9
W415-0665 / B / 02.11.08
REQUIRED VERTICAL
RISE IN FEET
VT
HORIZONTAL VENT RUN PLUS OFFSET IN FEET
HT
when (HT) < (VT)

FIGURE 10

For vent confi gurations requiring more than zero 90° elbow
(top exit) or one 90° elbow (rear exit), the following formulas
apply:

Formula 1: HT < VT

Formula 2: HT + VT < 40 feet
See graph to determine the required vertical rise VT for the
required horizontal run HT.
VERTICAL TERMINATION
The shaded area within the lines represents acceptable
values for HT and VT .
V1 = 5 ft
V2 = 6 ft
V3 = 10 ft
VT =
V1
+
V2
+
V3 =
5 + 6 + 10 = 21 ft
H1 = 8 ft
H2 = 2.5 ft
HR = H1 + H2 = 8 + 2.5 = 10.5 ft
HO = .03 (four 90° elbows - 90°)
= .03 (90 + 90 + 90 + 90 - 90) = 8.1 ft
HT = HR + HO = 10.5 + 8.1 = 18.6 ft
HT + VT = 18.6 + 21 = 39.6 ft
Formula 1: H
T < VT
18.6 < 21
Formula 2: H
T + VT < 40 feet
39.6 < 40
Since both formulas are met, this vent confi guration is
acceptable.
90°
90°
90°
H2
V2
V1
90°

FIGURE 11

Example 4:

H1
V3