RCD keeps tripping: find the leakage current, don't just reset

RCD, RCCB, "the 30 mA": whatever the name, the mechanism is the same. The device compares the current entering a circuit with the current leaving it, and cuts off as soon as the gap exceeds thirty milliamps — because that gap means current is going somewhere else, to earth, potentially through someone. Our page on a breaker that keeps tripping explains the difference from an ordinary breaker and gives the circuit-by-circuit isolation method. Here we go further: why the leak exists, where it hides, and how we find it when the simple method isn't enough.

Why an RCD trips "for no reason"

It's the sentence we hear most, and it deserves an explanation. An RCD doesn't need an appliance to be outright broken to trip. Three mechanisms explain most cases.

The build-up of small leaks

Every electronic appliance — router, television, computer, induction hob, washing machine with an electronic board — lets a tiny current through to earth via its filters, half a milliamp, a milliamp. That's normal and harmless. But a modern home easily has twenty or thirty of them on the same RCD, and the sum approaches the threshold. It then only takes a slightly tired appliance, or a damp day, to cross it. Nothing is broken, and yet it trips — often in the evening, when everything is running at once.

The appliance that leaks a little

A heating element whose insulation is ageing — scaled water heater, washing machine, oven, tumble dryer — lets through a current that rises with temperature. The appliance works, but as soon as it heats up the RCD drops out. It's the most frequent case after the build-up, and it's recognisable by the timing: it trips a few minutes after starting, not at switch-on.

The installation itself

A damp junction box, an outdoor cable whose sheath has let water in, an old circuit whose insulation is crumbling inside a wall: the leak is in the walls, not in an appliance. It's recognisable by one precise sign — the RCD trips with everything unplugged. Then we're no longer looking for an appliance, we're measuring circuits.

What the timing of the trip reveals

As with any fault, context speaks. If it trips when one particular appliance starts, it's that one. If it trips a few minutes later, it's a heating element leaking as it warms. If it trips in the rain or after a storm, look outside — garden lighting, gate, enclosure — as we explain for the houses of Auteuil. If it trips at night, with nobody about, it's the water heater switching on during off-peak hours. If it trips at the first cold snap, an electric radiator with a cracked element is suspect number one.

And if it trips with everything switched off and nothing plugged in, the fault is in the panel or in the walls — or the RCD itself is at the end of its life.

Is the RCD the right type?

There are several kinds of 30 mA RCD, and fitting the wrong one creates nuisance tripping that no leak search will ever resolve.

Type AC, the most common, only detects alternating leaks. Type A also detects leaks with a direct-current component, produced by appliances with electronic speed control: the standard requires it for the hob and the washing machine. An induction hob on a type AC device is the classic "it trips when I cook" scenario with no fault at all. Type HPI — high immunity — tolerates micro-cuts and the stray currents of motors and IT equipment: we reserve it for the freezer, so you don't find its contents thawed after a phantom trip, and for circuits feeding sensitive equipment.

Matching the type to the circuit is often the real answer to an RCD that trips "for nothing". And it's also the moment to check there isn't a single RCD for the whole home: in that case the slightest leak switches everything off, whereas two or three well-distributed RCDs limit the cut to one area and immediately show where to look — our electrical panel replacement page details that distribution.

What the electrician does

When the isolation method isn't enough — because the leak is diffuse, intermittent or inside the walls — we move on to measurement. A leakage clamp meter reads, circuit by circuit and appliance by appliance, the current actually escaping: you watch the washing machine go from two to twenty milliamps as it heats. An insulation tester, with the power off, tests each circuit and reveals the one whose insulation has aged, even with no appliance connected.

Only then do we repair: replacing the appliance or its element, reworking the circuit or box at fault, changing the RCD if it's tired or the wrong type, redistributing circuits across several RCDs. And we press the "T" button on every RCD before leaving — a test worth doing yourself once a month, because an RCD that doesn't trip on test is an RCD that no longer protects you.

Two things never to do: bypass an RCD "to have power in the meantime", and replace it with a less sensitive model so it holds. In both cases you remove the protection without removing the fault.

Our intervention

For an RCD that keeps tripping in Paris or the inner suburbs, we come within 24 to 48 hours, faster in the 15th where our base is. Callouts start at €132 incl. VAT, covering travel and the first half hour, which covers the leak measurement and identification of the circuit in most cases; if an appliance or a rework is needed, we tell you the amount before continuing. And if we don't find the fault, you aren't charged for the callout. For our general method, see the electrical troubleshooting page; our pricing is public, and you can contact us by phone or through the form.