Troubleshooting Guide - Millivolt; Troubleshooting The Millivolt Control System - Lennox Merit Series Care And Operation Instructions Manual

LENNOX HEARTH PRODUCTS • MERIT

TROUBLESHOOTING THE MILLIVOLT CONTROL SYSTEM

Note: Before troubleshooting, be sure that the appliance main line gas shut-off valve, the gas control valve and the wall
switch are in the "ON" position.
Important: Valve system troubleshooting should only be accomplished by a qualified service technician.
SYMPTOM
1. Spark igniter will not light pilot after
repeated triggering of igniter button.
WARNING: if the pilot will not light
after 1 minute of attempting, wait
for at least 5 minutes for gas to
clear before attempting again.
2. Pilot will not stay lit after
carefully following the lighting
instructions.
3. Pilot burning, no gas to burner, Valve
knob "ON," and the (standard) burner
OFF/ON switch is "ON." Read impor-
tant note below.
IMPORTANT NOTE: If an optional
*remote switch is used for burner
operation, the unit-mounted burner
OFF/ON switch (if installed) must be
in the "OFF" position.
*Optional remote switch kits - wall
switch, wall thermostat or remote
control.
4. Frequent pilot/burner outage prob-
lem.
SERIES DIRECT-VENT CONTEMPORARY DESIGN GAS FIREPLACES • MODEL MLDVTCD-35 • CARE AND OPERATION
®
POSSIbLE CAUSES
A. Defective igniter
(no spark at electrode).
b. Defective or misaligned electrode at pilot
(spark at electrode).
C. Gas supply pressure errant.
D. Pilot orifice plugged.
A. Defective pilot generator
(thermocouple).
A. Wall switch or wires defective.
b. Thermopile may not be generating suf-
ficient millivolts.
C. Plugged burner orifice.
D. OFF/ON Switch and *Remote Switch are
in the "ON" position resulting in excessive
resistance.
A. Pilot flame may be too low or blowing (high)
causing the pilot/valve safety to drop out.
CORRECTIVE ACTION
Check for spark at electrode and pilot; if no spark and
electrode wire is properly connected, replace igniter.
Using a match, light pilot. If pilot lights, turn off pilot
and trigger the igniter button again. If pilot lights, an
improper gas mixture caused the bad lighting and a
longer purge period is recommended. If pilot will not
light – check gap at electrode and pilot – should be
1/8" to have a strong spark. If gap does not measure
1/8", replace pilot (see Figures 9 or 10 on Page 15).
Check inlet gas pressure. It should be within the limits
as marked on the rating plate.
Clean or replace pilot orifice.
Check pilot flame, it must impinge on thermocouple
(see Figures 9 or 10 on Page 15). Clean and/or
adjust pilot for maximum flame impingement on
thermocouple. Ensure that the connection between
the valve and thermocouple are tight and secure.
Check wall switch and wires for proper connections.
Jumper wire across terminals at wall switch, if burner
comes on, replace defective wall switch. If okay, jumper
wires across wall switch wires at valve, if burner comes
on, wires are faulty or connections are bad.
Check thermopile with millivolt meter. Take reading
at thermopile terminals of gas valve. Should read
325 millivolts minimum with optional wall switch
"OFF." Replace faulty thermopile if reading is below
specified minimum.
Check burner orifice for blockage and remove.
When turning on the burner using a *remote switch,
ensure that the standard OFF/ON switch is in the "OFF"
position. If both switches are in the ON position, it may
result in excessive resistance (and millivolt drainage)
and the burner may not come on.
Clean and/or adjust pilot flame for maximum flame
impingement on thermocouple (see Figures 9 or 10
on Page 15).
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