12
W415-0341 / F / 11.21.05
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 4:
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
Formula 1:
H
T
< 4.2 V
T
4.2 V
T
= 4.2 x 6 = 25.2 ft
10.7 < 25.2
Formula 2:
H
T
+ V
T
< 24.75 feet
16.7 < 24.75
Since both formulas are met, this vent configuration is ac-
when
(H
T
)
>
(V
T
)
Simple venting configuration (only one 90° elbow)
See graph to determine the required ver-
tical rise V
T
for the required horizontal run
H
T
.
ceptable.
Example 5:
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 feet
19.1 < 24.75
Since both formulas are met, this vent configuration is ac-
ceptable.
FIGURE 12
REQUIRED
VERTICAL
RISE IN
INCHES
V
T
HORIZONTAL VENT RUN PLUS OFFSET IN FEET
H
T
The shaded area within the lines represents acceptable
values for H
T
and V
T
.
BGD34 & GD34 HORIZONTAL TERMINATION
FIGURE 14
H
2
H
4
V
2
90°
H
3
H
1
V
1
90°
H
2
H
1
V
1
90°
FIGURE 13
