12
W415-0244 / A / 05.15.03
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 VT for the
required horizontal run HT.
For vent configurations requiring elbows, the following for-
mulas apply:
FIGURE 13
VT=
V
1
+
V
2
+
V
3
=
2 + 1 + 1.5 = 4.5 ft
H
1
=6 f t
H
2
=2 f t
HR=H1 + H2 = 6 + 2 = 8 ft
HO=.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
3VT=
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 f t
VT=
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
HR=H1 + H2 + H3 + H4 = 1 + 1 + 1 + 10.75 = 13.75 ft
HO=.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
3VT =
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 (Ht) > (Vt)
Simple venting configurations
FIGURE 14
FIGURE 12
H1
H2
V3
V1

90° 90°

90°
V2
90°
H4
V1
V2

90° 45°

90°
H1

90° H3

H2
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 HT and VT .