UK Wiring Colours Guide
UK Wiring Colours Guide
UK mains electrical circuits follow a standardised cable colour system. All circuits use the same colours to identify wire types, such as live, neutral and earth. This is an important safety measure that allows people to correctly identify the wires in a circuit.
In the UK, mains circuit wires are now coloured according to a system that was introduced in 2006 and which is in line with the 18th edition of the IET Wiring Regulations. The system was changed in 2006 so the UK would match with mainland Europe. Before 2006, other colour systems were used.
The fact that the UK’s wiring colour scheme has changed can cause confusion. The wires in existing mains circuits might be coloured differently, according to when they were installed. This can make it difficult to correctly identify wires.
In this guide, we’ll explain the different colour schemes that have existed in the UK to help with wire identification.
Electrical work is always recommended to be carried out by a competent and suitably qualified electrician preferably registered with the NICEIC.
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The history of UK wiring colours
The colours that are used for mains wiring in the UK were set in 2006, when the government changed the UK’s wiring regulations to match with mainland Europe. This move was known as ‘harmonisation’, and the wiring colour designation system was changed to match the international standard IEC 60446.
The idea is to avoid confusion related to electrical circuits across Europe.
Nowadays, single-phase UK mains circuits are wired with a brown live wire, a blue neutral wire and a green and yellow earth wire.
In the scheme used from 1976 to 2006, the live wire was red, the neutral wire was black, and the earth wire was green and yellow. Before 1976, other systems were place. Between 1955 and 1976, the live wire was red, the neutral wire was black and the earth wire was either green and yellow, plain green or black. Other, older colour schemes have also existed.
Electric wire colours in the UK
Single-phase mains wiring circuits in the UK now follow this colour scheme:
-
Live – Brown
-
Neutral – Blue
-
Earth – Green and yellow
Having a standardised colour system helps electricians and other people who work with electrical circuits to identify the wires in a circuit.
What do the wires do?
-
The live wire (brown)
The live wire carries electricity to the appliance the electrical circuit is powering. The live wire will always carry electricity, as long as it is connected to the power source. -
The neutral wire (blue)
The neutral wire completes the electrical circuit for the appliance being powered by carrying electricity back to the power source. In all circuits, neutral wires present a risk of electric shock and should be treated with extreme caution. Be aware that in modern smart switches the neutral wire receives a constant flow of electricity, presenting a greater risk of electrical shock. -
The earth wire (green and yellow)
The earth wire is an important safety feature. It connects to the metal casing of the appliance and only comes into effect if there is a fault in the system. If the casing becomes live, current will flow through the earthing wire to the ground. In the process, it trips a switch, disconnecting the power from the circuit and making it safe.
Three-phase electrical circuits
A three phase circuit is a system that uses three alternating current (AC) conductors, called phases to transfer power. Three-phase electrical circuits use the same basic colour system as single-phase circuits, but there are also designated colours for the second and third live lines in the circuit.
-
Live line 1 – Brown
-
Live line 2 – Black
-
Live line 3 – Grey
-
Neutral – Blue
-
Earth – Green and yellow
In a three-phase system, live lines two and three also carry electricity to the unit being powered in the circuit.
Three-phase electrical circuits are used where a heavy power load is needed. They deliver higher power with greater efficiency.
Old electric wire colours in the UK
There is a potential for confusion where electrical circuits are installed according to old colour identification systems. Electricians and other people who work on electrical circuits need to know that different colour schemes existed in the UK before 2006. This is so they do not misidentify the wires if they encounter an old circuit, such as when doing minor repairs or rewiring a house.
Before 2006, single-phase mains wiring in the UK followed alternative colour schemes.
|
Function |
Current IEC scheme colour |
1976- 2006 |
1955- 1976 |
Pre 1955 |
|
Live (L) |
Brown |
Red |
Red |
Red |
|
Neutral (N) |
Blue |
Black |
Black |
Black, blue and green |
|
Protective earth (PE) |
Green and yellow |
Green and yellow |
Black, green, green and yellow |
Unspecified colour |
Three-phase electrical wiring
There were also different designated colours for the wires used in three-phase electricity in schemes used before 2006.
|
Function |
Current IEC scheme colour |
1976 - 2006 |
1955 - 1976 |
Colours used in schemes before 1955 |
|
Live Line 1 (L1) |
Brown |
Red |
Red |
Red |
|
Live Line 2 (L2) |
Black |
Yellow |
Yellow, white |
Yellow, white |
|
Live Line 3 (L3) |
Grey |
Blue |
Blue |
Blue, green |
|
Neutral (N) |
Blue |
Black |
Black |
Black, blue and green |
|
Protective Earth (PE) |
Green and yellow |
Green and yellow |
Black, green, green and yellow |
Unspecified colour |
How to identify and work safely with wiring
We always recommend that work with a mains electrical circuit is carried out by a competent and suitably qualified electrician, preferably registered with the NICEIC.
Before inspecting any electrical circuit, you should always:
- Make sure you have the correct protective gear
- Turn off the power supply
- Use a voltage tester to ensure there is no current in the circuit being inspected
Once the circuit is verified as safe, you can then remove any protective casings or coverings and inspect the wires in the circuit. For circuits installed after 1976, you should be able to identify wire types by colour according to the information given on this page.
The type of protective gear you need depends on the circuit in question and the type of work you’ll be doing. Typically, however, it includes at least protective gloves and non-conductive shoes.
Here’s a selection of common wiring accessories.
Wire strippers and insulated screwdrivers are also handy tools for electrical work.
Common wiring issues and troubleshooting
Remember to make sure you always follow the necessary safety precautions when working on an electrical circuit.
Here are some common issues with electrical circuits and some basic troubleshooting tips.
Incorrect wiring connections
If an electrical circuit is wired incorrectly, this can be very dangerous. Mixing the live and earth wires, for example, can create a serious risk of electrocution. It is important that all circuits are carefully inspected when they are installed, by a competent electrician.
Loose wires
Loose connections can simply cause intermittent faults in circuits, or they can cause buzzing, cracking or overheating issues. Overheating can be dangerous. Circuit connections can be tested if a circuit is disconnected and verified as safe.
Outdated wiring systems
Outdated wiring systems are more likely to have issues like loose connections or decayed wire coverings. Otherwise, they could have other less immediately obvious problems, such as power surges, that can damage appliances or cause faults.
Old wiring systems are something that an electrician should inspect for, and they should make a recommendation if they think it’s time to rewire a house.
Summary of UK wiring colours
Electrical wiring colour systems are an important safety feature that enable people to correctly identify the wires in an electrical circuit.
It is important for people who work on electrical circuits to understand the different systems that have existed in the UK, so they can correctly identify wires in old and new circuits. It’s also important that all new mains electrical installations follow the new colour system introduced in 2006.