Flammable vapor resistant water heater

Details Flammable vapor resistant water heater Flammable vapor resistant water heater

2000-05-03

2001-04-17

Wilson, Gregory (Department: 3749)

Liquid heaters and vaporizers

Stand boiler

C122S017100, C126S350100

Reexamination Certificate

active

06216643

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to water heaters. More particularly, the invention relates to flammable vapor resistant gas water heaters.
BACKGROUND
Gas-fired, storage-type water heaters often include a combustion chamber and air plenum disposed below a water tank. A burner element, gas manifold tube, ignition source, thermocouple, and a pilot tube typically extend into the combustion chamber. When the temperature of the water in the tank falls below a set minimum, gas fuel is introduced into the combustion chamber through the gas manifold tube and burner element. This gas fuel is ignited by the pilot flame or other ignition source, and the flame is maintained around the burner element. Air is drawn into the plenum, and mixes with gas fuel to support combustion within the combustion chamber. The products of combustion typically flow through a flue or heat exchange tube in the water tank to heat the water by convection and conduction.
In some cases, a water heater may be positioned in an area that is also occupied by lawnmowers, chain saws, snow blowers, trimmers, and other equipment having a gasoline-powered internal combustion engine. In such cases, it is not uncommon that there be gasoline and other flammable substances (e.g., kerosene, diesel, turpentine, solvents, alcohol, propane, methane, and butane) present in the same area. Such flammable substances often emit flammable vapors.
If the flammable substances are mishandled, the flammable vapors may encounter an ignition source, such as the pilot flame or burner flame of a gas-fired water heater. As a result of the mishandling of flammable substances, the flammable vapors may ignite, and the flame may follow the flammable vapors to their source, causing an explosion and/or a fire. Proposed governmental regulations would require residential gas-fired water heaters to be flammable vapor resistant in order to help reduce the occurrence of such dangerous situations caused by the mishandling of flammable substances.
SUMMARY
The present invention provides a water heater having a flame arrestor or flame trap. The water heater also includes a water tank, a combustion chamber, an air plenum, and a burner element in the combustion chamber. The burner element supports continuous combustion within the combustion chamber during heating of the water in the water tank. A radiation shield preferably helps to maintain heat within the combustion chamber and direct the heat toward the bottom of the water tank.
The invention requires substantially all air that is necessary for combustion to pass through the flame arrestor. When flammable vapors are mixed with the combustion air, the flammable vapors may be ignited and burned near the surface of the flame arrestor facing the combustion chamber. The flammable vapors burn until the flammable vapor mixture no longer supports combustion. The arrestor is designed such that it will not significantly deteriorate during the burning of the flammable vapors or over the life of the water heater. The flame arrestor is designed to have an air-flow path that substantially prevents flames from traveling through the flame arrestor. The arrestor is constructed of materials having low thermal conductivity so that the flame arrestor itself is not likely to become an ignition source for the flammable vapors. The flame arrestor is also designed to accommodate a wide variety of possible flammable vapor mixtures.
A retainer member holds the flame arrestor in place. Preferably, the retainer member includes a portion that helps provide a seal around the periphery of the flame arrestor so that substantially all air entering the combustion chamber must pass through the flame arrestor. Thus, substantially all flash-back that may occur due to flammable vapors entering the combustion chamber is quenched or arrested within the combustion chamber by the flame arrestor. A portion of the retainer member passes through a portion of the radiation shield. The portion of the retainer member preferably includes a protrusion that resists vertical movement of the radiation shield. Thus, the radiation shield is located and held in place within the combustion chamber by the retainer member. The retainer member may also support the burner tube or manifold tube and the burner element within the combustion chamber.
Another feature of the present invention is a screen that covers the air inlet of the air plenum. The screen traps airborne debris that would otherwise enter the air plenum and be trapped by the flame arrestor. This substantially prevents a buildup of such debris on the flame arrestor that could interfere with the flow of air through the flame arrestor, and that could cause flare-ups on the surface of the flame arrestor facing into the air plenum. The screen may therefore reduce or eliminate the need for servicing the flame arrestor.
The screen includes a protrusion that prevents air flow across the air inlet that might cause a partial vacuum and interfere with combustion. The screen protrusion may include a double-thick portion of screen material, to create a substantially dead-air region on the lee of the protrusion. The protrusion also serves to deflect at least some of the cross-flowing air into the air plenum. This may result in more reliable and efficient water heater performance.
The water heater preferably includes a one-piece base pan that includes a first level defining a bottom wall of the combustion chamber/plenum, a second level that supports the water tank, and a third level that supports the water heater insulation and outerjacket surrounding the water tank. The single-piece base pan thus serves several functions that are performed by separate components in known water beaters. The use of a single component to perform several functions may reduce the cost and complexity of manufacturing the water heater.
The water heater may also include a sealing member, such as a grommet or boot, that surrounds a burner operating conduit, such as the gas manifold tube, pilot light tube, ignition wire, or thermocouple. The sealing member creates a substantially airtight seal between the burner operating conduit and the side wall of the water heater. Preferably, a single grommet seals several burner operating conduits with respect to the side wall, and a boot seals the gas manifold tube with respect to the side wall. The boot may include a plurality of folds to permit some movement of the gas manifold tube with respect to the skirt without compromising the substantially airtight seal. Both the grommet and the boot may include a peripheral groove that permits them to be easily snapped into place within openings in the skirt.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.


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