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 TERMINATIONThe 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