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W415-0788 / A / 09.22.09
Simple venting configuration
(only two 90° elbows)
See graph to determine the required vertical rise V
T
for the
required horizontal run H
T
.
REQUIRED
VERTICAL
RISE IN
INCHES V
T
HORIZONTAL VENT RUN PLUS OFFSET IN FEET H
T
For vent configurations requiring more than two 90° elbows, the following formulas apply:
Formula 1: H
T
< 3.5V
T
Formula 2: H
T
+ V
T
< 24.75 feet
Example 4:
V
1
= 4 FT
V
2
= 1.5 FT
V
T
= V
1
+ V
2
= 4 + 1.5 = 5.5 FT
H
1
= 2 FT
H
2
= 1 FT
H
3
= 1 FT
H
4
= 1.5 FT
H
R
= H
1
+ H
2
+ H
3
+ H
4
= 2 + 1 + 1 + 1.5 = 5.5 FT
H
O
= .03 (four 90° elbows + one 45° elbow - 90°)
= .03 (90 + 90 + 90 + 90 + 45 - 90) = 9.45 FT
H
T
= H
R
+ H
O
= 5.5 + 9.45 = 14.95 FT
H
T
+ V
T
= 14.95 + 5.5 = 20.45 FT
Formula 1: H
T
< 3.5V
T
3.5V
T
= 3.5 x 5.5 = 19.25 FT
14.95 < 19.25
Formula 2: H
T
+ V
T
< 24.75 FT
20.45 < 24.75
Since both formulas are met, this vent configuration is acceptable.
The shaded area within the lines represents acceptable
values for H
T
and H
T
90°
V
1
V
2
H
1
H
2
90°
90°
90°
H
3
(H
T
) > (V
T
)
50
100
150
0
2.5 5 7.5 10 12.5 15 17.5 20
147
12
66
1
3.5
19.25
16.3_2
FIGURE 3.10c
FIGURE 3.10d