heating heat exchanger via the heat pump. In order to remove heat from the heating branch, same is opened and a low-temperature cooler, the condenser and the heating heat exchanger are operated connected in series.

Abstract: A control device, such as a smart thermostat, employs solid state relays as switches to activate and deactivate systems controlled by the device. Current flows through at least some of the solid state relays are monitored to determine the bulk heating produced in the solid state relays, and their associated circuitry and printed circuit board traces, and this determined amount of bulk heat is added to other determined amounts of bulk heat and is used to compensate the reading provided by temperature sensors within the control device which have been affected by the bulk heat. Further, by measuring the current flow through the power buses to one or more of the solid state relays of the control device, potentially damaging over current conditions can be distinguished from permissible transient over-current conditions and the control device can deactivate any solid state relays which would be damaged while allowing solid state relays which are experiencing allowable transients to remain operating.

Abstract: A thermostat includes a plurality of HVAC (heating, ventilation, and air conditioning) wire connectors for receiving a plurality of HVAC control wires corresponding to an HVAC system. The thermostat also includes a thermostat processing and control circuit operative to at least partially control the operation of the HVAC system and a powering circuit coupled to the HVAC wire connectors and configured to provide an electrical load power to the thermostat processing and control circuit. The thermostat includes circuitry and methods for maximizing efficiency of energy harvested from the HVAC system connected to the thermostat, and depending on which system is connected to the thermostat, different power schemes can be implemented in order to obtain power from the HVAC system.

Abstract: A method and system for operating a modulating furnace from a single-stage thermostat. The furnace control system may include a processor, a gas valve, a variable-speed motor, and a thermostat. The furnace control may execute a thermostat algorithm comprising the steps of: determining if a heating load needs to be satisfied; running burners at an intermediate input rate, a modulated input rate, and a maximum input rate for each respective first, second, and third time intervals until the heating load is satisfied; calculating a heating load requirement as function of the time intervals; and determining an initial input rate for a next cycle based on the calculated heating load requirement.

Abstract: A control device, such as a smart thermostat, employs solid state relays as switches to activate and deactivate systems controlled by the device. Current flows through at least some of the solid state relays are monitored to determine the bulk heating produced in the solid state relays, and their associated circuitry and printed circuit board traces, and this determined amount of bulk heat is added to other determined amounts of bulk heat and is used to compensate the reading provided by temperature sensors within the control device which have been affected by the bulk heat. Further, by measuring the current flow through the power buses to one or more of the solid state relays of the control device, potentially damaging over current conditions can be distinguished from permissible transient over-current conditions and the control device can deactivate any solid state relays which would be damaged while allowing solid state relays which are experiencing allowable transients to remain operating.

Abstract: A conveyor oven having a first mode of operation and a second mode of operation is provided. The conveyor oven generally includes an oven chamber in which food is cooked, a conveyor movable to convey the food through the oven chamber, a burner to generate heat for the oven chamber, at least one blower to circulate air within the oven chamber, and a controller. The burner has a combustion airflow rate, and operates at a first output during the first mode of operation and at a second output that is greater than the first output during the second mode of operation. The blower operates at a first speed during the first mode of operation and at a second speed that is faster than the first speed during the second mode of operation.

Abstract: A conveyor oven having a first mode of operation and a second mode of operation is provided. The conveyor oven generally includes an oven chamber in which food is cooked, a conveyor moveable to convey the food through the oven chamber, a burner to generate heat for the oven chamber, the burner having a combustion airflow rate, at least one blower to circulate air within the oven chamber, and a controller. The blower operates at a first speed during the first mode of operation and at a second speed that is faster than the first speed during the second mode of operation. The controller is responsive to at least one of a burner output and an internal temperature of the oven chamber, and adjusts the combustion airflow rate based in part on at least one of the burner output and the internal temperature of the oven chamber.

Abstract: The disclosure provides an HVAC system, an HVAC controller and a method of operating an HVAC system. In one embodiment, the HVAC controller includes: (1) an interface configured to receive a thermostat call and (2) a processor configured to initiate operation of the HVAC system in response to the thermostat call and control operation thereof based on a temperature difference across a conditioning unit of the HVAC system.

Abstract: A swing prism endoscope with an actuating mechanism that comprises a control element that oscillates in between proximal and distal ends of the endoscope and is coupled to a distally mounted swing prism, a control surface with a variable profile, and an engaging element that contacts the control surface and moves relative to the control surface while contacting the control surface causing the control element to oscillate. The distally mounted swing prism that alters the viewing angle of the endoscope between a forward direction that is substantially parallel to the longitudinal axis of the endoscope and a side direction that is angled relative to the longitudinal axis of the endoscope.

