Troubleshooting Guide - Millivolt Gas Control System - Lennox Hearth Products MERIT PLUS Care And Operation Instructions Manual

LENNOX HEARTH PRODUCTS • MERIT PLUS

TROUBLESHOOTING GUIDE - MILLIVOLT GAS CONTROL SYSTEM

NOTE: Before troubleshooting the gas control system, Ensure external gas shut off valve, located at gas supply inlet, (and wall switch, if applicable), is 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, if the standard burner
OFF/ON switch is still installed on
appliance it must be in the "OFF"
position.
*Optional remote switch kits - wall
switch, thermostat or timer, or
remote control.
4. Frequent pilot/burner outage prob-
lem.
28
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • CARE AND OPERATION INSTRUCTIONS
®
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 & *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 measures 1/8",
replace pilot (Figure 14 on Page 17).
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
(Figure 14 on Page 17). 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 (& millivolt drain-
age) and the burner may not come on.
Clean and/or adjust pilot flame for maximum flame im-
pingement on thermocouple (Figure 14 on Page 17).