Abstract: A diagnostic flame sensing circuit having less filtration so that an AC component of a flame sensing input is available for circuit diagnostics. Synchronized data sampling may used to detect the peak to peak magnitude of the residual AC component. A comparison of the magnitude of the component relative to a magnitude of the component during normal operation of the circuit may be used to check the condition of nearly all of the elements in the circuit.

Abstract: A locally powered intermittent pilot combustion controller may include an igniter, a thermal electric and/or photoelectric device that produces an electrical signal having power when exposed to a flame, and a local power source for providing power when the thermal electric and/or photoelectric device is not exposed to a flame. In some cases, the intermittent pilot combustion controller may include a memory for storing information about an ignition sequence for igniting a pilot flame, and a controller coupled to the memory. The controller may be configured to initiate the ignition sequence of the pilot flame using information stored in the memory, determine whether the ignition was successful by monitoring the electrical signal produced by the thermal electric and/or photoelectric device, and adjust the information stored in the memory based on whether the ignition sequence completed successfully.

Abstract: A flame powered intermittent pilot combustion controller may include a first power source and a second power source separate from the first power source, a thermal electric and/or photoelectric device, an igniter and a controller. The thermal electric and/or photoelectric device may charge the first power source when exposed to a flame. The controller and the igniter may receive power from the first power source when the first power source has sufficient available power, and may receive power from the second power source when the first power source does not have sufficient available power.

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 flame sensing system having a flame rod, a signal generator, a signal measurement circuit, and a controller, where the frequency and/or amplitude of the excitation signal may be variable. The signal measurement circuit may include a bias circuitry that references the flame signal to a voltage, a capacitor that varies the filtration, an AC coupling capacitor, a current limiting resistor, and a low-pass filter. The system may determine the flame-sensing rod contamination, the stray capacitance of the flame sensing system, and compensate for stray capacitance in the flame sensing system. The flame model may include a circuit that simulates a flame in the presence of the sensing rod, and another circuit that simulates a contact surface between the flame and the sensing rod.

Abstract: A furnace includes a combustion blower and one or more pressure switches. In some cases, the one or more pressure switches may be used to calculate one or more operating points for the combustion blower. Additional operating points may be calculated by interpolation and/or extrapolation, as appropriate. The furnace may temporarily alter these operating points as necessary to keep the furnace safely operating in response to minor and/or transient changes in the operating conditions of the furnace.

Abstract: A furnace includes a combustion blower and one or more pressure switches. In some cases, the one or more pressure switches may be used to calculate one or more operating points for the combustion blower. Additional operating points may be calculated by interpolation and/or extrapolation, as appropriate. The furnace may temporarily alter these operating points as necessary to keep the furnace safely operating in response to minor and/or transient changes in the operating conditions of the furnace.

Abstract: A system for operating a flame sensing device to obtain readings of increased accuracy without degrading the life of the sensor. There may be levels of a flame requiring a precise measurement. One improvement of accuracy uses higher voltage on the sensor, but this degrades the sensor and thus shortens it life. Further improvement may be achieved by limiting the time that the sensor is operated at a higher voltage. Readings, as if the sensor were operated at a higher voltage, may be inferred from actual readings of the sensor operated at a lower voltage.

Abstract: A system for generating a high DC voltage for a spark to ignite a flame in a combustion device, and a high AC voltage for a flame rod to sense a flame in the device, from a low voltage for combustion device control. The system may be an inexpensive mechanism.

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 furnace includes a combustion blower and one or more pressure switches. In some cases, the one or more pressure switches may be used to calculate one or more operating points for the combustion blower. Additional operating points may be calculated by interpolation and/or extrapolation, as appropriate. The furnace may temporarily alter these operating points as necessary to keep the furnace safely operating in response to minor and/or transient changes in the operating conditions of the furnace.

