Installation Instructions

5
Ducted Installations - Planning
the Duct Work
WARNING
• To prevent combustion by-products, smoke or odors
from entering the home and to improve efficiency,
tape all duct joints securely.
• Use only duct work deemed acceptable by state,
municipal and local codes.
• 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 of the hood.
CAUTION
To reduce the risk of fire and to properly exhaust air, do
not vent exhaust air into spaces within walls or ceilings
or into attics, crawl spaces or garages.
■ Local building codes may require the use of makeup
air systems with ventilation systems that move air
greater than the specified movement rate (CFM). The
specified rate varies based on locale. Consult a quali-
fied HVAC specialist when designing the system for
the requirements in your area and to assure optimal
performance.
■ 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. If existing duct work is smaller
than 8 inches in diameter, remove it and replace it
with 8-inch duct work.
■ Do not rely on tape alone to seal duct joints. Fasten
all connections with sheet metal screws and tape all
joints with certified silver tape or duct tape. Use sheet
metal screws as required 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.
Installation Specifications
Calculating the Maximum Duct Run Length
The maximum straight duct length for the hood is 50 feet.
To determine the actual maximum duct run, subtract the
equivalent length of each elbow, transition and cap from
50 feet.
EQUIVALENT LENGTHS
Piece Subtract Piece Subtract
8” 90° elbow 7 feet
10” 90°
elbow
5 feet
8” 45° elbow 3 feet
10” 45°
elbow
2 feet
3¼” X 10”
to round 90°
transition
25 feet
3¼” X 10” to
8”/10” round
transition
4 feet
Roof cap *
Wall cap
with damper
*
* The equivalent lengths of roof and wall caps vary with
model and configuration. For equivalent length, contact
the manufacturer or a qualified HVAC specialist.
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, and as much space between bends as pos-
sible.
■ For best performance, use round duct instead of rect-
angular, especially when elbows are required.
■ If multiple elbows are used, try to keep a minimum of
24 inches straight duct between them.
■ Avoid “S” or “back to back” use of adjacent elbows.
■ In regions where the weather gets extremely cold,
use thermal breaks, such as a short section of
non-metallic duct, to avoid indoor heat loss. Locate
the break as close as possible to the outside pass
through point.
■ Do not use flexible metal duct.
■ DO NOT use duct work that is smaller in cross-sec-
tional area than the recommended types above.