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15
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOXHEARTHPRODUCTS•MERIT
®
SERIESDIRECT-VENTCONTEMPORARYDESIGNGASFIREPLACES•MODELMLDVTCD-35•INSTALLATIONINSTRUCTIONS
If the vent system extends more than 5 feet (1.5
m)abovetheroofashing,stabilizersmaybe
necessary. Additional screws may be used at
section joints for added stability. Guide wires
may be attached to the joint for additional sup-
port on multiple joint configurations.
G. Continue installation of horizontal/inclined
sections - Continue with the installation of the
straight vent sections in horizontal/inclined run
as described in Step C. Install support straps
every 5 ft. (1.52 m) along horizontal/inclined
vent runs using conventional plumber’s tape.
See Page 18, Figure 26. It is very important
that the horizontal/inclined 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 acceptable all the
way down to at or near level. Use a carpenter’s
level to measure from a constant surface and
adjust the support straps as necessary.
It is important to maintain the required clear-
ances to combustibles: 1" (25 mm) at all sides
for all vertical runs; and 3" (76 mm) at the top,
1" (25 mm) at sides, and 1" (25 mm) at the
bottom for all horizontal/inclined runs.
H. Frame roof opening - Identify location for
vent at the roof. Cut and/or frame opening per
Roof Framing Chart (Figure 20).
One method of support is by utilizing field pro-
vided support straps (conventional plumber's
tape). Secure the plumber's tape to the framing
members with nails or screws. Loop the tape
around the vent, securing the ends of the tape
to the framing. If desired, sheet metal screws #6
x 1/2" length may be used to secure the support
straps to the vent pipe. Refer to Figure 18.
F. Change vent direction to horizontal/inclined
run - At transition from or to a horizontal/in-
clined run, install the SV4.5E45 and SV4.5E90
elbows in the same manner as the straight vent
sections. The elbows feature a twist section to
allow them to be routed about the center axis
of their initial collar section to align with the
required direction of the next vent run element.
Twist elbow sections in a clockwise direction
only so as to avoid the possibility of unlocking
any of the previously connected vent sections
(see Figure 19).
K. Install the vertical termination - The final
step involves installation of the SV4.5CGV-1
Vertical Termination. Extend the vent sections
to the height as shown in the "Vertical vent
termination section" in Figure 4B on Page 6.
The SV4.5CGV-1 Vertical Termination (Figure
22) can be installed in the exact same fashion
as any other Secure Vent™ section. Align the
termination over the end of the previously
installed section, adjusting the radial alignment
until the four locking dimples of the termination
are aligned with the inlets of the four incline
channels of the last vent section. Push the ter-
mination down until it fully engages, then twist
the termination clockwise running the dimples
down and along the incline channels until they
are seated at the end of the channels.
I. Install the roof flashing - Extend the vent
sections through the roof structure. Install the
roofashingovertheventsectionandposi-
tion such that the vent column rises vertically
(use carpenters level) (Figure 21). Nail along
perimetertosecureashingoradjustroong
tooverlaptheashingedgesattopandsides
only and trim where necessary. Seal the top
andbothsidesoftheashingwithwaterproof
caulking.
J. Install the storm collar - Install the storm
collar, supplied with the ashing, over the
vent/ashingjoint.SeeFigure 21. Loosen the
storm collar screw. Slide collar down until it
meetsthetopoftheashing.Tightenthead-
justing screw. Apply non-combustible caulking
or mastic around the circumference of the joint
to provide a water tight seal.
Figure 19
7-5/8”
(194 mm)
4-13/16
(122 mm)
Swivel Joint
(360° swivel)
SV4.5E45
45° Elbow)
Swivel Joint
(360° swivel)
SV4.5E90
90° Elbow)
(206 mm)
8-1/8"
Framing Dimensions for Roof
Inches (millimeters)
Pitch C D
0/12 10-1/2 in.
(267 mm)
10-1/2 in.
(267 mm)
6/12 10-1/2 in.
(267 mm)
12 in.
(305 mm)
12/12 10-1/2 in.
(267 mm)
17 3/4 in.
(451 mm)
C
D
Figure 20 - Roof Framing
Figure 21
Figure 22
Storm
Collar
Flashing