A vent proving system is described for use with a gas fired appliance. The gas fired appliance includes a gas burner, a vent damper for selectively opening or closing an exhaust vent from the gas fired appliance and a relay control for operatively controlling the vent damper and the gas burner to open the damper if the gas burner is on. The vent proving system comprises a sensor for sensing a variable in the vent representing air flow direction in the vent. An electrical switch is connected in series between the relay control and the vent damper. A controller is operatively connected to the sensor, the electrical switch and to the relay control. The controller determines if a back draft condition is present in the vent when the gas burner is on and selectively operates the electrical switch to open the connection between the relay control and the vent damper if a back draft condition is present in the vent when the gas burner is on.

In a fuel-fired water heater with a standing pilot burner and a motorized flue damper, a specially designed controller is utilized to prevent overheating of water stored in the tank portion of the water heater caused by the hot combustion gases continuously generated by the pilot burner during standby periods of the water heater in which its main fuel burner is not being fired. The controller has a selectively variable water temperature control set point temperature and is operable to sense both ambient temperature and the tank water temperature and to open the flue damper and/or keep it open, after the main burner is off, in response to the presence for a predetermined continuous time period of a predetermined relationship of at least the selected temperature control set point temperature and the sensed ambient temperature.

A controller for use in a gas appliance system includes a circuit board, a plurality of connectors and a processor mounted on the circuit board. The processor controls operation of the gas appliance using, in part, at least one connector of the plurality of connectors and control settings for an intermittent pilot (IP) system in response to a user selection to configure the controller to control an IP system, and controls operation of the gas appliance using, in part, at least one connector of the plurality of connectors and control settings for a direct spark ignition (DSI) system in response to a user selection to configure the controller to control a DSI system.

A burner box for use in an air handling system. The burner box includes a main body having a top wall, a bottom wall, side walls extending between the top and bottom walls, and intermediate walls extending between the top and bottom walls and positioned between the side walls. An open upstream end of the main body is divided by the intermediate walls into a first bypass opening and a second bypass opening spaced from the first bypass opening by a burner opening. A direct fired burner is positioned in the main body between the intermediate walls and adjacent the burner opening such that air drawn into the main body through the burner opening is directed over the direct fired burner for heating. An electronic control system is operatively connected to the burner box and configured to maintain a constant pressure difference across the direct fired burner.

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.

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.

A water heating tank comprises a reservoir having a cold water inlet and a hot water outlet; a can disposed in a lower portion of the tank enclosing at least a part of a heater; a chimney extending from the top of the can to an upper portion of the tank. A chimney valve is arranged between the can and the chimney. The chimney valve is configured to prevent water flowing from the can into the chimney when a temperature of water in the can exceeds a first chimney threshold temperature.

A water heating tank comprises a reservoir having a cold water inlet and a hot water outlet; a can disposed in a lower portion of the tank enclosing at least a part of a heater; a chimney extending from the top of the can to an upper portion of the tank. A chimney valve is arranged between the can and the chimney. The chimney valve is configured to prevent water flowing from the can into the chimney when a temperature of water in the can exceeds a first chimney threshold temperature.

An improved thermal store is provided. The thermal decouples the heat output from the thermal store from the energy provided to the heater.

An improved method and apparatus allows fresh air to be introduced into a building through action of a special manifold or manifolds designed to direct fresh air into the interior atmosphere of the building, while air from the interior of the building is directed to the furnace combustion system and ultimately exhausted to the exterior of the building.