The Electricity Wiring Regulations 2020 Pdf

[Achill Baldwin]

Electricalwiring in the United Kingdom is commonly understood to be an electrical installation for operation by end users within domestic, commercial, industrial, and other buildings, and also in special installations and locations, such as marinas or caravan parks.[1] It does not normally cover the transmission or distribution of electricity to them.

Electrical wiring is ultimately regulated to ensure safety of operation, by such as the building regulations, currently legislated as the Building Regulations 2010, which lists "controlled services" such as electric wiring that must follow specific directions and standards, and the Electricity at Work Regulations 1989. The detailed rules for end-use wiring followed for practical purposes are those of BS 7671 Requirements for Electrical Installations. (IET Wiring Regulations), currently in its 18th edition, which provide the detailed descriptions referred to by legislation.

UK electrical wiring standards are largely harmonised with the regulations in other European countries and the international IEC 60446 standard. However, there are a number of specific national practices, habits and traditions that differ significantly from other countries, and which in some cases survived harmonisation. These include the use of ring circuits for domestic and light commercial fixed wiring, fused plugs, and for circuits installed prior to harmonisation, historically unique wiring colours.

The standard wiring colours in the UK are (as of 2006[update]) the same as elsewhere in Europe and follow international standard IEC 60446. This colour scheme had already been introduced for appliance flexes in the UK in the early 1970s, however the original red/black colour scheme recommended by the IEE for fixed wiring was retained until 2006, albeit with change to a green/yellow striped earth in 1976. As a result, the international standard blue/brown scheme is as of 2006 found in most appliance flexes. In fixed wiring, the blue/brown scheme is only found in newer (post-2004) installations, and the old IEE red/black scheme is likely to be encountered in existing installations for many more decades.

Earlier in the 20th century, green and blue were used as a neutral alongside black, which became the only neutral colour from 1943. In the 13th edition of the IEE regulations, of 1955, black was used for both neutral and earth, although only for fixed wiring. It was changed to green in the 14th edition in 1966 and then a phased change to green/yellow in amendments to the 14th edition over the following decade.[6]

The UK changed colour codes three decades after most other European countries, as in 1977 the change of neutral and phase colours was not considered safe by the IEE. Blue, previously used as a phase colour, is now the colour for neutral. Black, which was previously used for neutral, now indicates a phase.

Household wiring does not usually use three-phase supplies and the clash only occurs in three-phase systems. Wiring to the old standard can be detected by use of a red wire. The new standard colour code does not use red. Where new wiring is mixed with old, cables must be clearly marked to prevent interchange of phase and neutral.

Variation in the earth/ground conductor's colour at an earlier date than the remainder of the colours means its colour should not be used as an indication of the old vs new standard cable or colour assignment.

There is a long history of colour changes; prior to 1964 white was used instead of yellow as the second phase, and before World War II, a black earth and a green third phase in place of green earth and white phase was permitted. The regulations permitted (and still do) the use of any wire colour that is not an earth colour, providing it is unambiguously identified at all connections by clear labelling or by correctly coloured over-sleeving. It was not uncommon on commercial builds of the 1960s with a three phase supply for the phase colours (red, yellow, blue) to be used throughout single phase sub circuits thus indicating the phase origin of the supply, in this case no over-sleeving was used and can give rise to confusion when encountered today.

Direct current mains supplies are only of historical interest in the UK but the colour coding was red for live and black for earthed (regardless of the polarity). Hardly any loads were polarity sensitive when direct current systems were introduced (principally incandescent lighting, heating systems or series direct current motors) and it was considered more important to identify the live wire than the polarity. In later years of direct current supplies, however, much more equipment became sensitive to polarity, such as many domestic radios & television sets. Where all three wires were available, the historical colour code was red (positive), black (middle) and white (negative). The negative line changed to yellow in 1964, and then to blue in 1966.

