8
TOP EXIT VERTICAL TERMINATION
when (HT) < (VT)
FIGURE 9
REQUIRED VERTI-
CAL 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 confi gurations requiring more than zero 90° elbow (top exit) or one 90° elbow (rear exit), the following formulas apply:
See graph to determine the required vertical rise VT | for the | Formula 1: HT < VT |
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Formula 2: HT | + VT | < 40 feet | |||
required horizontal run HT. |
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TOP VERTICAL TERMINATION
when (HT) > (VT)
Simple venting confi gurations
FIGURE 10
Formula 1: HT < 3VT
Formula 2: HT + VT < 40 feet
Example 7:
V1 | =2 ft |
V2 | =1 ft |
V3 | =1.5 ft |
FIGURE 11
See graph to determine the required vertical rise VT for the required horizontal run HT.
For vent confi gurations requiring more than two 90° elbow (top exit) or one 90° elbow (rear exit), the following formulas apply:
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 .
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
3VT = 3 x 4.5 = 13.5 ft
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 confi guration is unacceptable and a new fi replace location or vent confi guration will need to be established to satisfy both formulas.
