Lennox MPD35ST-NM-B Installation Instructions Manual page 14

Figure 19
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 20 ). 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 cre-
ate the positive twist lock connection.
Align the dimple (four places) of the
upper vent section with the opening
of the locking incline channel on the
lower vent section or appliance col-
lar. Twist vent component clockwise
to engage and seal until arrow and
dimple align.
Arrow
Dimple
Locking Incline
Channel
Connected Vent
Sections
Appliance Collar or
Vent Section
Figure 20
4
To attach a vent component to the appliance
collar, align the dimpled end over the collar,
0-/2" Min.
(267 mm)
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 20). 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
0-/2" Min.
until they seat at the end of the channels. The
(267 mm)
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 not required as the pipe will securely
lock when twisted.
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 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. 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 20.
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 " (25 mm)
Arrow
clearance to combustibles, framing members,
and attic or ceiling insulation when running ver-
tical chimney sections. Attic insulation shield
(96K94) may be used to obtain the required
clearances indicated here. See installation
accessories on Pages 34 & 35.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
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 (2.4 m) 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 21.
8 feet (2.4 m)
Figure 21
Another method, where the vent is not adjacent
to a wall, is illustrated in Figure 22. Here,
support straps (96K93) and support plates
(96K92) can be used to support the weight
of the vent.
Blocking
Support Straps
(Plumber's tape)
Maximum
 inch (25.4
mm) minimum
clearance to
combustibles