An RCD (Residual Current Device) is a safety switch that cuts power within milliseconds if it detects electricity leaking to earth — protecting you from electric shock.
🏠Homeowner view
An RCD is a safety device fitted in your consumer unit (fuse box) or built into sockets and extension leads. It constantly monitors the electricity flowing in and out of a circuit. If even a tiny amount leaks — for example, through a faulty appliance or someone touching a live wire — it cuts the power in less than 40 milliseconds, fast enough to prevent a fatal shock. You can identify one by the Test button on it. Press Test occasionally to make sure it trips — if it doesn't, call an electrician. Most homes built after 2008 have RCD protection on all circuits. Older homes may only have partial coverage or none at all.