3.8TOP EXIT HORIZONTAL TERMINATION
(HT) < (VT)
Simple venting configuration (only one 90° elbow)
39 40
15
See graph to determine the required vertical rise VT for the required horizontal run HT.
30 
REQUIRED
VERTICAL 20
RISE IN
FEET VT 10 
0 | 2.5 | 5 | 7.5 | 10 | 12.5 | 15 | 17.5 | 20 |
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 < VT
Formula 2: HT + VT < 40 feet
Example 1:
V1 | = 3 FT |
V2 | = 8 FT |
VT = V1 + V2= 3 FT + 8 FT = 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 FT
20.9< 40
Since both formulas are met, this vent configuration is acceptable.
90°
H2
V2
90°
90°
H1
V1
16.1A
