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W415-0788 / A / 09.22.09
3.8 TOP EXIT HORIZONTAL TERMINATION
(H
T
) > (V
T
)
Simple venting configuration (only one 90° elbow)
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 one 90° elbow, the following formulas apply:
Formula 1: H
T
< 4.2 V
T
Formula 2: H
T
+ V
T
< 24.75 feet
Example 2:
V
1
= V
T
= 6 FT
H
1
= 3 FT
H
2
= 5 FT
H
R
= H
1
+ H
2
= 3 + 5 = 8 FT
H
O
= .03 (two 90° elbows - 90°) = .03 (180° - 90°) = 2.7 FT
H
T
= H
R
+ H
O
= 8 + 2.7 = 10.7 FT
H
T
+ V
T
= 10.7 + 6 = 16.7 FT
Formula 1: H
T
< 4.2 V
T
4.2 V
T
= 4.2 x 6 = 25.2 FT
Formula 2: H
T
+ V
T
< 24.75 FT
16.7 < 24.75
Since both formulas are met, this vent configuration is acceptable.
0
515
20
100
50
150
12.5’
19 1/2”
57”
147”
2’
The shaded area within the lines represents acceptable
values for H
T
and V
T
90°
V
1
H
1
H
2
90°
Example 3:
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 - 90°) = .03 (360° - 90°) = 8.1 FT
H
T
= H
R
+ H
O
= 5.5 + 8.1 = 13.6 FT
H
T
+ V
T
= 13.6 + 5.5 = 19.1 FT
Formula 1: H
T
< 4.2 V
T
4.2 V
T
= 4.2 x 5.5 = 23.1 FT
13.6 < 23.1
Formula 2: H
T
+ V
T
< 24.75 FT
19.1 < 24.75
Since both formulas are met, this vent configuration is acceptable.
90°
90°
90°
90°
H
1
H
2
V
1
V
2
H
3
H
4
10
19.5’
16.1_2
FIGURE 3.8a
FIGURE 3.8b
FIGURE 3.8c