How do I test if my RCD is working properly?

How to Test Your RCD at Home An RCD (Residual Current Device) is a life-saving safety switch fitted in your consumer unit (fuse box) or plugged into a socket. It detects tiny electrical faults and cuts power within milliseconds — fast enough to prevent a fatal electric shock. The Simple Monthly Test Every RCD has a TEST button, usually labelled 'T' or 'TEST'. Here's how to use it safely: Before you test: Make sure any sensitive equipment (computers, recording devices, fish tanks with heaters) is turned off or unplugged, as the circuit will lose power briefly. Press the TEST button firmly — the RCD should trip instantly and the switch will move to the OFF or middle position. If it trips correctly: Press the reset button or push the switch back to ON. Your RCD is working. If it does NOT trip: The RCD is faulty and must be replaced by a qualified electrician as soon as possible. If it trips but won't reset: There may be a fault on the circuit. Try unplugging all appliances on that circuit and attempt to reset again. If it still won't reset, call an electrician. What RCDs Protect You From Electric shock — if you touch a live wire, the RCD detects current escaping to earth and cuts power in under 40 milliseconds. Electrical fires — caused by insulation faults and leakage currents. Types of RCD in Your Home Consumer unit RCD — covers multiple circuits in your fuse box. RCBO — individual device protecting one circuit with both overcurrent and RCD protection. Plug-in RCD adaptor — portable, used with outdoor or workshop equipment. When to Call an Electrician The TEST button does nothing. The RCD trips randomly without a test. It won't reset even with all appliances unplugged. The RCD is over 10 years old and has never been tested. You're unsure which circuits are protected. Test your RCD every month. It takes 10 seconds and could save your life.