Publication 2100-IN012B-EN-P - April 2005
Maintenance 9-3
10. Check power contacts for excessive wear and dirt accumulation.
Vacuum or wipe contacts with a soft cloth to remove dirt. Contacts are
not harmed by discoloration and/or slight pitting. Contacts should
never be filed, as this could reduce the life of the contacts. Contact spray
cleaners should not be used, as they cause sticking on magnetic pole
faces or in operating mechanisms, interfering with the electrical
continuity of the contacts. Contacts should be replaced only after the
silver has become badly worn. Always replace contacts in complete sets
to avoid misalignment and uneven contact pressure.
11. Check for loose wire connections on power and control circuit
terminals. Loose connections can cause overheating, hot spots or arcing
faults that could lead to equipment malfunction or failure. Replace any
damaged parts or wiring.
12. Check contactor and relay coils for evidence of overheating, such as:
cracking, melting or burning of insulation. If there is evidence of
overheating, the coil must be replaced. When replacing a coil, check and
correct the overvoltage or undervoltage conditions that may have
caused the coil failure. Be sure to clean any residue of melted coil
insulation from other parts of the device and replace as necessary.
13. Check all pilot lights. Replace lamps and/or damaged lenses as
necessary.
14. Check all fuses. If replacing fuses, install the same type and rated fuse
that was originally furnished with the motor control center.
15. Remove accumulated dust and dirt from structure and individual units
by vacuuming. Do not use compressed air, as it may contain moisture
and blow debris within the enclosure.
16. Refer to individual user policies, NFPA 70B, Recommended Practice for
Electrical Equipment Maintenance for MCC Servicing Guidelines.
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