Lennox MLDVT-30NM Installation Instructions Manual page 20

HORIZONTAL VENT FIGURES / TABLES (CONTINUED)
H 
u
Note - When using
Secure Flex , use
TM
Firestop/Spacer SF4.5VF.
v
When using Secure Flex,
use Firestop/Spacer
SF4.5HF.
Typical termination shown.
See Table 10 on Page 19 as an aid in venting
component selection for a particular range of
exterior wall thicknesses.
Figure 31
- Top Vent - TWO 90 DEGREE ELBOWS
20
v
Wall Firestop/Spacer
(SV4.5HF)
H
v Wall Firestop/Spacer
(SV4.5HF)
u
Ceiling
Firestop/Spacer
(SV4.5VF)
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
H Maximum
+ H

feet (meter)
3 (0.94)
V 5 (.524)
0 (3.048)
5 (4.572)
20 (6.096)
H
V + + H

H + H

Example: If 20 feet of (H + H
then 4 feet minimum of (V) vertical vent will be required.
This table shows a 1(V) to 5(H) ratio. For every 1 foot of (V)
vertical, you are allowed 5 feet of (H+ H
to a maximum horizontal run of 20 feet.
An elbow is acceptable as 1 foot of vertical rise except where
an elbow is the only vertical component in the system. See
Figure 29.
Table E
V Minimum
feet (meter)
Elbow Only
 (0.305)
2 (0.60)
3 (0.94)
4 (.29)
= 60 feet (8.3 m) Max.
= 20 ft. (6.096 m) Max.
) horizontal vent run is needed,
1
) horizontal run, up
1