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.

DANGER
Hazard of Electric Shock, Explosion, or Arc Flash Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E, NOM-029-STPS, CSA Z462, or local equivalent. This equipment must only be installed and serviced by qualified electrical personnel. Turn off all power supplying this equipment and follow lockout/tagout procedures 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 these instructions will result in death or serious injury.

DANGER

Hazard of Electric Shock, Explosion, or Arc Flash

Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E, NOM-029-STPS, CSA Z462, or local equivalent.
This equipment must only be installed and serviced by qualified electrical personnel.
Turn off all power supplying this equipment and follow lockout/tagout procedures 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 these instructions will result in death or serious injury.

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. One notable exception is the Compac 6 control unit, 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.

Modifying Units

If the unit is removable, follow steps 1–10. For step 2, follow the Removable Unit instruction.

If the unit is a fixed position unit, follow steps 1–6, step 8, and step 10. For step 2, follow the Fixed Unit instruction.

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.
Removable Unit: Remove the MCC unit from the structure. See the procedure for Initial Maintenance of the Control Units.

Fixed Unit: If drilling holes in the back of the MCC unit saddle is required, do not drill through the back of the saddle more than 0.1875 in. (5 mm). Use a drill stop device for this procedure.
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).
Maintain proper electrical spacings* in the unit.
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.
Perform the recommended maintenance procedures in Maintaining Bus Bars and Incoming Line Compartments.
Removable Unit: 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.
Use a megohmmeter to perform an insulation test as outlined in Insulation Test.
Removable Unit: Look for and clear any obstructions that would not permit proper installation of the MCC unit. Reinstall the unit.
Follow the procedures for Energizing the MCC.