A surface heater automatically adjusts the supply of fuel and/air to the burner in order to maintain a desired air/fuel ratio despite changes in ambient air temperature and/or pressure. The adjustment may be performed on a periodic or continuous basis and on either an open-loop basis or a closed-loop basis. The adjustment includes actuating one or more control devices that control the flow of air and/or fuel to the burner. If the adjustment is performed on a closed-loop basis, signals from a sensor can be used as feedback to control the flow of air and/or fuel into the burner to maintain a setpoint of a controlled parameter. The controlled parameter may include one or more of air mass flow rate, an intake O.sub.2 concentration, an exhaust O.sub.2 concentration, an exhaust gas composition, and an exhaust gas temperature.

The present invention relates to a dual venturi for a combustor and, specifically, to a dual venturi for a combustor, which adjusts the amount of gas and air supplied to a burner of a hot water heater and has a motor combined with a damper in order to increase a turn-down ratio (TDR), such that the damper is rotated by the driving of the motor so as to simultaneously open or close secondary air and gas inlets, thereby enabling efficient heating control. The present invention has a separate opening/closing means which is capable of controlling, in two stages, the amount of air and gas flowing into the combustor such as the hot water heater, wherein the opening/closing means comprises the motor and the damper, and the damper is rotated by the driving of the motor so as to simultaneously open or close the secondary air and gas inlets, thereby enabling the control of the amount of air and gas.

A modulating burner apparatus includes a variable speed blower feeding a multi-chamber burner having first and second burner chambers. A manifold system communicates the blower with the burner, and a flow control valve member is located between the blower and the second chamber of the burner. The flow control valve is configured to provide fuel and air mixture from the blower to only the first burner chamber at lower blower speeds of the blower and to both the first and second burner chambers at higher blower speeds of the blower.

The disclosed technology includes a device for extending the turndown ratio of a gas-fired burner system. The device can comprise a variable area device configured reduce the amount of fuel and air passed to the burner during low output conditions by adjusting the cross-sectional area of the passage between the blower and the burner. The variable area device can be controlled by an actuator that adjusts the position of the variable area device. The actuator can be manually controlled, mechanically controlled, or electronically controlled.

A gas appliance comprises a combustion device, an ignitor, a gas valve, a blower, a detecting device, and a control device. A control method thereof comprises: the control device is operated in a detection mode in which the control device controls the ignitor to ignite and controls the gas valve as well as the blower to provide a fixed gas flow and a fixed air flow to the combustion device. After igniting the flames, the control device determines burning states detected by the detecting device; if matching a first state, the control device controls the gas valve and the blower in correspondence to a first control data of the first natural gas; if matching the second state, the control device controls the gas valve and the blower in correspondence to a second control data of the second natural gas. In this way, the gas appliance is suitable for burning natural gas generating various heating values.

Combustion systems configured to achieve, and methods of operating combustion systems to attain, enhanced high turndown operation, are disclosed herein. In one example embodiment, a combustion system includes an air flow tube, an air inlet damper, a gas train, a mixing chamber, a burner, and a blower. A flow of air via the tube into the mixing chamber is governed at least in part by a status of the air inlet damper. Further, the air inlet damper includes a damper plate having an outer perimeter with a first edge portion that is complementary to an inner surface of the tube and one or more additional edge portions that define a first inwardly-extending cutout. In another example embodiment, the combustion system includes a control device configured to cause a control signal for receipt by the damper motor to vary nonlinearly in response to variation of a modulation signal.

An example includes a combustion device comprising: a burner; a feed duct; an actuator adjusting a feed of fluid through the feed duct; and a control apparatus programmed to adjust the actuator. The actuator, upon receipt a request signal, checks for a stored rate of change in an associated memory and, if the stored rate of change is present, sends a response signal to the control apparatus. The control apparatus determines a rate of change from the response signal, and generates a first automation signal as a function of the stored rate of change. The first automation signal causes the actuator to change a mechanical variable of the actuator so the mechanical variable changes no faster than the stored rate of change.

A wood stove that includes a hollow cylindrical outer skin with an coaxially aligned, insulated inner fire box. Located below the fire box is a fresh air inlet and an air control valve that controls the flow of fresh air into the stove's primary and secondary chambers. Surrounding the fire box are three longitudinally aligned air conduits that extend from the air inlet to an upper ledge located below a secondary combustion chamber. During use, the fresh air inside the air conduits is heated. Disposed transversely inside the outer jacket and above the primary chamber is a combustor assembly that includes a lower fin plate, a perforated intermediate plate and a perforated upper plate. During use, fuel is added to the fire box which undergoes initial combustion and produces hot gases and fumes that travel upward towards the chamber assembly. The air control valve controls flow of fresh air into the primary chamber only, both chambers, or into only the secondary chamber.

A selector valve and shutter mechanism for use with a gas burner unit is disclosed. The valve includes a pilot gas manifold which is in communication with two pilot flames and associated ODS for two different kinds of gas fuel. The shutter mechanism opens or closes an opening to a burner mixing chamber to thereby adjust the flow of air into the mixing chamber depending on the fuel selected, and preferably is in the form of a sleeve that in one approach is rotatably mounted on a part of the burner mixing chamber, with a part of the sleeve covering the mixing chamber opening in one orientation and opening it to airflow in another orientation. A first gear is mounted on the sleeve which is engageable with a second gear mounted on part of the valve which is rotatable to one position or another depending on the gas fuel selected, the sleeve thereby adjusting the airflow to the mixing chamber in response to the valve position. In another approach, the cover moves linearly along the burner tube between orientations. A novel selector mechanism having a manifold for gas flows and a plate-like element to adjust the manifold is also disclosed.

Techniques for controlling a solid fuel combustion appliance, e.g., a wood burning stove, are disclosed. A control system measures an exhaust gas temperature of airflow through an outlet of the solid fuel combustion appliance. The control system determines a derivative of the exhaust gas temperature with respect to time. The derivative of the exhaust gas temperature with respect to time is compared to a predetermined threshold. The control system modulates the inlet damper in response to determining that the derivative of the exhaust gas temperature with respect to time reaches the predetermined threshold.