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NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
WARNINGS
• 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.
CAUTIONS
• Sootwill beproducedif 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
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT
®
SERIES DIRECT-VENT GAS FIREPLACES • MODELS MLDVT-30/35/40/45 • CARE AND OPERATION INSTRUCTIONS
Electronic Appliance Checkout
To light the burner, refer to the lighting instruc-
tions on Page 23. Ensure the igniter lights the
pilot. The pilot flame should engulf the flame
sensor as shown in Figure 15.
ELECTRONIC PILOT ASSEMBLY
Thermocouple
Thermopile
Pilot
Nozzels
SIT MILLIVOLT PILOT ASSEMBLY
3/8" Min.
(9 mm)
Igniter Rod
Pilot Hood
Proper Pilot Flame Appearance
Millivolt Appliance Checkout
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 14).
To light the burner, refer to the lighting instruc-
tions on Page 21.
Figure 14
Note: If the igniter is damaged, a
replacement kit is available, order
Catalog Number 87L54.
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: Rotating 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, Pages 21 and 22
in this manual).
3. Allow the burner to operate for at least 15 min-
utes while observing the flame continuously
to ensure that the proper flame appearance
has been achieved (see Figure 11 or 12). 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 Page 15).
ELECTRONIC
Pilot
Hood
Sensor
Igniter
Main Burner Factory Air Shutter
Opening Setting - Inches (millimeter)
Model Natural
Gas
Propane
Gas
MLDVT-30
1/32"
(0.795 mm)
1/8"
(3.2 mm)
MLDVT-35
1/32"
(0.795 mm)
1/8"
(3.2 mm)
MLDVT-40
1/32"
(0.795 mm)
1/4"
(6.4 mm)
MLDVT-45
1/32"
(0.795 mm)
3/16"
(4.8 mm)
Adjustment
Rod Up
(closed min.
position)
Air Shutter
Burner
Tube
Adjustment Set-Screw
Ref. Air shutter Patent:
U.S. Pat. 5,553,603
Adjustment Rod Down
(fully open air opening
position)
Burner Air Shutter Adjustment
Figure 13
Figure 15