An MCB marking such as “C32 · 230/400 V~ · 6000” tells you the trip curve (C), the rated current (32 A), the rated voltage and — in the boxed number — the rated short-circuit capacity (6000 A = 6 kA). A small digit under that box is the energy-limiting class. Check each marking against the datasheet and the certificate for the ordering code.
Key facts
- The letter before the number is the trip curve; the number is the rated current In in amperes.
- The boxed number is the rated short-circuit capacity in amperes (6000 = 6 kA, 10000 = 10 kA).
- Rated current is defined at a reference ambient temperature (30 °C in IEC 60898-1) — hot enclosures need derating.
Marking decoder
| Marking | Meaning | Why it matters |
|---|---|---|
| C32 | Trip curve C, rated current 32 A | Curve decides tolerance to inrush; In must suit the cable |
| 230/400 V~ | Rated voltage (single-phase / three-phase), AC | Must match the system voltage |
| 50 Hz | Rated frequency | MCBs are frequency-insensitive; contactor coils are not |
| 6000 (in a box) | Rated short-circuit capacity, 6 kA | Must be at least the fault level at the board |
| 3 (below the box) | Energy-limiting class 3 | Higher class limits let-through energy better |
| IEC/EN 60898-1 | Standard the breaker is certified to | Household-type installations; see 60898-1 vs 60947-2 |
| CE / CB marks | Conformity and test-report scheme marks | Not a substitute for a destination scheme such as EAC or SONCAP |
| Laser batch, QR code | Traceability to the factory lot | The first thing to check against paperwork |
Example: NB1-63 and NB1-63H
The CHINT NB1-63 carries a 6 kA rating; the NB1-63H is the 10 kA version for feeders close to a transformer. Their housings look alike, so the boxed number is the quickest visible difference — and the first thing a counterfeit gets wrong.
How a wrong marking shows up
- The boxed value differs from the datasheet for that ordering code.
- Print quality or fonts differ between units in the same carton.
- No batch code, or a batch that does not match the paperwork.
- A QR code that does not return factory data when scanned.
Run the physical checks in our genuine-product checklist before you accept a delivery.
Frequently asked questions
What does the number in the box on an MCB mean?
It is the rated short-circuit capacity in amperes. 6000 means 6 kA; 10000 means 10 kA.
Is a C-curve MCB better than a B-curve?
Neither is better in general. C tolerates higher inrush than B, which suits mixed loads; B suits long cable runs and resistive circuits. See MCB trip curves.
Can I use a 6 kA MCB where 10 kA is required?
No. The breaking capacity must be at least the prospective fault current. See 6 kA vs 10 kA.
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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.