Emerson 50A55 Handbook

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TECHNICAL HELPTECHNICAL HELP
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