Equivalent number
Duct pieces
length x used
3- 1/ 4" x 10"
1 Ft.
Rect.,
straight
6", 7", 8", 10"
1 Ft.
Round,
straight
3- 1/ 4" x 10"
15 Ft.
Rect. 90
0
elbow
3- 1/ 4" x 10"
9 Ft.
Rect. 45
0
elbow
3- 1/ 4" x 10"
24 Ft.
Rect. 90
0
flat elbow
7" to 6" or
25 Ft.
8" to 7" Round
tapered
reducer
15
Ft.
6", 7", 8"
Round
in-line
damper
6", 7", 8", 10"
15 Ft.
Round,
90
0
elbow
6", 7", 8", 10"
9 Ft.
Round,
45
0
elbow
Subtotal column 1 =
Maximum Duct Length:
For satisfactory air movement,
the total duct length should not exceed 100 equivalent feet.
Duct pieces
=
T otal
Ft.
x (
) =
Ft.
x (
) =
Ft.
x (
) =
x (
) =
Ft.
Ft.
x (
) =
Ft.
x (
) =
x (
) =
Ft.
x (
) =
Ft.
x (
) =
Ft.
Ft.
5
Equivalent number
length x used
=
3- 1/ 4" x 10"
5 Ft.
x (
) =
Rect. to
6" round
transition
3- 1/ 4" x 10"
20 Ft.
x (
) =
Rect. to
6" round
transition
90
0
elbow
6" round to
1 Ft.
x (
) =
3- 1/ 4" x 10"
rect.
transition
6" round to
16 Ft.
x (
) =
3- 1/ 4" x 10"
rect.
transition
90
0
elbow
7" round to
8 Ft.
x (
) =
3 1/ 4" x 10"
rect.
transition
7" round to
23 Ft.
x (
) =
3- 1/ 4" x 10"
rect.
transition
90
0
elbow
3- 1/ 4" x 10"
30 Ft.
x (
) =
Rect.
wall cap
with damper
6", 7", 8", 10"
30 Ft.
x (
) =
Round, wall
cap with
damper
6", 7", 8", 10"
30 Ft.
x (
) =
Round
roof cap
Subtotal column 2 =
Subtotal column 1 =
Total ductwork
=
T otal
Ft.
Ft.
Ft.
Ft.
Ft.
Ft.
Ft.
Ft.
Ft.
Ft.
Ft.
Ft.