Brochure

3
• 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 down-drafts. 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 down-drafts.
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.
When to use a Draft Control
Draft Control
Illustration B demonstrates how pressure changes as
air/gases flow through the appliance (A), past the draft
control (B), through the vent pipe (C), and outside the
building (D/E).
Illustration B
Typical Natural Vent System