Professional Guide

Best RCBOs for Consumer Unit Safety: 2025 Expert Review

Oli at OR Electrics

18th Edition Qualified Electrician

Published 17 December 2025

If you have ever had a faulty toaster trip the power to your entire house, plunging you into darkness, you understand the frustration of split-load boards. This is where RCBOs (Residual Current Breaker with Overcurrent protection) change the game.

Unlike the older setup where one fault knocks out half the circuits, an RCBO protects each circuit individually. If a fault occurs on the kitchen sockets, the lights stay on elsewhere. In Leeds, where we see unique electrical challenges in converted Victorian terraces and HMOs, this level of separation is vital for safety and continuity.

In this review, I'm looking at a specific Crabtree option. Please remember: electrical protection devices are brand-specific. You cannot mix and match them. This guide highlights a solid choice if you are dealing with a compatible installation.

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Specs vs. The Real World

The Spec: "Universal Fit"

The Theory

"Some assume all circuit breakers fit all consumer units."

The Reality

This is a dangerous myth. You MUST use the same brand and type (e.g., Crabtree Starbreaker) as your consumer unit. Mixing brands voids warranties and violates type-testing standards (BS 7671).

The Spec: "DIY Installation"

The Theory

"It looks like a simple plug-and-play component."

The Reality

Replacing protection devices falls under Part P of the Building Regulations. It requires isolation, torque tools, and crucial testing (Zs, RCD times) to ensure it will actually trip during a fault. This is strictly a job for a qualified electrician.

My Top 3 Recommendations

Three options to cover different needs and budgets

Best Price Square SINGLE POLE RCBO 40A EACH BPSCA 61/C14030 - PL11980 By CRABTREE

Budget Option

Best Price Square / Crabtree

This is a Crabtree 40A Single Pole RCBO, listed here via Best Price Square. It is designed for Crabtree consumer units (specifically checks compatibility with the Starbreaker or Loadstar range). Being a Type C breaker, it handles higher inrush currents, often used for specific heavy loads.

Price£34.99 (at time of writing)

BrandCrabtree

Rating40 Amp

TypeType C (Inrush)

The Good

Combines RCD and MCB functions in one device
Prevents nuisance tripping affecting other circuits
High quality manufacturing from a trusted UK legacy brand (Crabtree)

The Bad

Strictly brand-specific (only fits Crabtree boards)
Type C curve may not be suitable for all domestic loop impedances (needs testing)

Installer Tip:

Watch out for the 'Type C' rating on this unit. In standard domestic properties in Leeds, we typically use 'Type B' for general circuits. Type C is for equipment with high startup currents (like some motors). Before fitting this, I'd always measure the loop impedance (Zs) to ensure it disconnects within 0.4 seconds, as Type C requires a lower earth loop impedance than Type B.

Priced at £34.99 at the time of writing

Check Price on Amazon

Frequently Asked Questions

What is the difference between an MCB and an RCBO?

An MCB (Miniature Circuit Breaker) only protects against overloads (too many appliances) and short circuits. An RCBO combines that with RCD protection, which detects earth leakage (electric shocks). RCBOs are safer and more convenient because they prevent one fault from tripping the whole board.

Can I fit this Crabtree RCBO into a Wylex or Hager board?

Absolutely not. Consumer units are type-tested assemblies. Mixing brands (e.g., putting a Crabtree breaker in a Hager board) is against manufacturer instructions and BS 7671 wiring regulations. It may fit physically, but it can cause arcing, fires, or mechanical failure.

Why use RCBOs instead of a dual RCD board?

A dual RCD board splits your house into two banks of circuits. If one circuit has a fault, you lose half the house (e.g., lights and freezer go off together). With an All-RCBO board, if the toaster faults, only the kitchen sockets trip. The rest of the house stays on. It is the preferred standard for modern installations.

What does Type B and Type C mean on an RCBO?

This refers to the 'tripping curve'. Type B trips faster at lower surge currents and is standard for most domestic lights and sockets. Type C tolerates higher 'inrush' currents (surges on startup) and is used for motors or specific fluorescent lighting loads. Always check with an electrician which one allows for safe disconnection times in your specific property.

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