12
REAR EXIT / HORIZONTAL TERMINATION
(HT) < (VT) | Example 4: | 90° |
| H3 | |
|
| |
Simple venting configuration |
| V2 |
(only two 90° elbows) |
|
H2
V190°
H1 | FIGURE 13 |
| 90° |
FIGURE 12
See graph to determine the required vertical rise VT for the required horizontal run HT
35
33.3
30 
REQUIRED
VERTICAL
20
RISE IN 17.5
FEET VT
10
0 .5 | 2.5 | 5 | 7.5 | 10 | 12.5 | 15 | 17.5 | 20 |
HORIZONTAL VENT RUN PLUS OFFSET IN FEET HT
The shaded area within the lines represents acceptable values for HT and VT .
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 | + VT | =HR + HO = 6.5 + 8.1 = 14.6 ft |
HT | =14.6 + 15 = 29.6 ft |
Formula 1: HT < VT 14.6 < 15
Formula 2: HT + VT < 35 feet 29.6 < 35
Since both formulas are met, this vent configuration is acceptable.
For vent configurations requiring more than two 90° elbows the following formulas apply:
Formula 1: HT < VT
Formula 2: HT + VT < 35 feet