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W415-0484 / A / 07.26.06

ELBOW VENT LENGTH VALUES

DEFINITIONS

HORIZONTAL TERMINATION
REQUIRED
VERTICAL
RISE IN FEET
(VT)
CALCULATED HORIZONTAL VENT RUN
PLUS OFFSETS IN FEET (HT)
FIGURE 5

45º

FIGURE 6
90°
H1
H2
when (HT) < (VT)
Simple venting configuration (only one 45º and 90° elbow)
for the following symbols used in the venting calcula-
tions and examples are:
>- greater than
>- equal to or greater than
<- less than
<- equal to or less than
HT- total of both horizontal vent lengths (HR) and off-
sets (HO) in feet
HR- combined horizontal vent lengths in feet
HO- offset factor: .03(total degrees of offset - 135°**
**
*) in
feet
VT- 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 first 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 configurations 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
VT=
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 configuration is ac-
ceptable.
V1
90°
The shaded area within the lines represents acceptable
values for HT and VT .