RCBO board or split-load RCD board?
The practical difference between a full RCBO board and a split-load RCD board, what each costs to fit, and which one suits your property.
When you replace a consumer unit you get one significant choice: protect groups of circuits with two RCDs, or protect every circuit individually with its own RCBO. Both meet current standards. They behave very differently the day something goes wrong.
The short version: split-load is cheaper today, RCBO is cheaper the first time a fault takes out half your house at 11pm. Which is right depends on the property and who lives in it.
- Split-load: two RCDs, circuits grouped, lower upfront cost
- RCBO: one device per circuit, faults isolated to that circuit
- RCBO removes the cumulative leakage that causes nuisance trips
- Both meet 18th Edition requirements when correctly specified
What happens when a fault occurs
On a split-load board, a fault on one circuit trips the RCD covering its whole group. Lose the upstairs RCD and you lose upstairs lighting and sockets together — including the freezer, if it happens to be on that side.
On an RCBO board, only the faulty circuit disconnects. Everything else keeps running, and you already know which circuit to investigate.
Nuisance tripping
Every appliance leaks a small current to earth. Group eight circuits behind one RCD and that leakage adds up until an ordinary appliance tips it over. This is the single most common reason people call us about a board that "keeps tripping for no reason".
Individual RCBOs give each circuit its own headroom, which removes the cumulative problem entirely.
Cost and when split-load still makes sense
RCBO boards cost more in devices, though the labour is similar. For a small flat with few circuits, split-load is perfectly reasonable. For a family house with a home office, a freezer, outdoor sockets and an EV charger, we recommend RCBOs and will explain why on the quote rather than just charging more.
Common questions
Can I mix the two?
Yes. A common approach is RCBOs for critical circuits (freezer, home office, EV) with RCD protection elsewhere.
Is a split-load board unsafe?
No — correctly specified it meets current standards. The difference is convenience and fault isolation, not safety.
Can RCBOs be retrofitted to an existing board?
Often yes, if the board accepts them. We check make and model first.
Get a fixed price
Send a photo of your existing board — we'll quote both options side by side so you can decide on real numbers.