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WORKSHEET—CALCULATE TOTAL EQUIVALENT DUCTWORK LENGTH*
DUCT
EQUIVALENT NUMBER
PIECES
LENGTH
3¼" x 10"
1 Ft.
Rect.,
straight
7" Round,
1 Ft.
straight
6" Round,
1 Ft.
straight
3¼" x 10"
14 Ft.
Rect. 90°
elbow
3¼" x 10"
8 Ft.
Rect. 45°
elbow
3¼" x 10"
33 Ft.
Rect. 90°
flat elbow
3¼" x 10"
24 Ft.
Rect.
(18 ft. w/o
wall cap
damper)
with
damper
3¼" x 10"
2 Ft.
Rect. to
6" round
transition
3¼" x 10"
4 Ft.
Rect. to
6" round
transition
90° elbow
6" Round,
12 Ft.
90° elbow
6" Round,
7 Ft.
45° elbow
Subtotal column 1
MAXIMUM DUCT LENGTH: For satisfactory air
movement, the total duct length of a 3¼" x 10"
rectangular, 6" or 7" diameter round duct should
not exceed 65 equivalent feet.
* 1 Ft = 0.3 m
1" = 2.5 cm
Installation Instructions
x USED
= TOTAL
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
x (
)
=
Ft.
=
Ft.
DUCT
PIECES
6" Round
wall cap
with
damper
6" Round
roof cap
6" Round
to
3¼" x 10"
rect.
transition
6" Round
to
3¼" x 10"
rect.
transition
90° elbow
7" Round,
90° elbow
7" Round,
45° elbow
7" Round
wall cap
with
damper
7" Round
roof cap
7" Round
to
3¼" x 10"
rect.
transition
7" Round
to
3¼" x 10"
rect.
transition,
90° elbow
6
EQUIVALENT
NUMBER
LENGTH
x USED
24 Ft.
x (
)
(18 ft. w/o
damper)
x (
)
33 Ft.
x (
)
2 Ft.
x (
)
4 Ft.
x (
)
14 Ft.
x (
)
9 Ft.
x (
)
28 Ft.
x (
)
(21 ft. w/o
damper)
x (
)
39 Ft.
x (
)
1 Ft.
x (
)
5 Ft.
x (
)
Subtotal column 2
Subtotal column 1
Total ductwork
= TOTAL
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
=
Ft.
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