Calculate Total Equivalent Ductwork Length
Equivalent
Duct Pieces
Length* x
6" round
straight
1 ft.
" x 10"
3
1
⁄
4
straight
1 ft.
6", 90°
elbow
15 ft.
6", 45°
elbow
9 ft.
24" max.
flexible
metal offset
adapter
34 ft.
" x 10"
3
1
⁄
4
90° elbow
16 ft.
" x 10"
3
1
⁄
4
45° elbow
5 ft.
" x 10"
3
1
⁄
4
90° flat elbow
18 ft.
6" round
" x 10"
to 3
1
⁄
4
transition
7 ft.
Subtotal Column 1 =
*Equivalent lengths of duct pieces are based on actual
tests and reflect requirements for good venting
performance with any downdraft cooktop.
†Measure and list feet of straight duct used. Count and
list the quantity of all other duct pieces for the "Number
Used" of each type.
IMPORTANT:
For maximum efficiency, use the shortest and straightest
duct run possible, with as few fittings as possible.
For satisfactory performance, the duct run should not
exceed 100 feet equivalent length.
Venting performance is improved by using larger
diameter duct.
Installation Instructions
DUCTWORK CALCULATIONS
Number
Equivalent
Used =
Length
x
(
)
†
=
ft.
x
(
)
†
=
ft.
x
(
) =
ft.
x
(
) =
ft.
x
(
) =
ft.
x
(
) =
ft.
x
(
) =
ft.
x
(
) =
ft.
x
(
) =
ft.
ft.
Duct Pieces
6" round
" x 10"
to 3
1
⁄
4
transition
90° elbow
" x 10"
3
1
⁄
4
to 6" round
transition
" x 10"
3
1
⁄
4
to 6" round
transition
90° elbow
6" round
wall cap
with damper
" x 10"
3
1
⁄
4
wall cap
with damper
6" round
roof cap
6" round
roof vent
DO NOT use flexible plastic ducting.
Vent installation should not exceed 100 feet
equivalent length.
20
Equivalent
Number
Equivalent
Length* x
Used =
Length
20 ft.
x
(
) =
5 ft.
x
(
) =
12 ft.
x
(
) =
21 ft.
x
(
) =
27 ft.
x
(
) =
20 ft.
x
(
) =
24 ft.
x
(
) =
Subtotal Column 2 =
Subtotal Column 1 =
TOTAL DUCTWORK =
Should not exceed 100 feet.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.