14
TOP OR REAR EXIT VERTICAL TERMINATION
when (HT) > (VT)
Simple venting configurations
FIGURE 17
See graph to determine the required vertical rise VT for the required horizontal run HT.
MAXIMUMVERTICAL
RISE IN
FEET
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 two 90° elbow (top exit) or one 90° elbow (rear exit), the following formulas apply:
Formula 1: HT < 3VTFormula 2: HT + VT < 40 feet
Example 7:90° |
| 90° |
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| V3 | |
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V |
| V | H2 |
1 |
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| H1 | 2 |
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| 90° | |
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| 90° | |
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FIGURE 18
V1 | =2 ft |
V2 | =1 ft |
V3 | =1.5 ft |
VT | = V1 + V2 + V3 = 2 + 1 + 1.5 = 4.5 ft |
H1 | =6 ft |
H2 | =2 ft |
HR | = H1 + H2 = 6 + 2 = 8 ft |
HO | = .03(four 90° elbows - 90°) |
| = .03(90 + 90 + 90 + 90 - 90) = 8.1 ft |
HT | =HR + HO = 8 + 8.1 = 16.1 ft |
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.
Example 8: |
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| 90° | H | V2 | |
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| 45° | |
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| 2 | |
| V1 |
| 90° | |
| H1 |
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| H3 |
| 90° |
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| FIGURE 19 |
V1 | =1.5 ft |
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V2 | =5 ft |
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VT | = V1 + V2 = 1.5 + 5 = 6.5 ft | |||
H1 | =1 ft |
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H2 | =1 ft |
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H3 | =10.75 ft |
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HR | = H1 + H2 + H3 = 1 + 1 + 10.75 = 12.75 ft | |||
HO | = .03(three 90° elbows + one 45° elbow - 90°) | |||
| = .03(90 + 90 + 90 + 45 - 90) = 6.75 ft | |||
HT | =HR + HO = 12.75 + 6.75 = 19.5 ft | |||
HT + VT | = 19.5 + 6.5 = 26 ft |
Formula 1: HT < 3VT
3VT = 3 x 6.5 = 19.5 ft19.5= 19.5Formula 2: HT + VT < 40 feet
26 < 40Since both formulas are met, this vent configuration is ac- ceptable.