A heating unit for a heating, ventilation and/or air conditioning (HVAC) system may have a first airflow path through the heating unit, a second airflow path through the heating unit, and a heater assembly having a first heating coil positioned within the first airflow path, a second heating coil positioned within the second airflow path, and a coil divider separating the first heating coil and the second heating coil.

A water heating system includes a plurality of water heaters of which exhaust paths are connected in common to an exhaust path assembly, a control device configured for centralized control of the plurality of water heaters, and a non-volatile storage unit. The plurality of water heaters include control units configured to control hot water supply operations based on communication with the control device, respectively. The storage unit is configured to store information on the water heater of which control unit is recorded to have established communication with the control device. The control device turns off all of the plurality of water heaters when information on the water heater of which control unit has currently established communication with the control device does not match with the information stored in the storage unit.

In a gas hot water heater, changes of the signal output of an A/F sensor are calibrated in the atmosphere, in which the A/F sensor detects an oxygen concentration in a combustion tube. The gas supplied via a gas supply pipe is injected, together with in-taken air, into a combustion tube, which is incorporated in a hot water supply tank, via an injection unit. A proportional valve controls a combustion state in the combustion tube based on the detected oxygen concentration to thereby heat water supplied in the hot water supply tank. A purging process is performed to supply air into the combustion tube, at a timing between an extinguishment operation first performed after the ignition the gas mixture in the combustion tube and a re-ignition operation. Changes of signal output characteristics of the A/F sensor are subject to the calibration after the purging process.

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.

The present invention relates to a method of controlling a gas furnace that performs heating operation according to a heating signal formed of one of a weak heating signal and a strong heating signal. The method includes: (a) receiving the heating signal; (b) determining whether the heating signal is the weak heating signal or the strong heating signal; (c) calculating a certain weak heating capacity smaller than a maximum heating capacity of the gas furnace, when the heating signal is the weak heating signal; and (d) operating a weak heating of the gas furnace with the calculated certain weak heating capacity, wherein the step (c) includes calculating the weak heating capacity according to a difference between a temperature of air (hereinafter, an intake air temperature) sucked into the gas furnace and a reference temperature set based on the intake air temperature.

This concept is very new, and it will allow for safe and continuous operation of gas heating units when the induced draft fan no longer operates. This device will allow the HVAC service technician to continue to operate the gas heating unit until the proper replacement induced draft fan can be acquired and installed on the gas heating unit. This invention is a supplemental induced draft fan that will attach to the exhaust output side of a gas heating units inoperable induced draft fan to draft air through the heat exchanger and create a vacuum to the pressure switch at a rate to be regulated by a control switch to make the gas heating unit operate safely until the correct part is acquired and installed.

A system and method of operating a gas fuel valve control circuit are disclosed. The gas valve control circuit includes a gas valve assembly configured to control a flow of a fuel gas to a load and a switch assembly including a switch in each leg of a plurality of legs of a power supply to the gas valve assembly. The switch assembly is configured to supply power and a return to the gas valve assembly in a first position and to open the plurality of legs of the power supply to the gas valve assembly in a second position. The switch assembly is configured to indicate a position of the switch assembly.

A system and method of operating a water heater controller that includes a powered vent electronic control circuit including a controller configured to control an operation of heating device having a powered draft inducer, a gas valve assembly configured to control a flow of a fuel gas to a burner of a heating device, and a switch assembly including a switch in each leg of a plurality of legs of a power supply to the gas valve assembly, the switch assembly configured to supply power and a return to the gas valve assembly in a first position and to open the plurality of legs of the power supply to the gas valve assembly in a second position, the switch assembly configured to indicate a position of the switch assembly to the controller.

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 system and method of operating a gas fuel valve control circuit are disclosed. The gas valve control circuit includes a gas valve assembly configured to control a flow of a fuel gas to a load and a switch assembly including a switch in each leg of a plurality of legs of a power supply to the gas valve assembly. The switch assembly is configured to supply power and a return to the gas valve assembly in a first position and to open the plurality of legs of the power supply to the gas valve assembly in a second position. The switch assembly is configured to indicate a position of the switch assembly.