17
W415-0812 / D / 08.16.12
(H
T
) > (V
T
)
Simple venting configurations.
See graph to determine the required vertical rise
V
T
for the
required horizontal run
H
T
.
REQUIRED
VERTICAL
RISE IN
FEET
V
T
HORIZONTAL VENT RUN PLUS OFFSET IN FEET
H
T
For vent configurations requiring more than one 45° and one 90° elbow, the following formulas apply:
Formula 1: H
T
< 3V
T
Formula 2: H
T
+ V
T
< 40 feet
Example:
V
1
= 1 FT
V
2
= 1.5 FT
V
T
=
V
1
+ V
2
= 1 + 1.5 = 2.5 FT
H
1
= 6 FT
H
2
= 2 FT
H
R
=
H
1
+ H
2
= 6 + 2 = 8 FT
H
O
= .03 (one 45° + three 90° elbows - 135°)
= .03 (45 + 270 - 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
3V
T
= 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 FT
15.9 < 40
Since only formula 2 is met, this vent configuration in unacceptable and a new fireplace location or vent configuration
will need to be established to satisfy both formulas.
Example:
V
1
= 1.5 FT
V
2
= 8 FT
V
T
=
V
1
+ V
2
= 1.5 + 8 = 9.5 FT
H
1
= 1 FT
H
2
= 1 FT
H
3
= 10.75 FT
H
R
=
H
1
+ H
2
+ H
3
= 1 + 1 + 10.75 = 12.75 FT
H
O
= .03 (three 90° two 45° elbows - 135°)
= .03 (270 + 90 - 135°) = 6.75 FT
H
T
=
H
R
+ H
O
= 12.75 + 6.75 = 19.5 FT
H
T
+ V
T
= 19.5 + 9.5 = 29 FT
Formula 1:
H
T
< 3V
T
3V
T
= 3 x 9.5 = 28.5 FT
19.5
<
28.5
Formula 2:
H
T
+ V
T
< 40 FT
29 < 40
Since both formulas are met, this vent configuration is acceptable.
The shaded area within the lines represents acceptable
values for
H
T
and
V
T
90°
V
1
H
2
90°
90°
18.3_2A
45°
0
5
10
15
20
10
20
3
25
30
19
V
2
H
1
90°
V
1
H
2
90°
90°
45°
V
2
H
1
45°
H
3
