Use an MCB for final circuits up to about 125 A, an MCCB for feeders, motor circuits and sub-distribution from roughly 63 A to 800 A, and an ACB at the main incomer of large boards from 630 A up to 6300 A. The dividing lines are rated current, breaking capacity and how adjustable the trip unit is — not brand or price.
Key facts
- MCB (miniature circuit breaker) — modular, DIN-rail mounted, fixed thermal-magnetic trip with curves B, C or D.
- MCCB (moulded case circuit breaker) — a frame-based breaker with higher ratings, higher breaking capacity and often adjustable trips.
- ACB (air circuit breaker) — a large, usually withdrawable breaker with electronic release units for main incomers.
Side-by-side comparison
| MCB | MCCB | ACB | |
|---|---|---|---|
| Typical rated current | 1 – 125 A | 63 – 800 A | 630 – 6300 A |
| Main standard | IEC/EN 60898-1 (some also 60947-2) | IEC/EN 60947-2 | IEC/EN 60947-2 |
| Breaking capacity (CHINT ranges) | 6 kA or 10 kA | Up to 65 kA | Up to 100 kA (range maximum) |
| Trip unit | Fixed, curve B / C / D | Thermal-magnetic or electronic | Intelligent electronic release |
| Typical use | Final circuits, lighting, sockets | Feeders, motors, sub-boards | Main incomer, generator and bus-tie |
| CHINT series | NB1-63, NB1-63H, NXB-63 | NM1, NXM, NM8 | NA1, NA8, NXA |
How to choose in five steps
- Load current and cable. The breaker must protect the cable, so choose In to suit the cable rating and the load — not just the load.
- Prospective short-circuit current. The breaker’s breaking capacity must be at least the fault level at its installation point. This is why a 6 kA MCB near a transformer can be the wrong part; see 6 kA vs 10 kA.
- Discrimination. Upstream breakers should not trip for a fault that a downstream breaker can clear. MCCB and ACB catalogues give coordination tables.
- Standard and application. Household-type installations use 60898-1; industrial use points to 60947-2. See IEC 60898-1 vs 60947-2.
- Certificate for the destination. The scheme your customs requires depends on the country — see the market guides.
Icu and Ics in one paragraph
Icu is the ultimate breaking capacity — the highest fault current the breaker can interrupt, after which it may not be usable again. Ics is the service breaking capacity, usually stated as a percentage of Icu; the breaker should remain serviceable after clearing a fault up to Ics. For main distribution, compare Ics as well as Icu.
Frequently asked questions
Can an MCCB replace an MCB?
Only if it has the right trip characteristic, rated current and physical fit. MCCBs start at higher ratings and are not designed for DIN-rail final circuits.
When do I need an ACB?
At main incomers and generator or bus-tie positions of large boards, typically above 630 A or where adjustable electronic protection and high fault ratings are required.
What is the difference between MCB curves B, C and D?
They set how many multiples of rated current the breaker tolerates before its magnetic trip operates. See MCB trip curve B, C or D.
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Reviewed by the HAZAM technical team, October 2026. CHINT, DELIXI and TENGEN are trademarks of their respective owners. HAZAM is a first-tier authorised distributor of CHINT products; the authorisation certificate is available on request from our sales manager. Ratings and designations refer to published manufacturer documentation; the certificate for your exact ordering code governs.