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.

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 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 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.

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 controller converts a detection result of an infrared sensor into overall thermal image data representing a temperature distribution within an infrared detection range of the infrared sensor, calculates, based on the overall thermal image data, a floor area of an air-conditioned space, and obtains, based on the overall thermal image data, floor thermal image data including a plurality of element data items each including coordinates within the floor area and a floor temperature within the floor area associated with the coordinates. The controller determines the presence or absence of a floor heating device in the air-conditioned space. When the controller determines the presence of the floor heating device, the controller determines, based on data that is included in the floor thermal image data and corresponds to an installation region of the floor heating device, an operation state of the floor heating device.

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.

Disclosed is a boiler blockage detection system and method utilizing inputs from a pressure sensing elements. A logic circuit may determine a boiler firing rate based on an input signal from the combustion controller. An indication of the exhaust pressure level and an indication of the inlet pressure level are received. A pressure differential between the exhaust pressure level and the inlet pressure level is determined. Alternatively, a pressure differential transmitter may determine the pressure differential. The determined pressure differential is compared to a predetermined pressure level differential threshold. The predetermined pressure level differential threshold is dependent on the determined firing rate. Based on a result of the comparison of the determined pressure differential to the predetermined pressure level differential threshold, it may be determined that there is a blockage of an intake or an exhaust of the boiler. In response to the blockage determination, an interrupt signal is output.

A heat balancing system for a natural draft gas burning appliance having a flue. When the appliance is in a standby mode, a main burner is shut off and the pilot light remains on. Temperature in the heat exchanger (e.g., temperature of water in a heater tank) may be decreased or increased, respectively, by opening or closing a damper in a flue as needed. If opening the damper does not sufficiently reduce the temperature of the heat exchanger, then the pilot light may be shut off to further reduce the temperature. The pilot light may be turned on again to bring up the temperature. There may be a control or controller to operate the damper to maintain the temperature of the exchanger within a certain range. Electrical power may be provided for the system from a power line, a storage device, or other source.

A method and apparatus for controlling a combustion heater are provided. An example method includes measuring a room temperature, measuring a combustion heater temperature, and measuring a fuel weight. Adjustments are computed to an operational parameter to adjust a room temperature. An anticipatory alert is provided to inform a user of a predicted time at which the fuel weight will be too low to maintain the room temperature.