Abstract: A variable secondary air intake device has a baffle member adapted to be attached within an upper area of a fire chamber of the firebox. The baffle member includes a top having a channel member hole therethrough, side walls, a bottom having a plurality of small holes therethrough, and a gas exit opening having side walls and extending through the top and bottom. A hollow chamber member adapted to be placed upon a top surface of the baffle member, the hollow chamber member includes a top having a channel member hole therethrough, and side walls extending downward from the top and forming a chamber having a periphery that includes a plurality of gas exit holes therethrough.

Abstract: A rotary aluminum kiln temperature regulation system comprising a temperature sensing device in the kiln that is configured to take temperature readings in an area of the kiln in proximity to the temperature sensing device. The system including a wireless transmitter operatively associated with the temperature sensing device and a receiver wirelessly associated with the transmitter, such that the transmitter and receiver wirelessly transmit the temperature readings taken by the temperature sensing device from the transmitter to the receiver. The system also including a control unit operatively connected to the receiver that is configured to receive the transmitted temperature readings and determine when the transmitted temperature readings exceed a predefined temperature setpoint.

Abstract: A modulating furnace having a variable rate burner and a controller is operated at a first burner firing rate for a first period of time, and a higher burner firing rate once the first period of time has expired. In some instances, the burner may be operated only while the controller is receiving a call for heat from a thermostat or the like.

Abstract: A method of preventing exhaust gas from leaking out of a drying furnace is disclosed. In the method, the temperature of an exhaust passage and the temperature of a heater are measured, and turning on/off the heater is controlled in response to the measured temperatures. The present invention can be applied to all kinds of apparatuses having drying furnaces which are heated by heaters and thus generate the exhaust gas and can effectively prevent exhaust gas from leaking out of the apparatuses. Furthermore, the present invention can be more effectively applied to food waste disposers which heat food waste containing a large amount of water. In particular, the present invention is effective for circulation food waste disposers in which exhaust gas is condensed and re-supplied into a drying furnace as recirculation gas.

Abstract: An electronic circuit for a hot water heating system an override thermostat; a timer operable to deactivate and reactivate the burner while a room thermostat is calling for heat; a differential temperature switch configured to disconnect the electrical supply to the water pump when the difference in temperature between the water at the boiler inlet and the water at the boiler outlet falls below an adjustable set point; and, a temperature switch configured to prevent operability of the timer until the temperature of the water at the burner outlet rises above an adjustable set point.

Abstract: A modulating furnace having a variable rate burner and a controller is operated at a first burner firing rate for a first period of time, and a higher burner firing rate once the first period of time has expired. In some instances, the burner may be operated only while the controller is receiving a call for heat from a thermostat or the like.

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: An exemplary heating system can be configured with a control system configured for controlling the heating system to reduce inefficiencies, and/or allow the heating system to operate in a relatively optimum manner. In accordance with an exemplary embodiment, a closed-loop control system may be configured to control various portions of the heating system based, at least in part, upon signals and/or information received from various sensors of the heating system. For example, among various other types of information provided within a closed-loop feedback, control may be configured based upon the pressure within the combustion chamber. In accordance with another exemplary embodiment, the closed-loop control system may determine a portion of the heating system is not operating properly, based at least in part upon feedback from one or more sensors configured within the heating system.

Abstract: Compact and efficient apparatuses for transferring heat, heat exchangers, and furnaces, as well as HVAC units, HVAC systems, and buildings therewith, plus methods of making such devices. Furnace heat exchangers, for example, have an added stage, added in an unconventional way, that improves efficiency without unduly increasing size, while maintaining required radiuses of bends in tubing. Various embodiments orient bends at particular angles to allow stages to fit together more closely, provide improved structure for connecting stages using two collectors that seal against a common junction plate, provide for indoor air passing through the heat exchanger to pass through different passes of the heat exchanger in an unconventional order in order to provide greater compactness, or a combination thereof, as examples.

Abstract: An apparatus for extracting heat from a heat source comprising a housing having a first end with a first opening and a second end with a second opening. The housing includes an internal compartment therein and the first end of the housing is connected to said heat source. A channel extends from the housing for providing access to the internal compartment. A hollow conduit is positioned within the internal compartment extending between the first opening and the second opening. A plurality of members are positioned on an exterior surface of the conduit and along the length thereof. The members are able to absorb heat from within the conduit and release the absorbed heat into the internal compartment creating heated air. The apparatus includes a means for drawing air through and expelling air from said conduit and means for moving said heated air out from said internal compartment to a second compartment. The apparatus is activated via means connected to each of the drawing means and the moving means.

