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)
First Vent
Component
Align the dimple (four places)
with the opening of the locking
incline channel on appliance
collar. Twist vent component
clockwise to engage and seal.
Locking
Incline Channel
Dimple
Appliance collar
Vent / Appliance Collar
Connection
Align the dimple (four places) of the
upper vent section with the opening of
the locking incline channel on the
lower vent section. Twist vent
component clockwise to engage and
seal until arrow and dimple align.
Locking
Incline Channel
Dimple
Arrow
Connected
Vent Sections
Vent / Vent Section
Connection
Arrow
Arrow
1 inch
(25.4 mm)
minimum
clearance to
combustibles
Support Straps
(Plumber’s tape)
8 feet (2.4 m)
Maximum
Blocking
Figure 21
Figure 22
Figure 24
Figure 23
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 23.
d. 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. Remember to maintain 1" (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 35 and 36.
E. Support the vertical vent run sections -
Note - Proper venting support is very important.
The weight of the vent must not be supported
by the fireplace in any degree.
Support the vertical portion of the venting
system every 8 feet (2.4m) above the fireplace
vent outlet. One method of support is by utiliz-
ing field 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" length may be used to secure the
support straps to the vent pipe. See
Figure 24.
Vertical (Offset) Installation
Analyze the vent routing and determine the
quantities of vent sections and number of el-
bows required. Refer to Vertical Vent Figures
and Tables on page 14 to select the type of
vertical installation desired. Vent sections are
available in net lengths of 4-1/2" (114 mm),
10-1/2" (267 mm), 22-1/2" (572 mm), 34-1/2"
(876 mm) and 46-1/2" (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° configurations. Refer
to
Figure 25
for the SV4.5E45 and SV4.5E90
elbow dimensional specifications.
Where required, a telescopic vent section
(SV4.5LA) may be used to provide the installer
with an option in installing in tight and confined
spaces or where the vent run made up of fixed
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" (38 mm)
to 7-1/2" (191 mm). The SV4.5LA is fitted 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" (25 mm) clearance to
combustible materials for all vertical elements.
Clearances for all horizontal elements are 3"
(76 mm) on top, 1" (25 mm) on sides and 1"
(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" x 10-1/2" (267mm x 267mm)
inside dimensions, about this center mark
(
Figure 21
).
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 22
). 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" 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 require-
ments of the vertical vent figures 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.
B. Attach vent components to appliance -
Secure Vent SV4.5 direct vent system compo-
nents are unitized concentric pipe components
featuring positive twist lock connections (
see
Figure 19
).
All of the appliances covered in this document
are fitted with collars having locking inclined
channels. The dimpled end of the vent com-
ponents fit over the appliance collar to create
the positive twist lock connection.
