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W415-0788 / A / 09.22.09
3.11 TOP OR REAR EXIT VERTICAL TERMINATION
Simple venting configurations.
See graph to determine the required vertical rise V
T
for the
required horizontal run H
T
.
REQUIRED
VERTICAL
RISE IN
FEET V
T
HORIZONTAL VENT RUN PLUS OFFSET IN FEET H
T
For vent configurations requiring one or more 90° elbows (top exit) or one or more 90° elbows (rear exit),
the following formulas apply:
Formula 1: H
T
< V
T
Formula 2: H
T
+ V
T
< 40 feet
Example 6:
V
1
= 5 FT
V
2
= 6 FT
V
3
= 10 FT
V
T
= V
1
+ V
2
+ V
3
= 5 + 6 + 10 = 21 FT
H
1
= 8 FT
H
2
= 2.5 FT
H
R
= H
1
+ H
2
= 8 + 2.5 = 10.5 FT
H
O
= .03 (four 90° elbows - 90°)
= .03 (360° - 90°) = 8.1 FT
H
T
= H
R
+ H
O
= 10.5 + 8.1 = 18.6 FT
H
T
+ V
T
= 18.6 + 21 = 39.6 FT
Formula 1: H
T
< 3.5 V
T
18.6 < 21
Formula 2: H
T
+ V
T
< 40 FT
39.6 < 40
Since both formulas are met, this vent configuration is acceptable.
90°
V
1
V
2
H
1
H
2
The shaded area within the lines represents acceptable
values for H
T
and H
T
90°
90°
90°
0
5101520
40
10
20
30
3
V
3
(H
T
) < (V
T
)
18.2
FIGURE 3.11a
FIGURE 3.11b