The colour of the outer sheath is currently grey, or white for low halogen material. Previously cables from different manufacturers were available variously in grey or white, with no significance attached to the sheath colour. The grey colour was adopted by cable manufacturers to match older lead or silver sheathed flat cables, with some manufacturers using a silver grey polyvinyl chloride. Additionally twin & earth cable was available in red for fire alarms until the early 2000s.

UK fixed wiring circuits, unlike those found in almost all other countries, make widespread use of ring circuit designs, as well as radial circuit designs often seen in other countries. (This was one of the recommendations of the Electrical Installations Committee, convened in 1942 as part of the Post War Building Studies programme, which in 1944 determined that the ring final circuit offered a more efficient and lower cost method to support a greater number of sockets.[9]) It continues to be the usual wiring method for domestic and light commercial socket and device wiring in the UK. Lighting circuits, which typically have lower power requirements, are usually radially wired, confusingly sometimes called "loop" wiring.

In both ring and radial circuits, the circuit wiring starts at a consumer unit or distribution board, and traverses in turn a number of sockets or devices (point-to-point style), before terminating. The difference is that a radial circuit simply ends upon reaching the last connected device in any branch, whereas in a ring circuit the termination is made by joining the end of the circuit from the last device back to its starting point. A ring circuit therefore forms a continuous ring, while a radial may be a simple linear chain, though it may split and have several branches. This means that in a ring there are two independent paths from the supply to every device. Ideally, the ring acts like two radial circuits proceeding in opposite directions around the ring, the dividing point between them dependent on the distribution of load in the ring. If the load is evenly split across the two directions, the current in each direction is half of the total, allowing the use of wire with half the current-carrying capacity. In practice, it is impossible to ensure the load does split evenly, so regulations require a thicker wire, of at least 2/3 the current capacity of the fuse or circuit breaker.

The innovation that made ring circuits feasible in the UK was the introduction of plugs that contained their own fuse. There were three competing designs but only one ultimately survived and became the version specified in British Standard 1363. BS1363 plugs, could historically be fitted with a range of fuses up to 13A though only the 3A and 13A are the official choices, though 5A are available and often fitted to small appliances that take a large inrush current. This means that every load plugged in is covered by an appropriate protective device in its plug, so that the whole ring may then be protected by (usually) a 32A breaker at the distribution panel. In contrast, circuits feeding any other kind of socket outlet need to be protected by a breaker that will not allow the socket's rating to be exceeded, and so the radial circuits generally used with outlets such as the European Schuko style outlets generally have to be protected by a 16A breaker at the distribution panel; this limits the total load on the circuit and hence such circuits tend to have fewer socket outlets.

Cables are most commonly a single outer sheath containing separately-insulated line and neutral wires, and a non-insulated protective earth to which sleeving is added when exposed. Such cable is commonly referred to as twin and earth or simply T & E. Standard sizes have a conductor cross sectional area of 1, 1.5, 2.5, 4, 6 and 10 mm2. With most domestic wiring using:

The earthing conductor is uninsulated since it is not intended to have any voltage difference from surrounding earthed articles. Additionally, if the insulation of a line or neutral wire becomes damaged, then the wire is more likely to earth itself on the bare earth conductor and in doing so either trip the circuit breaker, RCD, or rupture the fuse by drawing too much current.

Earthing and bonding are used together to provide shock protection by avoiding a dangerous combination of magnitude and duration of the voltage to which people may be exposed in the event of a fault within the installation or outside the installation. (Exposure may be from e.g. hand to hand or hand to foot, between simultaneously accessible conductive surfaces, which might include the earth itself, mildly conductive floors and walls, metal taps, pipes, electrical appliances etc. Examples of faults are an insulation failure between a line conductor and a metallic frame of an appliance within the installation, a break in a combined protective-earth and neutral conductor in the supply, or an insulation fault in the supply transformer causing the whole low-voltage system to rise in potential.) Conductors for these protective functions of earthing and bonding are insulated with green/yellow (striped) colour coding, which is not permitted for any other conductors.

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