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15
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
BURNER ADJUSTMENTS
(QUALIFIED TECHNICIANS ONLY)
Flame Appearance and Sooting
Proper flame appearance is a flame which is
blue at the base and becomes yellowish-orange
in the body of the flame. When the appliance
is first lit, the entire flame may be blue and will
gradually turn yellowish-orange during the first
15 minutes of operation. After 15 minutes of
operation, if the flame is blue, or if the flame is
orange with evidence of sooting (black tip), the
air shutter opening may need to be adjusted.
If the air shutter opening is closed too far, sooting
may develop. Sooting is indicated by black puffs
developing at the tips of very long orange flames.
Sooting results in black deposits forming on the
logs, appliance inside surfaces and on exterior
surfaces adjacent to the vent termination.
Sooting is caused by incomplete combustion in
the ames and lack of combustion air entering
the air shutter opening. To achieve a warm
yellowish-orange flame with an orange body
that does not soot, the shutter opening must be
adjusted between these two extremes.
Air Shutter Adjustment Guidelines
• If there is smoke or soot present, rst check
the log set positioning to ensure that the
flames are not impinging on any of the logs.
If the log set is properly positioned and a
sooting condition still exists, then the air
shutter opening should be increased.
• The more offsets in the vent system, the larger
the air shutter opening will need to be.
• An appliance operated with the air shutter
opened too far, may have flames that appear
blue and transparent. These weak, blue and
transparent flames are termed anemic.
• Propane models may exhibit ames which
candle or appear stringy. If this is present and
persists, adjust the air shutter to a more open
position, then operate the appliance for a few
more minutes to ensure that the flame normal-
izes and the flames do not appear sooty.
The following chart is provided to aid you in
achieving the correct air shutter adjustment
for your installation.
Air Shutter Adjustment Guidelines:
Amount of
Primary Air
Flame
Color
Air Shutter
Adjustment
If air shutter is
closed too far
Flame will
be orange
Air shutter
gap should be
increased
If air shutter is
open too far
Flame will
be blue
Air shutter
gap should be
decreased
Figure 11 - Burner Flame Appearance Models MLDVT-30 and MLDVT-35
Figure 12 - Burner Flame Appearance Models MLDVT-40 and MLDVT-45