Why is my earth conductor at the consumer unit showing 40°C when outside is cold?

Finding your earth conductor warm to the touch at the consumer unit is not normal and should be taken seriously. In a healthy electrical installation, the earth wire carries no current during normal operation. If it is warm, current is flowing through it, and that current is going somewhere it should not. What is most likely happening The most common reason is a fault where the neutral and earth conductors have become connected somewhere in your wiring or in a piece of appliance wiring. This creates two paths for the return current to travel home, and some of that current diverts down the earth wire. Even a small amount of sustained current will generate heat in a conductor. Other possible causes include a faulty appliance with an internal wiring fault, a deteriorated or damaged cable where the neutral and earth cores are touching, a loose neutral connection at the consumer unit or a junction box causing arcing, or an incorrectly wired socket or light fitting somewhere in your home. What you can safely do yourself You can feel along the earth cable carefully to see if the warmth extends beyond the consumer unit — but do not open the consumer unit yourself. You can switch off each circuit one at a time and feel whether the earth conductor cools down. If it cools when a specific circuit is off, that circuit is likely the source of the fault. You can unplug all appliances on the suspected circuit and see if the temperature drops further. When to call an electrician You should call a registered electrician today, not next week. A warm earth conductor indicates a live fault that may be getting worse. If the earth wire ever becomes damaged or disconnected while this fault exists, you lose your shock protection entirely. Look for an electrician registered with NICEIC, NAPIT, or SELECT in Scotland, and explain that you have a warm earth conductor at your consumer unit.