Rockwell Automation Publication 2100-IN012G-EN-P - August 2016
101
Maintenance
Chapter 9
12. Check power contacts for excessive wear and dirt accumulation and
vacuum or wipe contacts with a soft cloth to remove dirt as needed.
Contacts are not harmed by discoloration and slight pitting. Never file
contacts, as this could reduce the life of the contacts. Do not use contact
spray cleaners, as they cause sticking on magnetic pole faces or in
operating mechanisms, interfering with the electrical continuity of the
contacts. Replace contacts only after the silver has become badly worn.
Always replace contacts in complete sets to avoid misalignment and
uneven contact pressure.
13. 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.
14. 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 can cause the coil failure. Be sure to clean any residue of
melted coil insulation from other parts of the device and replace as
necessary.
15. Check all pilot lights and replace lamps and damaged lenses as necessary.
16. Check all fuses.
If replacing fuses, install the same type and rated fuse that was originally
furnished with the MCC.
17. Remove accumulated dust and dirt from structure and individual units
by vacuuming.
Do not use compressed air, as it can contain moisture and blow debris
within the enclosure.
18. Refer to individual user policies, NFPA 70B, Recommended Practice for
Electrical Equipment Maintenance for MCC Servicing Guidelines.