A method of protecting a single-stage furnace in a multi-zone system includes monitoring a temperature of each zone of a plurality of zones, determining if the temperature of at least one zone of the plurality of zones is less than a threshold temperature, powering on the HVAC system to satisfy a heating demand of the zone having a temperature less than the threshold temperature, monitoring an outlet temperature of the single-stage furnace, determining if the outlet temperature is greater than an outlet temperature threshold, and responsive to a determination that the outlet temperature is greater than the outlet temperature threshold, modulating a gas valve to reduce a flow of gas to the single-stage furnace.

A limit switch assembly including a shape memory member, a furnace system for incorporating the same, and a method for controlling a furnace are provided. The limit switch assembly includes a switch communicatively connected to a control board of a furnace. The switch is configured to send a signal to the control board when actuated. The shape memory member is configured to actuate the switch. The control board, in certain instances, shuts off the furnace and arrests the supply of combustible gas when receiving the signal from the switch. The shape memory member, in certain instances, actuates the switch as a result of being heated.

An air handler unit (AHU) in communication with a building automation system (BAS) or through direct programming of one or more smart valves within the AHU operates to meter an amount of water that flows through a coil in the AHU. In one embodiment, the BAS transmits a temperature setpoint signal to the smart valve and allows the smart valve to control its valve position without additional input from the BAS. In another embodiment, the AHU includes a master smart valve and a second valve. The BAS provides the temperature setpoint signal to the master smart valve, which in turn provides another temperature setpoint signal to the second valve. The second valve may take the form of a slave smart valve or a slave non-smart valve.

A furnace including a housing and a firebox in the housing having a combustion chamber. The furnace includes a combustion air delivery system for delivering combustion air to the combustion chamber. The combustion air delivery system includes a manifold mounted outside the combustion chamber and extending vertically along the front face of the combustion chamber from a lower end to an upper end. An air blower is mounted on the manifold. The combustion air delivery system includes a primary combustion air passage for delivering air from the air blower to a primary combustion air outlet at the front face of the combustion chamber. The combustion air delivery system includes a secondary combustion air passage for delivering air to a secondary combustion air outlet positioned inside the combustion chamber adjacent the top face of the combustion chamber.

A furnace including a combustion chamber for burning fuel can have increased fuel burning efficiency, increased heating efficiency, and decreased harmful emissions of combustion byproducts. A combustion air delivery system delivers primary and secondary combustion air to the combustion chamber. Primary and secondary combustion air may be delivered at amounts that increase burning efficiency. An amount of secondary combustion air can be controlled by a valve system. A heat transfer device efficiently transfers heat from products of combustion for heating an enclosed space.

A heating control system that includes a heating unit with a constant burner and a pulsed burner. The constant burner is configured to remain active during operation. The pulsed burner is configured to toggle between an active mode and an inactive mode. The heating control system further includes a memory operable to store a temperature map that maps temperatures to percentages of a period that the pulsed burner is active and a microprocessor operably coupled to the heating unit and the memory. The microprocessor is configured to transmit a first electrical signal to activate the constant burner, obtain a temperature set point, determine the percentage of the period that the pulsed burner is active using the temperature set point and the temperature map, and transmit a second electrical signal to toggle the pulsed burner based on the determination of the percentage of the period that the pulsed burner is active.

A heating control method includes determining a first speed for an air circulation fan that corresponds with a temperature set point using a temperature map that maps temperatures to speeds of the air circulation fan and operating the air circulation fan at the first speed and a heating unit in a first configuration with at least one active burner from a plurality of burners where less than all of the burners are active when the heating unit is in the first configuration. The method further includes measuring a first temperature while operating the air circulation fan at the first speed, determining a temperature difference between the first temperature and the temperature set point, comparing the temperature difference to a temperature difference threshold, and updating the temperature map to map the first speed to the first temperature when the temperature difference is greater than the temperature difference threshold.

An air handler unit (AHU) in communication with a building automation system (BAS) or through direct programming of one or more smart valves within the AHU operates to meter an amount of water that flows through a coil in the AHU. In one embodiment, the BAS transmits a temperature setpoint signal to the smart valve and allows the smart valve to control its valve position without additional input from the BAS. In another embodiment, the AHU includes a master smart valve and a second valve. The BAS provides the temperature setpoint signal to the master smart valve, which in turn provides another temperature setpoint signal to the second valve. The second valve may take the form of a slave smart valve or a slave non-smart valve.

A flameless heating apparatus is provided for heating and vaporizing a composition. The flameless heating apparatus may include a heating member, heating barrel, heat generation component, control component, and base member. A method for heating and vaporizing a composition using the flameless heating apparatus is also provided.

A heating system retrofitted to be operable through multiple heat stages at a constant fuel-air mixture includes a tube heat exchanger having a plurality of burners, a combustion air blower (CAB) having an exhaust vent connected with the plurality of burners, the CAB operable at a first speed and a second speed, a first valve connecting a fuel source to a first subset of the plurality of burners, and a second valve connecting a fuel source to a second subset of the plurality of burners.