Earth wire and earthed sockets: colour, size and connection

Written by Engin Demirel · Electrical technician, master instructor · 12 years of experience

Short answer: The earth wire (protective conductor, PE) is green-yellow and is never used for anything else. Live is brown, black or grey and neutral is blue (IEC 60445). As common practice, the PE cross-section equals the live conductor up to 16 mm²: 1.5 mm² on lighting, 2.5 mm² on sockets. An earthed Schuko socket has metal earth clips on both sides. If a socket has no earth, never link earth to neutral; have a qualified electrician fix the wiring.

Cable colours: live, neutral and earth

Across Europe and in Turkey, cable colours follow IEC 60445 (HD 308, which replaced IEC 60446):

Live (phase): brown. On three-phase circuits brown, black and grey.
Neutral: blue.
Protective earth (PE): green-yellow.

Green-yellow is reserved for the protective conductor only and may not be used as live or neutral. Older installations may use other colours, or someone may have ignored the rule during a renovation, so never rely on colour alone; a qualified electrician confirms each conductor by measurement. Local rules apply in every country.

What size should the earth wire be?

The protective conductor must carry a large fault current safely until the breaker or RCD trips, so its size follows the live conductor. Common practice under IEC 60364-5-54:

Live up to 16 mm²: PE the same size.
Live 16–35 mm²: PE usually 16 mm².
Live above 35 mm²: PE usually half the live size.

In a home this means 1.5 mm² earth on lighting, 2.5 mm² on sockets and the same size as the live conductor on ovens, air conditioners and EV chargers. Multi-core cables already include a green-yellow core of matching size. See cable sizing; the binding values come from local regulations and the installation design.

Where does the earth wire connect?

Earthing works like a chain; one broken link means no protection:

Earth electrode: the foundation earth or a driven rod, see foundation earthing.
Main earthing terminal: the conductor from the electrode lands on the earth bar in the consumer unit. Metal water and gas pipes are bonded here too.
Distribution: each circuit's green-yellow core leaves the earth bar.
End point: the earth terminal of the socket and the earth screw on metal-bodied fittings and appliances.

The green-yellow wire is never connected to the neutral bar or the neutral terminal. More on the board in consumer unit basics.

Bathroom bonding

In bathrooms, metal baths, shower trays and water or heating pipes are connected to each other and to earth with an extra green-yellow conductor (supplementary bonding), so no dangerous voltage can appear between two metal surfaces during a fault. See bathroom lighting zones.

How to tell if a socket is earthed

Turkey and most of continental Europe use Schuko sockets:

Earthed socket: metal earth clips on both sides of the recess; the plug has metal strips on its sides.
Unearthed socket: two holes only, no clips.
Warning: clips do not prove a wire is connected behind them; older buildings sometimes have earthed sockets with an empty earth terminal.
Plug-in testers show whether earth is connected, but not how good the earth is.

A qualified electrician gives the definite answer. Measurement methods are in what earthing is and how it is measured.

What never to do without an earth

Never link earth to neutral at the socket. If the neutral breaks or live and neutral are swapped, the appliance body becomes live.
Never use a radiator or water pipe as an earth.
Never run metal-bodied appliances (washing machine, oven, EV charger) through unearthed adaptors.
An RCD is essential but does not replace earthing, see RCD types.

The right fix is new cabling with a green-yellow conductor from the board, plus a check of the building's earth, see rewiring a home.

Why EV chargers need earth

EV chargers draw high current for hours and connect to a metal car body. Chargers and cars monitor the earth and many refuse to charge without a good one. The wallbox circuit needs its own breaker, RCD and a correctly sized earth, see charging at home. In Bursa we check the earth during the site survey: charger installation.

Earth wiring is work for a qualified electrician. ENGN wires new homes in Bursa from the foundation up: villa electrical installation.

Frequently asked questions

What colour is the earth wire?

Green-yellow, reserved for the protective conductor. Live is brown, black or grey and neutral is blue. Old installations may differ, so rely on measurement, not colour.

What size should the earth wire be?

As common practice it equals the live conductor up to 16 mm²: 1.5 mm² on lighting, 2.5 mm² on sockets. Local regulations and the design set the final value.

Where does the earth wire connect?

To the earth bar in the consumer unit, then to the socket earth terminals and appliance bodies. Never to neutral.

How can I tell if a socket is earthed?

A Schuko socket has metal clips on both sides, but that does not prove a wire is connected. A plug-in tester shows the connection; an electrician confirms it.

Can earth be linked to neutral if there is no earth?

No. It is dangerous: a broken neutral or swapped wires puts live voltage on the appliance body. Install a proper earth conductor instead.

Does an RCD replace earthing?

No. An RCD is essential but works together with earthing, not instead of it.