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—Comparing the options

MCB or RCBO

Both sit in the board and both switch circuits off. They protect against different things.

A miniature circuit breaker (MCB) protects a circuit against overcurrent — overloads and short circuits — so the cable does not overheat. It does not detect current leaking to earth through a person or damp insulation. That is the job of an RCD, which in many boards protects several circuits at once.

Comparison guides weigh two electrical options against each other and note where each one fits best.

An RCBO combines both functions for a single circuit. Replacing MCBs with RCBOs gives each circuit its own leakage protection, so a fault on one circuit switches off only that circuit rather than a whole group. Whether that upgrade suits a board depends on its make, space and condition.

01In short

The points that matter most

  • MCB: overcurrent only

    Protects cables from overload and short circuit.

  • RCBO: overcurrent and leakage

    Adds shock protection per circuit.

  • Fewer whole-area trips

    RCBOs isolate faults to one circuit.

02Detail

When each makes sense

  • MCBs with shared RCDs

    Common and acceptable where groups are sensibly arranged.

  • RCBOs on critical circuits

    Fridges, network equipment and medical devices avoid being caught by others’ faults.

  • Full RCBO boards

    Each circuit independently protected, often part of a board replacement.

  • Board compatibility

    Devices must suit the board’s make and busbar.

03Checklist

Before upgrading

  • Photograph the board

    Make and existing devices.

  • Note nuisance trips

    Which circuits go off together.

  • Identify critical loads

    Fridges, freezers, servers.

04Questions

Questions people ask

Are RCBOs always better?
They reduce disruption from faults, but the right choice depends on the board and installation.
Can I mix MCBs and RCBOs?
Many boards do, with careful arrangement.
Why does one fault turn off half the house?
A shared RCD protects several circuits.
Does upgrading need a new board?
Not always; compatibility and space decide.
What does an RCBO upgrade change day to day?
A fault switches off only its own circuit, so the rest of the house keeps power.

05Related

Related guides

This guide sits under electrical wiring. All topics are on the guides page.

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