14
W415-0889 / A / 08.11.10
3.8 HORIZONTAL
TERMINATION
16.12
Simple venting confi guration (only one 90° elbow)
(H
T
) < (V
T
)
For vent confi gurations requiring more than one 90° elbow, the following formulas apply:
Formula 1: H
T
< V
T
Formula 2: H
T
+ V
T
< 40 feet
Example 1:
V
1
= 3 FT
V
2
= 8 FT
V
T
=
V
1
+
V
2
= 3 FT + 8 FT = 11 FT
H
1
= 2.5 FT
H
2
= 2 FT
H
R
=
H
1
+
H
2
= 2.5 + 2 = 4.5 FT
H
O
= .03 (three 90° elbows - 90°) = .03 (270° - 90°) = 5.4 FT
H
T
=
H
R
+
H
O
= 4.5 + 5.4 = 9.9 FT
H
T
+
V
T
= 9.9 + 11 = 20.9 FT
Formula 1:
H
T
< V
T
9.9
<
11
Formula 2:
H
T
+ V
T
< 40 FT
20.9
<
40
Since both formulas are met, this vent con
fi
guration is acceptable.
See graph to determine the required vertical
rise
V
T
for the required horizontal run
H
T
.
The shaded area within the lines represents
acceptable values for
H
T
and
V
T
90°
90°
90°
V
1
V
2
H
1
H
2
0
2.5
5
7.5
10
12.5
15
40
10
20
30
17.5
20
39
REQUIRED
VERTICAL
RISE IN
FEET
V
T
HORIZONTAL VENT RUN PLUS OFFSET IN
FEET
H
T
