14
W415-0496 / B / 08.10.05
H1
VERTICAL TERMINATION
For vent configurations requiring more than one 45º and
one 90° elbow , the following formulas apply:
Formula 1: H
T

< 3V

T
Formula 2: H
T
+ V
T

< 40 feet

when (HT) > (VT)
Simple venting configurations
See graph to determine the required vertical rise VT for the
required horizontal run HT.

Example 4:

V
1
=1 ft
V
2
=1.5 ft
VT=
V
1
+
V
2
=
1 + 1.5 = 2.5 ft
H
1
=6 ft
H
2
=2 ft
HR=H1 + H2 = 6 + 2 = 8 ft
HO=.03(one 45º elbow + three 90º elbow - 135º)
=.03(45 + 90 + 90 + 90 - 135) = 5.4 ft
H
T
=H
R
+ H
O
= 8 + 5.4 = 13.4 ft
H
T
+ V
T
= 13.4 + 2.5 = 15.9 ft
Formula 1: H
T
< 3V
T
3VT=
3 x
2.5 = 7.5 ft
13.4 > 7.5
Since this formula is not met, this vent configuration is
unacceptable.
Formula 2: H
T
+ V
T
< 40 feet
15.9 < 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 5:

V
1
=1.5 ft
V
2
=8 ft
VT=
V
1
+
V
2
=
1.5 + 8= 9.5 ft
H
1
=1 ft
H
2
=1 ft
H
3
=10.75 ft
HR=H1 + H2 + H3 = 1 + 1 + 10.75 = 12.75 ft
HO=.03(three 90° elbows + two 45° elbow - 135°)
=.03(90 + 90 + 90 + 45 + 45 - 135) = 6.75 ft
H
T
=H
R
+ H
O
= 12.75 + 6.75 = 19.5 ft
H
T
+ V
T
= 19.5 + 4.5= 29 ft
Formula 1: H
T
< 3V
T
3VT =
3 x
9.5 = 28.5 ft
19.5 < 28.5
Formula 2: H
T
+ V
T
< 40 feet
29 < 40
Since both formulas are met, this vent configuration is ac-
ceptable.
REQUIRED
VERTICAL
RISE IN
FEET (VT)
HORIZONTAL VENT RUN PLUS OFFSET IN FEET (HT)
FIGURE 13
FIGURE 11
45°
45°
90°
90°
H1
H2
90°
H3
The shaded area within the lines represents acceptable
values for HT and VT.
90°
FIGURE 12
45°
V1
90°
V2
90°
H2
V2
V1