MCB or RCCB? Understanding the Difference Before You Order

One of the most common confusions we hear from buyers is the difference between a Miniature Circuit Breaker (MCB) and a Residual Current Circuit Breaker (RCCB).

They look similar in the distribution box, but they protect against completely different hazards.

An MCB protects the cable and equipment from overcurrent — overload and short circuit. It trips on the magnitude of current flowing through the line.

When selecting an MCB, three numbers matter: the rated current (1-63 A in our M7 series), the curve (B, C or D, describing how fast it trips on small overloads versus large inrush), and the breaking capacity (6 kA for the M7, per IEC 60898-1).

An RCCB, on the other hand, protects people. It continuously compares the current flowing out on the line conductor with the current returning on the neutral. Any imbalance above the sensitivity threshold — typically 30 mA for personal protection, or 100/300 mA for fire protection — trips the breaker within milliseconds. An RCCB does NOT protect against overload or short circuit, which is why it must always be paired with an MCB upstream.

The practical takeaway for buyers: a safe residential or light-commercial distribution board uses both. The MCB handles overcurrent on each outgoing circuit; the RCCB covers earth leakage for a group of circuits. If board space is tight, an RCBO — a device that combines both functions in one module — is the cleaner solution.

Our L8 series RCCBs comply with IEC 61008-1 and are available in 2-pole and 4-pole versions with 30/100/300 mA sensitivities. If you are unsure which combination suits your market's wiring practice, send us your distribution diagram — our engineers will mark up the recommended configuration within one working day.