11
REAR EXIT / HORIZONTAL TERMINATION
when (HT) < (VT) | Example 4: |
Simple venting configuration (only two 90° elbows) |
|
90°
H3
90° V2
H2 
90°
| FIGURE 12 |
FIGURE 11 | V1 |
H1
90°
See graph to determine the required vertical rise VT for the required horizontal run HT
REQUIRED
VERTICAL
RISE IN
FEET
VT
HORIZONTAL VENT RUN PLUS OFFSETS IN FEET HT
The shaded area within the lines represents acceptable values for HT and VT .
For vent configurations requiring more than two 90° elbows the following formulas apply:
Formula 1: HT < VT
Formula 2: HT + VT < 40 feet
V1 | =9 ft |
V2 | =6 ft |
VT | = V1 + V2 = 9 + 6 = 15 ft |
H1 | =3 ft |
H2 | =2 ft |
H3 | =1.5 ft |
HR | = H1 + H2 + H3 = 3 + 2 + 1.5 = 6.5 ft |
HO | = .03(four 90° elbows - 90°) |
| = .03(90 + 90 + 90 + 90 - 90) = 8.1 ft |
HT | = HR + HO = 6.5 + 8.1 = 14.6 ft |
HT + VT =14.6 + 15 = 29.6 ft
Formula 1: HT < VT 14.6 < 15
Formula 2: HT + VT < 40 feet 29.6 < 40
Since both formulas are met, this vent configuration is ac- ceptable.