Maintaining the MCC

Perform inspection, cleaning, and any required repair activities as part of the initial maintenance of the MCC and at periodic inspection and maintenance intervals.

1. Inspect the interior and exterior of the MCC for moisture, oil, or other foreign material. Eliminate all foreign material and clean the MCC.

2. Clean the interior and exterior of the MCC with a vacuum cleaner. (Do not use compressed air; it redistributes contaminants to other surfaces.) Check the enclosure for damage that might reduce electrical clearances.

3. Examine the finish of the enclosure. Touch up the paint if necessary. Replace any badly corroded or damaged enclosure parts.

4. Check the MCC interior carefully for moisture, condensation build-up, or signs of previous wetness. Moisture can compromise electrical insulation systems and cause rapid oxidation of current-carrying parts. Inspect all conduit entrances and cracks between the enclosure panels for dripping leaks. Condensation in conduits can be a source of moisture and must not be allowed to drip onto live parts or insulating material. Take the necessary steps to eliminate moisture and seal off leaks.

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 before working on or inside equipment. Always use a properly rated voltage sensing device to confirm power is off. Do not attempt to remove the unit from the structure with the disconnect in the ON position. The control unit is interlocked with the MCC structure to help prevent the unit from being withdrawn while the disconnect is in the ON position. Do not attempt to override the mechanism-to-structure interlock. 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.

The Model 6 MCC is designed for convenient and quick control unit removal and replacement. To remove control 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.

   NOTE: If a three-inch VeriSafe Absence of Voltage Tester (AVT) unit is being used to confirm that power is off, refer to the one-line diagram for the MCC to determine which parts of the MCC bus system the AVT monitors. The line side of the circuit breaker main supplying power to MCC lineup or other portions of the MCC bus system might still be powered.

2. Move the operator mechanism to the OFF position (see Operator Mechanism in the OFF Position).

   Operator Mechanism in the OFF Position

   

3. Loosen the captive fasteners (see Loosening Captive Fasteners) on the door and open it. Use a properly rated voltmeter to check for live circuits. De-energize any voltage sources.

   Loosening Captive Fasteners

   
   NOTE: Arc-rated units have additional fasteners at the top-middle and bottom-middle of the door that must be loosened to open the door (see Arc-Rated MCC Door Latches).

   Arc-Rated MCC Door Latches

   

4. Release the lock-in device located at the bottom front of the unit (when supplied) by turning the screw on the front of the device until the locking pawl is parallel to the bottom of the unit (see Releasing the Lock-in Device (when supplied)).

   Releasing the Lock-in Device (when supplied)

   

5. Disconnect the power wiring from the starter terminals or, if provided, the power terminal blocks. Tag the terminations for re-installation (see Disconnected Terminal Blocks).

   Remove the top portion of the pull-apart control terminal blocks to which field wiring is connected.

   Disconnected Terminal Blocks

   

6. Push the power leads and the top portion of the control pull-apart terminal blocks through the wiring port and into the vertical wireway (see Power Leads and Top of Terminal Blocks Fed Through Wiring Port).

   Power Leads and Top of Terminal Blocks Fed Through Wiring Port

   

7. Pull forward on the twin handle cam mechanism located at the top front of the unit to rack the unit partially out of the structure (see Pulling the Twin Handle Cam Mechanism Forward). This action disconnects the power stabs from the vertical bus. Continue pulling forward until the handles are fully extended.

   Pulling the Twin Handle Cam Mechanism Forward

   

8. The operator mechanism-to-structure interlock helps prevent the control unit from being withdrawn or inserted with the handle in the ON position (see Operating the Mechanism-to-Structure Interlock).

   Operating the Mechanism-to-Structure Interlock

   

9. If the withdrawn unit is left in the structure, use appropriate lock-out procedures to avoid re-loading by non-authorized personnel (see Locked Out Device).

   Locked Out Device

   

10. Remove the control unit from the structure for servicing (see Control Unit Removed). In units with a full bottom plate, additional accessibility to the components and wiring can be achieved by folding the bottom plate down. To do so, lean the unit on its back, remove the two front screws, and fold the bottom plate down (see Control Unit with Bottom Plate Folded Down).

    Control Unit Removed

    
    NOTE: Some MCC units can weigh up to 200 pounds (90.1 kg) and require two or more persons or special handling equipment. Lift only by supporting the bottom and/or the side panels of the unit. Refer to Proper/Improper Lifting Points for Plug-in Units Taller Than 24 in. (610 mm).

    Control Unit with Bottom Plate Folded Down

    

11. If necessary, the door can be taken off its hinges without removing the unit. To do so, drive the hinge pins out of the hinge collars, using a small flat-bladed screwdriver or small punch (see Driving Out Hinge Pin). Remove the bottom hinge pin first.

