RCBO Keeps Tripping Common Causes

An RCBO trips because it detects either excess current or residual earth-leakage current on its protected circuit. The most common causes are overload, accumulated earth leakage from multiple appliances, damaged insulation, moisture ingress, and a mismatch between the RCBO type and modern electronic loads. Identifying which of those applies — and measuring it — is the fastest route to a fix that holds.

An RCBO that trips instantly usually behaves differently from one that trips only under load or only after a few minutes. That simple detail often tells you whether you are dealing with a hard fault, leakage, or a circuit that is being asked to carry more than it should.

If the same circuit keeps failing after a reset, work from the symptom outward. Check what was running, what changed recently, and whether the issue follows a particular appliance, accessory, or area of the property.

An RCBO marked Type AC responds only to sinusoidal residual currents. Modern circuits feeding switchmode power supplies (phone chargers, LED drivers, computers), variable-speed drives, and EV chargers produce pulsating DC or mixed-waveform residual currents — which a Type AC device may not detect reliably, or may detect erratically, causing unexplained tripping behaviour.

Check the obvious items first: the connected load, any recent changes, outdoor accessories, and anything that gets hot, wet, or heavily used. If the fault is showing up on one circuit after another on the same board, the problem may be wider than the first symptom suggests.

If the issue is pointing toward a bigger condition problem rather than one simple repair, the EICR limitations guide is a useful companion when you need to explain why further work is being recommended.

A small local repair may be enough, but repeated trips often mean the installation needs a better long-term solution. That can mean repairing the damaged point, separating a heavy load, upgrading a weak circuit, or recommending a fuller change to the consumer unit arrangement.

When the job becomes a formal report or a follow-on remedial visit, move the paperwork into the digital EICR certificate flow or turn it into a clear consumer unit upgrade quote rather than leaving it as a loose note.

When an RCBO keeps tripping, the temptation is to swap the device and move on. Most of the time the RCBO is fine — the fault is downstream, intermittent, or shared with a neighbouring circuit. A short, structured test sequence will narrow the cause in fifteen minutes rather than two callbacks.

Start by isolating the circuit and disconnecting any load. Energise the RCBO alone. If it holds, the fault is on the load side. Reconnect each piece of fixed wiring in turn, and finally each appliance, watching for the trip. If the RCBO trips even with no load connected, the device itself is suspect — but verify by swapping to a known-good RCBO of the same rating before condemning.