Both devices protect against earth leakage. The distinction is coverage: an RCD typically protects a group of circuits, while an RCBO protects a single circuit and also provides overcurrent protection for it. That difference shows up on the day a fault occurs.
How they behave in a fault
With a split-load RCD board, a leak on the garden lighting takes out every circuit on that RCD — often including the fridge freezer and the router. With RCBOs, the garden circuit goes off and nothing else moves.
Cost and board space
RCBOs cost more per circuit and can require a wider board. On a small flat with six circuits the difference is modest; on a large house with eighteen circuits it is more noticeable. It remains one of the better value upgrades in a board change because it buys you diagnostic clarity as well as convenience.
Which we usually recommend
For most family homes, and particularly for anyone working from home or keeping freezers, we recommend RCBOs per circuit. Where budget is tight, a well-arranged split-load board with sensible circuit grouping is still a legitimate installation — the arrangement matters as much as the device.
Common questions
- Can RCBOs be added to my existing board?
- Sometimes, if the board accepts compatible devices. We check the make and model first.
- Do RCBOs stop nuisance tripping?
- They do not remove the fault, but they stop it disrupting unrelated circuits.
- Is a split-load board unsafe?
- No. It is a valid arrangement; RCBOs simply localise faults better.
- What about the freezer circuit?
- A dedicated RCBO for it is a common and sensible request.
Ask for both options on your board quote — we price them side by side so the choice is yours.
Related guides
- What Affects the Cost of a Consumer Unit UpgradeTwo identical-looking boards can be very different jobs once the cover comes off.
- Metal and Plastic Consumer Units ComparedThe move to non-combustible enclosures was a response to real failures, not a fashion.
- Arc Fault Detection Devices (AFDDs) at HomeAFDDs target a failure mode that other protective devices genuinely do not see.