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NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT
®
SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • CARE AND OPERATION INSTRUCTIONS
WARNING
• Air shutter adjustment should
only be performed by a quali-
fied professional service
technician.
• Ensure front glass panel are
in place and sealed during
adjustment.
CAUTION
• Soot will be produced if the
air shutter is closed too much.
Any damage due to carboning
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 Air Shutter Adjustment
Procedure
Electronic Appliance Checkout
To light the burner, refer to the lighting instruc-
tions on Page 24. Ensure the igniter lights the
pilot. The pilot flame should engulf the flame
sensor as shown in Figure 15.
APPLIANCE CHECKOUT
Millivolt Appliance Checkout
The pilot ame 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 14).
To light the burner, refer to the lighting instruc-
tions on Page 22.
Thermocouple
Thermopile
Pilot
Nozzels
SIT MILLIVOLT PILOT ASSEMBLY
3/8" Min.
(9 mm)
Igniter Rod
Pilot Hood
Proper Pilot Flame Appearance
Figure 14
1. Locate adjustment rod and adjust air shutter
to the standard setting as shown in Figure
13 (adjustment rod is located in the lower
control compartment).
Note: Move the adjustment rod DOWN
to decrease air and UP to increase air.
2. Light appliance (follow lighting procedure
on lighting label in control compartment or
see the lighting instructions on Pages 22
and 24 in this manual).
ELECTRONIC PILOT ASSEMBLY
ELECTRONIC
Pilot
Hood
Sensor
Igniter
Figure 15
Burner Air Shutter Adjustment
Figure 13
Main Burner Factory Air Shutter
Opening Setting
Inches (millimeter)
Model Natural
Gas
Propane
Gas
MLBV-35
1/32
(0.795)
3/16"
(4.763)
MLBV-40
1/32
(0.795)
3/16"
(4.763)
Adjustment
Rod Up
(Fully Open
Position)
Air Shutter
Adjustment Rod Down min.
air opening position)
Burner
Tube
Adjustment Set-Screw
Ref. Air shutter Patent:
U.S. Pat. 5,553,603
3. Allow the burner to operate for at least 15
minutes while observing the flame continu-
ously to ensure that the proper flame ap-
pearance has been achieved (see Figures 11
and 12 on previous Page). If the following
conditions are present, adjust accordingly.
• If ame appears weak or sooty, adjust
the air shutter, incrementally, to a more
open position until the proper flame
appearance is achieved.
• If ame stays lowered blue, adjust the
air shutter, incrementally, to a more
closed position until the proper flame
appearance is achieved.
4. Leave the control knob (off/pilot/on) in the
ON position and the burner OFF/ON switch
OFF (and remote switches, if applicable).
5. When satisfied that the burner flame ap-
pearance is normal, close the lower control
compartment door (see Figures 11 and 12
on previous Page).