A method, system, apparatus, and/or device for preheating air for a rooftop air handling unit (RTU). The method, system, apparatus, and/or device may include a barrier system configured to surround the RTU. The barrier system may include a structure to provide a frame for the barrier system, a first barrier configured to connect to a first side of the structure, and a collector configured to connect to a second side of the structure. The method, system, apparatus, and/or device may include a duct configured to connect between the collector and a chamber. The method, system, apparatus, and/or device may include a chamber configured to connect to an air intake hood of the RTU. The chamber may include a first opening to receive air stored in the cavity, a second opening to receive external air, and a diverter configured to switch between a first position and a second position.

Provided is a gas furnace including a primary heat exchanger and a secondary heat exchanger through which a combustion gas produced by the combustion of a fuel gas flows. The gas furnace includes: a coupling box serving as an intermediary to connect the primary heat exchanger and the secondary heat exchanger; a collect box connected to the secondary heat exchanger, for letting in the combustion gas passed through the secondary heat exchanger; an inducer connected to the collect box, for inducing a flow of the combustion gas; and a bypass pipe connected to one side of the coupling box and including a bypass pipe for guiding the combustion gas passed through the primary heat exchanger to a hot water supply tank for supplying hot water to an indoor space.

A fluid heating system including a burner unit is operated based on feedback control loops. The fluid heating system comprises a burner unit configured to heat a fluid, a sensor configured to sense a characteristic of the appliance, and a controller coupled to the burner unit and the sensor. The controller includes an electronic processor and a memory. The controller is configured to receive a first signal corresponding to the characteristic from the sensor, determine, based on the first signal, a first feedback loop control, control combustion of the burner unit based on the first feedback loop control, determine, based on the first feedback loop control, a second feedback loop control, and control combustion of the burner unit based on the second feedback loop control.

A method, system, apparatus, and/or device for preheating air for a rooftop air handling unit (RTU). The method, system, apparatus, and/or device may include a barrier system configured to surround the RTU. The barrier system may include a structure to provide a frame for the barrier system, a first barrier configured to connect to a first side of the structure, and a collector configured to connect to a second side of the structure. The method, system, apparatus, and/or device may include a duct configured to connect between the collector and a chamber. The method, system, apparatus, and/or device may include a chamber configured to connect to an air intake hood of the RTU. The chamber may include a first opening to receive air stored in the cavity, a second opening to receive external air, and a diverter configured to switch between a first position and a second position.

A flame sensor for a furnace of a heating, ventilation, and air conditioning (HVAC) system includes a sensor body and an electrically conductive member of the sensor body. The electrically conductive member is configured to be disposed within a flame region of a burner of the furnace and configured to receive electrical current from a controller of the furnace. The flame sensor also includes an anti-oxidation coating disposed on an outer surface of the electrically conductive member and configured to transmit the electrical current from the electrically conductive member. The anti-oxidation coating is configured to contact a flame produced by the burner and expose the electrical current to the flame.

An HVAC controller may wirelessly communicate with a mobile wireless device that provides a user interface for interacting with the HVAC controller. In some cases, the communication module wirelessly receives a sensed parameter from a remote wireless sensor in a living space of the building and receives a wired input from a return air sensor. A controller may be operatively coupled to the communication module and may control the HVAC system based at least in part on the sensed parameter from the remote wireless sensor when the sensed parameter from the remote wireless sensor is available and, in some cases, control the HVAC system based at least in part on the return air parameter when the sensed parameter from the remote wireless sensor is not available.

A water heater includes a water tank having an inlet and an outlet, and a flue extending through the tank. A nozzle is positioned near a first end of the flue, arranged so as to emit a fuel stream into the flue, and a flame holder is located within the flue in a position to receive the fuel stream and to hold a flame entirely within the flue. A controller variably controls a flow of fuel to the nozzle according to a temperature of water in the tank.

A turn down ratio (TDR) damper which controls an amount of gas and air flowing in the TDR damper and deliver the controlled gas and air to a turbo fan is disclosed. The TDR damper includes: air passages comprising a first air passage and a second air passage, the first air passage and the second air passage separately formed so that the air move through each path; gas passages comprising a first gas passage and a second gas passage, the first gas passage and the second gas passage separately formed so that the gas move through each path; and opening and closing means for opening and closing the second air passage and the second gas passage at the same time. The air passages and the gas passages may be separately formed and reached outlets connected to the turbo fan so that the air and gas may be delivered to the turbo fan through a separate path.

A method for controlling a water heater is provided. The method includes: controlling operation of a blower when a first condition is satisfied; and controlling an air outlet to be partially or fully opened according to a first parameter or a first instruction. Furthermore, a device for controlling a water heater is provided, including a processor and a memory having program instructions stored thereon. When the program instructions are executed, the processor performs the method for controlling the water heater. Moreover, the water heater is provided, including a housing, a blower, an air-out channel, a heating part, and the device for controlling the water heater.

A portable indirect fuel fired heater includes a burner assembly having a fuel burner to deliver fuel from a fuel supply to a combustion chamber of the heater and a combustion air blower to deliver combustion air to the combustion chamber with the fuel for combustion in the combustion chamber to produce exhaust gases. A heat exchanger receives air to be heated in heat exchanging relationship with at least a portion of the combustion chamber. A sensor senses an oxygen level as a partial pressure of oxygen in the exhaust gases. A controller operates an actuator operatively connected to the burner assembly to controllably vary the delivery rate of combustion air and thus vary the ratio of the air and fuel responsive to the oxygen level sensed by the combustion sensor so as to maintain the sensed oxygen level at a prescribed set point level stored on the controller.