8
W415-0583 / D / 07.24.07
REQUIRED VERTICAL
RISE IN FEET
VT
HORIZONTAL VENT RUN PLUS OFFSET IN
FEET
HT
when (HT) < (VT)

FIGURE 9

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.
TOP EXIT VERTICAL TERMINATION
The shaded area within the lines represents ac-
ceptable values for HT and VT .
MAXIMUM
VERTICAL
RISE IN
FEET
VT
HORIZONTAL VENT RUN PLUS OFFSET IN FEET
HT
The shaded area within the lines represents acceptable
values for HT and VT .
See graph to determine the required vertical rise VT for the
required horizontal run HT.

FIGURE 11

Example 7:

V1 = 2 ft
V2 = 1 ft
V3 = 1.5 ft
VT =
V1
+
V2
+
V3 =
2 + 1 + 1.5 = 4.5 ft
H1 = 6 ft
H2 = 2 ft
HR = H1 + H2 = 6 + 2 = 8 ft
HO = .03(four 90° elbows - 90°)
= .03(90 + 90 + 90 + 90 - 90) = 8.1 ft
HT = HR + HO = 8 + 8.1 = 16.1 ft
HT + VT = 16.1 + 4.5 = 20.6 ft
Formula 1: H
T < 3VT
3VT =
3 x
4.5 = 13.5 ft
16.1 > 13.5
Since this formula is not met, this vent confi guration is
unacceptable.
Formula 2: H
T + VT < 40 feet
20.6 < 40
Since only formula 2 is met, this vent confi guration
is unacceptable and a new fi replace location or vent
confi guration will need to be established to satisfy both
formulas.

FIGURE 10

H1
H2
V3
V1

90° 90°

90°
V2
90°
when (HT) > (VT)
Simple venting confi gurations
TOP VERTICAL TERMINATION
For vent confi gurations requiring more than two 90° elbow
(top exit) or one 90° elbow (rear exit), the following formulas
apply:

Formula 1: HT < 3VT

Formula 2: HT + VT < 40 feet