Why Do RCDs Keep Tripping? Common Causes and Fixes

An RCD (Residual Current Device) is a safety device — when it trips, it's doing its job. But if it keeps tripping, something is wrong. Here's how to diagnose the most common causes.

What Is an RCD and Why Does It Trip?

An RCD monitors the current flowing through a circuit. If it detects even a small imbalance — as little as 30 milliamps — it cuts the power in milliseconds. This prevents electric shock and reduces the risk of fire. When the RCD trips, it's protecting you.

Common Causes of RCD Tripping

A Faulty Appliance

The most common cause. A faulty appliance — a washing machine with a failing motor, a kettle with a damaged element, a damaged extension lead — can cause the RCD to trip when it's switched on or used. Test this by unplugging all appliances on the circuit and resetting the RCD. Plug them back in one at a time to identify the culprit.

A Wiring Fault

If the RCD trips even with nothing plugged in, there's likely a wiring fault — damaged cable insulation, a loose connection or moisture in a socket or fitting. This needs a qualified electrician to trace and repair.

Water Ingress

Water getting into outdoor sockets, garden lighting or bathroom fittings is a common cause of RCD tripping — especially after rain. All outdoor electrics should be IP-rated and regularly inspected.

Nuisance Tripping

Some appliances — particularly older motors, some types of lighting and certain IT equipment — can cause nuisance tripping even when functioning correctly. This can be addressed by installing a dedicated circuit or using a high-sensitivity RCD.

What to Do When Your RCD Trips

1. Unplug all appliances on the affected circuit.
2. Reset the RCD and see if it holds.
3. If it holds, plug appliances back in one at a time to find the faulty one.
4. If the RCD trips with nothing plugged in, call an electrician — there's a wiring fault.
5. Never tape the RCD in the on position or bypass it.

When Should You Call an Electrician?

Call an electrician if: the RCD trips with nothing plugged in; you can't identify the faulty appliance; the RCD trips repeatedly on the same circuit; or the RCD is hot or shows signs of burning. Don't keep resetting a tripping RCD without finding the cause.