The latest editions and how they adapt with change
The voltage used throughout Europe has been harmonised during a period from 1989 through to 2008 (2003 in UK) at a nominal 230 V 50 Hz, this was formerly 240 V in the UK. In reality the target voltage hasn’t changed. However, the permitted tolerance changed from a nominal 240 V ± 6% (225.6 V – 254.4 V) to a nominal 230V -6% +10% (216.2 V – 253.0 V)
In 2004, BS 7671 was amended to incorporate the requirements of CENELEC Standard HD 384.5.514: Identification of conductors. This meant that the traditional colour identification for conductors changed in the UK.
In 2005 the Government introduced Part P of the Building Regulations entitled 'Design and installation of electrical installations'.
Part P states that anyone responsible for electrical design or installation work in a home, must make reasonable provisions to protect the persons operating, maintaining or altering the installation from fire or injury.
Part P included the following:
- The start of the introduction of requirements for protective measures against voltage disturbances
- Additional protection by means of an RCD with a rated residual operating current not exceeding 30 mA, for socket-outlets up to 20 A, and mobile equipment for use outdoors up to 32 A, is required for all installations. However, an exception is permitted for a specific labelled socket-outlets up to 20 A, other than a dwelling, a documented risk assessment is required to determine that RCD protection is not necessary
- A requirement was introduced for cables concealed in a wall or partition at a depth of 50 mm or less, to be provided with additional protection by means of an RCD with a rated residual operating current not exceeding 30 mA for all installations, unless other protection, such as mechanical protection was afforded
- Minimum values of insulation resisted were amended to 0.5 M ohm for SELV and PELV circuits when tested at 250 V, and 1 M Ohms for systems up to and including 500 V.
In 2011 the 17th Edition included the following new requirements:
- Maximum earth fault loop impedance values were revised to account of the change in nominal voltage, from 240 V to 230 V.
In 2015 the 17th edition of BS 7671 saw some major changes from previous editions, which included:
- Maximum earth fault loop impedance values were revised to take account of the introduction of a new correction factor of 0.95 known as Cmin, which is a factor to take account of the minimum supply voltage
- A new Regulation requiring consumer units and similar switchgear within domestic premises to be made from non-combustible material, which saw the deprecation of plastic consumer units
- The reference to ordinary persons was deleted with respect to utilisation classification of external influences
- The introduction of particular requirements for electric vehicle charging installations as a special installation.
The IET Wiring Regulations Eighteenth Edition BS 7671:2018 was published on 1 July 2018. Some of the major changes included:
- It was specifically stated that ‘metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding’. The primary reason for this was to encourage installers/designers to assess installations with respect to extraneous conductive parts as with the use of polyurethane pipes those parts that had previously assumed to be extraneous may no longer be extraneous. The wording was modified to suit BS 7671 users
- The maximum disconnection times were revised to apply to final circuits up to 63 A with one or more socket-outlets and final circuits rated up to 32 A supplying only fixed connected current-using equipment
- The requirement for additional protection by RCD for socket-outlets was increased to cover 32 A. There is an exception, where other than for a dwelling, a documented risk assessment determines that RCD protection is not necessary
- A new Regulation requires that, within domestic (household) premises, additional protection by an RCD with a rated residual operating current not exceeding 30 mA shall be provided for AC final circuits supplying luminaires
- It has to be said that the introduction of surge protection, probably made the biggest noise for the Eighteenth Edition. It was no longer possible to ignore it because it was a dwelling and most installations would require it
- Arc Fault Detection Devices (AFDD) got a mixed reception when they were introduced as a recommendation for buildings with increased fire risk
- Changes to Section 722 for Electric Vehicle Charging Installations recognised the issues with a PME earthing system. The previous exception which stated it was only applicable if it was reasonably practicable was removed
- Only minor modifications were made to the model forms
- Appendix 17 was introduced to provide recommendations for design and erection of electrical installations having local production and storage of energy, for optimising the overall efficient use for electricity.
In January 2020, Amendment 1 to BS 7671:2018 was published. It contained amendments to Section 722 for electric vehicle charging only.