16
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Framing Dimensions for Roof
Pitch C D
0/12 10 1/2 in. 10 1/2 in.
(267 mm) (267 mm)
6/12 10 1/2 in. 12 in.
(267 mm) (305 mm)
12/12 10 1/2 in. 17 3/4 in.
(267 mm) (451 mm)
Figure 24
Figure 26
Figure 25
If the vent system extends more than 5' (1.5
m) above the roof fl ashing, stabilizers may be
necessary. Additional screws may be used at
section joints for added stability. Guide wires
may be attached to the joint for additional
support on multiple joint confi gurations.
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.
It is very important that the horizontal/
inclined run be maintained in a straight
(no dips), slightly elevated plane. The
recommended incline is approximately
1/4 in. per foot (20 mm per meter)
horizontal, in a direction away from the
fi replace. The 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
clearances to combustibles: 1 in. (25 mm)
at all sides for all vertical runs; and 3 in.
(76 mm) at the top, 1 in. (25 mm) at sides,
and 1 in. (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 and Figure 24.
F. Change vent direction to horizontal/
inclined run—At transition from or to a
horizontal/inclined 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 possiblity of unlocking any of
the previously connected vent sections. See
Figure 23.
Figure 23
SV4.5E90
(90
°
Elbow)
8-1/8"
(206 mm)
Swivel Joint
(360
°
swivel)
4-13/16"
(122 mm)
SV4.5E45
(45
°
Elbow)
Swivel Joint
(360
°
swivel)
C
D
Storm
Collar
K. Install the vertical termination—The
fi nal 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" on
Page 6. The SV4.5CGV-1 Vertical Termination
(Figure 26) installs 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 termination down until
it fully engages, then twist the termination
clockwise running the dimples down and
along the incline channels until they seat at
the end of the channels.
I. Install the roof fl ashing—Extend the vent
sections through the roof structure. Install
the roof fl ashing over the vent section and
position such that the vent column rises
vertically (use carpenters level) (Figure 25 ).
Nail along perimeter to secure fl ashing or
adjust roofi ng to overlap the fl ashing edges at
top and sides only and trim where necessary.
Seal the top and both sides of the fl ashing
with waterproof caulking.
J. Install the storm collar—Install the storm
collar, supplied with the fl ashing, over the
vent/fl ashing joint. See Figure 25. Loosen
the storm collar screw. Slide collar down
until it meets the top of the fl ashing. Tighten
the adjusting screw. Apply non-combustible
caulking or mastic around the circumference
of the joint to provide a water tight seal.
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