10
TOP VERTICAL TERMINATION
when (HT) > (VT)
Simple venting configurations
FIGURE 10
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:
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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 .
FIGURE 11
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 | |
HT + VT | = 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 20.6 < 40
Since only formula 2 is met, this vent configuration is unacceptable and a new fireplace location or vent con- figuration will need to be established to satisfy both for-