9
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
DIRECT VENT GAS FIREPLACES (MPDP35/40) • INSTALLATION INSTRUCTIONS
Side
Framing
Unit Nailing Flange
(No clearance to
combustible framing
is required.)
Unit Secured to Framing
by Nailing Flange
Header Spacing Top Standoffs
(two pairs on front edge of firebox top)
Lift up outer pair for
1/2" finish materials.
Lift up inner pair for
5/8" finish materials.
Left Side Front Corner of Fireplace Shown
(Right side requirements are the same)
Note: The nailing flanges, combustible members
and screw heads located in areas directly adjacent
to the nailing flanges, are EXEMPT from the 1/2"
clearance to combustible requirements for the
firebox outer wrapper
. Combustible framing may be
in
direct contact with the nailing flanges and may
be located closer than 1/2" from screw heads and
the firebox wrapper in areas adjacent to the nailing
flanges. Frame the opening to the exact dimensions
specified in the framing details of this manual.
IMPORTANT!
Install top standoff
and bend up appropriate
drywall backstops (1/2" or 5/8")
before installing fireplace.
Figure 11
Figure 10
PRE-INSTALLATION STEPS
The appliance is shipped with all gas controls
and components installed and pre-wired.
Before installing the fireplace, follow these steps:
1. Remove the shipping carton.
2. Remove the shipping pad, exposing the front
glass door.
3. Open the two spring latches securing the
glass door (under the firebox floor). Remove
the door by tilting it outward at the bottom
and lifting it up. Set aside the door, taking
care to protect it from inadvertent damage
(see Removing and Installing the Glass Door
on Page 32).
4. Remove the log set and top vent flue
restrictor from the firebox. Handle logs
carefully to prevent breakage.
5. Remove the embers and volcanic stone from
the control compartment.
6. Remove top standoff and hood (taped to
back of outer wrapper).
7. Remove the 4 screws on top, and install the
top standoff with the 4 screws (Figure 10).
DETAILED INSTALLATION STEPS
Step 1. FRAMING
Frame the appliance as illustrated in Figures
12 and 13 on Pages 10 and 11 (Figure 13
applies to corner framing installations only).
All framing details must allow for a minimum
clearance to combustible framing members as
shown in Table 5 on Page 8.
If the appliance is to be elevated above floor level,
a solid continuous platform must be constructed
below the appliance.
Headers may be in direct contact with the ap-
pliance top standoff spacer, maintaining the 4"
clearance to the fireplace top, but must not be
supported by them or notched to fit around
them. All construction above the appliance
must be self-supporting. DO NOT use the ap-
pliance for structural support.
Secure the fireplace to the side framing members
using the unit’s nailing flanges — one top and
bottom on each side of the fireplace front. See
Figure 11. Use 8d nails or their equivalent.
TYPICAL INSTALLATION SEQUENCE
The typical sequence of installation is outlined
below; however, each installation is unique and
may result in variations to the steps described.
See the pages referenced in the following steps
for detailed procedures.
Step 1. FRAMING (Page 9): Construct the ap-
pliance framing. Position the appliance within
the framing and secure with nailing brackets.
IMPORTANT! Before installing the fireplace,
install the top standoff on the top front edge
of the fireplace using the 4 existing screws
on the fireplace top (see Figure 10). Then,
bend up the applicable drywall backstops on
the top standoff (1/2" or 5/8"), based on the
thickness of the drywall/finish material to be
used (see Figure 10).
Bend out the appropriate side nailing flanges for
the drywall/finish material to be used. Nailing
flanges are provided for flush framing, 1/2-inch
and 5/8-inch framing depths (see Figure 11).
Step 2. ROUTING GAS LINE (Page 11): Route
gas supply line to appliance location.
Step 3. PREPARING APPLIANCE VENT COLLAR
(Page 12).
Step 4. INSTALLING VENT SYSTEM (Page 12):
Install the vent system and exterior termination.
Step 5. FIELD WIRING (Page 26): Field wire
and install operating control switch.
Step 6. REMOTE CONTROL SYSTEM (Page
27).
Step 7. CONNECTING GAS LINE (Page 28):
Make connection to gas supply.
Step 8. VERIFYING APPLIANCE OPERATION
(Page 28).
Step 9. INSTALL LOGS, VOLCANIC STONE,
AND GLOWING EMBERS (Page 29).
Step 10. INSTALLING GLASS DOOR ASSEM-
BLY (Page 32).
Step 11. BURNER ADJUSTMENTS (Page 32):
Adjust burner to ensure proper flame appear-
ance.
Step 12. HOOD INSTALLATION (Page 34).
Step 13. ATTACHING SAFETY-IN-OPERATION
WARNINGS (Page 35).
NOTE: The nailing flanges, combustible
members, and screw heads in areas directly
adjacent to the nailing flanges are EXEMPT
from the 1/2" clearance to combustible
requirements for the firebox outer wrapper.
Combustible framing may be in direct contact
with the nailing flanges and may be located
closer than 1/2" from screw heads and the
firebox wrapper in areas adjacent to the
nailing flanges.
Frame the opening to the exact dimensions
specified in the framing details in this manual.
Top Standoff
(installed)
Drywall Backstops
(bent up for 1/2"
or 5/8")
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