Short answer: the three devices sense three different things, and each is certified to a different standard. An MCB protects the cable against overload and short circuit (IEC/EN 60898-1) and has no residual-current function at all. An RCCB protects people against earth leakage current (IEC/EN 61008-1) and has no overload or short-circuit detection. An RCBO does both in one device (IEC/EN 61009-1). Because the standards differ, the tests differ: a “6 kA MCB” tells you how much fault current the device survives, and nothing whatever about how it responds to leakage current.
That single sentence resolves most of the confusion. The rest of this page is what each device does, what it ignores, and how to choose between them.
Three jobs, three standards
| Device | Protects against | Standard | Does not detect | Range in our catalogue |
|---|---|---|---|---|
| MCB | Overload and short circuit | IEC/EN 60898-1 | Residual (earth leakage) current | NB1-63, NB1-63H, NXB-63 |
| RCCB | Residual current only | IEC/EN 61008-1 | Overload and short circuit | NL1-63 |
| RCBO | Residual current plus overload and short circuit | IEC/EN 61009-1 | — | NB1L, NXBLE-63, NB2LE |
Notice what the standards column is really telling an engineer. 60898-1, 61008-1 and 61009-1 are three separate standards, so they are three separate test regimes. A device certified under one of them has been tested for that function and not for the others. A tender document that asks for “a 30 mA protection device with 6 kA breaking capacity” is asking for two different properties that may sit in two different devices — or in one RCBO.
The devices and their verified ratings
The table below lists the series we quote and the ratings published for them. Read it by column: the device type tells you what it can sense, and the model row tells you the ratings for the code you are buying.
| Model | Type | Standard | Voltage | Rated current | Residual sensitivity | Breaking capacity |
|---|---|---|---|---|---|---|
| NB1-63 | MCB | IEC/EN 60898-1 | 230/400–240/415 V AC | 1–63 A | Not applicable | Icn 6 kA |
| NB1-63H | MCB (high breaking) | IEC/EN 60898-1 | 230/400–240/415 V AC | ≤ 63 A | Not applicable | Icn 10 kA |
| NXB-63 | MCB | IEC/EN 60898-1 | 220/230/240 V (1P, 1P+N, 2P); 380/400/415 V (2–4P) | 1–63 A | Not applicable | Icn 6 kA; H version 10 kA |
| NL1-63 | RCCB | IEC/EN 61008-1 | 230/400–240/415 V AC | 16/25/32/40/63 A | 0.01/0.03/0.1/0.3/0.5 A | Inc 6 kA |
| NB1L | RCBO | IEC/EN 61009-1 | 240/415 V AC | 1–40 A (1P+N); -63 type up to 63 A | 30/100/300 mA | Icn 6 kA |
| NXBLE-63 | RCBO | IEC/EN 61009-1 | 230/400 V AC | 6–63 A | 30/100/300 mA | 6 kA |
| NB2LE | RCBO | IEC/EN 61009-1 | AC 230/240 V | 6–40 A (40 A frame) | 0.03/0.1/0.3 A | Icn 6 kA |
Two details worth noting. The NB1L, NXBLE-63 and NB2LE are available as Type AC and Type A, which describes the residual-current waveforms the device is tested to detect — the AC type sees sinusoidal AC leakage, the A type adds pulsating DC components. And the RCCB and RCBO lines are published with B and C trip curves, matching the MCB conventions.
When to use which
- MCB: where residual-current protection is not required, or is already provided upstream. Overload and short-circuit protection for the cable is the whole job.
- RCCB: group protection. One RCCB can cover several final circuits where the requirement is earth-fault protection rather than per-circuit trip indication. Since it does not break on overload, it must be paired with overcurrent protection.
- RCBO: a single final circuit that needs both residual and overcurrent protection, and above all needs to lose only itself when it trips. On a board where one shared RCCB serves many circuits, a single fault takes out the whole group — an RCBO does not.
The rail-space trade-off
The classic choice on a final distribution board is between a 2-pole RCCB protecting a group of MCBs, and 1P+N RCBOs on each outgoing way.
The RCCB route uses less rail space per circuit, because one residual-current device serves several ways. Its cost is that a single nuisance or real earth fault trips the entire group, and the designer has deliberately decided that losing the group is acceptable. The RCBO route uses one device per outgoing way, so it occupies more rail space in total, but each circuit keeps its own protection and its own trip indication, and only the faulty circuit is lost. In practice the trade-off is almost never about device price; it is about what happens on the day something trips, and how hard it is to find.
Certificates follow the code, not the family
One more point that trips up buyers: a certificate issued for a family does not automatically cover every ordering code inside it. The residual sensitivity, the pole configuration and the curve are all part of what was tested. Ask for the certificate that covers the exact code on your purchase order, and treat “the whole range is approved” as a sentence that needs evidence behind it. Our verification checklist explains what we send with each order.
FAQ
Q: What is the difference between an MCB, an RCCB and an RCBO?
A: An MCB protects against overload and short circuit only (IEC/EN 60898-1). An RCCB protects against residual current only (IEC/EN 61008-1) and has no overcurrent function. An RCBO combines both (IEC/EN 61009-1).
Q: Can an RCCB replace an MCB?
A: No. An RCCB does not detect overload or short circuit, so it cannot protect the cable. Where an RCCB is used it must be backed by overcurrent protection, normally an MCB.
Q: Can an MCB replace an RCCB?
A: No. An MCB has no residual-current sensing, so it will not detect earth leakage. The two devices measure different quantities and are not substitutes.
Q: If I fit an RCBO, do I still need a separate MCB for that circuit?
A: No. The RCBO provides the overload, short-circuit and residual-current protection for that final circuit in one device, which is exactly why it is often used on outgoing ways where each circuit must trip independently.
Q: Why are the three devices certified to three different standards?
A: Because they are tested for different things. 60898-1 covers household MCBs, 61008-1 covers residual-current devices without integral overcurrent protection, and 61009-1 covers residual-current devices with integral overcurrent protection. Different standards, different test regimes.
Q: What does Type AC versus Type A mean?
A: It describes the residual-current waveforms the device is tested to detect. Type AC responds to sinusoidal AC residual current; Type A also responds to pulsating DC residual current. The NB1L, NXBLE-63 and NB2LE lines are available in both types.
Send the circuit, get the right device back
Tell us the circuit: load and cable, whether residual-current protection is required and at what sensitivity, the required breaking capacity at the operating voltage, quantity, destination country and the certificate your client needs. You get the datasheet page and the certificate for the exact ordering code, plus packing data, within 24 hours. Request a quotation.
Related: RCCB and RCBO catalogue · MCB catalogue · RCCB Type AC vs Type A · IEC 60898-1 vs IEC 60947-2 · How to size a distribution board · FAQ · Contact
CHINT is a trademark of its respective owner. HAZAM is an independent trading company; we are not the manufacturer and we are not an appointed distributor. Certificates and ratings always refer to the exact ordering code. Values above reflect manufacturer datasheets; the certificate for your code governs.