18th Edition Wiring Regulations

The 18th Edition Wiring Regulations are the latest update of The Official Requirements for Electrical Installations, which were first released in 1882. BS 7671:2018 was published on the 2nd of July 2018, with compliance compulsory for projects designed from the 1st of January 2019. Here we highlight a few of the key changes that may affect installers in the coming months.

Clause 443.4 refers to the protection of electrical installations against transient overvoltage, in part due to the increasing prevalence of lightning strikes but also relating to switching loads causing transients on a network. Where overvoltage could cause serious injury or loss of human life, disruption to commercial and industrial activity or interruption of public services, the regulations now stipulate that surge protection must be provided. Outside of these consequences, a risk assessment must be carried out to determine whether overvoltage protection is required. If deemed necessary, a surge protection device (SPD) must be installed within a suitable enclosure, designed to immediately drive any overvoltage to earth. Consumer units with pre-populated SPDs are available for new or replacement installations, whilst enclosure only units are ideal for retrofit.

The amended requirements for protection against fire, burns and overheating caused by arc faults in electrical equipment are contained within Clause 421.1.7. Arc faults can be caused by defects or damage to cables which results in a high power discharge of electricity and converts into heat. The regulations recommend the installation of Arc Fault Detection Devices (AFDDs) in specified circumstances to alleviate the risk of fire due to any potential arc fault currents. Designed to perform when a dangerous arc is detected, AFDDs are installed in a consumer unit or similar enclosure with combined AFDD and RCBO devices also available.

In Clause 521.10.202, new requirements for wiring systems expands on the regulations which previously only applied to escape routes. Under the 18th Edition, all cable support systems must be constructed from appropriate materials that will protect against premature collapse, typically caused by exposed heat during a fire. In the event of a blaze, the installation of heat resistant support structures should prevent falling cables which could otherwise create hazards for anyone travelling through a building. This prohibits the use of non-metallic cable management as the sole means of cable support and requires fire rated elements to be incorporated. Not limited to trunking systems, this covers all cable and cable management in a building which means that even cable fixed on to the surface of a wall should be resistant to premature collapse.

The previous requirement for protection to socket outlets affected those with a rated current not exceeding 20A. As noted in Clause 411.3.4, this has now been updated to apply to socket outlets up to 32A and lighting circuits within domestic premises. This can be achieved by use of a 30mA RCD in an AC circuit. Previously, an exception to this regulation was made if a risk assessment had been carried out where RCD protection was not applied in domestic dwellings, however this is no longer applicable. Compliance with other installation requirements is likely to mean that circuits with RCDs are already being fitted.