12
W415-0210 / R / 02.27.08
See graph to determine the required vertical rise
V
T
for the
required horizontal run
H
T
For vent confi gurations requiring more than two 90° elbows
the following formulas apply:
Formula 1: H
T
< V
T
Formula 2: H
T
+ V
T
< 40 feet
Example 4:
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 confi guration is
acceptable.
FIGURE 12
FIGURE 11
H
2
V
1
H
3
90°
90°
90°
90°
The shaded area within the lines represents acceptable
values for H
T
and V
T
.
REAR EXIT / HORIZONTAL TERMINATION
H
1
V
2
Simple venting confi guration
(only two 90° elbows)
(H
T
) < (V
T
)
REQUIRED
VERTICAL
RISE IN
FEET
V
T
HORIZONTAL VENT RUN PLUS OFFSET IN FEET
H
T
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