Filter
Top Products
12
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT
®
PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
FIREPLACE FRAMING SPECIFICATIONS
Schedule 40
Black Iron Pipe
Inside Diameter (Inches)
Schedule 40 Pipe
Length (feet)
Natural
Gas
Propane
Gas
0-10 1/2 3/8
10-40 1/2 1/2
40-100 1/2 1/2
100-150 3/4 1/2
150-200 3/4 1/2
Table 6
Notes:
• All appliances are factory-equipped with
a flexible gas line connector and 1/2 inch
shutoff valve (see Figure 50 on Pagec 25).
• See Massachusetts Requirements on Page
4 for additional requirements for installations
in the state of Massachusetts in the USA.
• The gas supply line should Not be connected
to the appliance until Step 6 (Page 25).
• A pipe joint compound rated for gas should be
used on the threaded joints. Ensure propane
resistant compounds are used in propane
applications. Be very careful that the pipe
compound does not get inside the pipe.
• It is recommended to install a sediment trap
in the supply line as close as possible to the
appliance. Appliances using Propane should
have a sediment trap at the base of the tank.
• Check with local building official for local
code requirements (i.e. are below grade
penetrations of the gas line allowed?, etc).
IMPORTANT: If propane is used, be aware that
if tank size is too small (i.e. under 100-lbs, if
this is the only gas appliance in the dwelling.
Ref. NPFA 58), there may be loss of pressure,
resulting in insufficient fuel delivery (which
can result in sooting, severe delayed ignition
or other malfunctions). Any damage resulting
from an improper installation, such as this,
is not covered under the limited warranty.
Proper Sizing of Gas Line
Properly size and route the gas supply line
from the supply regulator to the area where the
appliance is to be installed per requirements
outlined in the National Fuel Gas Code, NFPA
54 - latest edition (USA) or CAN/CSA-B149.1
- latest edition (Canada).
Step 2. ROUTING GAS LINE
Route a 1/2" (13 mm) gas line to the left side
of the appliance as shown in Figure 15. Gas
lines must be routed, constructed and made
of materials that are in strict accordance with
local codes and regulations. All appliances
are factory-equipped with a flexible gas line
connector and 1/2-inch shutoff valve. (See
Step 6 on Page 25).
Never use galvanized or plastic pipe. Refer to
Table 6 for proper sizing of the gas supply line,
if black iron pipe is being used. Gas lines must
be routed, constructed and made of materials
that are in strict accordance with local codes
and regulations. We recommend that a quali-
fied individual such as a plumber or gas fitter
be hired to correctly size and route the gas
supply line to the appliance. Installing a gas
supply line from the fuel supply to the appliance
involves numerous considerations of materials,
protection, sizing, locations, controls, pressure,
sediment, and more. Certainly no one unfamil-
iar and unqualified should attempt sizing or
installing gas piping.
Figure 14: Corner Framing with Horizontal Termination
Also see Figure 13.
Figure 15: Route Gas Line
3"
(76 mm)
Left Side Front
Corner of Fireplace
Framing
6-1/2"
(152 mm)
Pipe Coupling
(Recommended)
Note:
• Rear Vent Applications in Corner Installations: The horizontal vent length
(from
a
to
b
) must not exceed 28 inches (711 mm).
• MPDT-3328 AND MPDR-3328 Models: Dimensions A through F occur when
one 45-degree elbow is connected directly to the appliance collar.
• MPD-3530, MPD-4035, and MPD-4540 Models: Dimensions D through F
occur when one 45-degree elbow is connected directly to the appliance collar.
.oNledoM A B C D E F
8233-TDPM
8233-RDPM
.ni 8/133 2/184 61/543 61/371 4/142 5
mm 148 2321 278 734 616 721
0353-DPM
.ni 8/153 2/175 8/504 61/391 4/382 8/16
mm 298 1641 2301 784 037 651
5304-DPM
.ni 8/104 61/316 23/1134 61/391 61/1103 8/77
mm 9101 4551 1011 784 977 002
0454-DPM
.ni 8/154 8/366 61/5164 61/391 61/333 4/39
mm 6411 6861 2911 784 348 842
C
Back wall of chase/enclosure (including any finishing materials)
7"
(178 mm)
MPD and MPDR units
D
E
F
A
B
MPD and MPDT units
b
a