80459-641-01E Model 6 Motor Control Centers
10/2012 Section 10—Expansion
© 1999–2012 Schneider Electric All Rights Reserved
93
ENGLISH
Modifying MCC Units Most MCC units are designed for easy removal from the MCC structure.
Some units are not removable due primarily to the physical size of the unit.
De-Energizing Equipment and
Identifying Unit Type
Identify whether the unit intended for modification is a removable style or a
fixed position unit. All removable units have stab connections to the vertical
bus as shown on the electrical schematics and one-line diagrams provided
with the MCC. Most removable units also have a twin handle cam
mechanism (see Figure 78 on page 58). One notable exception is the
Compac™ 6 control unit (see Figure 84 on page 61), which is removable but
does not have the twin handle cam mechanism.
NOTE: Modifications to arc-rated MCC units or structures can adversely
affect the arc containment features and/or performance. Modifications to
control circuit wiring are allowed. Modifications specifically covered in this
instruction bulletin are allowed. However, additional components, changes
to the power circuit, or mechanical modifications to the unit saddle or MCC
exteriors must be approved by Schneider Electric. Contact your local
Schneider Electric representative for more information.
If the unit is removable, follow the instructions below. If the unit is a fixed
position unit, follow the instructions for “Modifying Fixed Units” below.
Modifying Removable Units 1. Turn off all power supplying this equipment before working on or inside
the equipment, and follow lockout/tagout procedures. Always use a
properly rated voltage sensing device to confirm the power is off.
2. Remove the MCC unit from the structure. See the procedure for
“Maintaining the Control Unit” on page 56 of this manual.
3. Perform the required modifications. Use thread-forming screws to mount
devices. Do not use bolts and nuts, as they could loosen over time and
cause property damage or personal injury. The hardware must not extend
beyond the back of the MCC unit saddle more than 0.25 in. (6 mm) or
beyond the sides and bottom pan by more than 0.125 in. (3 mm).
4. Make sure that proper electrical spacing
1
between uninsulated live parts
of opposite polarity and an exposed or uninsulated dead metal part is
maintained.
5. Use a vacuum cleaner to remove all debris left in the unit as a result of
the modifications. Do not use compressed air to blow out the unit,
because all debris may not be fully removed.
6. Perform the recommended maintenance procedures beginning on 56 of
this manual.
7. Ensure that vertical bus closing plugs are in place (with the exception of
one plug where the MCC unit will stab on the vertical bus). If other vertical
bus closing plugs are not in the proper position, ensure that all power is
removed from the vertical bus and reinstall the vertical bus closing plugs.
8. Use a megohmmeter to perform an insulation test as outlined on 66.
9. Look for and clear any obstructions that would not permit proper
energizing of the MCC unit.
10. Reinstall the MCC unit and follow the procedures for “Energizing the
MCC” on page 54 of this manual.
1
Electrical spacings are specified in UL 845, Tables 18 and 19. Electrical spacing in a control or
metering circuit or within a motor control unit (251–600 V) is 0.375 in. (10 mm) through air and
0.50 in. (13 mm) over surface; for power circuits of main and feeder units, it is 1 in. (25 mm)
through air and 2 in. (51 mm) over surface.
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