RCBO Keeps Tripping

An RCBO in your consumer unit keeps tripping, cutting power to a single circuit.

£100 – £250Medium Risk

What is this?

An RCBO (Residual Current Breaker with Overcurrent protection) combines the functions of an MCB and an RCD in a single device. It protects a single circuit against overload, short circuit, and earth leakage. When an RCBO trips, it could be due to any of these fault types. The advantage is that only the affected circuit loses power, not half your house.

Common causes

Earth leakage from a faulty appliance or damaged cable on that circuit
Overload on the circuit from too many appliances
Short circuit in the wiring or an appliance
Moisture ingress into a fitting on that circuit
Faulty RCBO that has become oversensitive
Cumulative earth leakage from multiple appliances on the circuit

Is it dangerous?

The same risks apply as with MCB and RCD faults. The RCBO is providing protection, so the underlying fault is what matters. The good news is that only the faulty circuit is affected, so the rest of your home retains power.

Can I fix it myself?

Check which RCBO has tripped and its circuit label. Most RCBOs have a small indicator or flag showing whether they tripped on overload (overcurrent) or earth leakage (RCD function). This helps narrow down the fault type. Unplug all appliances on that circuit and try resetting. If it holds, plug things back in one at a time.

When to call an electrician

Call an electrician if the RCBO trips with nothing on the circuit, if it keeps tripping regardless of what you do, if the trip indicator shows earth leakage and you cannot find the source, or if the RCBO itself appears damaged or will not latch.

What will an electrician do?

Determine whether the RCBO is tripping on overcurrent or earth leakage

Test the circuit with insulation resistance and loop impedance tests

Check all fittings on the circuit for moisture, damage, or loose connections

Test the RCBO itself to verify correct operation

Repair the underlying fault on the circuit

Replace the RCBO if it is faulty or oversensitive

Typical cost

£100 – £250

RCBO replacement costs £40–£70 for the device plus labour. Fault-finding on the circuit is the main cost.

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Sources & References

Frequently Asked Questions

What is an RCBO and how is it different from an MCB?

An RCBO combines MCB and RCD protection in one device. An MCB only protects against overload and short circuit. An RCBO also protects against earth leakage (shock risk). Each RCBO protects one individual circuit.

Is an RCBO board better than a split-load RCD board?

Yes, for convenience. In a split-load board, one RCD covers multiple circuits, so a fault on any circuit trips them all. With RCBOs, only the faulty circuit is affected. RCBO boards cost more but cause far less disruption.

How do I tell if it tripped on overcurrent or earth leakage?

Many RCBOs have a small trip indicator. Some have a flag that shows differently for each trip type. Check the manufacturer's markings on the device. If in doubt, an electrician can test which type of fault is present.

Can I replace an RCBO myself?

As with MCBs, work inside a consumer unit is notifiable under Part P of the Building Regulations and should be carried out by a registered electrician. Incorrect installation of an RCBO can leave you unprotected.

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