Electrical wiring in the United Kingdom

Electrical wiring in the UK refers to setups in buildings like homes, offices, and factories for using electricity. This also includes special places like marinas. It doesn't though include creating and moving electricity over long distances to the towns/buildings where it is used, i.e. generation and distribution. The electrical setups of buildings can differ based on factors like voltage, phase, cable type, and circuit design.

Rules for electrical wiring safety are overseen by regulations like the Building Regulations 2010 and the Electricity at Work Regulations 1989. These rules specify standards for things like wiring. The specific guidelines are found in British Standard BS 7671 Requirements for Electrical Installations (IET Wiring Regulations), currently in its 18th edition.

Wiring colours

As of 2006, the standard wiring colours in the UK are the same as in the rest of Europe, following the international standard IEC 60446. This colour pattern was initially used for appliance cords in the UK in the early 1970s. However, the original red/black colour scheme recommended for permanent (building) wiring remained in use until 2006, though a change to a green/yellow striped wire for earthing (grounding) was made in 1976. For a transitional period (April 2004 – March 2006) either set of colours were allowed (but not both), provided that any changes in the colour scheme were clearly labelled.

The international standard brown/blue scheme is thus now commonly seen in most appliance cords, and in permanent (building) wiring installed since 2004. The old red/black scheme will still be found in existing older installations for many more years.

		Pre-1977	Pre-2004	Current
Protective earth (PE)
Neutral (N)
Single phase	Line (L)
Three-phase	L1
	L2
	L3

Single-phase (three-wires, line, neutral and earth) is what is almost always used for homes and small businesses. Three-phase (usually five-wire, L1, L2, L3, neutral and earth) is used for larger businesses.

Note that use of the word line in the above is not a mistake. The term live is commonly misused to refer to the line wire only. The term live actually applies to both line and neutral because it applies to any wire through which electricity is expected to flow under normal use. Since line and neutral are both used together to form a circuit for electricity to flow (in and out), they are thus both live wires! The earth wire however is not a live wire since it only carries electricity under certain fault conditions.