Requirements for Electrical Installations, IET Wiring Regulations, 18th Edition, BS 7671:2018

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Requirements for Electrical Installations, IET Wiring Regulations, Eighteenth Edition, BS 7671:2018

Surge protection devices (SPDs) and the 18th Edition Regulations


The arrival of the 18th Edition of the IET Wiring Regulations further reshapes the regulatory landscape for electrical contractors. Surge protection devices (SPDs) are designed to prevent electric shock and having excess voltage damaging the installation’s wiring infrastructure.

18th Edition requirements for surge protection

The arrival of the 18th Edition of the IET Wiring Regulations further reshapes the regulatory landscape for electrical contractors. A number of important areas have been scrutinised and reviewed; among them is the issue of surge protection and devices designed to mitigate any excess voltage risks. Surge protection devices (SPDs) are designed to prevent electric shock and having excess voltage damaging the installation’s wiring infrastructure. Should an over-voltage event occur, the SPD diverts the resulting excess current flow to Earth.

Regulation 443.4 requires, (except for single dwelling units where the total value of the installation and equipment therein does not justify such protection), that protection against transient over-voltages is provided where the consequence caused by over-voltage could result in serious injury, damage to culturally sensitive places, interruption of supply or affect large numbers of co-located persons or loss of life.

When should surge protection be fitted?

For all other installations a risk assessment should be carried out to determine whether SPDs should be installed. Where a risk assessment is not carried out, then SPDs should be installed. Electrical installations in single dwelling units are not required to have SPDs installed, but their use is not precluded and it may be that in discussion with a client such devices are installed, reducing significantly risks associated with transient over-voltages.

This is something contractors have not previously had to consider to any great extent, and will need to be taken account of, both in terms of time allocation for project completion as well as cost add-ons for the customer. Any electronic equipment may be vulnerable to transient over-voltages, which can be caused by lightning activity or a switching event. This creates a voltage spike increasing the wave’s magnitude to potentially several thousand volts. This could cause expensive and instant damage or significantly reduce an item of equipment’s lifespan.

The need for SPDs will depend on many differing factors. These include the level of exposure of a building to lightning-induced voltage transients, the sensitivity and value of the equipment, the type of equipment used within the installation, and whether there is equipment within the installation that could generate voltage transients. While the shift in responsibility of risk assessment falling on the contractor is likely to be a surprise to many, by accessing the correct support they can seamlessly integrate this function into their traditional work approach and ensure adherence to the new regulations.

LSP Surge Protection Devices

LSP has a range of Type 1 and 2 surge protection devices to ensure you comply with the new 18th Edition Regulations. For more information on SPDs and LSP Electrical’s range visit:

Visit out 18th Edition BS 7671:2018 for free, downloadable guides on the key regulation changes of BS 76:71. Including information on RCD Selection, Arc Fault Detection, Cable Management, Electric Vehicle charging, and Surge Protection. Download these guides straight to any device so you can read them whenever and wherever.

Requirements for Electrical Installations, IET Wiring Regulations, Eighteenth Edition, BS 7671-2018Item Subjects: Electrical Regulations

Pages: 560

ISBN-10: 1-78561-170-4

ISBN-13: 978-1-78561-170-4

Weight: 1.0

Format: PBK

Requirements for Electrical Installations, IET Wiring Regulations, Eighteenth Edition, BS 7671:2018

The IET Wiring Regulations are of interest to all those concerned with the design, installation and maintenance of electric wiring in buildings. This includes electricians, electrical contractors, consultants, local authorities, surveyors and architects. This book will also be of interest to professional engineers, as well as students at university and further education colleges.

The 18th Edition of the IET Wiring Regulations published in July 2018 and came into effect in January 2019. Changes from the previous edition include requirements concerning Surge Protection Devices, Arc Fault Detection Devices and the installation of electric vehicle charging equipment as well as many other areas.

How will the 18th Edition change daily work for electrical installers

How will the 18th Edition change daily work for electrical installers?

The 18th Edition of the IET Wiring regulations has landed, bringing with it an array of new things for electrical installers to be aware of and make part of their day to day.

We are now one month in to a six-month adjustment period for electricians to make sure they have everything in place. From January 1st 2019 installations must be fully compliant to the new regulations, meaning all electrical work that takes place from December 31st 2018 must abide by the new rules.

In line with the latest technology advances and updated technical data, the new regulations aim to make installations safer for both electricians and the end user, as well as impact on energy efficiency.

All changes are important, however we have picked out four key points that we think are particularly interesting:

1: Metal Cable Supports

Regulations currently outline that only cable located on fire escape routes must be supported against early collapse in the event of a fire. The new regulations now demand that metal fixings, rather than plastic ones, be used to support all cables throughout installations, to reduce risk to occupants or fire fighters from falling cables as a result of failed cable fixings.

2: Installation of Arc Fault Detection Devices

Considering that UK buildings now have more electrical equipment in them than ever before, and electrical fires are occurring at roughly the same rate year-on-year, the installation of Arc Fault Detection Devices (AFDDs) to moderate fire risk in some circuits has been introduced.

Electrical fires caused by arc faults usually occur at poor terminations, loose connections, though old and failing insulation or in damaged cable. These sensitive AFDDs can lower the likelihood of electrical fires resulting from arcs by early detection and isolation.

Installation of AFDDs started in the US several years ago, and there has been a reduction in related fires by about 10%.

3.All AC sockets rated up to 32A now require RCD protection

Residual Current Devices (RCDs) constantly monitor the electric current in the circuits they protect and trips the circuit if flow through an unintended path to earth is detected—such as a person.

