22
(HT) > (VT)
Simple venting configurations.
FIGURE 3.11c
See graph to determine the required vertical rise VT for the
required horizontal run HT.
| 19 | 20 |
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REQUIRED |
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VERTICAL |
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RISE IN |
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FEET VT | 3 |
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| 0 | 5 | 10 | 15 | 20 | 25 | 30 |
HORIZONTAL VENT RUN PLUS OFFSET IN FEET HT
The shaded area within the lines represents acceptable
values for HT and HT
For vent configurations requiring more than two 90° elbows (top exit) or one 90° elbow (rear exit), | |||||||||||
the following formulas apply: | 90° |
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Formula 1: HT | < 3 VT | 90° | |||||||||
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Formula 2: HT | + VT < 40 feet |
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Example 7: |
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| V1 | H2 V2 | |||||
V1 | = 2 FT |
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| H1 | |||
V2 | = 1 FT |
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V3 | = 1.5 FT | + V |
| = 2 + 1 + 1.5 = 4.5 FT |
| 90° | |||||
V | T | = V + V | 2 | 3 |
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H1 | = 6 FT |
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H2 | = 2 FT |
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HR | = H1 | + H2 = 6 + 2 = 8 FT |
| FIGURE 3.11d | |||||||
HO | = .03 (four 90° elbows - 90°) |
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| = .03 (360° - 90°) = 8.1 FT |
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HT | = HR | + HO = 8 + 8.1 = 16.1 FT |
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HT | + VT | = 16.1 + 4.5 = 20.6 FT |
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V3 |
90°
Formula 1: | H | < 3.5 V |
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| T | 3.5 V T | = 3 x 4.5 = 13.5 FT |
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| 16.1 < 13.5 |
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Since this formula is not met, this vent configuration is unacceptable.
Formula 2: | HT + VT < 40 FT |
| 16.1 < 13.5 |
Since only formula 2 is met, this vent configuration is unacceptable and a new fireplace location or vent configuration will need to be established to satisfy both formulas.
18.2_2