    Driving Out Hinge Pin

    

12. When reinstalling a hinge pin, make certain that the hooked end is fully engaged into the hinge collar.

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 before working on or inside it. 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.

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 power is off.

2. Move the operator handle to the OFF position (see Operator Handle in the OFF Position).

   Operator Handle in the OFF Position

   

3. Loosen the captive fasteners (see Loosening Captive Fasteners) on the door and open it.

   NOTE: Arc-rated units have additional fasteners at the top-middle and bottom-middle of the door that must be loosened to open the door (see Arc-Rated MCC Door Latches).

   Loosening Captive Fasteners

   

4. Check for live circuits using a properly rated voltage sensing device. De-energize any voltage sources.

   NOTE: Removal of the control station plate may be necessary to perform steps 5 and 6. To remove the control station plate:

   1. Loosen the captive mounting screws holding the plate to the front of the unit.

   2. Remove the plate from the unit (see Control Station Plate Removed).

   3. Re-attach the plate after disconnecting the load wires and control terminal block.

      NOTE: Do not disconnect the wires to the control station plate.

   Control Station Plate Removed

   

5. Disconnect the power wiring from the starter terminals. Tag the terminations for re-installation.

6. Remove the top portion of the pull-apart control terminal block to which field wiring is connected.

7. Push the power leads and the top portion of the control pull-apart terminal blocks through the wiring port and into the vertical wireway.

8. Grasp the operator handle flange and press down on the structure interlock release (see Operator Handle and Interlock Release).

   Operator Handle and Interlock Release

   

9. Firmly pull the unit forward to disengage the power stabs from the vertical bus. The unit should now slide freely from the MCC structure.

10. The operator mechanism-to-structure interlock helps prevent the control unit from being inserted or withdrawn with the handle in the ON position.

11. If the withdrawn unit is left in the structure, use appropriate lock-out/tag-out procedures to avoid re-loading by non-authorized personnel.

12. Remove the control unit from the structure and place it on a flat surface for servicing.

    NOTE: Partial disassembly of the unit may be necessary to gain access to various electrical connections for servicing.

Stab Assembly

Circuit Breaker or Disconnect Switch: Verify proper operation of the circuit breaker or disconnect switch. Inspect switch blades; if evidence of arcing or excessive heat is present, replace the switch assembly. Exercise the push-to-trip feature on the circuit breakers.

Operator Mechanism: Verify proper operation of the operator mechanism (see Operator Mechanism in the Tripped Position).

Operator Mechanism in the Tripped Position

Fuses: Inspect all fuses and fuse clips (see Inspecting Fuses). Replace any parts showing signs of overheating or arcing.

Inspecting Fuses

Starter Contacts: Check the starter contacts (see Starter Contacts). Replace any that are badly worn or pitted. (See the Schneider Electric Literature Lists for the appropriate instruction bulletin.)

Starter Contacts

Control Devices—Check for proper operation of starters, relays, timers, and other control devices (see Control Devices).

Control Devices

Overload Relay: Manually trip the overload relay to help ensure proper operation (see Tripping the Overload Relay). Verify that the thermal unit is the proper size for the application. Refer to the thermal unit selection tables (Thermal Overload Unit Selection).

Tripping the Overload Relay

Wiring and Electrical Connections: Verify that all electrical connections are correct; tighten them if necessary (see Tightening Electrical Connections). For any inaccessible electrical connections, contact Schneider Electric Services. Also inspect all power and control wiring, replacing any wire that has worn insulation or shows signs of overheating or cracking.

Verify that all network connections are secured and all cable insulation is in good condition. Replace if cable shows signs of stress, particularly on cable bends and connecting plugs.

Tightening Electrical Connections

Starter Interlocks: Check the mechanical interlocks on reversing, multispeed, or reduced voltage starters.

Barriers/Insulators: Inspect all insulators, braces, and barriers (see Manual and Automatic Bus Shutters); replace any that show signs of arcing damage, tracking, excessive heat, or cracking.

Manual and Automatic Bus Shutters
Manual Bus Shutter	Automatic Bus Shutter

Special Units: Follow the manufacturer’s recommended maintenance procedures for special units (for example: drives, soft starts, and automatic transfer switches).

To reassemble the MCC after testing and maintenance:

1. Reinstall Compac 6 units by reversing removal steps 1–12 in Removing the Compac^™ 6 Control Unit. Reinstall all other units by reversing removal steps 1–12 in Removing the Control Unit.

2. Confirm the cam mechanism is in the open position; position the mounting slides of the control unit onto the slots of the mid-shelf. Slide the unit inward to engage the cam mechanism.

