Higher volumes of air exhausted by the vent system result in better overall removal
of smoke and fumes from the kitchen. Longer duct runs and greater numbers of
duct transitions reduce air volume, therefore it is extremely important to keep
duct runs as short and straight as possible.
Model
Duct
Size
E30DD75ESS
10"
E36DD75ESS
3 1/4" x 10"
E46DD75ESS
E48DD75ESS
We recommend using a certified HVAC contractor for all installations.
To ensure that your installation
meets this requirement, add the
actual straight length of duct to the
equivalent straight length of all duct
fittings to determine the total
equivalent straight length of duct.
(Refer to the table on the right,
which shows various common duct
fittings with their equivalent straight
lengths for various common duct
sizes). If this total equivalent
straight length is less than or equal
to the maximum limits specified,
then the installation is proper.
Consider the duct size that
corresponds to the majority of the duct used in the installation.
Sample problem - for reference only:
Given a system installation having 25 feet of 3 ¼" x 10" rectangular duct, one (1)
90-degree 3 ¼" x 10" elbow, and one (1) 3 ¼" x 10" to 10" round transition, would
this installation be proper?
Solution:
1. Add the total length of straight duct:
25' (of 3 ¼" x 10") = 25'.
2. Using Table above, determine the equivalent straight length of all duct fittings:
90-degree 3 ¼" x 10" elbow = 15'. 3 ¼" x 10" to 10" round transition = 4'.
Duct Preparation
Maximum Equivalent Straight Lengths
70'
60'
3 1/4" x 10" 90° Elbow
15 Feet
Transistion
3 1/4" x 10" to Round
10" Diameter - 4 Feet
3 1/4" x 10" 45° Elbow
3 1/4" x 10" Wall Cap
7 Feet
2 Feet
45° Elbow - Round Duct
90° Transistion
3 1/4" x 10" to 10" Round
25 Feet
10" Diameter - 2 Feet
11
3 1/4" x 10"
90° Flat Elbow
20 Feet
90° Elbow - Round Duct
10" Diameter - 5 Feet
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