Lennox Merit MLDVT-35NM-FB Installation Instructions Manual page 18

LENNOX HEARTH PRODUCTS • MERIT
Horizontal Termination System
Figure 21, and Table 20 to Table 23 on
Page 20 illustrate the various horizontal
venting configurations that are possible for
use with these appliances. Secure Vent
pipe applications are shown in these
figures; Secure Flex pipe may also be
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used. A horizontal vent table summarizes
each system's minimum and maximum
vertical and horizontal length values that
can be used to design and install the vent
components in a variety of applications.
Both of these horizontal vent systems
terminate through an outside wall. Building
Codes limit or prohibit terminating in
specific areas. Refer to Figure 3 on
Page 5 for location guidelines.
Secure Vent SV4.5 direct vent system
components are unitized concentric pipe
components featuring positive twist
lock connection (Figure 15). All of the
appliances covered in this document are
fitted with collars having locking inclined
channels. The dimpled end of the vent
components fit over the appliance collar to
create the positive twist lock connection.
1. Plan the vent run—Analyze the vent
routing and determine the types and
quantities of sections required:
• 4 1/2 in. (114 mm),
• 10 1/2 in. (267 mm),
• 22 1/2 in. (572 mm),
• 34 1/2 in. (876 mm), and
• 46 1/2 in. (1181 mm)
net section lengths are available. It is
recommended that you plan the venting
so that a joint does not occur in the
ceiling or roof joists. Allow for elbows
as indicated in (Figure 17).
Maintain a minimum 1 in. (25 mm)
clearance to combustibles on the
vertical sections. Clearances for the
horizontal runs are:
• 3 in. (76 mm) on top,
• 1 in. (25 mm) on sides, and
• 1 in. (25 mm) at the bottom.
NOTE: Top vent clearance can be
reduced to 2 in. on horizontal runs
when first elbow is located at least 6 ft
above the fireplace.
2. Frame exterior wall opening—
Locate the center of the vent outlet
on the exterior wall according to
the dimensions shown in Table 9
on Page 10. Cut and/or frame
an opening, 10 1/2 x 12 1/8 in.
(267 x 308 mm) inside dimensions,
about this center.
3. Frame ceiling opening—If the
vertical route is to penetrate a ceiling,
use plumb line to locate the center
above the appliance. Cut and/or
frame an opening, 10 1/2 x 10 1/2 in.
(267 x 267 mm) inside dimensions,
about this center (Figure 14).
18
SERIES DIRECT-VENT GAS FIREPLACES • MLDVT-30/35/40/45 • INSTALLATION INSTRUCTIONS
®
4. Attach vent components to
appliance—To attach a vent
component to the appliance collar,
align the dimpled end over the collar,
adjusting the radial alignment until the
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four locking dimples are aligned with
the inlets of the four incline channels
on the collar (Figure 15). Push the vent
component against the collar until it
fully engages, then twist the component
clockwise, running the dimples down
and along the incline channels until they
are seated at the end of the channels.
The unitized design of the Secure Vent
components will engage and seal both
the inner and outer pipe elements
with the same procedure. Sealant and
securing screws are not required.
NOTE: An elbow may also be attached
to the appliance collar. Attach in
the same manner as you would a
vent section.
5. Attach vent components to each
other—Other vent sections may be
added to the previously installed section
in accordance with the requirements
of the vent tables. To add another vent
component to a length of vent run,
align the dimpled end of the component
over the inclined channel end of the
previously installed section, adjusting
the radial alignment until the four
locking dimples are aligned with the
inlets of the four incline channels of
the previous section. Push the vent
component against the previous section
until it fully engages, then twist the
component clockwise running the
dimples down and along the incline
channels until they seat at the end of
the channels.This seating position is
indicated by the alignment of the arrow
and dimple as shown in (Figure 15).
6. Install firestop/spacer at ceiling—
When using Secure Vent, use SV4.5VF
firestop/spacer at ceiling joists; when
using Secure Flex, use SF4.5VF
firestop/spacer. If there is living space
above the ceiling level, the firestop/
spacer must be installed on the bottom
side of the ceiling. If attic space is
above the ceiling, the firestop/ spacer
must be installed on the top side of the
joist. Route the vent sections through
the framed opening and secure the
firestop/spacer with 8d nails or other
appropriate fasteners at each corner.
NOTE: Maintain 1 in. (25 mm) clearance
to combustibles, framing members, and
attic or ceiling insulation when running
vertical chimney sections.
7. Support the vertical run sections—On
the vertical run, support the venting
system every 8 ft (2.4 m) above the
fireplace vent outlet with field provided
support straps (Plumber's tape). Attach
the straps to the vent pipe and secure
to the framing members with nails or
screws (Figure 16).
DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
8. Change vent direction—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
(Figure 17).
9. Continue installation of horizontal/
inclined sections—Continue with the
installation of the straight vent sections
in horizontal/inclined run as described
in Step 5. Install support straps
every 5 ft. (1.52 m) along horizontal/
inclined vent runs using conventional
plumber's tape (Figure 21). 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 fireplace. Rise per foot run ratios
are acceptable 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) on all sides for all
vertical runs; and
• 3 in. (76 mm) at the top,
• 1 in. (25 mm) on sides, and
• 1 in. (25 mm) at the bottom for all
horizontal/inclined runs.
NOTE: Top vent clearance can be
reduced to 2 in. on horizontal runs
when first elbow is located at least 6 ft
above the fireplace.
10. Assemble vent run to exterior wall—If
not previously measured, locate the
center of the vent at the exterior wall.
Prepare an opening as described in
Step 2. Assemble the vent system
to point where the terminus of the
last section is within 7 in. (178 mm)
to 11 1/4 in. (286 mm) inboard of
the exterior surface to which the
SV4.5HT termination is to be attached
(Figure 23). If the terminus of the last
section is not within this distance,
use the telescopic vent section
SV4.5LA, as the last vent section.
For wall thicknesses greater than that
shown in Figure 23, refer to Table 19
on Page 20. This table lists the
additional venting components needed
(in addition to the termination and
adaptor) for a particular range of wall
thicknesses.