RCD keeps tripping: causes & solutions

An RCD switches off when there's leakage current to earth, often caused by a defective appliance or moisture. With a systematic search method you can identify the culprit.

Why an RCD trips and when to call an electrician

An RCD compares the current going into a circuit with the current coming back. If there's a difference, current is leaking somewhere: via an appliance, via moisture or in the worst case via a person. The device then cuts the power in a fraction of a second. So this isn't a fault in the RCD, but a sign that it's doing its job.

The most common causes

• Appliances with a heating element, such as a washing machine, dishwasher, dryer, oven, kettle or electric water heater. The element can start to leak after years of use.
• Moisture in an outdoor socket, garden lighting, an outdoor lamp or a socket in the bathroom. If the RCD trips mainly when it rains, this is the first place to look.
• A leak in the house causing water to reach a junction box, light fitting or socket.
• A damaged cable, for example after drilling or nailing into a wall.
• Many appliances on the same RCD (residual current device). Each appliance leaks a tiny bit; together that can be just too much.
• An old RCD that's becoming more sensitive or no longer working properly.

What you can safely do yourself

You may switch the circuits and the RCD (residual current device) using the switches on the front, as in the step-by-step plan above. Also unplug appliances from the socket to rule out an appliance. Nothing more: never remove a cover plate from the fuse box (consumer unit), don't unscrew sockets and don't hold the switch up or tape it up. Press the test button (T) of the RCD (residual current device) every so often. It should trip immediately. If it doesn't, have the device checked.

When an installer is needed

• The RCD (residual current device) trips even when all appliances are unplugged.
• You smell burning, see discolouration or the fuse box feels warm.
• Water has got near sockets, lights or the fuse box.
• The switch won't go back up or doesn't respond to the test button.

A qualified electrician measures the insulation of each circuit with special equipment. That way he sees exactly which cable, which point or which fixed appliance is causing the leakage current. He then repairs the fault, replaces a defective switch or distributes the circuits better across multiple RCDs. Would you like this investigated? On our electrical fault page you can read how we tackle it.