Types of Electrical Wiring and Cables Explained: A UK Guide

Updated October 2026 · Meteor Electrical guides · 10 min read

This guide explains the different types of electrical wiring and cables you will find in UK and Irish homes and buildings: what each cable is, how to recognise it and what it is used for. It also covers cable codes, the UK cable colours and how single-phase and three-phase wiring differ.

If you already know the cable types and need help sizing cable for a particular circuit, see our guide to the best electrical cable for home wiring, which focuses on choosing cable sizes for house wiring.

What are the main types of electrical cable?

Every cable has three basic parts: one or more conductors (almost always copper in buildings), insulation around each conductor, and usually an outer sheath for protection. The way these parts are built decides where a cable can go and what it can do. The table below gives a quick reference to the cable types covered in this guide.

You can browse every type in our electrical cables range, from twin and earth and SWA to data and coaxial cable.

What do cable codes like 6242Y mean?

UK cables are often known by a British Standard type code. You will see 6242Y for PVC twin and earth, 6243Y for 3 core and earth and 6491X for single-core cable. In many of these codes, a final Y or X marks the PVC version and a final B marks the low smoke zero halogen (LSZH) version, such as 6242B or 6491B. Always check the product data, as codes vary between cable families.

Copper or aluminium conductors?

Copper is used for almost all wiring inside homes and commercial buildings because it conducts well, is easy to terminate and resists fatigue. Aluminium is lighter and cheaper, so it appears in some large supply and distribution cables, but it needs specific terminations and is not used for domestic final circuits.

What is twin and earth cable used for?

Twin and earth (T&E, 6242Y) is the flat, grey or white sheathed cable that wires almost every UK house. It has a brown line core, a blue neutral core and a bare circuit protective conductor (CPC), which must be sleeved green and yellow wherever it is terminated.

It is used for lighting circuits, ring and radial socket circuits, cookers, showers and immersion heaters. Sizes run from 1.0mm² to 16mm², and the right size depends on the circuit design. Shop our twin and earth cable in PVC and low smoke versions.

What is 3 core and earth cable used for?

3 core and earth (6243Y) looks like twin and earth but has three insulated cores, coloured brown, black and grey, plus a bare CPC. The extra core is what makes it useful for switching.

Its main job is two-way and intermediate lighting, where the black and grey cores act as strappers between switches. It is also used for extractor fan feeds through a fan isolator, where the fan needs a permanent live, a switched live and a neutral. Most domestic jobs use 1.0mm² or 1.5mm². See our 3 core and earth cable range, and our detailed comparison of 3 core and earth vs twin and earth for wiring and colour guidance.

What is SWA armoured cable?

Steel wire armoured (SWA) cable has insulated cores, a bedding layer, a layer of galvanised steel wires and a tough outer sheath, usually black PVC. The armour protects the cable from impact, digging and crushing, and can act as the CPC where the circuit design confirms it is adequate.

SWA is the usual choice for supplies to garden rooms, garages, outbuildings, outdoor lighting and EV chargers, and for sub-mains in commercial and industrial buildings. It comes in 2, 3, 4 and 5 core versions. Underground, it should be laid at a suitable depth with warning tape above and terminated with the correct glands. Browse our SWA armoured cable, and see our SWA installation guide for cutting, laying and glanding.

What is flex and when do you use it?

Flexible cable, or flex, has conductors made of many fine copper strands, so it can bend again and again without breaking. A standard 3 core flex (3183Y) has brown line, blue neutral and green and yellow earth cores; 2 core flex (3182Y) is for double-insulated equipment.

Flex is for the final connection to appliances, pendant lights, heaters and portable equipment, not for fixed circuit wiring. There are versions for different conditions:

• PVC flex (3183Y): general appliances and pendants indoors.
• Heat-resistant flex (3093Y): immersion heaters, storage heaters and hot light fittings.
• Arctic flex: stays flexible in cold weather, so it suits outdoor tools and site equipment.
• Rubber flex (H07RN-F): heavy-duty and outdoor use, where oil, abrasion or water are likely.
• LSZH flex: where low smoke materials are specified.

Shop our full range of flexes, including heat-resistant, arctic and LSZH versions.

What is single-core cable (6491X)?

Single-core cable has one insulated conductor. Unsheathed 6491X (PVC) and 6491B (LSZH) are drawn into conduit or trunking, used inside distribution boards and control panels, and used for earthing and main protective bonding conductors in green and yellow. Because they have no outer sheath, they must be enclosed and never clipped bare to a wall or buried in plaster.

Double-insulated single-core cable, such as 6181Y, has a sheath as well as insulation. It is used for meter tails between the meter and consumer unit. View our single-core cable in all the common sizes and colours.

What is fire-resistant cable?

Fire-resistant cable keeps working for a set time in a fire, so life-safety systems stay powered while people get out. It is used for fire alarm systems, emergency lighting, voice alarms and smoke ventilation. Insulation such as mica tape or ceramifiable silicone helps it keep circuit integrity, and the sheath is usually low smoke zero halogen.

Fire alarm cable comes in standard and enhanced grades, and the system design (for example to BS 5839-1 for fire alarms or BS 5266-1 for emergency lighting) states which is needed. Fire alarm cable often has a red sheath, so it is easy to identify. Shop our fire-resistant cable and read our fire-resistant cable buying guide for where to specify it.

Data, coaxial and other low-voltage cables

Not every cable carries mains power. Data and signal cables carry information at low voltage and need to be kept apart from power cables, or segregated, to avoid interference and for safety.

