Barometric Draft Controls

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When to Use a Draft Control

• Draft Inducers/Power Venters

 With these devices, draft is increased or created, causing fluctuations in air flow through the combustion chamber. These fluctuations can be negated by the use of a barometric draft control located between the draft inducer or power venter and the furnace, boiler, or water heater it services. Use a single-acting control for oil and gas-fired equipment with a power vented system. Use a single acting control for oil, and a double-acting control for gas-fired equipment with a draft induced system.

 • Power Burners

 A power burner is designed so that a fan delivers negative air pressure to the combustion chamber. A single-acting draft control for oil maintains that negative pressure. A power burner designed to burn natural or LP gas operates in the same manner. While a draft hood (diverter) is often used on gas units fired with an atmospheric burner, a double-acting barometric draft control should be used for furnaces or boilers fired with power burners.

 • Forced Draft Burners

 Forced Draft installed with a stack height in excess of 30' will probably develop excessive natural draft, reducing the amount of pressure within the furnace or boiler. A barometric draft control will help eliminate this undesirable stack action and permit the unit to be pressurized.

 • Dual Fuel Appliances

 Burners capable of burning either gaseous fuels or oil should be equipped with a barometric draft control. We suggest using a double-acting control on units where fuels are frequently changed. The double-acting feature is important for gas-firing appliances because it allows spillage of combustion products in case of blocked flues or downdrafts. To detect flue gas spillage on dual fuel installation, a Field Thermal Safety Switch is recommended.

 • Gas-Fired Appliances

 Gas-fired furnaces and boilers generally require a double-acting draft control. Like a single-acting control, it opens inwardly to maintain a uniform draft. But, unlike a single-acting control, it is also free to open outwardly to spill the products of combustion, in case of blocked flues or downdrafts. National codes often mandate the use of a draft control. Usage is generally limited to furnaces or boilers designed for use with power burners and incinerators. Draft controls are generally used when oil-fired units are converted to gas.