BS 7671

British Standard BS 7671 "Requirements for Electrical Installations. IET Wiring Regulations", informally called in the UK electrical community "The Regs", is the national standard in the United Kingdom for electrical installation and the safety of electrical wiring systems

Electrical installations
Wiring practice by region or country
Regulation of electrical installations
Cabling and accessories
Switching and protection devices

SCOPE of BS 7671

The regulations in BS7671 applies to the design, selection, erection and verification of electrical installations within;

  1. residential properties
  2. commercial properties
  3. public premises
  4. industrial premises
  5. prefabricated building
  6. low voltage generating sets
  7. highway equipment and street furniture
  8. locations containing a bath or shower
  9. rooms or cabins that contain a sauna
  10. swimming pools and other basins
  11. construction and demolition sites
  12. agricultural and horticultural premises
  13. caravan/camping parks and similar locations
  14. marinas and similar locations
  15. medical locations
  16. exhibitions, shows and stands
  17. Solar photovoltaic (PV) power supply systems (Domestic and commercial)
  18. outdoor lighting installations
  19. extra-low voltage lighting
  20. mobile and transportable units
  21. caravans and motor caravans
  22. temporary installations for structures, amusement devices/booths at fairgrounds, amusement parks, circuses and professional stage and broadcast applications
  23. operating and maintenance gangways
  24. floor and ceiling heating systems
  25. onshore units of electrical shore connections for inland navigation vessels.

Exclusions from the scope of BS 7671 are the following.

  1. systems for the distribution of electricity to the public other than prosumer's installations covered by Chapter 82
  2. Railway traction equipment, rolling stock and signalling equipment
  3. Equipment of motor vehicles, except those to which the requirements of the Regulations concerning caravans or other types of mobile unit are applicable.
  4. Equipment on board ships covered by BS 8450, BS EN 60092-507, BS EN ISO 13297 or BS EN ISO 10133
  5. Equipment of mobile or fixed offshore installations.
  6. Equipment within and aircraft.
  7. Those aspects of mines covered by Statutory Regulations
  8. Radio interference suppression equipment, except so far as it affects safety of the electrical installation.
  9. Lightning protection systems for buildings and structures covered by BS EN 62305.
  10. Those aspects of Lift Installations covered by relevant parts of BS 5655 and BS EN 81 and those aspects of escalator or moving walkway installations covered by relevant parts of BS 5656 and BS EN 115.
  11. Electrical equipment of machines covered by BS EN 60204.
  12. Electric fences covered by BS EN 60335-2-76
  13. The DC side of cathodic protection systems complying with the relevant part(s) of BS EN 12696, BS EN 12954, BS EN ISO 13174, BS EN 13636 and BS EN 14505.

BS 7671 only covers electrical systems that the IET defines as those covered by the following.

  • Circuits supplied at a nominal voltage up to, but not exceeding 1000V AC or 1500V DC.
  • For AC the preferred frequencies of the supply are 50Hz, 60Hz and 400Hz. The use of other frequencies for special purposes in not excluded.

Part 2 - Definitions the voltages covered by BS7671 are defined thus.

Voltage, nominal (U0). The voltage by which an installation (or part of an installation) is designated and the following ranges of nominal voltage (rms values for AC) are defined

  • Extra-low. Not exceeding 50V AC or 120V ripple free DC, whether between conductors or Earth
  • Low. Exceeding extra-low voltage but not exceeding 1000V AC or 1500V DC between conductors or 600V AC or 900V DC between conductors and Earth.
  • High. Voltages that normally exceed those of Low voltage.


It did not become a recognized British Standard until after the publication of the 16th edition in 1992. The standard takes account of the technical substance of agreements reached in CENELEC.

The current version is BS 7671:2018+A2:2022 (the 18th Edition) issued in 2022, and came into effect from 28 March 2022 (the previous version BS 7671:2018+A1:2020 being withdrawn on 27 September 2022). BS 7671 is also used as a national standard by Mauritius, St Lucia, Saint Vincent and the Grenadines, Sierra Leone, Singapore, Sri Lanka, Trinidad and Tobago, Uganda, Cyprus, and several other countries, which base their wiring regulations on BS 7671.

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