RCD Keeps Tripping? What It Means and What to Do
The switch on the fuse box keeps going off, sometimes when the kettle or shower goes on, sometimes in the rain, sometimes for no reason you can see. Resetting it works for a while and then it goes again. This guide explains what the RCD is doing, what you can safely check, and when to stop and have the cause found.
What an RCD is, and why it trips
An RCD (residual current device) is the switch on the fuse box that watches for current leaking out of a circuit, usually to earth through a fault or through a person. When it sees that leak it cuts the power in a fraction of a second. It is there to protect people, not to protect the wiring, and it is very sensitive on purpose.
So when an RCD keeps tripping, it is doing its job. Something on one of the circuits it covers is leaking current. Resetting the switch puts the power back on, but it does not remove the fault, which is why it keeps happening.
The usual reasons an RCD keeps tripping
Most repeated trips are caused by leakage on an appliance, circuit or the installation. If testing points to the protective device itself, that can be checked too. The usual causes are:
A faulty appliance. A kettle, washing machine, dishwasher, oven or immersion heater with a failing element or damp inside it. Often the trip happens only when that appliance is used.
Water in an outside socket or light. Rain getting into a garden socket, a security light or a shed supply. These trips follow the weather.
A damaged cable. A nail or screw through a cable, a cable chewed by a mouse, or one disturbed by building work.
An old circuit with tired insulation. Older wiring can leak a little everywhere, and a modern RCD notices. In one AJS job the lights in the old part of the house kept tripping until the circuit turned out to need rewiring.
A fitting or accessory that has failed. A light fitting, a shower isolator or a socket with a loose or burnt connection.
A fault that only shows up when something new is added. New equipment can introduce additional earth leakage or reveal an existing fault that was not obvious before.
Not sure which it is? Note what was on when it tripped, and whether it had been raining.
What you can safely check before calling
There are only a few things worth doing yourself, and none of them involves opening the fuse box.
Unplug everything on the affected circuits. Kettles, chargers, lamps, the lot. Then reset the RCD once.
If it stays on, plug things back in one at a time. The one that trips it is the likely culprit; leave it unplugged.
If it trips straight away with everything unplugged, leave it off. The fault is in the fixed wiring, an outside circuit or a fitting, and it needs testing rather than guessing.
Do not hold, tape or bypass it. An RCD is a safety device designed to disconnect when leakage is detected.
If it will not reset, or there is any smell of burning, stop there. Leave the power off to that part of the house and call. Those two situations are covered on the emergency electrician page.
How the cause is found
You say what trips, when it started, whether it follows an appliance or the weather, and what has been added or changed recently. A photo of the fuse box on WhatsApp helps.
The circuits the RCD covers are isolated and tested one at a time, so the faulty one is identified rather than guessed.
On that circuit, the sockets, fittings, outside points and cable runs are checked until the leak is found.
You are told plainly what it is, what it will take to put right, and what it will cost before any repair beyond the fault finding is agreed.
The work itself is described on the electrical fault finding and repairs page. If the fault turns out to be the board rather than a circuit, that is covered on the consumer unit upgrades page, and it is only suggested when the tests show it is needed.
Half the house has gone off
Many fuse boxes have one RCD covering several circuits: perhaps the downstairs sockets, the kitchen, the outside lights and the shower together. One leaking outside socket can therefore take all of them off at once. That is why “no power in half the house” and “the RCD keeps tripping” are usually the same problem. If the whole street is off, that is the network operator: dial 105.
What customers have said
“Talked me through the fuse box over the phone to identify the problem. When they turned up to repair the issue , they were on time and polite and resolved the problem quickly.”
Checkatrade review, lights tripping fuse box, TN16
“Informed me of their estimated time of arrival. Mr Marsh was courteous, polite and listened to what I needed doing and then got on with fixing the problems. One of the problems was not fixed the way I thought it might be but Mr Marsh worked out what the problem was quickly and now I have my downstairs plug points working again as well as my bathroom lighting.”
Checkatrade review, locating and disabling a tripping electrical fuse, CR5
“Alex is a real find. Not only is he an expert electrician, but also he was friendly, he offered great advice, he was communicative when booking/confirming appointments, he was punctual and ....he doesn't overcharge. Happy to recommend AJS Electrical Services.”
Checkatrade review, stopped electrics tripping and installed new oven, RH1
Common questions
Is it dangerous if the RCD keeps tripping?
The trip itself is the protection working. The danger is the fault it is reacting to, which is why it should be found rather than reset over and over. If it will not reset, leave it off.
Can i just keep resetting it?
Do not keep resetting it repeatedly. If it trips again after one reset and there is no obvious appliance cause, leave it off and have the fault investigated.
Why does it trip when it rains?
Water is getting into something outside: a socket, a light, a shed supply or a junction. Unplug anything outside, reset once, and have the outdoor circuit checked.
Why does it trip at night when nothing is on?
Fridges, freezers, heating controls and immersion heaters switch themselves on and off, and a failing one can trip the RCD at random. It can also be a damp outside fitting as the temperature drops.
Will i need a new fuse box?
Usually not. In most cases a tripping RCD is a fault on a circuit, not a fault in the board. A new board is only suggested when the tests show the board itself is the problem or cannot be made safe.
Tell us what trips and when
What goes off, when it started, whether it follows an appliance or the weather, and what has been added recently. You can send a photo of the fuse box on WhatsApp. Finding the cause is part of electrical fault finding and repairs.