From HSE publication HSR 25.
British Standard BS 7671 Requirements for Electrical Installations (also known as the IEE Wiring Regulations)
The British Standard BS 7671 Requirements for Electrical Installations is also known as the IEE Wiring Regulations* ? they are non-statutory regulations. They ?relate principally to the design, selection, erection, inspection and testing of electrical installations, whether permanent or temporary, in and about buildings generally and to agricultural and horticultural premises, construction sites and caravans and their sites?. BS 7671 is a code of practice which is widely recognised and accepted in the UK and compliance with it is likely to achieve compliance with relevant aspects of the 1989 Regulations.
There are however many types of system, equipment and hazard to which BS 7671 is not applicable; for example, certain installations at mines and quarries, equipment on vehicles, systems for public electricity supply and explosion protection. Furthermore, BS 7671 applies only to installations operating at up to 1000 volts ac or 1500 volts dc.
Installations to which BS 7671 is relevant may have been installed in accordance with an earlier edition, now superseded but then current. That, in itself, would not mean that the installation would fail to comply with the 1989 Regulations.
* Obtainable from the Institution of Engineering and Technology, Michael Faraday House, 6 Hills Way, Stevenage, Herts, SG1 2AY.
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http://www.hse.gov.uk/pubns/priced/hsr25.pdf