Loading ...
Loading ...
Loading ...
6
Elbows, Transitions, Wall and Roof caps
Several duct pieces may present additional resistance to airflow and are equivalent to a section of
straight duct which is longer than their actual physical size. When calculating the total duct length,
add the equivalent lengths of all transitions and adaptors plus the length of all straight duct sections.
The chart below shows you how to calculate total equivalent ductwork length using the approximate
feet of equivalent length of some typical ducts.
DUCT PIECES
EQUIVALENT
LENGTH
x
NUMBER
USED
=
EQUIVALENT
LENGTH
Rectangular-to-
Round
Transition
Adaptor*
5 Ft.
x
(
)
=
Ft.
Wall Cap
40 Ft.
x
(
)
=
Ft.
90° Elbow
10 Ft.
x
(
)
=
Ft.
45° Elbow
5 Ft.
x
(
)
=
Ft.
90° Elbow
25 Ft.
x
(
)
=
Ft.
45° Elbow
5 Ft.
x
(
)
=
Ft.
Roof Cap
24 Ft.
x
(
)
=
Ft.
Straight Duct 6 "
Round or 3¼" x 10"
Rectangular
1 Ft.
x
(
)
=
Ft.
Total Duct
work
=
F t.
NOTE: If a rectangular-to-round transition adaptor is used, the bottom corners of the damper will
have to be cut to fit, using the tin snips, in order to allow free movement of the damper.
Equivalent lengths of duct pieces are based on actual tests and reflect requirements for good
venting performance with any vent hood.
Loading ...
Loading ...
Loading ...