39
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Step 9. Refer to Figure 64. Remove the
pilot hood assembly to access the hexed
pilot orifi ce. Remove and replace the orifi ce
with the one provided with the kit. Exercise
extreme care to prevent damage to or
breakage of the igniter assembly.
Pilot
Orifice
Figure 64: Millivolt Pilot
(electronic pilot is similar)
Step 10. Remove the orifi ce from the
manifold and replace it with the one provided
in the kit. See Table 10 for orifi ce sizes for
natural and propane models. Figure 65
illustrates the orifi ce.
Use pipe joint compound or Tefl on tape on
all pipe fi ttings before installing (ensure
propane resistant compounds are used in
propane applications, do not use pipe joint
compounds on fl are fi ttings).
Step 11. Retrieve the burner and hold the
venturi tube above the orifi ce. Place the
shutter adjusting rod in the slot of the shutter
arm (see Figure 60 on Page 34). Set the
burner assem bly into its position and secure
the trapezoidal plate with the two screws
previously removed.
Step 12. Reinstall the baffl e with the two
baffl e securing screws.
Step 13. Reassemble the remaining
components by reversing the procedures
outlined in the Steps 1–5.
Step 14. Attach the conversion label provided
in the conversion kit next to the rating plate
on the appliance.
Step 15. Turn on gas supply and test for gas
leaks (refer to Page 27).
Step 4. Carefully remove the logs. Exercise
care so as not to break the logs.
Step 5. Refer to Figure 53, 54, or 55.
A. Remove the grate and sub fl oor.
B. Remove the two (2) screws securing the
burner assembly.
C. Remove the burner assembly with
attached venturi tube.
Millivolt and Electronic Ignition
System Appliances
Step 6. SIT Systems—Refer to Figure 63
and the instructions provided with the SIT
Regulator Conversion Kit. Using a Torx
T20 driver (with 1/4 in. shank and center
hole) or slotted screwdriver, remove and
discard the pressure regulator mounting
screws (two screws for electronic models,
three screws for millivolt models), pressure
regulator tower, the diaphragm assembly
(if applicable) and the spring. Discard all
removed components.
Step 7. Install the new pressure regulator
assembly using the supplied screws as
shown in Figure 63. Tighten the screws to
25 lb-in.
Step 8. Install the enclosed identifi cation
label to the valve body where it can be easily
seen.
Step 16. 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 Page 33.
Step 17. Inspect the pilot system for proper
fl ame. The pilot fl ame should engulf the fl ame
sensor as shown in Figures 49 and 50 on
Page 27.
Step 18. 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.
Figure 65: Orifi ce
Figure 63: Regulator Conversion
Pressure
Regulator
Remove
These
Components
Electronic Valve
Millivolt Valve
Model
Series
Nat.Gas
drill size (inches)
Propane
drill size (inches)
MPDT33
MPDR33
#47 (0.0785 in.)*
99K74•
0.048 in.
99K78•
MPD35
#44 (0.086 in.)*
60J80•
#55 (0.052 in.)*
19L52•
MPD40
#38 (0.102 in.)*
99K76•
0.062 in.
21L01•
MPD45
#37 (0.104 in.)*
24M10•
#52 (0.0635 in.)*
37G00•
Table 10: Burner Orifi ce Sizes
Elevation 0–4500 ft ( 0–1372 m)
* Standard size installed at factory
• Part /Cat. Number
To Next Page
Loading...
Need help?
General
