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LENNOX HEARTH PRODUCTS • MERIT
Burner Assembly
Gas Valve
Assembly
Figure 31: SIT Millivolt System
Pressure
Regulator
Figure 32: SIT Millivolt System
Step 6. (Millivolt systems only): Attach ma-
nometer to the manifold side pressure
test fitting and verify manifold pressure
reads 3.5 inches water column (0.87
kPa) for natural gas, and 10.0 inches
water column (2.49 kPa) for propane
gas.
Step 7. (Millivolt systems only): Refer to Figure
33. Remove the pilot hood assembly to
access the hexed pilot orifice. Remove
and replace the orifice with the one
provided in the kit.
Skip to Step 10.
Pilot
Orifice
Figure 33: SIT Millivolt System
26
SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS
®
Electronic Appliances
Step 8. dexen Electronic Valves: Refer to
Orifice
Supply Gas
Inlet
Remove
Pilot Gas Outlet
These
Components
Figure 34: Dexen Electronic Gas Valve
Step 9. Refer to Figure 35. Follow these steps
ELECTRONIC
Sensor
Igniter
Figure 35: Dexen Electronic System
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Figure 34 and the instructions pro-
vided with the kit.
a. Remove and discard the two pres-
sure regulator mounting screws.
b. Remove the pressure regulator and
diaphragm.
c. discard all removed components.
d. Make sure the provided diaphragm
is installed properly onto the re-
placement pressure regulator.
e. Install the new pressure regulator
using the new screws supplied with
the kit; tighten the screws.
Pressure-Tap
Burner Stage
(Manifold)
Terminal
Regulator
Mounting
Screw
To Burner
PILOT
Pressure-Tap
Pilot Stage
(Inlet)
Terminal
Ground (TP)
to replace the pilot orifice:
a. Remove pilot hood assembly to
access the phillipped pilot orifice.
b. 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.
Pilot
Hood
All Models
Note the following:
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 10. Refer to Figure 31.
a. VERIfY PROPER ORIfICE SIzE
BEfORE INSTALLING IT.
b. Remove the orifice from the mani-
fold and replace it with the one
provided in the kit. See Table 7 for
orifice sizes for natural and propane
models. Figure 36 illustrates the
orifice. Always check and verify
orifice size.
Gas
Outlet
c. Retrieve the burner. Slide the venturi
tube over the orifice.
d. Adjust the burner air shutter as
shown in Figure 26 on Page 21.
Burner Orifice Sizes
Elevation 0-4500 feet ( 0-1372 meters)
Model
Nat.Gas
Series
drill size (inches)
#48 (0.076")*
MLBV-35
H1236•
#43 (0.089")*
MLBV-40
99K75•
*
Standard size installed at factory.
Table 7
• Part /Cat. Number.
Figure 36
Step 11. Reassemble the remaining compo-
nents by reversing the procedures
outlined in the preceding steps.
Step 12. Attach the conversion label (provided
in the conversion kit) next to the rat-
ing plate on the appliance.
Step 13. Turn on gas supply and test for gas
leaks (refer to Page 16).
ALWAYS TEST PRESSURES WITH THE VALVE
REGULATOR CONTROL AT THE HIGHEST
SETTING.
Propane
drill size (inches)
#56 (0.046")*
62L37 •
#55 (0.052")*
19L52•
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