20
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
WARNING
•
Air shutter adjustment should
only be performed by a
qualified professional service
technician.
•
Ensure the 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.
Main Burner Factory Air Shutter
Opening Setting - Inches (millimeter)
Model
Natural Gas
Propane Gas
MPB33
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
(minimum air
opening position)
Air Shutter
Burner Tube
Adjusting Set Screw
Adjustment Rod Down
(fully open position)
1
. Refer to
Figures 32, 33, and 34
for proper
flame appearance. To adjust the flame, refer
to
Figure 35
and 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 8
.
2.
Light appliance (follow lighting procedure
on lighting label in control compartment or
in the 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 appear-
ance is normal, reinstall the lower control
compartment door, then proceed to finish
the installation.
Figure 32 - MPB33 MODEL
Figure 33 - MPB35 MODEL
Figure 34 - MPB40 AND MPB45 MODEL
Figure 35 - Air Shutter Opening Setting
Burner Air Shutter Adjustment
