Table 1. Ventilator performance calculation
DUCT
FITTINGS
Equivalent
Quantit
Total
1D Vata dices)
Lenght*
Used
a
Use this chart to compute maximum
10" round
permissable lengths for duct runs to
to8" roun d
sft
outdoors.
Round
-
ound,
.
.
.
G—
straight
(per foot
Note:
Do not exceed maximum permissable
length)
equivalent lengths!
oo)
t/a"
x10"
lft
-
x
.
Maximum recommended duct
3-1/4" x12"
(per foot
length for these hoods: 150 feet
straight
length)
8" Dia. 17 ft.
Flexible
ducting:
90° elbow
10" Dia. 24 ft
.
If flexible metal ducting
is used, all
the equivalent feet values in the table
8" Dia. 10 ft.
should be doubled. The flexible
45° elbow
10" Dia. 14 ft .
metal duct should
be straight and
smooth and extended as much as
3-144" x 12"
15 ft.
possible.
3-1/4"
x 10"
14 ft.
90° elbow
Do NOT use flexible plastic ducting.
3-1/4" x 10"
8 ft.
3-1/4" x12"
9 ft.
45° elbow
Note:
Any home ventilation system, such as a
h
h
ventilation hood, may interrupt the proper flow of
3 Va
x 10"
33
combustion air and exhaust required by fireplaces,
31/4
x12
36
f t .
gas furnaces, gas water heaters and other naturally
90°
flat elbow
vented systems. To minimize the chance of interruption
10" round transition
of such naturally vented systems, follow the heating
to 3-1/4"
x 10" or
equipment manufacturer's guidelines and safety
_
3-1/4" x 12"
9 ft.
standards such as those published by NFPA and ASHRAE.
3-1/4"
x10"
-
x
or
Q
3-1/4" x 12" to
Fate
10" round transition
6 ft.
S
10" round to 3-1/4" x 10"
16 ft.
Ten oe te
yee
~
3-1/4"
x 12"
transition
13 ft.
-
90° elbow
For 10" Round Duct
3-1/4"
x10"
9 ft.
.
.
3-1/4"x12"t
010" round = 8 ft.
*Hoods are supplied with a 10"
Ye
transition 90° elbow
round transition. A locally
Roun d
8" Dia
32 ft
supplied transition is required
J
wall cap
in "2.
2 i
for other sizes.
with damper
Note: Outlet on top of hood is
31/4" x 10"
7
24 rt
8-1/8" x8".
3-1/4
X 12"
wall
cap
26
ft.
with damper
Round
8" Dia. 44 ft.
roof cap
10" Dia. 56 ft.
Total Duct Run