17
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
B-VENT GAS FIREPLACES (MPB33/35/40/45) • CARE AND OPERATION INSTRUCTIONS
WARNING
•
Air shutter adjustment should
only be performed by a
qualifi ed professional ser-
vice technician.
•
Ensure front glass panel is
in place and sealed during
adjustment.
CAUTION
•
Soot will be produced if
the air shutter is closed
too much. Any damage due
to sooting, resulting from
improperly setting the air
shutter, is not covered under
the warranty.
•
The air shutter door and
nearby appliance surfaces
are HOT. Exercise caution to
avoid injury while adjusting
fl ame appearance.
BURNER FLAME ADJUSTMENTS
1
. Refer to
Figures 11, 12, and 13
for
proper fl ame appearance. To adjust the
fl ame, move the rod up and down (the
adjustment rod is located in the lower
control area). Position the air shutter to
the factory setting as shown in
Table 7
.
2.
Light appliance (follow lighting procedure
on lighting label in control compartment
or in this
Care and Operation
Instructions
).
3.
Allow the burner to operate for at least
15 minutes while observing the fl ame
continuously to ensure that the proper
fl ame appearance has been achieved
.
If the following conditions are present,
adjust accordingly.
•
If
fl ame appears weak or sooty, adjust
the air shutter, incrementally, to a
more open position until the proper
fl ame appearance is achieved.
• If fl ame remains blue, adjust the air
shutter, incrementally, to a more
closed position until the proper fl ame
appearance is achieved.
4.
When satisfi ed that the burner fl ame
appearance is normal, turn the ON/OFF
control (unit-mounted or remote switch,
depending on your application) to the
OFF position.
5.
Reinstall the lower control access panel,
then proceed to fi nish the installation.
Millivolt Appliance Checkout
To light the burner, rotate the gas valve
control knob counterclockwise to the ON
position (“ON” will be at the top side of
the valve).
The pilot fl ame should be steady, not lifting
or fl oating. Flame should be blue in color
with traces of orange at the outer edge.
The top 3/8 in. (10 mm) at the pilot generator
(thermopile) and the top 1/8 in. minimum
(tip) of the quick drop out thermocouple
should be engulfed in the pilot fl ame.
The fl ame should project 1 in. (25 mm)
beyond the hood at all three ports
(see
Figure 14
)
.
Replace logs if removed for
pilot inspection.
MILLIVOLT
Thermocouple
Hood
Igniter Rod
3/8 in. Min.
(9 mm)
Thermopile
Pilot
Nozzels
Figure 14: Millivolt Pilot
Adjustment Rod Up
Air Shutter
Burner Tube
Adjusting Set Screw
Adjustment Rod Down
(fully open position)
(minimum air
opening position)
Model
Natural Gas
Propane Gas
MPB33
Fully Closed
3/16 in. (4.76 mm)
MPB35
Fully Closed
3/16 in. (4.76 mm)
MPB40
Fully Closed
3/16 in. (4.76 mm)
MPB45
Fully Closed
3/16 in. (4.76 mm)
Table 7: Main Burner Factory Air
Shutter Opening Settings