• Data cable (Cat5e and Cat6): twisted-pair cable for wired broadband, Wi-Fi access points, IP CCTV and smart home hubs. Cat6 has a higher bandwidth than Cat5e and is a common choice for new installations. Shop network cable.
• Coaxial cable: a centre conductor inside a screen, used for TV aerials and satellite dishes (RG6 and CT100) and analogue CCTV (RG59). Shop coaxial cable.
• Alarm, bell, speaker and telephone cable: multi-core low-voltage cables for intruder alarms, doorbells, audio and phone lines. See our communication cable range.

What is LSZH cable?

LSZH stands for low smoke zero halogen. It is not a separate type of cable but a type of insulation and sheath, available for twin and earth, singles, flex, SWA and fire-resistant cable. If LSZH materials burn, they give off much less smoke and no halogen acid gases, which helps people see escape routes and reduces damage to equipment.

LSZH cable is often specified for escape routes, flats, schools, hospitals, offices and other public buildings. Standard PVC cable is still widely used in houses. You may also see the term LSF (low smoke and fume), which is not as tightly defined, so check the product data when LSZH is specified.

What are the UK cable colours?

Colour coding shows which conductor is which, so installers can connect them correctly. The UK changed to harmonised colours in 2004, and from 31 March 2006 all new work had to use them. Ireland uses the same harmonised colours.

Older installations may still have red and black wiring. That is not a fault in itself, but where old and new colours meet on the same installation, BS 7671 requires a warning notice at the consumer unit. Black and grey cores in 3 core and earth used as line conductors should be sleeved brown at their terminations.

Single-phase vs three-phase wiring

Most homes and small premises have a single-phase supply at a nominal 230V, with one line conductor, a neutral and an earth. Larger commercial and industrial buildings often have a three-phase supply at a nominal 400V between phases, with three line conductors (brown, black and grey), usually a neutral and an earth.

Three-phase supplies suit motors, large heating loads, commercial kitchens and big EV charging installations. They use 4 or 5 core cable, often SWA, for the supply and sub-mains.

How do cable types fit together in a house?

In a typical house, the consumer unit feeds radial and ring final circuits wired in twin and earth. 3 core and earth is added for two-way lighting, SWA supplies anything outside, flex makes the final connections to appliances, and green and yellow singles carry the earthing and bonding. Data and coaxial cables run separately for broadband and TV.

Cable size matters as much as cable type. Sizes are measured by the cross-sectional area of the conductor in mm², and the right size depends on the load, cable length, installation method and protective device. Every circuit should be designed to BS 7671 by a competent person. For typical sizes by circuit, see our guide to the best electrical cable for home wiring and our overview of electrical regulations and standards.

Types of electrical wiring and cables: the summary

Knowing the different types of electrical wiring and cables makes it easier to read an existing installation and to buy the right cable. Twin and earth does most of the work in a home, 3 core and earth handles switching, SWA goes outside, flex connects appliances and singles carry the earthing. Fire-resistant, LSZH, data and coaxial cables cover the special jobs. Match the cable to the job and the location, size it to BS 7671, and use a qualified electrician for new circuits and notifiable work.

Need help choosing? Call our team on 028 8675 1515 (048 from ROI), Monday to Friday, 8am–5pm.

FAQs

What are the main types of electrical cable used in UK homes?

The main types are twin and earth (6242Y) for most fixed wiring, 3 core and earth (6243Y) for two-way lighting, SWA armoured cable for outdoor and underground runs, flex for appliances, and single-core cable (6491X) in conduit, trunking and earthing. Homes also use data, coaxial and sometimes fire-resistant cable.

What is the most common electrical cable in a house?

Flat PVC twin and earth cable, code 6242Y, is the most common. It has a brown line core, a blue neutral core and a bare earth conductor inside a grey or white sheath. It wires lighting, socket, cooker and shower circuits, in sizes chosen for each circuit.

What is the difference between cable and flex?

Fixed wiring cable, such as twin and earth, has solid or few-stranded conductors and is installed permanently in walls, floors and ceilings. Flex has many fine strands, so it bends repeatedly without breaking. Use flex for the final connection to appliances, pendants and portable equipment, not for fixed circuit wiring.

What is 6491X cable used for?

6491X is single-core PVC insulated cable. It is drawn into conduit or trunking, used for earthing and main bonding conductors in green and yellow, and used inside distribution boards and control panels. It has no outer sheath, so it must not be clipped bare to walls or buried in plaster.

What are the UK electrical cable colours?

In single-phase fixed wiring, brown is line, blue is neutral and green and yellow is the protective earth. In three-phase wiring, the lines are brown, black and grey. Before the change, installations used red for line and black for neutral, and red, yellow and blue for the three phases.

What cable should I use underground or outdoors?

Steel wire armoured (SWA) cable is the usual choice for underground and outdoor runs, such as to a garden room, garage or outdoor socket. It should be buried at a suitable depth with warning tape above, terminated with the correct glands, and protected by an RCD where BS 7671 requires it.

What is LSZH cable and where is it needed?

LSZH stands for low smoke zero halogen. The insulation and sheath give off much less smoke and no halogen acid gases if they burn. LSZH cable is often specified for escape routes, flats, public buildings and anywhere many people may need to get out safely during a fire.

Related guides

• Best electrical cable for home wiring: UK sizes and colours
• 3 core and earth vs twin and earth: 2-way lighting and colours
• SWA armoured cable installation guide
• Fire-resistant cable buying guide