Why Does My RCD Keep Tripping?

An RCD that keeps tripping is one of the most common electrical problems we attend to across Greenwich and the surrounding area. It's frustrating when circuits keep going off — but the RCD is doing its job. The question is what's causing it to operate, and whether the problem is a faulty appliance, a wiring issue or something more fundamental.

What Is an RCD and Why Does It Trip?

An RCD (Residual Current Device) is a protective device that monitors the current flowing in and out of a circuit. If even a tiny amount of current is going somewhere it shouldn't — through a fault to earth, or through a person — the RCD detects the imbalance and disconnects the circuit in milliseconds.

An RCD tripping is never a false alarm. It means something is causing a leakage to earth on that circuit. The cause might be a faulty appliance, deteriorating wiring, moisture ingress, or a fault in the wiring itself.

Step 1: Identify Which RCD Has Tripped

Go to your consumer unit and look for any switch that is in the DOWN position. On most consumer units, RCDs are the wider switches. The ones that have tripped will have flipped down. Note which one it is — this tells you which circuits are affected.

Step 2: Unplug Everything on the Affected Circuits

Before trying to reset the RCD, unplug everything connected to the circuits it controls — starting in the rooms that have lost power. This includes all appliances, phone chargers, lamps and anything else with a plug.

Step 3: Try to Reset the RCD

With everything unplugged, try to switch the RCD back up. If it holds, the cause was almost certainly a faulty appliance. Plug things back in one at a time — when the RCD trips again, you've found the culprit. Discard or have that appliance inspected by a professional.

If the RCD Won't Reset

If the RCD won't stay up even with everything unplugged, the problem is in the fixed wiring rather than an appliance. This could be:

• Damaged or deteriorated cable insulation causing current to leak to earth
• Moisture in a socket, light fitting or junction box
• A wiring fault behind a wall or in the ceiling void
• A faulty consumer unit or RCD device itself

At this point you need an electrician. Fault finding in fixed wiring requires testing equipment and experience — you won't be able to resolve it by trial and error with the appliances.

RCDs That Trip Randomly (Not After Appliances)

If the RCD trips at random times — not apparently linked to any appliance being switched on — the most likely causes are:

• Aging wiring with deteriorated insulation, especially common in Greenwich's Victorian and 1930s properties
• A socket or light fitting with moisture ingress
• An RCD that's reaching the end of its service life and becoming oversensitive
• Multiple slightly-leaky appliances or circuits whose cumulative leakage trips the shared RCD

Nuisance Tripping on Older Consumer Units

Many older properties in Greenwich have dual-RCD consumer units where one RCD controls half the circuits in the property. When one of those circuits develops a fault — however minor — the entire half of the board goes off. This is one of the reasons RCBO-protected consumer units (where every circuit has its own individual protection) are now preferred: a fault on one circuit only takes out that circuit, not everything on the same RCD.

Should I Keep Resetting It?

Resetting is fine as a temporary measure, but a repeatedly tripping RCD is telling you something needs attention. If you can identify and remove the faulty appliance, the problem is solved. If you can't, or if the circuit keeps tripping even with nothing plugged in, don't keep forcing it — get an electrician to investigate.