Whirlpool RH8930XLS manual Duct

Guidellne to Proper Duct Sizing for Ventllattng An Indoor Electric Grill

These Guidelines are to insure adequate ventilation for an indoor Electric Grrll. Indoor electric grtlls produce more smoke than normal cooking and requrres at least 410 CFM to provtde adequate ventrlation. Less strmgent ventilating requirements can devrate from these recommendattons.

HORtZONTAL VENTtNG

Figure two on page two shows a direct aischarge to the outside through a wall rain cap. Due to the lower CFM rating In thus venting posrtron, duct must be limrted la a maximum of 2 feet of 3% x 10 inch duct capped with a wall rain cap with a free discharge area of at least 66 inches square. There should be no bends in the connecting duct between the hood and the wall rain cap.

Figure 9shows an installation requiring more duct length. A transrtion to round is used as close to the hood as possible to eliminate the restriction caused by the 3% x 10 duct. 4S0 bends should be used instead of 90° bends wherever possrble.

VERTICAL

VENTING:

TABLE

I

Figure

one

on

page

two

shows

an

installation

using

3 feet

of

Vertical

Venttnq

3% x 10 inch duct

termrnating

In a roof rain cap. In table one we

see

that

3 feet of 3% x 10 inch duct is the maximum length of 3% x

10 inch

duct

recommended.

For example, if the straight lengths of duct In Fig 9 total 9 ft.

the elbow is 45O and the roof rain cap has 113 In2 free area,

choose

the

duct

size

required.

The

45O

elbow

can

be

approximated

by

dtvtding

the

equivalent

duct

lengths

In Table

2

by

two.

Table I shows the maxrmum length of duct to be

Since

we already

have

9 ft. of

straight

duct,

Tdble 1 tells us

that

used In conjuncttan

with

a roof

ram

cap

having a

7” dia. is too small. So we try 8” dia.

free area of 113 inz.

9

ft.

Straight

Duct

6

ft.

Equivalent

straight

length of

4S0 elbow

(8”

Dia.)

TABLE

2

15

ft.

Duct

Fifteen

feet

is over

the

maximum

of

13 ft. for

8”

dia.

duct,

so

8”

Equivalent

length

of

Size

strarght

duct

of

same

dia.

duck

is

too

small.

Move

to 9” dia.

duct

and

run

through

the

calculatrons

again.

7”

dia.

l*l

ft.

9

ft.

Straight

Duct,

0”

dia.

12

ft.

7

ft.

Equivalent

strarght

length

of 9”

dia.

duct

for

45O elbow.

900

9”

dia.

14

ft.

16

ft.

10”

dia.

16

ft.

Elbow

Sixteen feet is under the maximum of 25 ft. for 9” dia. duct, so 9”

duct is a good choice.

CFM

vs. DUCT

LENGTH

.25			355	26		61		104
.275			330	34		73		145
.30			250	65		136
.35			180	140
NOTE:	The	above	table is based on	vertical	discharge.	The values	rn this	table are for duct length only
and do	not	account	for static pressure loss		through	roof mounted	ram	caps.

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