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LENNOX HEARTH PRODUCTS • MERIT PLUS
Step 2. Install the new pressure regulator
assembly using the supplied screws. Tighten
the screws with a torque of 25 lb-in.
Pressure
Regulator
Remove
These
Components
Millivolt Valve
Electronic Valve
Figure 38 - Regulator Conversion
Step 3. Install the enclosed identification label
to the valve body where it can be easily seen.
Step 4. Refer to Figure 39. Remove the pilot
hood assembly to access the hexed pilot orifice.
Remove and replace the orifice with the one
provided with the kit. Exercise extreme care to
prevent damage to or breakage of the igniter
assembly. Step 5. Remove the burner orifice
from the manifold and replace it with the one
provided in the kit. See Table 8 for orifice sizes
for natural and propane models. Figure 40
illustrates the orifice.
Lennox Hearth Products reserves the right to make changes at any time, without notice, in
design, materials, specifications, prices and also to discontinue colors, styles and products.
Consult your local distributor for fireplace code information.
LENNOX
, the LENNOX design, DAVE LENNOX, the image of DAVE LENNOX and other related
®
LENNOX marks are registered or common law trademarks of Lennox Industries Inc. and are used
with permission.
Printed in U.S.A. © 2012 Lennox Hearth Products LLC
P/N 506015-05 Rev. D 04/2013
B-VENT GAS FIREPLACES (MPB33/35/40/45) • INSTALLATION INSTRUCTIONS
®
Pilot
Orifice
Figure 39 - Millivolt Pilot
Figure 40 - Orifice
Use pipe joint compound or Teflon tape on all
pipe fittings before installing (ensure propane
resistant compounds are used in propane
applications, do not use pipe joint compounds
on flare fittings).
Step 6. Retrieve the burner and hold the venturi
tube above the orifice. Set the burner assem bly
into position and secure with the two screws
previously removed.
Step 7. Reassemble the remaining components
by reversing the procedures outlined in the
Steps 1 - 5.
Step 8. Attach the conversion label provided
in the conversion kit next to the rating plate on
the appliance.
Step 9. Turn on gas supply and test for gas
leaks (refer to Page 12).
Step 10. Reapply electrical power at the circuit
breaker.
Step 11. Relight the main burner. The lighting
instructions can be found on the lighting label
in the control compartment or in the Care and
Operation Manual provided with the appliance.
Verify proper burner ignition and operation.
See Burner Adjustments and Burner Flame
Appearance on Pages 19 and 20.
Step 12. Inspect the pilot system for proper
flame. The pilot flame should engulf the flame
sensor as shown in Figures 24 and 25 on
Page 14.
Step 13. Using a manometer, test the inlet and
manifold gas pressures (see Tables 2 and 3
on Page 4).
ALWAYS TEST PRESSURES WITH THE VALVE
REGULATOR CONTROL AT THE HIGHEST
SETTING.
Burner Orifice Sizes
Elevation 0-4500 feet ( 0-1372 meters)
Model
Nat.Gas
Series
drill size (inches)
#47 (0.0785")*
MPB33
99K74 •
#44 (0.086")*
MPB35
60J80 •
#38 (0.102")*
MPB40
99K76 •
#37 (0.104")*
MPB45
24M10 •
* Standard size installed at factory
Table 8
• Part /Cat. Number
1508 Elm Hill Pike, Suite 108 • Nashville, TN 37210
Propane
drill size (inches)
(0.048")*
99K78 •
#55 (0.052")*
19L52 •
(0.062")*
21L01 •
#52 (0.0635")*
37G00 •
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