Equivalent Number
Equivalent
Duct Pieces
Length* x
Used
= Length
5
″
round
to 3
1
⁄
4
″
x 10
″
transition
90° elbow
37 ft. x (
)
=
ft.
6
″
round
to 3
1
⁄
4
″
x 10
″
transition
90° elbow
4 ft.
x (
)
=
ft.
3
1
⁄
4
″
x 10
″
to 6
″
round
transition
2 ft.
x (
)
=
ft.
3
1
⁄
4
″
x 10
″
to 6
″
round
transition
90° elbow
4 ft.
x (
)
=
ft.
Tapered
5
″
round
to 6
″
round
transition
6 ft.
x (
)
=
ft.
5
″
round collar
to 6
″
round
cap transition
13 ft. x (
)
=
ft.
5
″
round
wall cap
with damper
84 ft. x (
)
=
ft.
6
″
round
wall cap
with damper
24 ft. x (
)
=
ft.
3
1
⁄
4
″
x 10
″
wall cap
with damper
24 ft. x (
)
=
ft.
6
″
round
roof cap
33
x (
)
=
ft.
Subtotal Column 2
=
ft.
Subtotal Column 1
=
ft.
TOTAL DUCTWORK =
ft.
Should not exceed 100 feet.
If flexible metal ducting is used, all the equivalent feet
values in the table should be doubled. The flexible metal
duct should be straight and smooth and extended as
much as possible.
DO NOT use flexible plastic ducting.
Vent installation should not exceed 100 feet equivalent
length.
Blower is rated at
400 CFM
at 0.1 inch of water back
pressure.
34
INSTALLATION INSTRUCTIONS
(continued)
TABLE 1
Calculate Total Equivalent Ductwork Length
Equivalent Number
Equivalent
Duct Pieces
Length* x
Used
= Length
5
″
round
straight
2.7
x (
ft.)
†
=
ft.
6
″
round
straight
1
x (
ft.)
†
=
ft.
3
1
⁄
4
″
x 10
″
straight
1
x (
ft.)
†
=
ft.
5
″
,
90
°
elbow
37 ft. x (
)
=
ft.
6
″
,
90
°
elbow
12 ft. x (
)
=
ft.
5
″
,
45
°
elbow
18 ft. x (
)
=
ft.
6
″
,
45
°
elbow
7 ft.
x (
)
=
ft.
Flexible
Metal Offset
See Calculations
Adapter
in Step 5A
ft.
3
1
⁄
4
″
x 10
″
90° elbow
14 ft. x (
)
=
ft.
3
1
⁄
4
″
x 10
″
45° elbow
8 ft.
x (
)
=
ft.
3
1
⁄
4
″
x 10
″
90
° flat elbow
33 ft. x (
)
=
ft.
5
″
round
to 3
1
⁄
4
″
x 10
″
transition
3 ft.
x (
)
=
ft.
6
″
round
to 3
1
⁄
4
″
x 10
″
transition
2 ft.
x (
)
=
ft.
Subtotal Column 1
=
ft.
* 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.
