8
HORIZONTAL TERMINATION
when (HT) > (VT)
Simple venting confi guration (only one 90° elbow)
FIGURE 6
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 OFFSET IN FEET HT
The shaded area within the lines represents acceptable values for HT and VT .
For vent configurations requiring more than one 90° elbow the following formulas apply:
Example 3:
| 90° | |
H1 | H4 | |
V2 | ||
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90° | H2 H3 | |
V1 |
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| FIGURE 8 |
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 - 90°) = .03(360° - 90°) = 8.1 ft |
HT | = HR + HO = 5.5 + 8.1 = 13.6 ft |
HT + VT = 13.6 + 5.5 = 19.1 ft
Formula 1: HT < 4.2 VT
4.2VT = 4.2 x 5.5 = 23.1 ft
13.6< 23.1
Formula 2: HT + VT < 24.75 feet
19.1 < 24.75
Formula 1: HT < 4.2 VT
Formula 2: HT + VT < 24.75 feet
Example 2:
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V1 |
| 90° | |
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H1
H2
FIGURE 7
Since both formulas are met, this vent configuration is acceptable.
= VT = 6 ft = 3 ft
= 5 ft
= H1 + H2 = 3 + 5 = 8 ft
= .03(two 90° elbows - 90°) = .03(180° - 90°) = 2.7 ft
= HR + HO = 8 + 2.7 = 10.7 ft HT + VT= 10.7 + 6 =16.7
Formula 1: HT < 4.2 VT
4.2VT = 4.2 x 6 = 25.2 ft
10.7< 25.2
Formula 2: HT + VT < 24.75 feet
16.7 < 24.75
Since both formulas are met, this vent confi guration is ac- ceptable.
