13
W415-0381 / H / 12.07.07
H1
VERTICAL TERMINATION
For vent confi gurations requiring more than one 45º and one
90° elbow , the following formulas apply:

Formula 1: HT < 3VT

Formula 2: HT + VT < 40 feet
when (HT) > (VT)
Simple venting confi gurations
See graph to determine the required vertical rise VT for the
required horizontal run HT.

Example 5:

V1 = 1.5 ft
V2 = 8 ft
VT =
V1
+
V2 =
1.5 + 8= 9.5 ft
H1 = 1 ft
H2 = 1 ft
H3 = 10.75 ft
HR = H1 + H2 + H3 = 1 + 1 + 10.75 = 12.75 ft
HO = .03(three 90° elbows + two 45° elbows - 135°)
= .03(90 + 90 + 90 + 45 + 45 - 135) = 6.75 ft
HT = HR + HO = 12.75 + 6.75 = 19.5 ft
HT + VT = 19.5 + 4.5= 24 ft
Formula 1: H
T < 3VT
3VT =
3 x
9.5 = 28.5 ft
19.5 < 28.5
Formula 2: H
T + VT < 40 feet
24 < 40
Since both formulas are met, this vent confi guration is
acceptable.
REQUIRED
VERTICAL
RISE IN
FEET (VT)
HORIZONTAL VENT RUN PLUS OFFSET IN FEET (HT)
FIGURE 12
The shaded area within the lines represents acceptable
values for HT and VT.
90°
FIGURE 13
45°
V1
90° V2
90°
H2
FIGURE 14
45°
45°
90°
90°
H1
H2
90°
H3
V2
V1

Example 4:

V1 = 1 ft
V2 = 1.5 ft
VT =
V1
+
V2 =
1 + 1.5 = 2.5 ft
H1 = 6 ft
H2 = 2 ft
HR = H1 + H2 = 6 + 2 = 8 ft
HO = .03(one 45º elbow + three 90º elbow - 135º)
= .03(45 + 90 + 90 + 90 - 135) = 5.4 ft
HT = HR + HO = 8 + 5.4 = 13.4 ft
HT + VT = 13.4 + 2.5 = 15.9 ft
Formula 1: H
T < 3VT
3VT =
3 x
2.5 = 7.5 ft
13.4 > 7.5
Since this formula is not met, this vent confi guration is
unacceptable.
Formula 2: H
T + VT < 40 feet
15.9 < 40
Since only formula 2 is met, this vent confi guration is
unacceptable and a new fi replace location or vent con-
fi guration will need to be established to satisfy
both formulas.