Lennox MPD35ST-NM-B Installation Instructions Manual page 22

HORIZONTAL VENT FIGURES / TABLES (CONTINUED)
Square termination
(SV4.5HT-2) shown
Figure 37
- Side Vent, TWO 90 DEGREE ELBOWS
H
1
Square termination
(SV4.5HT-2) shown
Example: If 20 feet of (H + H
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 36.
Figure 38
- Top Vent, TWO 90 DEGREE ELBOWS
22
H 1
V
v
Wall Firestop/
Spacer (SV4.5HF)
v
Spacer (SV4.5HF)
) horizontal vent run
1
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
H
H
feet
5
0
5
v Wall Firestop/
Spacer (SV4.5HF) 20
u
Ceiling Firestop
/ Spacer (SV4.5VF)
H
Wall Firestop/
u
Ceiling Firestop
/ Spacer (SV4.5VF)
Table G
Maximum H Maximum
+H

(meter) feet (meter)
(.524) 2 (0.60)
(3.048) 4 (.29)
(4.572) 6 (.829)
(6.096) 8 (2.438)
V + H + H  = 40 feet (2.2 m) Max
H = 8 feet (2.438 meters) Max.
H + H  = 20 feet (6.096 meters) Max.
u
When using Secure Flex, use Firestop /
Spacer SF4.5VF
When using Secure Flex, use Firestop /
v
Spacer SF4.5HF
Example: If 20 feet of (H + H
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.
See Table 11 on Page 21 as an aid in venting
component selection for a particular range of
exterior wall thicknesses.
H Maximum
+ H

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

H
+ H = 20 ft. (6.096 m) Max.

u
When using Secure Flex, use Firestop
/ Spacer SF4.5VF
When using Secure Flex, use Firestop
v
/ Spacer SF4.5HF
See Table 11 on Page 21 as an aid in vent-
ing component selection for a particular
range of exterior wall thicknesses.
V Minimum
feet (meter)
 (0.305)
2 (0.60)
3 (0.94)
4 (.29)
) horizontal vent
1
Table H
V Minimum
feet (meter)
Elbow Only
 (0.305)
2 (0.60)
3 (0.94)
4 (.29)
= 40 feet (2.2 m) Max.