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80459-641-01E Model 6 Motor Control Centers
10/2012 Section 6—Maintaining the MCC
© 1999–2012 Schneider Electric All Rights Reserved 67
ENGLISH
Record all megohmmeter readings on the insulation resistance chart on 104.
Any sudden change in resistance values (even within the acceptable range)
may indicate potential insulation failure. Early detection and replacement of
faulty insulating components helps avoid equipment damage.
If megohmmeter readings are below 5 megohms (one megohm during
start-up) consult your Schneider Electric field sales representative.
Re-energize the equipment in sequence, starting with the main devices, the
feeder devices next, and then the motor starter devices. (See “Energizing
the MCC” beginning on page 54).
Maintenance After a Fault Has
Occurred
NOTE: After a fault has occurred, arc-rated MCCs must be inspected,
repaired, and re-qualified by Schneider Electric Services personnel to
maintain the arc containment ratings.
Excessive currents occurring during a fault may result in structure,
component, bus or conductor damage. This damage is caused by
mechanical distortion, thermal damage, metal deposits, or smoke from fault
currents. After a fault, locate and correct the cause of the fault. Inspect all
equipment and make any necessary repairs or replacements before putting
the equipment into service again. Make sure all replacement parts are rated
properly and are suitable for the application. If in doubt, consult your
Schneider Electric field sales representative.
After any fault, perform all maintenance procedures, starting on page 55
and continuing to “Insulation Test” beginning on page 66. Also perform the
following procedures after a fault:
1. If the fault occurred downstream from the MCC, perform appropriate
maintenance on all equipment involved.
2. Examine the enclosure. External evidence of enclosure damage usually
indicates damage within. Extensive damage requires replacement of the
enclosure parts and the enclosed equipment.
3. Replace any parts that are damaged or deformed. Pay particular
attention to door hinges and door closing hardware. Inspect the area
around any damaged units (both inside and out) for displaced parts from
the damaged unit. See “Examining the Enclosure” on 55.
DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH
• Apply appropriate personal protective equipment (PPE) and follow safe
electrical work practices. See NFPA 70E or CSA Z462.
• This equipment must only be installed and serviced by qualified
electrical personnel.
• Turn off all power supplying this equipment before working on or inside
equipment.
• Always use a properly rated voltage sensing device to confirm power is
off.
• Replace all devices, doors, and covers before turning on power to this
equipment.
Failure to follow this instruction will result in death or serious injury.