Abstract: A method for effecting cooperation between a modulating air conditioning system and a two-stage thermostat for satisfying an air conditioning load demand in a conditioned space includes: (a) operating the thermostat in a plurality of succeeding operating cycles to issue a first call signal or a second call signal indicating a first or second stage operation by the air conditioning system; the first and second stage operation being effected according to a first operating regimen to satisfy the air conditioning load demand; (b) operating the air conditioning system in response to the first and second call signals; the air conditioning system operating at a first power level when receiving the first call signal and operating at a predetermined second power level when receiving the second call signal; the first power level being established by the air conditioning system according a second operating regimen.

Abstract: A semiconductor memory device enabling efficient repair of defects by using limited redundant memory while suppressing a drop of access speed accompanied with the repair of defects of the memory, wherein a first memory array is divided into a plurality of memory regions for each 16 word lines and wherein defective memory addresses in regions are stored in a second memory array. When a memory address for accessing the first memory array is input, the defective memory address of the memory region including the memory to be accessed is read out from the second memory array. In this way, the addresses of defective memory in 16 word lines worth of a memory region are stored in the second memory array 2, therefore addresses of a wider range of defective memory can be stored. For this reason, it becomes possible to repair defects occurring at random efficiently.

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: 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 thermostat is operable from battery, common-wire (“C-wire”), or furnace relay power. The thermostat includes a power source selector, such as a jumper wire, that is set when the thermostat is installed in a heating system. In a gas millivolt heating system, the thermostat operates off of battery power. In heating systems having a C-wire, a diode bridge converter converts alternating-current voltage to direct-current voltage to provide operating power to the thermostat. In heating systems without a C-wire and having sufficient furnace relay current, a triac converter in series with the furnace relay provides voltage spikes to the diode bridge converter to provide operating power to the thermostat when the furnace is on, and the diode bridge converts AC to DC voltage when the furnace is not on. The thermostat can also be used in cooling systems and heating, ventilation, and air-conditioning systems. Thus, the thermostat can be used in a wide variety of applications.

Abstract: A thermostat is operable from battery, common-wire (“C-wire”), or furnace relay power. The thermostat includes a power source selector, such as a jumper wire, that is set when the thermostat is installed in a heating system. In a gas millivolt heating system, the thermostat operates off of battery power. In heating systems having a C-wire, a diode bridge converter converts alternating-current voltage to direct-current voltage to provide operating power to the thermostat. In heating systems without a C-wire and having sufficient furnace relay current, a triac converter in series with the furnace relay provides voltage spikes to the diode bridge converter to provide operating power to the thermostat when the furnace is on, and the diode bridge converts AC to DC voltage when the furnace is not on. The thermostat can also be used in cooling systems and heating, ventilation, and air-conditioning systems. Thus, the thermostat can be used in a wide variety of applications.

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: 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 system for heating and cooling the interior of a motor vehicle is provided which includes a first climate control device designed to heat or cool a front area of the interior, a second climate control device designed to heat or cool a rear area of the interior, a first evaporator connectable to a first cooling agent circuit assigned to the first climate control device and a second evaporator connectable to a second cooling agent circuit assigned to the second climate control device. The second evaporator is located in a latent storage in order to charge the latent storage with cold and the second climate control device contains a first heat exchanger designed to transfer the cold removed via a heat transfer medium circuit or the second cooling agent circuit from the latent storage for cooling the rear area of the interior by an air flow.

Abstract: A gas furnace control arrangement includes a control unit control unit and an operating unit adapted to control the control unit, the control unit having a valve seat holding a set of solenoid valves, the solenoid valves including a main valve for fuel gas input control, a mother flame valve adapted to control a gas passage from the valve seat to a mother flame nozzle, a high flow rate valve and a medium flow rate valve and a low flow rate valve adapted to control a respective gas passage from the valve seat to a main flame nozzle, the operating unit including a power switch adapted to switch on/off an electronic igniter and to close/open the main valve and the mother flame valve, a strong flame switch adapted to close/open the high flow rate valve, a medium flame switch adapted to close/open the medium flow rate valve, and a weak flame switch linked to the strong flame and the medium flame switch and adapted to close/open the low flow rate valve.

