14
BGD36CF(G) TOP OR REAR EXIT VERTICAL TERMINATION
when (HT) < (VT)
Simple venting confi guration (only two 90° elbows)
FIGURE 29
REQUIRED
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 .
See graph to determine the required vertical rise VT for the required horizontal run HT
For vent confi gurations 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
Example 6:
90° V2
FIGURE 30
H2
H1 V1
90°
V1=5 ft | 90° |
|
V2=10 ft
VT=V1 + V2 = 5 + 10 = 15 ft H1=3 ft
H2=2.5 ft
HR=H1 + H2 = 3 + 2.5 = 5.5 ft HO=.03 (three 90° elbows - 90°)
=.03(90 + 90 + 90 - 90) = 5.4 ft
HT=HR + HO = 5.5 + 5.4 = 10.9 ft
HT + VT= 10.9 + 15 = 25.9 ft
Formula 1: HT < VT 10.9 < 15
Formula 2: HT + VT < 40 feet 25.9 < 40
Since both formulas are met, this vent confi guration is ac- ceptable.
when (HT) > (VT)
Simple venting confi gurations
FIGURE 31
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 confi gurations requiring more than two 90° elbows (top exit) or one 90° elbow (rear exit), the following formulas apply:
Formula 1: HT < 3VT
Formula 2: HT + VT < 40 feet
Example 7:
90° | 90° | V3 | |
V1 | |||
V2 H2 |
| ||
| H1 | 90° | |
| 90° |
FIGURE 32
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
3VT = 3 x 4.5 = 13.5 ft
Since this formula is not met, this vent confi guration is unac- ceptable.
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.
