14
W415-0777 / 03.02.09
(H
T
) < (V
T
)
Simple venting configuration (only one 45° and 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 45° elbow and 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
= 4 FT
V
2
= 1.5 FT
V
T
=
V
1
+
V
2
= 4 FT + 1.5 FT = 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 (one 45° elbow + four 90° elbows - 135°) = .03 (405 - 135°) = 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 FT = 23.1 FT
Formula 2:
H
T
+ V
T
< 24.75 FT
19.1 < 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
V
T
16.5_2
90°
90°
45°
V
1
H
1
H
4
0
5
15
20
100
50
150
12.5’
57”
147”
10
90°
90°
H
3
H
2
V
2
FIGURE 2.8c
FIGURE 2.8d
