A system includes a modulating furnace and control circuitry. The control circuitry is configured to receive a call for heating associated with a quick heat cycle. In response to the call for heating, the control circuitry is also configured to operate the modulating furnace in a quick heat operating mode for a threshold time period. Subsequent to the threshold time period, the control circuitry is also configured to operate the modulating furnace in a modulating heat operating mode.

A heating, ventilation, and/or air conditioning (HVAC) system includes a control system configured to initiate an operating cycle of a furnace of the HVAC system at an initial operating stage in response to a call for heating, monitor a duration of time associated with the operating cycle of the furnace to satisfy the call for heating, adjust the initial operating stage to provide an adjusted initial operating stage of the furnace based on the duration of time, and initiate a subsequent operating cycle of the furnace at the adjusted initial operating stage.

Apparatus and methods for a gas furnace are disclosed. The gas furnace includes a variable combustion control which monitors the temperature of the burner and modifies one of the amount of combustion air supplied and the amount of gas fuel supplied to the mixing chamber. The described systems can dynamically accommodate differences in air quality and gas fuel supply to provide an optimum BTU output irrespective of differences in geographic location of usage. The gas furnace can include a dynamic response unit which predicts an optimum rate of heating to maintain a target room temperature, thereby preventing unnecessary shut down and costly re-ignition sequences, and maintaining the gas furnace at an optimum BTU output level.

A system for controlling a combustion appliance based on one or more localized environmental factors and an inlet/exhaust system enclosed within a single enclosure. The control system includes an electrically controlled fuel valve, coupled to a source of combustion appliance fuel, and responsive to a fuel valve control signal, for controlling the flow of fuel to the appliance. An air pressure detector is disposed in an area proximate the combustion appliance and configured for detecting negative air pressure in the proximate area and in response for providing a negative air pressure detection signal to a relay which will deactivate the fuel valve until negative air pressure is not present thereby preventing operation of the combustion appliance. Further, if negative air pressure is detected, the relay energizers a makeup air device to bring an outside air into the area near the combustion appliance.

A method of generating a control signal for a temperature control system is disclosed. The control signal has one of an “on” state in which the temperature control system is to be activated and an “off” state in which the temperature control system is to be deactivated. The method comprises calculating a temperature error measure in dependence on a target temperature and a current temperature value. A rate of temperature change in the environment is determined and used to set a variable error threshold. The method switches between a continuous “on” signal mode and a pulse-width-modulation (PWM) mode, in which the output signal comprises alternating “off” and “on” periods in accordance with a PWM pattern. The switch occurs in dependence on the temperature error measure and the variable error threshold.

Control system for controlling the pilot flame of a combustible gas device, which includes a pilot burner, a main burner, and a valve assembly, which includes a pilot valve that allows/intercepts a flow of gas directed towards the pilot burner, and a main valve that allows/intercepts a gas flow to the main burner, the valve assembly moveable between a closed OFF state, a PILOT state, and an ON state, where gas flows to the main burner. The control system includes a detection device that generates a state signal, and a control unit including a timer, the control unit is operatively connected to the detection device to receive a state signal and to an actuator to close the valve. The control unit starts the timer when the state signal represents the PILOT state, and actuates the actuator for the pilot valve to close it when the timer reaches a preset limit.

A combination boiler provides heated water to a boiler loop and heated domestic hot water (DHW) to a DHW loop. A primary heat exchanger is connected to the boiler loop. A burner provides heat to the primary heat exchanger and an input fan supplies a fuel and air mixture to the burner. A secondary heat exchanger transfers heat energy from the boiler loop to a domestic water loop. A controller determines a boiler loop flow rate. The controller measures an input temperature of the boiler loop, an output temperature of the boiler loop, and a DHW output temperature of the domestic water loop. The controller determines a DHW input temperature and estimates a DHW flow rate. The input fan speed is initiated or operated according to a required heat output of the burner corresponding to the DHW flow rate.

A combination boiler provides heated water to a boiler loop and heated domestic hot water (DHW) to a DHW loop. A primary heat exchanger is connected to the boiler loop. A burner provides heat to the primary heat exchanger and an input fan supplies a fuel and air mixture to the burner. A secondary heat exchanger transfers heat energy from the boiler loop to a domestic water loop. A controller determines a boiler loop flow rate. The controller measures an input temperature of the boiler loop, an output temperature of the boiler loop, and a DHW output temperature of the domestic water loop. The controller determines a DHW input temperature and estimates a DHW flow rate. The input fan speed is initiated or operated according to a required heat output of the burner corresponding to the DHW flow rate.

Control system for controlling the pilot flame of a combustible gas device, which includes a pilot burner, a main burner, and a valve assembly, which includes a pilot valve that allows/intercepts a flow of gas directed towards the pilot burner, and a main valve that allows/intercepts a gas flow to the main burner, the valve assembly moveable between a closed OFF state, a PILOT state, and an ON state, where gas flows to the main burner. The control system includes a detection device that generates a state signal, and a control unit including a timer, the control unit is operatively connected to the detection device to receive a state signal and to an actuator to close the valve. The control unit starts the timer when the state signal represents the PILOT state, and actuates the actuator for the pilot valve to close it when the timer reaches a preset limit.

Apparatus and methods for a gas furnace are disclosed. The gas furnace includes a variable combustion control which monitors the temperature of the burner and modifies one of the amount of combustion air supplied and the amount of gas fuel supplied to the mixing chamber. The described systems can dynamically accommodate differences in air quality and gas fuel supply to provide an optimum BTU output irrespective of differences in geographic location of usage. The gas furnace can include a dynamic response unit which predicts an optimum rate of heating to maintain a target room temperature, thereby preventing unnecessary shut down and costly re-ignition sequences, and maintaining the gas furnace at an optimum BTU output level.