Abstract: A flame rod drive signal generator and system for producing a flame rod drive signal for a flame rod of a combustion system. In one illustrative embodiment, the flame rod drive signal generator may include a voltage source, an input signal having a frequency, an LC oscillator and a drive mechanism. The drive mechanism may be powered by the voltage source, and may have an output coupled to the LC oscillator. The drive mechanism may receive the input signal, and produces a current in the LC oscillator that has a frequency that is related to the frequency of the input signal. The LC oscillator may then provide a flame rod drive signal to a flame rod that has an amplitude that is larger than the amplitude of the voltage source. In some cases, a controller may monitor the amplitude of the flame rod drive signal and adjust the frequency, duty cycle, or both, of the input signal to achieve a desired amplitude of the flame rod drive signal.

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 furnace includes a combustion blower and one or more pressure switches. In some cases, the one or more pressure switches may be used to calculate one or more operating points for the combustion blower. Additional operating points may be calculated by interpolation and/or extrapolation, as appropriate. The furnace may temporarily alter these operating points as necessary to keep the furnace safely operating in response to minor and/or transient changes in the operating conditions of the furnace.

Abstract: A signal generation system for flame ignition and sensing. The ignition signal generation is adaptive for improving flame ignition while eliminating excess energy usage. High voltage signals for flame sensing may also be provided. If more energy or speed is needed for ignition signal generation, then the flame sensing signal generation portion may be disabled to increase the amount of available energy. Adaptation for ignition signal generation may be guided by the results of flame sensing. The flame sensing voltage may be regulated based on the flame current strength. The flame current may be controlled within an optimum range to reduce rod contamination rate and yet provide reliable flame sensing when the rod contamination built up. The adaptation may be algorithmic-based with the facilitation of a microcontroller. The system may provide the high voltage signals from a low voltage power supply, such as that of 24 VAC.

Abstract: A furnace includes a combustion blower and one or more pressure switches. In some cases, the one or more pressure switches may be used to calculate one or more operating points for the combustion blower. Additional operating points may be calculated by interpolation and/or extrapolation, as appropriate. The furnace may temporarily alter these operating points as necessary to keep the furnace safely operating in response to minor and/or transient changes in the operating conditions of the furnace.

Abstract: A flame sensing system having a flame rod, a signal generator, a signal measurement circuit, and a controller, where the frequency and/or amplitude of the excitation signal may be variable. The signal measurement circuit may include a bias circuitry that references the flame signal to a voltage, a capacitor that varies the filtration, an AC coupling capacitor, a current limiting resistor, and a low-pass filter. The system may determine the flame-sensing rod contamination, the stray capacitance of the flame sensing system, and compensate for stray capacitance in the flame sensing system. The flame model may include a circuit that simulates a flame in the presence of the sensing rod, and another circuit that simulates a contact surface between the flame and the sensing rod.

Abstract: A method and apparatus for determining a health status of a water heating device is disclosed. The water heating device may have a controller that incorporates logic to regulate the heater responsive to water temperatures detected at different areas within the water heating device by first and second sensors. Unfortunately, the first and second sensors may fail. To detect fault conditions or otherwise determine the heath status of the water heating device, a logic unit in the controller may perform a test on the first and/or second sensors so as to provide a test output. The logic unit may also determine whether the test output satisfies one or more predetermined thresholds. These predetermined thresholds may be indicative of a properly-functioning sensor. When the test output does not satisfy the at least one predetermined threshold, the logic unit may then set a fault condition indicative of improperly functioning sensors.

Abstract: A system for adjusting a bias voltage of a flame sensing system. The system may use pulse width modulation to adjust the bias voltage. The system may have a flame sensing rod that conveys an electrical equivalent circuit of a flame presence to a detector via low pass filter. An excitation voltage may be conveyed via a DC blocking mechanism to the sensing rod. A pulse width modulation signal may be conveyed via a bias resistor to a node of the low pass filter and the detector. The input of an A/D converter may be that of the detector for flame signals. Also, leakages between the node of the A/D converter connection and the voltage source and/or ground may be detected and compensated. Further, leakage of the DC blocking mechanism may be minimized.

Abstract: A system for detecting stacking and controlling temperature in a water heater. A controller with a connection to a temperature sensor and heating element in a water tank of the heater may be designed to limit stacking and its effects. The controller may use a sensing and calculation technique to detect the stacking. If stacking is detected, then the setpoint for the heater may be lowered so that the outlet water temperature is within a safe limit. If stacking is not detected, then the setpoint may be gradually restored to optimize water heater capacity.