TOP EXIT / horizontal termination
when (Ht) > (Vt)
Simple venting configuration (only one 90° elbow)
figure 6
See graph to determine the required verti- cal rise Vt for the required horizontal run Ht.
V1 | = VT | = 6 ft |
H1 | = 3 ft | |
H2 | = 5 ft | |
HR | = H1 | + H2 = 3 + 5 = 8 ft |
HO | = .03(two 90° elbows - 90°) = .03(180° - 90°) = 2.7 ft | |
HT | = HR | + HO = 8 + 2.7 = 10.7 ft |
HT | + VT= 10.7 + 6 =16.7 | |
Formula 1: | HT < 4.2 VT | |
|
| 4.2 VT = 4.2 x 6 = 25.2 ft |
|
| 10.7 < 25.2 |
Formula 2: | HT + VT < 24.75 feet | |
|
| 6.7 < 24.75 |
Since both formulas are met, this vent configuration is ac- ceptable.
required vertical rise in inches
VT
Example 3:
V
1
90° | H4 | |
H1 | ||
V2 | ||
H2 | ||
H3 | ||
90° |
|
figure 8
horizontal vent run PLUS OFFSET in feet HT
The shaded area within the lines represents acceptable values for HT and VT .
For vent configurations requiring more than one 90° elbow the following formulas apply:
Formula 1: HT < 4.2 VT
Formula 2: HT + VT < 24.75 feet
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 |
H | = .03(four 90° elbows - 90°) = .03(360° - 90°) = 8.1 ft | ||
Example 2:
V1 
H1
H2
90°
figure 7
HOT | + VT | = HR + HO = 5.5 + 8.1 = 13.6 ft |
HT | = 13.6 + 5.5 = 19.1 ft |
Formula 1: HT < 4.2 VT
4.2 VT = 4.2 x 5.5 = 23.1 ft 13.6 < 23.1
Formula 2: HT + VT < 24.75 feet
9.1 < 24.75
Since both formulas are met, this vent configuration is acceptable.
