9
W415-0341 / F / 11.21.05
when
(H
T
) < (V
T
)
Simple venting configuration (only two 90° elbows)
for the following symbols used in the venting calcula-
tions and examples are:
>
- greater than
>
- equal to or greater than
<
- less than
<
- equal to or less than
H
T
- total of both horizontal vent lengths (
H
R
) and offsets
(
H
O
) in feet
H
R
- combined horizontal vent lengths in feet
H
O
- offset factor: .03(total degrees of offset - 90°
*
) in
feet
V
T
- combined vertical vent lengths in feet
feet
inches
1°
0.03
0.5
15°
0.45
6.0
30°
0.9
11.0
45°
1.35
16.0
90°
*
2.7
32.0
*
the first 90° offset has a zero value and is shown in
the formula as
-90°
DEFINITIONS
ELBOW VENT LENGTH VALUES
Example 1:
See graph to determine the required vertical rise
V
T
for the
required horizontal run
H
T
For vent configurations requiring more than two 90° el-
bows the following formulas apply:
Formula 1:
H
T
< V
T
Formula 2:
H
T
+ V
T
< 40 feet
REQUIRED
VERTICAL
RISE IN
FEET
V
T
HORIZONTAL VENT RUN PLUS OFFSETS IN FEET
H
T
V
1
= 9 ft
V
2
= 6 ft
V
T
=
V
1
+
V
2
= 9 + 6 = 15 ft
H
1
= 3 ft
H
2
= 2 ft
H
3
= 1.5 ft
H
R
=
H
1
+
H
2
+
H
3
= 3 + 2 + 1.5 = 6.5 ft
H
O
= .03(four 90° elbows - 90°)
= .03(90 + 90 + 90 + 90 - 90) = 8.1 ft
H
T
=
H
R
+
H
O
= 6.5 + 8.1 = 14.6 ft
H
T
+ V
T
= 14.6 + 15 = 29.6 ft
Formula 1:
H
T
< V
T
14.6 < 15
Formula 2:
H
T
+ V
T
< 40 feet
29.6 < 40
Since both formulas are met, this vent configuration is ac-
ceptable.
FIGURE 7
FIGURE 6
H
1
H
2
V
1
V
2
H
3
90°
90°
90°
90°
The shaded area within the lines represents acceptable
values for H
T
and V
T
.
BGD33 & GD33 HORIZONTAL TERMINATION