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MCCB vs MCB: When to Step Up to Molded Case Protection

When a molded case circuit breaker (MCCB) beats a miniature (MCB): higher current, adjustable trips, and selective coordination.

Both MCBs and MCCBs protect against overcurrent, but they live at different points in the installation. The miniature breaker handles final circuits; the molded case breaker handles the feeders that supply those circuits. Knowing where the line sits saves money and prevents whole-board blackouts.

1. Current and frame size

MCBs top out around 125 A; MCCBs start where MCBs end and run to 1600 A and beyond. If the feeder you are protecting exceeds ~100–125 A, you are in MCCB territory by default. A 100 A MCCB also occupies less rail space than a stack of paralleled MCBs that would be wrong anyway.

2. Adjustable trips and selectivity

An MCB's trip curve is fixed by type; an MCCB's thermal and magnetic thresholds are adjustable, so you can set it to coordinate with the downstream MCBs — the MCCB trips only for a feeder fault and leaves the branch breaker to clear a local one. That selectivity keeps a fault in one sub-board from dropping the whole installation.

3. Where each belongs

MCBMCCB
RoleFinal circuit / branchFeeder / main incomer
Range~0.5–125 A~10–1600 A
TripFixed typeAdjustable
SelectivityLimitedDesigned-in

For a main incomer or a sub-board feeding many MCB branches, specify an MCCB with adjustable settings. For the individual circuits off that board, use MCBs.

4. What to specify

  1. Feeder current and prospective fault level at that point.
  2. MCCB frame size with adjustable thermal/magnetic settings.
  3. Coordination with downstream MCBs (time/current margin).
  4. Breaking capacity at or above the fault current.

ELEHPD MCCBs, MCBs, busbar and isolators let you build a coordinated feeder-and-branch board.

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