Gas valves are commonly used in conjunction with gas-fired appliances for regulating gas flow and/or gas pressure at limits established by the manufacturer or by industry standard. In many cases, such devices can include pressure regulators to, for example, establish and/or maintain a gas pressure to help prevent over-combustion or fuel-rich combustion within the appliance, and/or to prevent combustion when the supply of gas is insufficient to permit proper operation of the appliance. Examples of gas-fired appliances that may employ such gas valves can include, but are not limited to, water heaters, furnaces, fireplace inserts, gas stoves, gas clothes dryers, gas grills, or any other such device where gas control is desired. Typically, such appliances utilize fuels such as natural gas or liquid propane as the primary fuel source, although other liquid and/or gas fuel sources may be provided depending on the type of appliance to be controlled.
In a gas-fired appliance, a combustion chamber and air plenum are typically provided along with a gas valve. A burner element, fuel manifold tube, ignition source, thermocouple, and/or pilot tube can also be provided as part of the burner system. During operation, when a heat demand is present, metered fuel is typically introduced via the gas valve through the fuel manifold tube and burner element and into the combustion chamber. The fuel is ignited by a pilot flame or other ignition source, causing fuel combustion at the burner element. In some cases, air may be drawn into the air plenum, sometimes under the assistance of an air blower, causing the air to mix with the fuel to support the combustion within the combustion chamber. The products of the combusted air-fuel mixture are typically fed through a flue or heat exchanger tube in the gas-fired appliance to heat by convection and conduction.
In some cases, the gas valve may include a pressure regulator to regulate the flow of gas at a pressure. In many cases, the pressure regulator references the pressure of the combustion chamber to help maintain and/or achieve a desired combustion level in the combustion chamber. Typically, a hose can be coupled to the pressure regulator and the combustion chamber or burner box to fluidly connect the pressure regulator and the reference pressure within the combustion chamber. It has been found, however, that in some cases, the hose may become blocked by condensate build-up or other particulate matter. Also, in some cases, the hose may become kinked or otherwise obstructed. In either case, the blockage may cause the pressure in the pressure regulator to increase or decrease resulting in over-combustion or under-combustion in the combustion chamber.
In some gas-fired systems, a separate fitting including a bleed orifice may be coupled between the pressure regulator and the hose to provide a reference pressure such as atmosphere if the hose becomes blocked. This additional fitting can, however, be removed from the system or not installed properly during installation. Also, the bleed orifice in the fitting may become blocked with grease or other material during handling.