Maintenance After a Fault Has Occurred
WARNING All equipment must be de-energized,
disconnected and isolated to prevent accidental
contact with live parts Check voltage on all control
terminals and on all line and load terminals of
circuit breakers, disconnect switches, and starters
or contactors before working on this equipment
Only qualified personnel should be involved in the
Inspection and repair procedure, and all safety
procedures must be observed.
M-39 The excessive currents occurring during a fault
may result in structure, component and/or bus or
conductor damage due to mechanical distortion,
thermal damage, metal deposits or smoke. After a
fault, correct the cause of the fault, inspect all
equipment and make any necessary repairs or
replacements before putting the equipment into
service again. Be sure all replacement parts are of
the proper rating and are suitable for the
application If in doubt, consult your local Square D
The complete maintenance procedure (Sections
M-1 through M-38, pages 14 through 23) should
be followed after any fault The following are
additional Items to watch for In these
M-40 Locate and correct the cause of the fault If the fault
occurred downstream from the motor control
center, appropriate maintenance should be carried
out on all equipment involved.
M-41 Enclosure - External evidence of enclosure
Extensive damage will require replacement of the
enclosure parts and the enclosed equipment.
Follow Maintenance Procedures M-2 through M-3
(page 14) 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.
M-42 Bus Bars and Incoming Line Compartments -
Follow Maintenance Procedures M-4 -through M-
10 tightening all electrical connections to their
proper torques. Replace any deformed bus bars or
connectors as well as any showing signs of arcing
M-43 Units - Follow Maintenance Procedures M-11
1. Examine the disconnect means for evidence of
mechanism properly turns ON" and "OFF" the
disconnect Exercise the push-to-trip feature on
circuit breakers and be sure that the operator
properly resets the breaker.
2. Check that the door interlock prevents the
opening of the unit door while the disconnect is
in the "ON" position. See Section 1-20 (page
13) for interlock operation
Check motor starters for any damage
Replace contacts and contact springs if the
contacts are welded or show heat damage If
deterioration extends beyond the contacts.
replace the entire contactor or starter.
Replace the complete overload relay if
thermal units have been burned out. If there
are any Indications of arcing or burning on
the overload relay, also replace it.
Inspect all fuses and fuse clips. Always
replace all fuses in a set even if only one or
two are open circuited.
Check all conductors and other devices
within the units for any signs of damage.
M-44 Complete an insulation test (Procedure M-37,
page 23) before attempting to put the motor
control center back into service.
M-45 Complete pre-operational check list Procedure 1-
16 (page 12).
M-46 Re-energize the equipment following Procedure 1-
17 (page 12).