15
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Min. 10-1/2"
(267 mm)
Min. 10-1/2"
(267 mm)
Figure 20
Figure 22
Figure 21
E. Support the vertical vent run sections—
Note: Proper venting support is very
important.
Support the vertical portion of the venting
system every 8 feet (2.4m) above the
fi replace vent outlet. One method of support
is by utilizing fi eld provided 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 in. length may be used to secure
the support straps to the vent pipe. See
Figure 22.
Vertical (Offset) Installation
Analyze the vent routing and determine the
quantities of vent sections and number of
elbows required. Refer to Vertical Vent
Figures and Tables on Page 17 to select
the type of vertical installation desired.
Vent sections are available in net lengths of
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). Refer to the Vent
Section Length Chart on Page 14 for an aid
in selecting length combinations. Elbows are
available in 90° and 45° confi gurations. Refer
to Figure 23 for the SV4.5E45 and SV4.5E90
elbow dimensional specifi cations.
Where required, a telescopic vent section
(SV4.5LA) may be used to provide the
installer with an option in installing in tight
and confi ned spaces or where the vent run
made up of fi xed length pieces develops a
joint in a undesirable location, or will not
build up to the required length. The SV4.5LA
Telescopic Vent Section has an effective
length of from 1 1/2 in. (38 mm) to 7 1/2 in.
(191 mm). The SV4.5LA is fi tted with a
locking inclined channel end (identical to a
normal vent section component) and a plain
end with 3 pilot holes. Slip the plain end over
the locking channel end of a standard SV4.5
vent component the required distance and
secure with three screws.
Maintain a minimum 1 in. (25 mm)
clearance to combustible materials for
all vertical elements. Clearances for all
horizontal elements are 3 in. (76 mm)
on top, 1 in. (25 mm) on sides and 1 in.
(25 mm) on the bottom.
A. Frame ceiling opening—Use a plumb line
from the ceiling above the appliance to locate
center of the vertical run. Cut and/or frame
an opening, 10 1/2 in. x 10 1/2 in. (267 mm
x 267 mm) inside dimensions, about this
center mark (Figure 20).
B. Attach vent components to appliance—
Secure Vent
®
SV4.5 direct vent system
components are unitized concentric pipe
components featuring positive twist lock
connections (see Figure 19). All of the
appliances covered in this document are
fi tted with collars having locking inclined
channels.
The dimpled end of the vent components
fi t over the appliance collar to create the
positive twist lock connection.To attach a
vent component to the appliance collar, align
the dimpled end over the collar, adjusting
the radial alignment until the four locking
dimples are aligned with the inlet of the
four inclined channels on the collar (refer
to Figure 21). 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 seat at the end of the channels.
The unitized design of the Secure Vent
®
components will engage and seal both the
inner and outer pipe without the need for
sealant or screws. If desired a #6 x 1/2 in.
screw may be used at the joint, but it is not
required as the pipe will securely lock when
twisted.
Note: An elbow may also be attached to the
appliance collar. Attach in the same manner
as you would a vent section.
C. Attach vent components to each other—
Other vent sections may be added to the
previously installed section in accordance
with the requirements of the vertical vent
fi gures and tables. To add another vent
component to a length of vent run, align the
dimpled end 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 21.
D. Install fi restop/spacer at ceiling—
When using Secure Vent, use SV4.5VF
fi restop/spacer at ceiling joists; when using
Secure Flex
®
, use SF4.5VF fi restop/spacer. If
there is living space above the ceiling level,
the fi restop/spacer must be installed on the
bottom side of the ceiling. If attic space is
above the ceiling, the fi restop/spacer must
be installed on the top side of the joist. Route
the vent sections through the framed opening
and secure the fi restop/spacer with 8d nails
or other appropriate fasteners at each corner.
Remember to maintain 1 in. (25 mm)
clearance to combustibles, framing
members, and attic or ceiling insulation
when running vertical chimney sections.
Attic insulation shield (96K94) may be used
to obtain the required clearances indicated
here. See installation accessories table on
Pages 36 and 37. The gap between the vent
pipe and a vertical fi restop can be sealed
with non-combustible caulking.
Align the dimple (four places) of
the upper vent section with the
opening of the locking incline
channel on the lower vent sec-
tion or appliance collar. Twist
vent component clockwise to
engage and seal until arrow and
dimple align.
Dimple
Locking
Incline
Channel
Connected Vent
Sections
Arrow
Arrow
Appliance Collar or
Vent Section
Blocking
Support Straps
(Plumber's tape)
8 feet (2.4 m)
Maximum
1/2 inch (12.7
mm) minimum
clearance to
combustibles
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