Why Your RCD Keeps Tripping and What an EICR Would Find

An RCD that keeps tripping is one of the most common reasons London households call an electrician. It is annoying when the power drops out at random, but the RCD is doing its job: it has seen current leaking somewhere it should not. This guide explains the usual causes, what you can safely check yourself, and what an EICR would look for.

What an RCD actually does

A residual current device compares the current going out on the live conductor with the current coming back on the neutral. If they differ by more than a small amount, usually 30 milliamps for socket and bathroom circuits, it switches off in a fraction of a second. That difference means current is escaping to earth, which could be through damaged cable, water, or a person. The RCD is one of the most important safety devices in a modern consumer unit.

Common reasons it keeps tripping

• A faulty appliance. Kettles, washing machines, dishwashers, immersion heaters and outdoor lights are the usual suspects, especially as elements age.
• Water getting in. Outside sockets, garden lighting, leaks above light fittings and damp in cellars or extensions all cause trips, often after rain.
• Damaged cable. A nail or screw through a cable, rodent damage under floors, or old rubber insulation breaking down in older London houses.
• Too many circuits on one RCD. Split load boards put half the house on one RCD, so small leakages from many appliances add up until it trips.
• A neutral and earth fault. A borrowed neutral or a neutral touching earth, often left behind by an earlier DIY job.
• A worn RCD. Less often, the device itself has become over sensitive and needs replacing.

What you can safely check yourself

Switch everything off at the plug, reset the RCD, then plug appliances back in one at a time. If the RCD trips when one item goes back on, that appliance is the likely cause and should be checked or replaced. If it trips with everything unplugged, or when you switch on one particular circuit breaker, the fault is in the fixed wiring and needs an electrician. Do not tape the switch up or swap the RCD for something less sensitive.

What an EICR would find

An Electrical Installation Condition Report tests every circuit, so it usually pins down a nuisance trip quickly. During the inspection we measure insulation resistance on each circuit, which shows cable that is leaking current, and we test each RCD for trip time. We also check that circuits are on the right RCD and that neutrals are not shared between circuits. Findings are coded on the report, and a fault causing repeated tripping is often recorded as a C2 or an FI until it is traced.

When the board is the problem

Older split load boards with one or two RCDs covering many circuits are a common cause of trips that never quite go away. Upgrading to a consumer unit with RCBOs gives each circuit its own protection, so one fault only switches off one circuit rather than half the house. We cover what affects the cost in our guide to fuse board replacement in London.

Getting it fixed

Energy North Ltd traces tripping faults and carries out EICR inspections across North, East and West London. Our City & Guilds certified electricians can usually attend within 48 hours, and any certificate is emailed the same day. If you are planning a car charger, it is worth sorting a tripping RCD first, as a new circuit needs a healthy installation. See our EV charger installation page for more.