It only trips when I run the washing machine — is it the machine?

Almost always yes, but two cases are worth separating. Tripping as the programme starts usually points to the motor or the element; tripping only during the heating phase points to the element with near certainty. Try the machine on a socket on a different circuit: if it trips there too, the appliance is the culprit.

Why does it trip in the early hours when nobody is awake?

Because some appliances run on their own overnight. The electric water heater comes on during the cheapest tariff window and air conditioning cycles. If the trip always happens at the same time, whatever switches on at that hour is the first suspect.

Is it normal for an RCD to trip occasionally?

No. A healthy RCD may trip during a severe storm or on a one-off appliance fault, but not repeatedly. More than once a month with no obvious cause means there is a real fault that is getting worse.

What is the difference between the RCD and the breakers?

The RCD protects people: it detects current escaping to earth, typically from 30 mA, and disconnects. The breakers protect the cable against overload and short circuits. That is why a short circuit trips a breaker and an earth fault trips the RCD.

Is a super-immunised RCD worth fitting?

It is worth fitting when the problem is nuisance tripping from transients and electronic harmonics — drives, poor-quality LED lighting, IT equipment — because it discriminates those signals without losing sensitivity to a genuine leak. It is not a way to paper over an existing fault: if there is a real leakage it will still trip, and it should.

RCD keeps tripping and will not reset — what to do

If there is also a burning smell, visible smoke, or the consumer unit feels warm as you approach it: switch off the main isolator, leave the property and call 112. Stop testing.

Right now

1Unplug everythingDisconnect the washing machine, dishwasher, water heater, air conditioning and anything else in a socket. An appliance with moisture inside is the most common cause.
2Switch all the small breakers offLeave the row of smaller switches to the right of the RCD in the off position. Only the RCD stays up.
3Reset the RCDIf it now stays up, the leak is in one of the circuits rather than in the RCD itself.
4Switch the breakers back on one at a timeWait a few seconds between each. The one that trips the RCD identifies the circuit with the fault: leave it off, and you already know what to tell us.

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Why it happens

Moisture in an appliance

Water heaters, washing machines and dishwashers collect moisture around the element or the cable gland. It is the most common cause, and it typically starts tripping in the early hours when the water heater kicks in.

A fault on the outdoor circuit

In coastal properties, junction boxes on terraces, pools and gardens take in water over time. Salt accelerates corrosion at the terminals, so the fault often appears after a storm or after watering.

Many small leakages adding up

Every electronic device leaks a little to earth. With enough equipment connected the total can approach the RCD's 30 mA without anything being faulty. The giveaway is that it only trips when everything is running at once.

An aged RCD

The mechanism loses precision over the years and ends up tripping below its rated threshold. If it trips with every circuit switched off, the device itself is the problem.

Neutral touching earth

A neutral and protective conductor in contact inside a junction box trips the RCD in an apparently random pattern. It is typical after refurbishment or after a new light point is installed.

What we do on arrival

We measure insulation resistance circuit by circuit with the board isolated, until the faulty one is identified.
We check continuity of the protective conductor and that neutral and earth are separated in every box on the affected circuit.
We verify that the RCD actually trips at its rated threshold: a device that fails to trip is as dangerous as one that trips too readily.
We repair the specific point — terminal, box, cable run or appliance — and re-measure to confirm the leakage is gone.
You get a written record of what was measured and the values found, so the state of the installation is documented.

Frequently Asked Questions

Yes, provided the property has no power with it off and you do not depend on a fridge or medical equipment. What must never be done is bypassing it or replacing it with a plain breaker: the RCD is the device that protects people from a shock.