TOP EXIT VERTICAL termination
when (Ht) < (Vt)
See graph to determine the
required vertical rise VT for the required horizontal run HT.
figure 9
required vertical rise in feet
VT
horizontal vent run PLUS OFFSET in
feet HT
The shaded area within the lines represents ac- ceptable values for HT and VT .
For vent configurations requiring more than zero 90° elbow (top exit) or one 90° elbow (rear exit), the following formulas apply:
Formula 1: HT < VT
Formula 2: HT + VT < 40 feet
TOP VERTICAL termination
when (Ht) > (Vt)
Simple venting configurations
figure 10 | 90° |
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| 90° | V3 | |
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| V |
| V H2 | |
| H1 |
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| 1 | 2 |
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| 90° | 90° |
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figure 11
See graph to determine the required vertical rise VT for the required horizontal run HT.
maximum vertical 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 < 3VT
Formula 2: HT + VT < 40 feet
Example 7:
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°) | |
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| = .03(90 + 90 + 90 + 90 - 90) = 8.1 ft | |
HT | + VT | =HR + HO = 8 + 8.1 = 16.1 ft | |
HT | = 16.1 + 4.5 = 20.6 ft | ||
Formula 1: | HT < 3VT | ||
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| 3VT = 3 x 4.5 = 13.5 ft |
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| 16.1 > 13.5 |
Since this formula is not met, this vent configuration is unacceptable.
Formula 2: HT + VT < 40 feet 0.6 < 40
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.
