What is an RCBO? A plain-English guide
By Azzeddine Kebbi, NAPIT-registered electrician and director of Kebbi Electrical Services · Updated 10 November 2026
An RCBO protects a single circuit against earth leakage, overloads and short circuits. Here is how it works, how it differs from an RCD and MCB, and when it is worth having.
RCBO in one sentence
RCBO stands for Residual Current Breaker with Overcurrent protection. It is an MCB and an RCD combined in one device, protecting one circuit.
RCBO vs RCD vs MCB
| Device | What it protects against | Covers |
|---|---|---|
| MCB | Overload and short circuit | One circuit |
| RCD | Earth leakage (electric shock and some fire risk) | Usually a group of circuits |
| RCBO | Earth leakage, overload and short circuit | One circuit |
Why RCBOs are better
One fault, one circuit
If a kettle leaks to earth, only the kitchen sockets go off, not the lights and fridge as well.
Easier fault finding
You know straight away which circuit has the problem.
Less nuisance tripping
Small leakages from many circuits do not add up on one shared RCD.
Full protection
Each circuit gets shock and overload protection in one device.
Do I need RCBOs?
Current wiring regulations require 30 mA RCD protection for most circuits in homes. A board with RCBOs is one way to provide it, and the one we usually recommend. If your board has one or two RCDs covering everything, or no RCD at all, see does my fuse board need replacing?
If your RCD keeps tripping and taking several circuits with it, moving to RCBOs often solves it. See RCD keeps tripping.
Common questions
Considering a full RCBO board? Read RCBO consumer unit: is it worth it?
What does RCBO stand for?
Residual Current Breaker with Overcurrent protection. It combines an MCB and an RCD in one device for a single circuit.
What is the difference between an RCD and an RCBO?
An RCD protects against earth leakage only, usually for a group of circuits. An RCBO protects one circuit against earth leakage, overload and short circuit.
Can I change an MCB to an RCBO myself?
No. It means working inside the consumer unit. The RCBO must suit your board, and the circuit should be tested afterwards. It is a job for a registered electrician.
Why does my RCBO keep tripping?
Usually an appliance or wiring fault on that one circuit, or water getting in. Unplug everything on that circuit and reset it. If it still trips, call an electrician.
Thinking about upgrading your board?
We fit consumer units with RCBO protection across Bristol, test every circuit and register the work. See our fuse board upgrades.