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W415-1285 / L / 10.25.21
EN
20
minimum venting requirements
(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
(METERS) V
T
HORIZONTAL VENT RUN PLUS OFFSET IN FEET (METERS)H
T
The shaded area within the lines represents acceptable
values for H
T
and V
T
90°
V
1
H
2
90°
90°
14.3_2
45°
0
5
(1.5)
10
(3.1)
15
(4.6)
20
(6.1)
10 (3.1)
20 (6.1)
3 (0.9)
25
(7.6)
30
(9.1)
19 (5.8)
V
2
H
1
90°
V
1
H
2
90°
90°
45°
V
2
H
1
45°
H
3
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 (12.2m)
Example:
V
1
= 1 FT (0.3m)
V
2
= 1.5 FT (0.5m)
V
T
= V
1
+ V
2
= 1 FT (0.3m)+ 1.5 FT (0.5m)= 2.5 FT (0.8m)
H
1
= 6 FT (1.8m)
H
2
= 2 FT (0.6m)
H
R
= H
1
+ H
2
= 6FT (1.8m) + 2FT (0.6m) = 8 FT (2.4m)
H
O
= .03 (one 45° + three 90° elbows - 135°)
= .03 (45 + 270 - 135°) = 5.4 FT (1.6m)
H
T
= H
R
+ H
O
= 8FT (2.4m) + 5.4FT (1.6m) = 13.4FT (4.1m)
H
T
+ V
T
= 13.4FT (4.1m)+ 2.5FT (0.8m) = 15.9FT (4.8m)
Formula 1: H
T
< 3V
T
3V
T
= 3FT (0.9m) x 2.5FT(0.8m) = 7.5FT (2.3m)
13.4 FT (4.1m) > 7.5 FT (2.3m)
Since this formula is not met, this vent configuration is unacceptable.
Formula 2: H
T
+ V
T
< 40 FT (12.2m)
15.9FT (4.8m) < 40FT (12.2m)
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 (0.5m)
V
2
= 8 FT (2.4m)
V
T
= V
1
+ V
2
= 1.5 FT (0.5m) + 8 FT (2.4m) = 9.5 FT (2.9m)
H
1
= 1 FT (0.3m)
H
2
= 1 FT (0.3m)
H
3
= 10.75 FT (3.3m)
H
R
= H
1
+ H
2
+ H
3
= 1FT(0.3m) + 1FT(0.3m) + 10.75FT(3.3m) = 12.75FT(3.9m)
H
O
= .03 (three 90° elbows + two 45° elbows - 135°)
= .03 (270 + 90 - 135°) = 6.75 FT (2.1m)
H
T
= H
R
+ H
O
= 12.75 FT (3.9m) + 6.75 FT (2.1m) = 19.5 FT (5.9m)
H
T
+ V
T
= 19.5FT (5.9m) + 9.5FT (2.9m) = 29 FT (8.8m)
Formula 1: H
T
< 3V
T
3V
T
= 3 x 9.5 = 28.5 FT (8.7m)
19.5 FT (5.9m) < 28.5 (8.7m)
Formula 2: H
T
+ V
T
< 40 FT (12.2m)
29 FT (8.8m) < 40 FT (12.2m)
Since both formulas are met, this vent configuration is acceptable.
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