Why is my earth wire carrying AC voltage when the main switch is off – Advice from Electriman, North London Electricians

Finding voltage on your earth wire when the main switch is off is understandably alarming, and it should be taken seriously. Here is what is happening and what you should do.

What the earth wire is supposed to do

The earth wire in your home is a safety conductor. Under normal conditions it carries no current and sits at zero volts. Its job is to give fault current somewhere to go safely, which in turn trips the breaker or blows the fuse before anyone gets hurt.

Why it might be showing voltage

There are a few common reasons this happens.

1. A faulty appliance is leaking current onto the earth. Even with the main switch off at the consumer unit, some supplies such as a smart meter tail or a neighbour sharing a TNC-S supply may still be energised.

2. There is a wiring fault inside the property, such as a live or neutral conductor touching the earth conductor inside a socket, light fitting, or junction box.

3. Your property is connected to a TNC-S (PME) supply. In this arrangement the supply neutral and earth are combined at the cutout, so if the supply neutral loses its connection, the earth conductors in your home can rise to a dangerous voltage relative to true earth.

4. Voltage is being coupled in from a neighbouring circuit, especially in older properties where cables run close together for long distances.

What you can safely check yourself

Unplug every single appliance and turn off every circuit breaker inside the consum

Need a qualified electrician in North London?

Electriman covers Mill Hill, Barnet, Finchley, Edgware, Enfield, Watford and surrounding areas. All work is Part P certified and fully insured.