Why is my RCD tripping but the electrician can't find the fault – Advice from Electriman, North London Electricians

Why Your RCD Keeps Tripping But the Electrician Can't Find the Fault

This is one of the most frustrating electrical problems a homeowner faces. Your RCD (Residual Current Device) is doing exactly what it should — detecting a leakage of current to earth — but the fault is either intermittent, very small, or spread across multiple sources, making it hard to pin down during a routine visit.

What an RCD actually does

An RCD monitors the difference between current flowing out through the live wire and returning through the neutral. If more than 30mA escapes (to earth or through a person), it trips instantly to protect you. Something doesn't have to be dramatically wrong for it to trip.

Common reasons it's hard to find

The fault only appears under load or heat — wiring insulation that's fine when cold can break down when warm

Damp or moisture — a wet garden cable, a damp outdoor socket, or condensation in a light fitting can cause leakage that dries out before the electrician arrives

Ageing appliances — washing machines, dishwashers, electric ovens, and immersion heaters develop small earth leakage over time

Cumulative leakage — each appliance on a circuit may pass individual tests, but together they exceed the RCD threshold

Time-of-day patterns — if it trips at night, suspect a storage heater, overnight appliance, or moisture build-up

Faulty RCD itself — RCDs can bec

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Electriman covers Mill Hill, Barnet, Finchley, Edgware, Enfield, Watford and surrounding areas. All work is Part P certified and fully insured.