13
BGD36CF(G) REAR EXIT / HORIZONTAL TERMINATION
when (HT) < (VT)
Simple venting confi guration (only two 90° elbows)
FIGURE 25
See graph to determine the required vertical rise VT for the required horizontal run HT
REQUIRED VER-
TICAL RISE IN
FEET
VT
HORIZONTAL VENT RUN PLUS OFF-
SETS 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 the fol- lowing formulas apply:
Formula 1: HT < VT | 90° |
Formula 2: HT + VT < 40 feet | H3 |
90°V2
when (HT) > (VT)
Simple venting confi guration (only two 90° elbows)
FIGURE 27
See graph to determine the required vertical rise VT for the required horizontal run HT
REQUIRED VERTICAL
RISE IN INCHES VT
HORIZONTAL VENT RUN
PLUS OFFSETS 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 the fol- lowing formulas apply:
Formula 1: HT < 3.5VT | 90° |
Formula 2: HT + VT < 24.75 feet | H4 |
H2 
FIGURE 26
Example 5: | 90° | V |
|
|
| 45° | 2 |
90°
V1
H1 90°
Example 4:
V1 = 9 ft V2 = 6 ft
VT = V1 + V2 = 9 + 6 = 15 ft H1 = 3 ft
H2 = 2 ft H3 = 1.5 ft
HR = H1 + H2 + H3 = 3 + 2 + 1.5 = 6.5 ft HO = .03 (four 90° elbows - 90°)
= .03(90 + 90 + 90 + 90 - 90) = 8.1 ft
HT = HR + HO = 6.5 + 8.1 = 14.6 ft
HT + VT = 14.6 + 15 = 29.6 ft
Formula 1: HT < VT 14.6 < 15
Formula 2: HT + VT < 40 feet 29.6 < 40
Since both formulas are met, this vent confi guration is ac- ceptable.
H2 | 90° |
V1 | H3 |
| |
H1 | FIGURE 28 |
| 90° |
V1=4 ft V2=1.5 ft
VT=V1 + V2 = 4 + 1.5 = 5.5 ft H1=2 ft
H2=1 ft H3=1 ft H4=1.5 ft
HR=H1 + H2 + H3 + H4 = 2 + 1 + 1 + 1.5 = 5.5 ft HO=.03 (four 90° elbows + one 45° elbow - 90°)
=.03(90 + 90 + 90 + 90 + 45 - 90) = 9.45 ft HT=HR + HO = 5.5 + 9.45 = 14.95 ft
HT + VT= 14.95 + 5.5 = 20.45 ft
Formula 1: HT < 3.5VT
3.5VT = 3.5 x 5.5 = 19.25 ft
14.95< 19.25
Formula 2: HT + VT < 24.75 feet
20.45< 24.75
Since both formulas are met, this vent confi guration is ac- ceptable.
