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W415-0429 / C / 11.04.05
Formula 1: H
T
< 3V
T
Formula 2: H
T
+ V
T
< 40 feet
Example 5:
V
1
=2 ft
V
2
=1 ft
V
3
= 1.5 ft
See graph to determine the required vertical rise V
T
for the
required horizontal run H
T
.
For vent configurations requiring elbows, the following for-
mulas apply:
FIGURE 13
V
T
=
V
1
+
V
2
+
V
3
=
2 + 1 + 1.5 = 4.5 ft
H
1
=6 ft
H
2
=2 ft
H
R
= H
1
+ H
2
= 6 + 2 = 8 ft
H
O
= .03(four 90° elbows - 90°)
= .03(90 + 90 + 90 + 90 - 90) = 8.1 ft
H
T
=H
R
+ H
O
= 8 + 8.1 = 16.1 ft
H
T
+ V
T
= 16.1 + 4.5 = 20.6 ft
Formula 1: H
T
< 3V
T
3V
T
=
3 x
4.5 = 13.5 ft
16.1 > 13.5
Since this formula is not met, this vent configuration is
unacceptable.
Formula 2: H
T
+ V
T
< 40 feet
20.6 < 40
Since only formula 2 is met, this vent configuration is unac-
ceptable and a new fireplace location or vent configuration
will need to be established to satisfy both formulas.
Example 6:
V
1
= 1.5 ft
V
2
=5 ft
V
T
=
V
1
+
V
2
=
1.5 + 5 = 6.5 ft
H
1
=1 ft
H
2
=1 ft
H
3
=1 ft
H
4
=10.75 ft
H
R
=H
1
+ H
2
+ H
3
+ H
4
= 1 + 1 + 1 + 10.75 = 13.75 ft
H
O
=.03(four 90° elbows + one 45° elbow - 90°)
=.03(90 + 90 + 90 + 90 + 45 - 90) = 9.45 ft
H
T
=H
R
+ H
O
= 13.75 + 9.45 = 23.2 ft
H
T
+ V
T
= 23.2 + 6.5 = 29.7 ft
Formula 1: H
T
< 3V
T
3V
T
=
3 x
6.5 = 19.5 ft
19.5 = 19.5
Formula 2: H
T
+ V
T
< 40 feet
29.7 < 40
Since both formulas are met, this vent configuration is ac-
ceptable.
when (H
t
) > (V
t
)
Simple venting configurations
FIGURE 14
FIGURE 12
H
1
H
2
V
3
V
1
90°
90°
90°
V
2
90°
H
4
V
1
V
2
90°
45°
90°
H
1
90°
H
3
H
2
TOP EXIT VERTICAL TERMINATION
MAXIMUM
VERTICAL
RISE IN
FEET
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
.