Earthing and Electrical Safety at Home

Why earthing matters, the risks of two-wire circuits in older buildings, three-wire systems, equipotential bonding and what to check during a renovation.

Feeling a faint tingle when touching the washing machine, or a small shock from a metal sink: many people shrug these off as "normal in an old flat". In reality they show that current is leaking to the appliance casing and there is no safe path for it to earth. Earthing is one of the key elements that protect people in exactly these situations, and a renovation is the best time to get it right.

What earthing does

If insulation fails inside an appliance, the live conductor can touch the metal casing. If the casing is not earthed, it stays live, and current flows to earth only when someone touches it, through their body. If the casing is earthed, the current flows through the protective conductor, and protective devices, a breaker or an RCD, open the circuit.

In other words, earthing is not protection on its own but part of a protection system. It creates a safe path for fault current, and protective devices detect that current and disconnect the circuit.

A simple example helps. The insulation of a heating element inside a water heater deteriorates over time. In an unearthed home this can continue for months without any sign, until someone touches the tap or casing with wet hands. In a home with earthing and an RCD, the fault disconnects the circuit immediately and the owner knows at once that an electrician is needed.

Two-wire circuits in older buildings

In many older buildings, flat wiring has only two conductors: live and neutral. Sockets either have no earth contact or it is connected to nothing. Sometimes the earth contact is linked to the neutral inside the socket, which is a dangerous "fix": if the neutral breaks, the appliance casing can become live.

So a major renovation of an older flat should include rewiring with a three-wire system: live, neutral and a separate protective earth conductor. Whether the earth bar in the flat's panel is connected to the building's earthing system must be checked by an electrician and clarified with the building management.

Where it matters most

All socket circuits should be earthed, but some appliances and areas are particularly important:

• washing machines and dishwashers, combining water and metal casings;
• electric water heaters and heated towel rails;
• electric ovens and hobs;
• underfloor heating;
• computers and office equipment, where earthing also helps equipment work properly;
• sockets on balconies and terraces.

Equipotential bonding

In a bathroom, earthing the sockets is not enough. There are water pipes, a metal bath, metal shower parts and a heated towel rail. During a fault, voltage differences can arise between these metal parts, and in a wet environment the body's resistance is lower.

Equipotential bonding connects all these metal parts with separate conductors to one bar, which is connected to the earthing system. As a result, all metal parts in the bathroom stay at the same potential and no dangerous voltage difference can develop between them. This system must be installed at the concealed-work stage, before tiling.

Earthing and RCDs together

An RCD detects leakage current; earthing provides a path for it. On an unearthed circuit an RCD trips only when someone touches a live casing; with earthing it can disconnect as soon as a fault occurs, before anyone touches anything. The two systems do not replace each other; they work together.

In a private house, the earth electrode system is built in the ground outside with driven electrodes. Its resistance is measured and must meet the relevant standards. This takes design and testing; burying a single pipe is not enough.

Renovation checklist

• are all sockets on three-wire circuits with a working earth contact;
• is the earth conductor never joined to the neutral anywhere;
• has equipotential bonding been installed in the bathroom;
• are the earth and neutral bars separate in the panel;
• has the electrician measured earth continuity and insulation resistance and recorded the results.

The test record is more than a safety document. When a new appliance is added or circuits are extended later, another electrician can learn the condition of the existing system from it.

The electrical division of Zaferoğlu İnşaat installs and upgrades wiring in residential and public buildings. If your sockets have no earth contact and there is no RCD in the panel, that is the first thing to check before renovating, and we can start there with you.