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NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOXHEARTHPRODUCTS•MERIT
®
SERIESDIRECT-VENTCONTEMPORARYDESIGNGASFIREPLACES•MODELMLDVTCD-35•INSTALLATIONINSTRUCTIONS
u
When using Se-
cure Flex, use
Firestop / Spac-
er SF4.5VF
u Ceiling Firestop /
Spacer (SV4.5VF)
A Vent
Restrictor, as
shown in Figure
14 on Page 12,
must be used in
this application
Figure 23 - Top Vent - STRAIGHT
u Ceiling Firestop /
Spacer (SV4.5VF)
vWall Firestop/
Spacer (SV4.5HF)
u When using Secure Flex, use Firestop /
Spacer SF4.5VF.
v When using Secure Flex, use Firestop /
Spacer SF4.5HF.
H
V
V1
40 feet
(12.2 meters)
Maximum
Table A
H Maximum
V Minimum
feet (meter) feet (meter)
5 (1.524) 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 + V
1
+ H = 40 feet (12.2 m) Max.
H = 20 feet (6.096 meters) Max.
WARNING
Under no circumstances, may sepa-
rate sections of concentric flexible
vent pipe be joined together.
VERTICAL VENT FIGURES/TABLES
Notes:
pipe) may also be used.
-
clined run be maintained in a straight (no
dips) and recommended to be in a slightly
elevated plane, in a direction away from
the fireplace of 1/4" rise per foot (20 mm
per meter) which is ideal, though rise per
foot run ratios that are smaller are accept-
able all the way down to at or near level.
SV4.5VF (Secure Vent), SF4.5VF (Secure
Flex) firestop/spacer must be used anytime
vent pipe passes through a combustible
floor or ceiling. SV4.5HF (Secure Vent),
SF4.5HF (Secure Flex) firestop/spacer must
be used anytime vent pipe passes through
a combustible wall.
Two 45 degree elbows may be used in place
of one 90 degree elbow. The same rise to
run ratios, as shown in the venting Figures
for 90 elbows, must be followed if 45 degree
elbows are used.
VERTICAL RISE EXCEPT WHERE AN ELBOW
IS THE ONLY VERTICAL COMPONENT IN
THE SYSTEM (See Figure 29).
Figure 24 - Top Vent - TWO 90 DEGREE ELBOWS
Example: If 20 feet of (H) 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) 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.