Step 3. Preparing Appliance Vent Collar; Step 4. Installing Vent System - Lennox MPDT33RNM Installation Instructions Manual

LENNOX HEARTH PRODUCTS • MERIT PLUS
Step 3. PREPARING APPLIANCE VENT
COLLAR (
MPd35/-40/-45 models with
combined top/rear vent)
Each of the unit's two vent collars are sealed
with a cover plate and a seal plate and gasket.
The cover, and seal plate and gasket must be
removed from the vent collar being used. Refer
to Figure 15 for top vent usage and Figure 16
for rear, and the following steps to prepare the
appropriate collar for use.
From the vent collar being used, remove the four
screws securing the vent seal plate and gasket.
Remove and discard the seal plate and gasket.
When the top vent collar is being used, from
inside the firebox, loosen the two screws in the
keyhole slots of the cover plate and remove the
remaining two cover plate securing screws.
Remove and discard the cover plate. Reinstall
and securely tighten all four screws.
When the rear vent collar is being used, from
inside the firebox, remove the two screws
securing the lintel to the rear wall of the firebox,
then remove the lintel. Remove the four cover
plate securing screws. Remove and discard
the cover plate.
Reinstall and securely tighten all four cover
plate screws. Re-secure the lintel to the rear
wall of the firebox.
WARNING
Failure to reinstall and securely
tighten cover plate screws could
result in leakage of flue products
into the living space. Vent cover
plate and vent seal cap must
remain securely installed on
unused vent collar. Failure to
do so could result in leakage of
flue products into living space.
Installation of Vent Restrictor
A vent restrictor may be needed with this
appliance, install vent restrictor (provided)
in the appliance top flue outlet as shown in
Figure 17 (MPDT33, MPD35, MPD40 and
MPD45) or rear flue outlet as shown in Figure
18 (MPD35, MPD40 and MPD45). It is held in
place by friction, only.
NOTE: The vent restrictor is included in the
firebox.
12
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
®
TOP VENT SEAL AND COVER PLATE REMOVAL
WHEN USING THE TOP VENT
KNOCKOUT
(OUTSIDE UNIT)
GASKET
CABINET TOP
TOP VENT
FIREBOX TOP
VENT
COVER PLATE
COVER PLATE
SECURING SCREWS
(INSIDE UNIT)
CROSS SECTION
Figure 15 - Top vent seal and cover plate
removal - MPD35/40/45 series models
(combined top and rear vent units)
REAR VENT SEAL AND COVER PLATE REMOVAL
WHEN USING THE REAR VENT
COVER PLATE
SECURING SCREWS
CAP AND
GASKET
REAR VENT
(INSIDE UNIT) (OUTSIDE UNIT)
CROSS SECTION
Figure 16 - Rear vent seal and cover plate
removal - MPD35/40/45 series models
(combined top and rear vent units)
A vent restrictor may be needed when vertically
terminating the vent system above the roof
(when using the appliance top vent),install vent
restrictor in the top vent of the fireplace outlet
on MPd35/40/45 and MPdT33 series models.
If needed, install the restrictor orientated as
shown, either from inside or outside the unit,
in the inner fireplace collar.
U-Shaped Vent
Restrictor
Inner Fireplace
Appliance Top
Collar
Vent Outlet
Figure 17 - Vent restrictor installation -
Top vent
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
A vent restrictor may be needed when
horzontally terminating the vent system from
the rear of the appliance (when using the
appliance rear vent), install vent restrictor in
the rear vent of the fireplace outlet on
MPD35/40/45 series models, in any
installation that has a vertical vent run in
excess of three feet (0.914 meters).
If needed, install the restrictor orientated as
shown, either from inside or outside the unit,
in the inner fireplace collar.
INNER FIREPLACE
COLLAR
Figure 18 -Vent restrictor installation -
KNOCKOUT
Rear vent
Select Venting System - Horizontal or Vertical
With the appliance secured in framing, determine
vent routing and identify the exterior termination
location. The following sections describe
vertical (roof) and horizontal (exterior wall)
vent applications. Refer to the section relating
to your installation. A list of approved venting
CABINET BACK
components are shown on Pages 36 and 37.
Use only approved vent components (see
Approved Vent Components on Page 2).
These fireplaces must be vented directly
to the outside.
The vent system may not service multiple
appliances, and must never be connected to
a flue serving a separate solid fuel burning
appliance. The vent pipe is tested to be run
inside an enclosed wall (such as a chase). There
is no requirement for inspection openings in the
enclosing wall at any of the joints in the vent pipe.

Step 4. INSTALLING VENT SYSTEM

These instructions should be used as a
guideline and do not supersede local codes
in any way. Install venting according to local
codes, these instructions, the current National
Fuel Gas Code (ANSI-Z223.1) in the USA or
the current standards of CAN/CGA-B149.1
in Canada.
Ensure clearances are in accordance with
local installation codes and the requirements
of the gas supplier.
dégagement conforme aux codes d'installa-
tion locaux et aux exigences du foumisseunde
gaz.
APPLIANCE REAR
VENT OUTLET
U-SHAPED VENT
RESTRICTOR