Emerson 50A55 User Manual

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INTEGRATED FURNACE
CONTROL MODULE
TROUBLESHOOTING
GUIDE
50A55 INTEGRATED FURNACE CONTROL MODULE
QualiedServiceman’sTroubleshootingGuide
TROUBLESHOOTING PROCEDURE
Ifthelightonthemoduleisoncontinuously,thefaultislikelytobeinternaltothe
module.Tomakesure,interruptlineor24voltthermostatpowerforafewseconds
andthenrestore.Ifinternalfaultisindicatedagain,andamesensorisnotshorted
toground,replacecontrol.Aashinglightindicatestheproblemismostlikelyinthe
external components or wiring. Proceed as follows:
WARNING
!
Failure to read and follow all
instructions carefully before in-
stalling or operating this control,
could cause personal injury and/
or property damage.
WARNING
!
Turn power off before any troubleshooting or servicing begins.
Line voltage (120 VAC) could be present on the surface of the ignitor, if the sys-
tem is not correctly wired. Such voltage can cause serious injury or death.
Thefollowingstepsmustbeperformedrstbeforeanytroubleshootingbegins.
1)Disconnectelectricpowertosystematmainfuseorcircuitbreaker.
2)Visuallyinspectequipmentforapparentdamage.Checkwiringforloose
connections.
3)Checkforpropergroundingandreversedpolarity.
A. CheckcontinuityforCterminalonmoduletoelectricalservicegroundand
connectionatthefurnacejunctionbox.Ifgroundconnectionisopen,check
module ground connection and the electrical service ground connection.
Repair and retest.
B. Re-connect electric power to system.
C. Checkforvoltagebetweenthelineneutralterminalandfurnaceground.If
voltage exists, the main power supply lines are improperly connected to the
furnace (REVERSED POLARITY). Again disconnect electric power to system;
then reverse incoming supply leads to furnace. Repeat step.
D. Rechecksystemforproperoperation.
If neither apparent damage, loose connection nor reversed polarity is the problem,
proceed to troubleshooting chart or fault index chart that is suggested by the actual
condition.
NOTE: This troubleshooting guide is not for 50A55-4XX modules found on Trane
equipmentor50A55-1XXmodulesfoundonLennoxequipment.
FAULT INDEX CHART
No manual fan ............................................ 1A - 1K
Power supply and voltage .......................... 1C - 1G
No fan at cooling speed .............................. 2A - 2L
No induced draft motor ............................... 3A - 3H
LEDashing2Xwithoutinducer................. 3E
LEDashing3Xwithinducer...................... 3I - 3O
Ignitor does not glow .................................. 4A - 4D
Burner does not stay lit ............................... 4E - 4N
Gas supply problem.................................... 4F - 4K
No outlet pressure ...................................... 4H - 4J
Gas valve does not energize ...................... 4L - 4N
Flame sensor fault ...................................... 5A - 5P
Burner ground............................................. 5K
Polaritycheck ............................................. 5L - 5M
Ignitor stays on after burner ignition ........... 5B - 5C
TECHNICAL HELP
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