Abstract: A space heater for the interior of a building has a support enclosure containing a gas burner and a gas conduit connecting the burner to a source of combustible gas. An electronically controlled proportional valve is located in the gas conduit. A fan and motor assembly are in the enclosure for distributing heated air from the burner when gas is communicated through the conduit and to the burner for combustion. A control system and a PC interface of a PC are located in the support enclosure to receive a data processing card having a predetermined temperature set point relating to temperature conditions within the building.

Abstract: A high reliability heating system that includes dual furnace control mechanisms wherein each furnace control mechanism includes blowers and control elements and each is independently operable to control the operation of a shared furnace burner unit and heat exchanger. The heating system preferably includes a controller mechanism selector mechanism that detects an abnormal operating condition, malfunction, in the controlling furnace controller mechanism and, in response, automatically switches control to the other furnace controller mechanism.

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: To anticipate potential failure of a temperature modification device (e.g., heating, ventilating and air conditioning equipment used in a commercial building), an efficiency value representing the ability of the temperature modification device to change temperature in a predetermined zone is repeatedly computed. When one of these values is computed, it is used in determining whether the ability of the temperature modification device to change temperature in the predetermined zone has deteriorated over time. This is done by comparing a current efficiency value with a previous efficiency value. In response to a determined deterioration exceeding a predetermined tolerance, a control signal for initiating inspection of the temperature modification device is communicated, thereby enabling the device to be serviced in response to a detected operating condition of the device and before actual failure of the device.

Abstract: Furnace combustion in a multi-stage or variable input furnace is controlled by operating the furnace in a high fire mode at furnace start-up until the temperature of the products of combustion, or a temperature corresponding to the products of combustion, equals or exceeds a selected temperature. A temperature sensor, preferably a thermostat, is located downstream of the furnace zone of combustion (e.g., in a flue collector box at an outlet from the heat exchanger). The thermostat provides an indication of the products of combustion temperature and has a set point corresponding to the selected temperature. When the products of combustion temperature is less than the selected temperature, the thermostat contacts remain closed. The furnace is operated in the high fire mode while the thermostat contacts remain closed in response to a demand for heating, irrespective of whether the demand is for first stage or second stage heating.

Abstract: Systems and methods for controlling a draft inducer for use with a furnace. The draft inducer includes a fan for moving combustion chamber gases for inducing a draft in the furnace combustion chamber that causes a pressure drop across a heat exchanger. The density of the gases flowing across the heat exchanger and the fan differs from a first operating state of the furnace to a second operating state of the furnace. A motor drives the fan in response to a motor control signal so that different motor speeds result as a function of the density of the gases flowing across the fan. A control circuit generates the motor control signal as a function of a first set of speed/torque curves until a speed signal indicates that the motor has reached a predetermined speed. After the speed signal indicates that the motor has reached the predetermined speed, the control circuit generates the motor control signal as a function of a second set of speed/torque curves.

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: An electronic thermostat having a safety feature includes a controller which sends control signals to circuitry used for activating a system for conditioning air. The control signals are used to control the active state of the system for conditioning air. Furthermore, safety cutoff circuitry is incorporated into the thermostat whereby the safety cutoff circuitry is used to override the control signal sent from the controller when a predetermined temperature is reached in the space being heated or cooled.

Abstract: An electromechanical thermostat has a fixed value voltage anticipator resistor and a variable anticipator resistor for series connection with the load. This allows a single thermostat to control either a high efficiency furnace requiring a relatively low cycle rate or a furnace of conventional efficiency which can function at a higher cycle rate. Preferably, the voltage anticipator resistor is selected to give the cycle rate required by high efficiency furnaces when the resistance of the variable anticipator resistor is set to zero ohms. If the thermostat is shipped with the variable resistor set to zero ohms, the installer will not have to adjust the variable resistor whenever the thermostat is installed in a system requiring that cycle rate.

Abstract: A method for providing a low fire mode and a high fire mode of a heating cycle in a current cycle of a furnace as a function of the previous heating cycle wherein the current heating cycle is a function exclusively of time run in low fire mode and time run in high fire mode of the previous heating cycle, comprising the steps of: (1) determining the existence of a heating load to be satisfied; (2) running burners in low fire mode for a first time interval that does not exceed a predetermined limit, L.sub.des ; (3) running the burners in high fire mode for a second time interval until the heating load is satisfied; (4) calculating a BtU load requirement, as a function of the first time interval and the second time interval; and (5) determining the desired low fire mode time limit, L.sub.des, for the next cycle from the calculated BtU load requirement.

