Lennox International Inc. MERIT PLUS MPB3530CNM-B User Manual
Page 9

9
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
.
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406
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222
MPB33
MPB35
MPB40
MPB45
in.
mm
33-1/8
841 432
765 841
699
21-1/2
33-1/8
4
546
102
273
27-1/2
17
30-1/8
24-7/8
621
12-7/16
10-3/4
J
K
H
6-1/2
165
Schedule 40 Pipe
Length (feet)
Natural
Gas
Propane
Gas
0–10
1/2 in.
3/8 in.
10–40
1/2 in.
1/2 in.
40–100
1/2 in.
1/2 in.
100–150
3/4 in.
1/2 in.
150–200
3/4 in.
1/2 in.
Table 6: Schedule 40 Black Iron Pipe—
 Inside Diameter
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, ANSI Z223.1 (NFPA 54)—latest 
edition (USA) or CAN/CGA-B149.1—latest 
edition (Canada).
STEP 2. ROUTING GAS LINE
Route a 1/2" (13 mm) gas line as shown 
in Figure 11. Gas lines must be routed, 
constructed and made of materials that are 
in strict accordance with local codes and 
regulations. The appliance, as set up at the 
factory, is best suited for use with a gas line 
routed from the left side. The gas line may 
however be alternately routed from the right 
side. All appliances are factory-equipped 
with a fl exible gas line connector and 1/2 inch 
shutoff valve. (See Step 6 on Page 12).
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 qualifi ed individual such as a plumber 
or gas fi tter 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 
unfamiliar and unqualifi ed should attempt 
sizing or installing gas piping.
Notes:
• All appliances are factory-equipped with
a fl exible gas line connector and 1/2 inch 
shutoff valve (see Figure 46 on Page 25).
Also see Figure 12.
Figure 11: Route Gas Line
3"
(76 mm)
6-1/2"
(152 mm)
Pipe Coupling
(Recommended)
•
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 on
Page 12).
• 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.
• Check with local building offi cial for local
code requirements.
F
E
B
D
C
G
T op View
FRAMING
STANDOFFS
(Top, Sides,
and Rear)
Front View
3 (76)
A
J
H
Flue Outlet For B-V ent Connection
OPTIONAL ELECTRICAL
INLET KNOCKOU T
REQUIRING A FIELD
PROVIDED JUNCTION
BOX (Either Side)
GAS INLET 
(Either Side 
and bottom ) 
NOTE - Hood shown
as positioned
in louvered
front model.
ELECTRICAL INLET
2-3/4 x 2 (70 x 51) COVER 
PLA TE with KNOCKOUT) 
K
1/2 (13)
3 (76)
1
³⁄ ₈
(35)
(140)
5-1/2
9-3/8
(238)
2
(53)
Right Side View
(140)
5-1/2
9-3/8
(238)
1-3/8
(35)
Left Side View
GAS INLET
(See Also
Right Side View
)
ELECTRICAL INLET
(See Also
Right Side View )
3
(76)
OUTSIDE AIR
SHUTTER
8-15/16
(227)
7-3/8 
(187) 
ELECTRICAL
INLET
(Optional)
Figure 10: Fireplace Specifi cations
