DEFINITIONS
for the following symbols used in the venting calculations and examples are:
>- greater than
>- equal to or greater than
<- less than
<- equal to or less than
HT - total of both horizontal vent lengths (HR) and offsets (HO) in feet
HR - combined horizontal vent lengths in feet
HO - offset factor: .03 (total degrees of offset - 90°*) in feet
VT - combined vertical vent lengths in feet
11
ELBOW VENT LENGTH VALUES
| feet | inches |
1° | 0.03 | 0.5 |
15° | 0.45 | 6.0 |
30° | 0.9 | 11.0 |
45°* | 1.35 | 16.0 |
90°* | 2.7 | 32.0 |
*BGD36CF the fi rst 90° offset has a zero value and is shown in the formula as - 90°
*BGD42CF the fi rst 45° and 90° offset has a zero value and
is shown in the formula as
combined.
BGD36CF(G) TOP EXIT / HORIZONTAL TERMINATION
when (HT) < (VT)
Simple venting confi guration (only one 90° elbow)
See graph to determine the required vertical rise VT for the required horizontal run HT.
FIGURE 20
Formula 1: HT < VT
Formula 2: HT + VT < 40 feet
Example 1:
90°
H2
V2
For vent configurations requiring more than one 90° elbow, the following formulas apply:
V E R T I C A L
RISE IN FEET
VT
90°
H1
90°
V1 | FIGURE 21 |
HORIZONTAL VENT RUN PLUS OFFSET IN FEET HT
The shaded area within the lines represents acceptable values for HT and VT .
V1 = 3 ft V2 = 8 ft
VT = V1 + V2 = 3 + 8 = 11 ft H1 = 2.5 ft
H2 = 2 ft
HR = H1 + H2 = 2.5 + 2 = 4.5 ft
HO = .03 (three 90° elbows - 90°) = .03(270° - 90°) = 5.4 ft HT = HR + HO = 4.5 + 5.4 = 9.9 ft
HT + VT = 9.9 + 11 = 20.9 ft
Formula 1: HT < VT 9.9 < 11
Formula 2: HT + VT < 40 feet 20.9 < 40
Since both formulas are met, this vent confi guration is ac- ceptable.
