5
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-
sectional area than the recommended size duct (8”
round).
