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NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
See Table 8 on Page 20 as an aid in venting
component selection for a particular range of
exterior wall thicknesses.
HORIZONTAL VENT FIGURES / TABLES (CONTINUED)
Example: If 20 feet of (H + H
1
) horizontal vent 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
1
) horizontal run, up
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.
Typical termination shown.
LENNOXHEARTHPRODUCTS•MERIT
®
SERIESDIRECT-VENTCONTEMPORARYDESIGNGASFIREPLACES•MODELMLDVTCD-35•INSTALLATIONINSTRUCTIONS
V
H
H
1
Wall Firestop/Spacer
(SV4.5HF)
Wall Firestop/Spacer
(SV4.5HF)
WhenusingSecureFlex,
use Firestop/Spacer
SF4.5HF.
Ceiling
Firestop/Spacer
(SV4.5VF)
Note - When using
Secure Flex
TM
, use
Firestop/Spacer SF4.5VF.
Table E
H
+ H
1
Maximum
V Minimum
feet (meter) feet (meter)
3 (0.914) Elbow Only
5 (1.524) 1 (0.305)
10 (3.048) 2 (0.610)
15 (4.572) 3 (0.914)
20 (6.096) 4 (1.219)
V + H + H
1
= 40 feet (12.2 m) Max.
H + H
1
= 20 ft. (6.096 m) Max.
Figure 31 - Top Vent - TWO 90 DEGREE ELBOWS