Earth leakage (fuga a tierra, ground fault)

What earth leakage is

In a healthy circuit, all the current that goes out on the live (phase) wire comes back on the neutral. If some of it strays to earth, through an appliance casing, a damp wall or a person’s body, there is a leak. The RCD (diferencial) compares outgoing and returning current: when the difference reaches its sensitivity, 30 mA in homes, it cuts the power.

Usual causes

• Damp: outdoor sockets, terraces, boxes with water ingress or splashes. That is why so many leaks show up when it rains.
• Faulty appliances: washing machines, water heaters (termos) with a damaged element, fridges or ovens.
• Worn cables from age, rodents, heat or building work.
• Many small leaks from electronic devices all on a single RCD.

How to find the culprit

1. Switch off all the circuit breakers (MCBs) and switch the RCD back on.
2. Switch the MCBs on one at a time. The one that trips the RCD is the circuit with the leak.
3. With that circuit off, unplug its appliances and try again. If it stops tripping, an appliance is to blame; if not, the fault is in the wiring.

Without earthing (grounding), a leak may not trip the RCD until someone touches the casing and feels a shock.

When to call us

If the RCD will not reset with everything unplugged, trips whenever it rains or you feel tingling from taps or appliances, the insulation needs testing with instruments. See RCD keeps tripping and electric shocks from taps in Seville, Spain.