Why Your RCD Keeps Tripping, and How Electricians Actually Find It

An RCD that trips is doing its job. The question is what is causing the leakage, and the answer is almost never 'the RCD is faulty', though that is the diagnosis people most often arrive at after an hour of guessing.

The usual suspects

• Water ingress, outdoor sockets, garden lighting, bathroom extractors and leaking roofs above ceiling roses. Trips that only happen after rain are almost always this.
• Faulty appliances, immersion heaters, washing machines, kettles and old fridges are the classic four.
• Accumulated standing leakage, every appliance leaks a few milliamps. Ten of them on one 30mA RCD is enough to sit permanently on the edge.
• Damaged cable, a picture hook or screw through a wall cable. Often intermittent for months first.
• Neutral-to-earth faults, frequently caused by a badly wired socket or a light fitting swapped by someone in a hurry.

Safe checks before you call

1. 1Unplug everything on the affected circuits, then reset. If it holds, plug things back one at a time, waiting a few minutes between each.
2. 2Note whether tripping correlates with weather, time of day, the shower, or the washing machine's heat cycle. This information genuinely halves diagnosis time.
3. 3Check for water anywhere near an outdoor socket or garden light.
4. 4Do not repeatedly reset a breaker that will not hold. It is protecting you from something.

How we find it properly

Professional fault finding is systematic, not intuitive. We isolate the installation and run insulation resistance testing at 500V between live conductors and earth, circuit by circuit. A healthy circuit reads above 1MΩ, in practice a good one reads hundreds. A wet or damaged circuit will read in the kilohms and reveal itself immediately.

From there we half-split: disconnect at the mid-point of the circuit, retest, and keep halving until the fault is isolated to a single accessory or cable run. On an intermittent fault we may also leave a leakage clamp meter logging over time, because a fault that only appears when a heating element expands will never show up in a ten-minute visit.

“They were very good and they managed to fix our sockets and wiring, it stopped working 3 times while they were with us and they stayed to fix it a lot more times.”

That review is the standard we hold ourselves to. Intermittent faults are the hardest kind, and we do not leave while one is still hiding. Call 07938 382020 for same-day fault finding across London.