18
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
qualified 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
flame appearance.
BURNER FLAME ADJUSTMENTS
1
. Refer to
Figures 12, 13, and 14
for proper
flame appearance. To adjust the flame, 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
Figure 15
.
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 flame
continuously to ensure that the proper
flame appearance has been achieved
.
If the
following conditions are present, adjust
accordingly.
• If flame appears weak or sooty, adjust
the air shutter, incrementally, to a more
open position until the proper flame
appearance is achieved.
• If flame remains blue, adjust the air
shutter, incrementally, to a more
closed position until the proper flame
appearance is achieved.
4.
When satisfied that the burner flame
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 finish 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 flame should be steady, not lifting
or floating. Flame should be blue in color with
traces of orange at the outer edge.
The top 3/8" (10 mm) at the pilot generator
(thermopile) and the top 1/8" minimum (tip)
of the quick drop out thermocouple should be
engulfed in the pilot flame.
The flame should project 1" (25 mm) beyond
the hood at all three ports
(see
Figure 16
)
.
Replace logs if removed for pilot inspection.
Electronic Appliance Checkout
Turn the ON/OFF control (unit-mounted or
remote switch, depending on your application)
to the ON position.
The pilot flame should engulf the flame rod, as
shown in
Figure 17
.
Thermocouple
Hood Igniter Rod
Thermopile
Pilot
Nozzels
3/8”
(9 mm)
Min
Figure 16 - Millivolt Pilot
Figure 17 - Electronic Pilot
Pilot
Hood
Flame Rod
(Sensor)
Igniter
Model
Natural Gas
Propane Gas
MPB 33
Fully Closed 3/16" (4.76 mm)
MPB35
Fully Closed 3/16" (4.76 mm)
MPB40
Fully Closed 3/16" (4.76 mm)
MPB45
Fully Closed 3/16" (4.76 mm)
Adjustment Rod Up
Air Shutter
Burner Tube
Adjusting Set Screw
Adjustment Rod Down
(fully open position)
(minimum air
opening position)
Figure 15
Main Burner Factory
Air Shutter Opening Settings
