12
REAR EXIT / HORIZONTAL TERMINATION
when (HT) > (VT) | Example 5: |
Simple venting configuration (only two 90° elbows) |
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| 90° |
| 90° |
| H4 |
FIGURE 13 |
| V2 | |
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H2 |
| 45° | 90° |
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| H3 |
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V1 |
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H1 | 90° |
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| FIGURE 14 | |
See graph to determine the required vertical rise VT for the required horizontal run HT
REQUIRED
VERTICAL
RISE IN
INCHES
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 < 3.5VT
Formula 2: HT + VT < 24.75 feet
V1 | =4 ft |
V2 | =1.5 ft |
VT | = V1 + V2 = 4 + 1.5 = 5.5 ft |
H1 | =2 ft |
H2 | =1 ft |
H3 | =1 ft |
H4 | =1.5 ft |
HR | = H1 + H2 + H3 + H4 = 2 + 1 + 1 + 1.5 = 5.5 ft |
HO | = .03(four 90° elbows + one 45° elbow - 90°) |
| = .03(90 + 90 + 90 + 90 + 45 - 90) = 9.45 ft |
HT | =HR + HO = 5.5 + 9.45 = 14.95 ft |
HT + VT | = 14.95 + 5.5 = 20.45 ft |
Formula 1: HT < 3.5VT
3.5VT = 3.5 x 5.5 = 19.25 ft
14.95 < 19.25
Formula 2: HT + VT < 24.75 feet
20.45 < 24.75
Since both formulas are met, this vent configuration is ac- ceptable.