An MCB (miniature circuit breaker) and an RCCB (residual current circuit breaker) look similar in a distribution board, but they do different jobs.
What an MCB does
An MCB protects the wiring and equipment on a circuit. It trips when the circuit is overloaded or when there is a short circuit, cutting the supply before cables overheat.
What an RCCB does
An RCCB protects people. It monitors the balance between the live and neutral currents and trips when some current leaks to earth, for example through a person touching a live part or a faulty appliance body.
Do you need both?
They complement each other: an MCB does not detect earth leakage, and an RCCB does not protect against overload. Most modern installations use an MCB on each circuit, with an RCCB (or a combined RCBO) protecting the circuits where people could be exposed to shock risk.
For sizing and the correct rating for your installation, always consult a qualified electrician or engineer.
Can an RCCB replace an MCB?+
No. An RCCB does not protect against overload or short circuit, so it is used together with an MCB.
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