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The RCD keeps tripping: the four most common causes

A tripping residual current device is not a defect but a message. How to narrow down the source in a few steps.

10 min read

A residual current device trips when electricity takes a path it should not take. That is precisely its job. The only question is where that path comes from.

How to narrow it down yourself

Switch off all fuses in the affected circuit, switch the RCD back on, then add the fuses one by one. If it trips again on a particular one, the fault is in that circuit. Then disconnect every device there and plug them in one at a time.

The four most common causes

  • Moisture in outdoor sockets or in the laundry room.
  • A faulty heating element in a washing machine, dryer or dishwasher.
  • Damaged cables after drilling into a wall.
  • Several devices each with a small leakage current that add up.

That last point is often missed: every power supply has a permitted leakage current. Ten of them on one circuit are enough to reach the trip threshold without a single device being faulty.

If the RCD cannot be switched on at all, or trips with no discernible pattern, the installation needs measuring. In case of a fault we come the same working day.