Burner Flame Adjustments; Millivolt Appliance Checkout; Electronic Appliance Checkout - Lennox Hearth Products MERIT PLUS Care And Operation Instructions Manual

LENNOX HEARTH PRODUCTS • MERIT PLUS

Burner Flame Adjustments

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.
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • CARE AND OPERATION INSTRUCTIONS
®
1. Refer to Figures 10, 11, and 12 for proper
flame appearance. To adjust the flame, rotate
the adjustment rod toward the back or toward
the front of the fireplace (rod located in the
lower control area). Position the air shutter
to the factory setting as shown in the table
in Figure 13.
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.
Adjusting Set Screw
Adjustment Rod Up
Burner Tube
Air Shutter
Adjustment Rod Down
(fully open position)
Factory Air
Gas
Models Shutter Setting
Type
inches (mm)
Nat. 1/32 (0.8)
MPD33
Prop. 3/16 (4.76)
Nat. 1/32 (0.8)
MPD35
Prop. 3/16 (4.76)
Nat. 1/8 (3.2)
MPD40
Prop. 1/2 (13)
Nat. 1/8 (3.2)
MPD45
Prop. 1/2 (13)
Figure 13
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.

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 14).
Replace logs if removed for pilot inspection.
Thermocouple
Pilot
Nozzels
Figure 14 - SIT Millivolt Pilot

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 15.
(minimum air
opening position)
Flame Rod
(Sensor)
Figure 15 - SIT Electronic Pilot
Hood Igniter Rod
3/8 in. Min.
(9 mm)
Thermopile
Igniter
Pilot
Hood
17