17
3.8TOP EXIT HORIZONTAL TERMINATION
(HT) > (VT)
Simple venting configuration (only one 90° elbow)
See graph to determine the required vertical rise VT for the
required horizontal run HT.
147”
150
FIGURE 3.8a
REQUIRED | 100 |
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VERTICAL |
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RISE IN |
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INCHES VT | 57” |
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| 50 |
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| 19 1/2” |
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| 0 | 5 | 10 | 15 | 20 |
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| 2’ |
| 12.5’ | 19.5’ |
HORIZONTAL VENT RUN PLUS OFFSET IN FEET HT
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| The shaded area within the lines represents acceptable | |||
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| values for HT and VT | ||
For vent configurations requiring more than one 90° elbow, the following formulas apply: |
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Formula 1: HT | < 4.2 VT |
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Formula 2: HT | + VT < 24.75 feet |
| 90° |
| H1 | H2 | ||||||
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Example 2: |
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V1 | = VT = 6 FT |
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| FIGURE 3.8b |
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| 90° |
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H1 | = 3 FT |
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| V1 |
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H2 | = 5 FT |
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HR | = H1 | + H2 | = 3 + 5 = 8 FT |
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HO | = .03 (two 90° elbows - 90°) = .03 (180° - 90°) = 2.7 FT |
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HT | = HR | + HO | = 8 + 2.7 = 10.7 FT |
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HT | + VT | = 10.7 + 6 = 16.7 FT |
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Formula 1: |
| H | < 4.2 V |
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Formula 2: |
| T | 4.2 VTT = 4.2 x 6 = 25.2 FT |
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| HT | + VT < 24.75 FT |
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| 90° | |||||
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| 16.7 < 24.75 |
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| 90° | ||
Since both formulas are met, this vent configuration is acceptable. | 90° | H | H4 | |||||||||
Example 3: |
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| 1 | V2 | |||||
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| H3 | ||||||
V1 | = 4 FT |
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V2 | = 1.5 FT | = 4 + 1.5 = 5.5 FT | FIGURE 3.8c | V1 | 90° |
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V | T | = V + V | 2 |
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H1 | = 2 FT |
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H2 | = 1 FT |
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H3 | = 1 FT |
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H4 | = 1.5 FT | + H3 + H4 = 2 + 1 + 1 + 1.5 = 5.5 FT |
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HR | = H1 | + H2 |
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HO | = .03 (four 90° elbows - 90°) = .03 (360° - 90°) = 8.1 FT |
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HT | = HR | + HO | = 5.5 + 8.1 = 13.6 FT |
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HT | + VT | = 13.6 + 5.5 = 19.1 FT |
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Formula 1: |
| HT | < 4.2 VT |
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| 4.2 VT = 4.2 x 5.5 = 23.1 FT |
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| 13.6 < 23.1 |
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Formula 2: |
| HT | + VT < 24.75 FT |
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| 19.1 < 24.75 |
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Since both formulas are met, this vent configuration is acceptable.
16.1_2