Abstract: In a heating system containing twinned furnaces capable of independently operating at multiple levels, a method for providing multiple heating modes to satisfy a required heating load during a given cycle, there being some total number of heating modes, wherein each heating mode may be activated for a time interval whose length is a function of furnace activity during the most recent previous cycle.

Abstract: An adaptor is designed to mount a duty cycling control switch for a furnace or air conditioning system which has flexible duct work. The adaptor includes two opposite cylindrical sections with a central section which includes an arcuate portion and a planar rectangular portion. The planar rectangular portion is tangential to the surfaces of the first and second cylindrical sections. The duty cycling control switch is mounted to this planar portion. Thus, air passing through the duct work will pass through this adaptor altering the temperature of the rectangular plate, thus, altering the temperature of the duty cycling switch causing it to activate.

Abstract: Provided is a hot-air type heater including a heat generating means such as a burner heater from which hot air is produced and blown out the heater into a living room so as to warm up the inside of the room with a uniform temperature distribution even among various heating rate conditions. The hot-air heater includes at least of variable angle louvers which are vertically swingable, and a control means for swinging the louver in association with at least either a hot air flow rate at a hot air outlet opening of the heater or the heating value of the heat generating means, so that the louver is vertically swung in accordance with an output from the control means in order to minimize differences in temperature distribution in the room during operation of the heater under various heating conditions.

Abstract: An emergency heat circuit for a microprocessor-controlled furnace has a first emergency heat switch with one terminal in contact with a rectifier circuit that provides a DC voltage when the thermostat calls for heat, and another terminal connected to an emergency heat-active input of the microprocessor. A first opto-isolator has an optical actuator, such as an LED connected to the microprocessor failure output and a switched element unless such as a photo-transistor, with terminals connected in parallel to the first emergency heat switch. A second opto-isolator is also connected to the emergency heat switch and has an AC photo-actuated switch element, such as a photo-triac, connected, for example, to the W conductor and with an output connected to the rectifier circuit. The photo-triac latches on until the thermostat is satisfied.

Abstract: A two-stage gas furnace control system automatically shifts into a high fire only mode if, in two consecutive low fire heating cycles a limit switch is tripped to indicate that a gas valve is stuck in a high fire condition. In this way, continued operation is allowed to proceed in a safe manner. Provision is also made to lock out the system from further operation if, while in the high fire only mode, the limit switch is tripped in a predetermined consecutive number of cycles or if, while in a preemptive low fire only mode, the limit switch is tripped.

Abstract: Control apparatus for controlling the operation of a gas valve in a gas heating system which includes thermostatic switch means and a source of AC voltage which are connected to form a series circuit with the gas valve is disclosed. The control apparatus comprises switch means which is connected to provide continuity in the series circuit upon receipt of a first control signal and to remove the continuity in the series circuit upon removal of the first control signal. Isolation means receives a second control signal having a high state and an alternate low state and generates the first control signal when receiving the high state of the second control signal. A power supply receives the AC voltage when the thermostatic switch means is closed and provides a DC voltage to a timer means. The timer means then generates the second control signal.

Abstract: A heating system and air conditioning system incorporating a duty cycling control switch are disclosed. The duty cycling control switch for either the furnace or air conditioning system is mounted within the supply side duct of the system, i.e., the hot air duct for a furnace or cold air duct for an air conditioner. The duty cycling control is a bi-metal switch totally enclosed within a case having a metal base whereby the heat from the air in the duct contacts the metal base which is transferred to a bi-metallic element which in turn opens or closes a switch. This makes the switch particularly responsive to gradual changes in the temperature of the output air but prevents the duty cycling switch from responding to rapid fluctuations of air temperature within the duct.

Abstract: A self-correcting control system and method is provided for a furnace to correct certain operating conditions that exceed normal limits. Upon sensing insufficient air flow as a function of the pressure drop across the heat exchangers, the control system and method cause the inducer motor to increase in speed, thereby to increase the flow of combustion air. Similarly, upon sensing that the flow of air to be heated exceeds a predetermined temperature, the control system and method will increase the speed of the air blower to increase the flow rate of air to be heated through the furnace, thereby resulting in lowering the temperature of the air to be heated below the predetermined temperature. Upon sensing a gas flow leak through the gas regulator, the control system and method will recycle the gas regulator to properly seat a gas flow control valve therein. If none of the self-correcting features correct the particular occurring problem, the control system and method will shut down the furnace.