6
p
lan
the
D
uct
w
ork
i
nStallation
WARNING
To reduce the risk of fire and to properly exhaust
•
air, be sure to duct air outside the house or building.
Do not vent exhaust air into spaces within walls or
ceilings or into attics, crawl spaces or garages.
Tape all duct joints securely
•
to prevent combustion
by-products, smoke or odors from entering the home.
Doing so will also improve system efficiency.
Do not exhaust more than one
•
vent into a single duct.
Use only
•
duct work constructed of materials deemed
acceptable by state, municipal and local codes.
Range hoods may interrupt the proper flow of
•
smoke and combustion gases from furnaces, gas
water heaters and fireplaces. To avoid drawing
lethal gases into the home, follow the manufactures
recommendation for these devices and consult NFPA
and ASHRAE recommendations.
DO NOT
•
install an additional in-line or external
blower to increase the length of the duct run. Even
small differences between blower air flow rates can
greatly reduce the air draw by the hood.
All duct work materials (including screws and duct tape)
•
must be purchased separately by the customer. When
planning new duct work, always look for the shortest,
most direct route to the outside.
The hood exhaust connects to an 8-inch round duct.
•
You can increase the duct size over the duct run if
desired. To prevent a back draft, never decrease the
duct size over the run.
Do not rely on duct tape alone to seal duct joints.
•
Fasten all connections with sheet metal screws and
tape all joints with duct tape. Use sheet metal screws
as require to support the duct weight.
To prevent back-drafts, a damper at the duct outlet may
•
also be required.
Make sure duct work does not interfere with floor joists
•
or wall studs.
Calculating the Maximum Duct Run Length
The maximum straight duct length for the hood is 100
feet. For each elbow and transition added to the duct
work, a certain number of feet must be subtracted from
the maximum straight length to compensate for wind
resistance. To determine the length the duct work cannot
exceed, subtract all of the equivalent lengths of the elbows
and transitions listed below from 100 feet.
Duct Work Equivalent Lengths
DUCT PIECE
SUBTRACT
90° elbow (8” Dia.)
7 feet
45° elbow (8” Dia.)
3 feet
3 1/4” x 10” to 8” round
4 foot
Wall cap with damper
30 feet
Roof cap
30 feet
Duct Work Design Tips
Wherever possible, reduce the number of transitions
•
and turns to as few sharp angles as possible. Two
staggered 45° angles are better than one 90°.
Keep turns as far away from the hood exhaust as
•
possible, with as much space between each bend as
possible.
For best performance, use round duct instead of
•
rectangular, especially when elbows are required.
If multiple elbows are used, try to keep a minimum of
•
24” (61 cm) of straight duct between them.
Avoid “S” or “back to back” configurations of adjacent
•
elbows.
In regions where the weather gets extremely cold,
•
thermal breaks, such as a short section of non-metallic
duct, should be used to avoid indoor heat loss. The
break should be located as close to the pass through
point to the outside as possible.
Do not use flexible metal duct.
•
Do not
•
use duct work that is smaller in cross-sectional
area than the recommended size duct (8” round).
p
reparing
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nsTallaTion
Summary of Contents for DHI361
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