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FIGURE 5 FIGURE 6
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Guideline to Proper Duct Sizing for Ventilating An Indoor Electric Grill
These Guidelines are to insure adequate ventilation for an indoor
Electric Grill. Indoor electnc grills produce more smoke than
normal cooking and requtres at least 41 O CFM to provide adequate
ventllatton. Less sinngent venttlating requtrements can deviate
from these recommendations.
HORIZONTAL VENTING:
Frgure 2 on page 1 shows a direct discharge to the outside
through a wall rain cap. Due to the lower CFM rating in this venting
posItron. duct must be limtted to a maximum of 2 feet of 3;/r x 10
Inch duct capped with a wall rain cap with a free discharge area of
al least 66 inches square. There should be no bends in the
connec:lng duct between the hood and the wall ratn cap.
VERTICAL VENTING:
Figure 1 on page 1 shows an installation using 3 feet of 3% x 10
inch duct term:nating in a roof rain cap. In table 1 we see that 3 feet
of 3:. x 10 inch duct is the maxlmum lengtn of 3’;; x 10 Inch duct
recommended.
Figure 7 shcws an installation requiring more duct length. A
transr!lon to round is used as close to the hood as possible to
elrmtnate the restriction caused by the 3’; x 10 duct. 4jJ bends
should be used Instead of 90g bends wherever possible.
For example, if the straight lengihs of duct In FIN. 7 total 9 ft. the
elbow
IS
45’ and the roof rain cap has 113 in’ free area. choose the
duct size required. The -15; elbow can be approximated by dividing
the equivalent duct !engths In Table 2 by two.
Since we already have9 ft. of straight duct, Table 1 tells us that 7”
dia.
IS
too small. So we try 8” dia.
9 ft. Straight Duct
6 Equrvalent straight length of 4.Y elbow (8” Dia.)
15 ft.
Frfteen feet is ever the maximum of 13 ft. for 8” dia. duct, so 8”
duct
IS
to small.
!-dove to 9” dia. duct and run :hrough the calculations again.
9 ft. Straight Duct.
7 ft. Equrvalent stratght leng!h cf 9” dia. duct for 45” elbow.
i-6-K
Sixteen fee!
IS
under the maxrmum of 25 ft. for 9” dia. duct, so 9”
duct IS
a gocd chotce.
TABLE I
Vertical Venting
I
Duct
Size I
3’/. x 10”
I
7” dm
I
8” dia.
I
9” dia.
1 10” dia. 1
,uax
Duct
Length
(Feet)
3
7. 13
25 40
Table 1 shows the maxlmum length of duct to be used In
COnjunct;on wltn a roof rain cap i-,avlng a free area of 113 II-I?.
TABLE 2
.
Duct
Equivalent length of
Size
straight ducr of same dia.
11 ft.
12 ft.
c
FIGURE 7
CFM vs. DUCT LENGTH FOR F?GH SERIES HOOD
Equivalent Duct Length (ft.)
Static
Pressure
/ cFh4 j 3-;;t:0 / 7” dia. 1 8” dia. 1 9” dia.1
I L I
4
.06 460 4 8.5 17 30 i
I i
~~~~
:
.lO 440
7 16.0 31 55.5 1
.15 417 12 25.0 50
.20
/
390 /
18
1
40 1
77 /
142!
.25 355
330
I
.30 250 65 1 1361 -I
.35
180
?40 i .;
--
l
90”
9” dia. 14 ft.
NOTE: Tne above table
IS
basec on-~ertlcal disc
Elbow
10” dta.
:6 ft.
IT&?. Thevaiues
.
In lhls !able are for duct length only and co not account for Sldtic
pressure loss :hroucn roof mounted rain c. 0s