10
W415-0381 / H / 12.07.07
ELBOW VENT LENGTH VALUES
DEFINITIONS
HORIZONTAL TERMINATION
REQUIRED
VERTICAL
R I S E I N
FEET (V
T
)
CALCULATED HORIZONTAL VENT RUN
PLUS OFFSETS IN FEET (H
T
)
FIGURE6
45º
FIGURE 7
90°
H
1
H
2
when
(H
T
) < (V
T
)
Simple venting confi guration (only one 45º and 90° elbow)
for the following symbols used in the venting calculations
and examples are:
>
- greater
than
>
- equal to or greater than
<
- less
than
<
- equal to or less than
H
T
- total of both horizontal vent lengths (
H
R
) and offsets
(
H
O
) in feet
H
R
- combined horizontal vent lengths in feet
H
O
- offset factor: .03(total degrees of offset - 135°
*
) in
feet
V
T
- combined vertical vent lengths in feet
feet
inches
1°
0.03
0.5
15°
0.45
6.0
30°
0.9
11.0
45°
*
1.35
16.0
90°
*
2.7
32.0
*
the fi rst 45º and 90° offset has a zero value and is
shown in the formula as
-45°
and
-90º
respectively or
-135º
when combined.
For vent confi gurations requiring more than one 45º and 90°
elbow, the following formulas apply:
Formula 1: H
T
< V
T
Formula 2: H
T
+ V
T
< 40 feet
Example 1:
V
1
= 8
ft
V
T
=
V
1
= 8 ft
H
1
= 2.5
ft
H
2
= 2
ft
H
R
=
H
1
+
H
2
= 2.5 + 2 = 4.5 ft
H
O
= .03(one 45º elbow + two 90º elbows - 135º)
=0.3(225-135º) = 2.7ft
H
T
=
H
R
+
H
O
= 4.5 + 2.7 = 7.2 ft
H
T
+ V
T
= 7.2 +8 =15.2ft
Formula 1:
H
T
< V
T
7.2 < 8
Formula 2:
H
T
+ V
T
< 40 feet
15.2
<
40
45º
90°
Since both formulas are met, this vent confi guration is
acceptable.
V
1
90°
The shaded area within the lines represents acceptable
values for H
T
and V
T
.
