Removing the Control 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-2011, 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. 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 The control unit is interlocked with the MCC structure to prevent the unit from being withdrawn while the disconnect is in the on position.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. Follow these steps 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 3-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 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 Figure 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).

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.

   Power Leads and Top of Terminal Blocks Fed Through Wiring Port

   

   Pulling the Twin Handle Cam Mechanism Forward

   

8. The operator mechanism-to-structure interlock prevents the control unit from being withdrawn or inserted with the handle in the ON position (see 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).

   Operating the Mechanism-to-Structure Interlock

   

   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 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..

    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.