10
W415-0244 / A / 05.15.03
H2
H1
V190°
when (Ht) > (Vt)
Simple venting configuration (only one
90° elbow)
See graph to determine the required ver-
tical rise VT for the required horizontal
run HT.
V1=VT = 6 ft
H1=3 ft
H2=5 ft
HR=H1 + H2 = 3 + 5 = 8 ft
HO= .03(two 90° elbows - 90°) = .03(180° - 90°) = 2.7 ft
HT=HR + HO = 8 + 2.7 = 10.7 ft
H
T
+ V
T
=
10.7 + 6 =16.7
Formula 1: HT < 4.2 VT
4.2 VT = 4.2 x 6 = 25.2 ft
10.7 < 25.2
Formula 2: HT + VT < 24.75 feet
16.7 < 24.75
Since both formulas are met, this vent configuration is ac-
ceptable.
For vent configurations requiring more than one 90° elbow
the following formulas apply:
Formula 1: HT < 4.2 VT
Formula 2: HT + VT < 24.75 feet
Example 2:
Example 3:
V
1
=4 ft
V
2
= 1.5 ft
VT=V1 + V2 = 4 + 1.5 = 5.5 ft
H
1
=2 ft
H
2
=1 ft
H
3
=1 ft
H
4
= 1.5 ft
HR=H1 + H2 + H3 + H4 = 2 + 1 + 1 + 1. 5 = 5.5 ft
HO= .03(four 90° elbows - 90°) = .03(360° - 90°) = 8.1 ft
H
T
=H
R
+ H
O
= 5.5 + 8.1 = 13.6 ft
H
T
+ V
T
= 13.6 + 5.5 = 19.1 ft
Formula 1:H
T
< 4.2 V
T
4.2 VT = 4.2 x 5.5 = 23.1 ft
13.6 < 23.1
Formula 2:H
T
+ V
T
< 24.75 feet
19.1 < 24.75
Since both formulas are met, this vent configuration is ac-
ceptable.
FIGURE 7
FIGURE 8
FIGURE 9
H2
H4
V2
90°
H3
H1
V1
90°
TOP EXIT / HORIZONTAL TERMINATIONREQUIRED
VERTICAL
RISE IN
INCHES
VT
HORIZONTAL VENT RUN PLUS OFFSET IN FEET HT
The shaded area within the lines represents acceptable
values for HT and VT .