Why Do RCDs Keep Tripping?

An RCD that keeps tripping is one of the most common reasons we get called to properties across Petts Wood, Orpington and Chislehurst. Sometimes it's a faulty appliance — easily sorted in five minutes. Other times it's a wiring fault that needs proper diagnosis. Here's how to tell the difference.

What Is an RCD and What Does It Do?

A Residual Current Device (RCD) monitors the balance of current flowing in and out of a circuit. If it detects that some current is leaking to earth — even a tiny amount, 30 milliamps — it cuts power within milliseconds. This is fast enough to prevent a fatal electric shock in most circumstances.

RCDs are designed to be sensitive, and that sensitivity is a good thing. But it also means they can trip from causes that aren't immediately dangerous — a damp appliance, a worn cable, even moisture in a light fitting.

Step One: Find Which RCD Has Tripped

Go to your consumer unit. Look for a switch in the middle position — neither fully up nor fully down — or one that's pushed down. That's your tripped RCD. Make a note of which circuits it protects. Most boards have the circuits labelled.

Is It an Appliance?

The most common cause of RCD trips is a faulty appliance. The most likely culprits are washing machines (especially older ones), dishwashers, tumble dryers, fridge-freezers and kettle. If the RCD trips when you plug something in, or when a machine starts its cycle, the appliance is almost certainly the cause.

Try this: reset the RCD. Then unplug everything on the affected circuits. Reset again. If it holds, start plugging appliances back in one at a time. The one that makes it trip again is the problem. Take it to be tested or replace it.

Does It Trip Even With Nothing Plugged In?

If the RCD trips when everything is unplugged, the fault is in the fixed wiring — not an appliance. This is a wiring issue and needs a qualified electrician to investigate properly. Wiring faults that cause nuisance tripping include: degraded insulation that allows current to leak to earth (common in older Petts Wood properties), water ingress into a cable or fitting, a damaged cable that's been trapped or kinked at some point, or a light fitting that has overheated and damaged its insulation.

Does It Trip at Night?

Night-time tripping is often caused by the fridge-freezer, which cycles on and off regularly, or storage heaters if your property has them. Immersion heaters on a night tariff can also be the culprit. The same unplugging process applies — identify the appliance that's triggering it.

Does It Trip in Wet Weather?

Outdoor sockets, outdoor lights and garden circuits are particularly prone to moisture ingress. If your RCD trips when it rains or after using an outdoor tap, look at anything on the affected circuit that's exposed to the elements. Even a small amount of water in a garden light fitting or an outdoor socket with a damaged cover can cause nuisance trips.

When Should You Call an Electrician?

You should call an electrician when the appliance removal test doesn't locate the cause, when the RCD trips immediately on reset even with nothing connected, when you can smell burning or see evidence of heat damage near any fitting, or when it's happening repeatedly and affecting your daily routine.

Fault finding in fixed wiring requires test equipment and the knowledge to interpret the results correctly. Attempting to diagnose or fix wiring faults yourself without training is not safe or legal for notifiable work.