Lennox MLDVT-30NM Installation Instructions Manual page 21

HORIZONTAL VENT FIGURES / TABLES (CONTINUED)
Typical termination shown.
H 
v
Wall Firestop/Spacer
(SV4.5HF)
See Table 10 on Page 19 as
an aid in venting component
selection for a particular
range of exterior wall thick-
nesses.
Figure 32
- Top Vent - THREE 90 DEGREE ELBOWS
u
When using Secure Flex,
use Firestop/Spacer
SF4.5VF.
v
When using Secure
Flex, use Firestop/Spacer
Firestop/Spacer
V 
v
Wall Firestop/Spacer
(SV4.5HF)
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
SF4.5HF.
u
Ceiling
(SV4.5VF)
H
Table F
H Maximum
+ H

feet (meter) feet
5 (.524)
5 (.524)
0 (3.048)
5 (4.572)
20 (6.096)
H
+ H = 20 feet (6.096 m) Max.

V H
+ V + + H = 60 ft. (8.3 m) Max.
 
Example: If 20 feet total (H+H
V
run is needed, 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 ) horizontal run, up to a maximum horizontal
1
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.
V Minimum
(meter)
Elbow Only
 (0.305)
2 (0.60)
3 (0.94)
4 (.29)
) horizontal vent
1
2