Motor Control Centers

Motor Control Centers

NEMA MCCs

CENTERLINE 2100 — Design and Specifications

Wiring Types

Type A Wiring — No Terminal Blocks

Type A wiring is available for Class I Motor Control Centers. When Type A wiring is specified, components within the unit are wired directly to each other, and no terminal blocks are supplied for customer wiring. The customer must connect external control and load wiring directly to the electrical devices within the unit.

Type B Wiring — Terminal Blocks

Type B wiring is available for Class I and Class II Motor Control Centers.
NEMA/EEMAC defines Type B wiring as follows:

ICS 2-322.10 Types of wiring — .02 Type B

1. Type B user field load wiring for combination motor control units size 3 or smaller shall be designated as B-D or B-T, according to the following:
   • B-D connects directly to the device terminals, located immediately adjacent, and readily accessible, to the vertical wireway;
   • B-T connects directly to a load terminal block in, or adjacent to, the unit.
     NEMA Standard 3-6-1985
2. Type B user field load wiring for combination motor control units larger than size 3, and for feeder tap units, shall connect directly to unit device terminals.
   NEMA Standard 3-6-1985
3. Type B user field control wiring shall connect directly to unit terminal block(s) located in or adjacent to each combination motor control unit.
   NEMA Standard 3-6-1985

• CENTERLINE Motor Control Centers Size and Type Matrix

  NEMA Size	Type B-T Load wired to terminal blocks	Type B-D Load wired to device (breaker or disconnect) terminals	Type B
  Size 1, 2 (Except 0.5 space factor)	Pull-apart terminals on control wires. Pull-apart terminals on load.	Pull-apart terminals on control wires. Load wired directly to device.	N/A
  Size 3	Pull-apart terminals on control wires. Load terminals do not pull apart.	Pull-apart terminals on control wires. No load terminals.	N/A
  Size 4 and larger	N/A	N/A	Pull-apart terminals on control wire. No load terminals.
  0.5 space factor and all IEC (Bulletin 2400) units	Pull-apart control terminal blocks. No load terminal blocks.	Pull-apart control terminal blocks. No load terminal blocks.	Pull-apart control terminal blocks. No load terminal blocks.

  
  

  N/A = Not applicable, undefined by NEMA/EEMAC

Type C Wiring — Master Terminal Compartment

Type C wiring is available for Class II Motor control Centers.

• Control wiring from each unit within an MCC section is wired from the unit's terminal blocks to master terminal blocks contained in a separate unit mounted to the top or bottom of that section.
• Connect the external control wires to the master terminal blocks.
• Connect load wiring for size 3 or smaller to the master terminal blocks.
• Connect the load wiring for size 4 or larger to unit device terminals.

Control Circuit Wiring

NEMA Units (Bulletin 2100) — 16 AWG copper wire with Type MTW (TEW) insulation (standard). Optional 14 AWG (tinned) copper wire with Type MTW (TEW) insulation; and 14 AWG (tinned) copper wire with Type SIS insulation.

IEC Units (Bulletin 2400) — 18 AWG copper wire with Type MTW (TEW) insulation (standard). Optional 16 AWG copper wire with Type MTW (TEW) insulation.