   For Compac 6 units, position the mounting slides of the control unit onto the slots of the mid-shelf. Slide the unit inward until the unit is halfway in, then move it inward with a quick push. This movement easily overcomes the compression of the stabs as they engage the vertical bus.

3. Replace all barriers and cover plates and close and fasten all doors.

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 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.

Before an MCC is energized, take resistance measurements. Use an insulation tester (megohmmeter) with a potential of 500–1000 V. Take readings between each phase and from each phase to ground, with the branch disconnects off. Make sure the main disconnect is off during all insulation tests.

Readings from a megohmmeter with all disconnects off are typically 5–20 megohms or higher. Do not energize the MCC if readings below one megohm are found. Contact your local Schneider Electric representative. Record all megohmmeter readings for future reference. Any sudden change in resistance values (even within the acceptable range) may indicate a potentially damaged insulation system. Early detection and replacement of a potentially damaged insulation system helps avoid equipment damage.

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 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.

Excessive currents occurring during a short circuit or arcing event may result in structure, component, bus, or conductor damage. This damage is caused by mechanical distortion, thermal damage, metal deposits, or smoke from the event. Locate and correct the cause of the event. 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 unusual electrical system event, perform all maintenance procedures, starting in Maintaining the MCC and continuing to Insulation Test. Also perform the following procedures after an event:

1. If the event 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 Inspecting the Enclosure.

4. Examine bus bars and incoming line compartments; tighten all electrical connections to their proper torques (Bus Connection Torque Values and Typical Bus Connection Points show typical bus connection points and torque values.) Replace any deformed bus bars or connectors, as well as any showing signs of arcing damage. Inspect all insulators for cracks or burn marks; replace any displaying these characteristics.

   Bus Connection Torque Values

   Bolted Connection Location	Torque Range
   Horizontal bus (all locations)	68–70 lb-ft. (92.29–94.54 N•m)
   Horizontal ground bus (all locations)	5–6 lb-ft. (6.75–8.44 N•m)
   Splice bars–0.375 in. diameter bolts	31–32 lb-ft. (41.64–43.33 N•m)
   Splice bars–0.5 in. diameter bolts	68–70 lb-ft. (92.29–94.54 N•m)

   Typical Bus Connection Points
   Typical Top-Located 600 A or 800 A Main Lug Compartment
   Typical Splice Bar Connection	Typical Horizontal Bus Connection

5. If the event occurred between an upstream protection device and the section containing an ArcBlok 1200 main device, inspect line-side connections within the ArcBlok and the line-side isolation cable vault. Inspect the interior, looking for evidence of an event, including burn marks and damaged parts. Inspect the front covers, overlapping seals, dampers, springs, and gasket material in and around the vault (see Inspection Points After an Event). Replace any parts that are damaged or deformed. If there is evidence of damage in ArcBlok components such as the interphase barriers or phase-line lug connectors, contact Schneider Electric Services before returning the equipment to service.

   Inspection Points After an Event

   

6. If an internal arc interruption occurs on incoming power of ArcBlok Main device, refer to Return to Service Protocol—R Frame ArcBlok Instruction Bulletin—PKR25993. In addition, inspect the Fuse Disconnect Switch and its wiring inside the cable vault for damage of discoloration. See Inspection Point After an Event. Contact Schneider Electric Services if any damage or discoloration is found. Refer to deployment guide 7EN42-0247-00 for the ArcBlok Event Indicator and CL110 thermal sensors commissioning procedure.

   Inspection Point After an Event

   

7. Follow maintenance procedures for control units. Begin with Maintaining the Control Unit, and continue to Insulation Test. Also, perform the steps listed below:

   1. Examine the disconnect means for evidence of damage. Make sure that the operator mechanism properly turns the disconnect on and off. Exercise the push-to-trip feature on circuit breakers. Make sure that the operator mechanism properly resets the circuit breaker.

   2. Check that the door interlock keeps the unit door from opening while the disconnect is in the on position.

      NOTE: If the unit door must be opened while the unit is energized, only authorized personnel may operate an interlock defeat mechanism (see Operating Door Interlock Defeat Mechanism).

      Operating Door Interlock Defeat Mechanism

      

   3. Inspect the motor starters for 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.

   4. Replace the complete overload relay if the thermal units are burned out, or if any indications of arcing or burning are present on the relay.

   5. Inspect all fuses and fuse clips. Replace all fuses in a set, even if only one or two are open-circuited.

   6. Check all conductors and other devices within the units for signs of damage.

8. Complete an insulation test (see Insulation Test) before placing the MCC back into service.

9. Complete the Pre-operation Checklist.

10. Re-energize the equipment. See Energizing the MCC.