These are life safety devices and potentially a life-saving update. Previously, all sockets rated up to 20A required RCD protection, but this has been extended in an effort to reduce electric shocks to installers working with live AC socket outlets. It will also protect the end user in cases where a cable is damaged or cut and the live conductors could be accidentally touched, causing current to flow to earth.

To prevent the RCD being overwhelmed by the current wave form, however, care must be taken to ensure the appropriate RCD is used.

4: Energy efficiency

The draft of the 18th Edition update featured a clause on the energy efficiency of electrical fixings. In the final version published, this has been changed to full recommendations, found in Appendix 17. This recognises the nationwide need to reduce energy consumption overall.

The new recommendations encourage us to make the most of overall use of electricity, in the most efficient way.

Overall, the revised installation processes may call for investments in new equipment, and of course further training. Most importantly though, if working on a new build project, for example, electricians may now have opportunities to take on more leading roles in the design process of a building, to ensure the whole project complies to the new regulations

The 18th Edition brings new progress toward safer installation and safer spaces for end users. We know that electricians across the UK are working hard to prepare for these changes and we want to know what you think will affect you most and what you are doing to make the transition as smooth as possible.

Requirements for Electrical Installations

BS 7671

Ensure that your work meets the requirements of the Electricity at Work Regulations 1989.

BS 7671 (IET Wiring Regulations) sets the standards for electrical installation in the UK and many other countries. The IET co-publishes BS 7671 with the British Standards Institution (BSI) and is the authority on electrical installation.

About BS 7671

The IET runs the JPEL/64 committee, (the national Wiring Regulations committee), with representatives from a wide range of industry organisations. The committee takes on board information from international committees and UK specific requirements, to ensure consistency and improve safety throughout the UK electrical industry.

The 18th Edition

The 18th Edition IET Wiring Regulations (BS 7671:2018) published in July 2018. All new electrical installations will need to comply with BS 7671:2018 from 1st January 2019.

To help industry apply the requirements of BS 7671, and to get up to date with the 18th Edition, the IET provides a wealth of resources, from guidance materials, events and training, to free information such as Wiring Matters online magazine. See the boxes below for more information on our range of resources.

18th edition changes

The following list provides an overview of the main changes within the 18th Edition IET Wiring Regulations (publishing 2nd July 2018). This list is not exhaustive as there are many smaller changes throughout the book not included here.

BS 7671:2018 Requirements for Electrical Installations will be issued on 2nd July 2018 and is intended to come into effect on 1st January 2019.

Installations designed after 31st December 2018 will have to comply with BS 7671:2018.

The Regulations apply to the design, erection and verification of electrical installations, also additions and alterations to existing installations. Existing installations that have been installed in accordance with earlier editions of the Regulations may not comply with this edition in every respect. This does not necessarily mean that they are unsafe for continued use or require upgrading.

A summary of the main changes is given below. (This is not an exhaustive list).

Part 1 Scope, object and fundamental principles

Regulation 133.1.3 (Selection of equipment) has been modified and now requires a statement on the Electrical Installation Certificate.

Part 2 Definitions

Definitions have been expanded and modified.

Chapter 41 Protection against electric shock

Section 411 contains a number of significant changes. Some of the main ones are mentioned below:

Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding (Regulation 411.3.1.2).

The maximum disconnection times stated in Table 41.1 now apply for final circuits up to 63 A with one or more socket-outlets and 32 A for final circuits supplying only fixed connected current-using equipment (Regulation 411.3.2.2).

Regulation 411.3.3 has been revised and now applies to socket-outlets with a rated current not exceeding 32A. There is an exception to omit RCD protection where, other than a dwelling, a documented risk assessment determines that RCD protection is not necessary.

A new Regulation 411.3.4 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.

Regulation 411.4.3 has been modified to include that no switching or isolating device shall be inserted in a PEN conductor.

Regulations 411.4.4 and 411.4.5 have been redrafted.

The regulations concerning IT systems (411.6) have been reorganized. Regulations 411.6.3.1 and 411.6.3.2 have been deleted and 411.6.4 redrafted and a new Regulation 411.6.5 inserted.

A new Regulation group (419) has been inserted where automatic disconnection according to Regulation 411.3.2 is not feasible, such as electronic equipment with limited short-circuit current.

Chapter 42 Protection against thermal effects

A new Regulation 421.1.7 has been introduced recommending the installation of arc fault detection devices (AFDDs) to mitigate the risk of fire in AC final circuits of a fixed installation due to the effects of arc fault currents.

Regulation 422.2.1 has been redrafted. Reference to conditions BD2, BD3 and BD4 has been deleted. A note has been added stating that cables need to satisfy the requirements of the CPR in respect of their reaction to fire and making reference to Appendix 2, item 17. Requirements have also been included for cables that are supplying safety circuits.

Chapter 44 Protection against voltage disturbances and electromagnetic disturbances

Section 443, which deals with protection against overvoltages of atmospheric origin or due to switching, has been redrafted.

The AQ criteria (conditions of external influence for lightning) for determining if protection against transient overvoltages is needed are no longer included in BS 7671. Instead, protection against transient overvoltages has to be provided where the consequence caused by overvoltage (see Regulation 443.4)

(a) results in serious injury to, or loss of, human life, or(b) results in interruption of public services/or damage to and cultural heritage, or
(c) results in interruption of commercial or industrial activity, or
(d) affects a large number of co-located individuals.

For all other cases, a risk assessment has to be performed in order to determine if protection against transient overvoltage is required.

There is an exception not to provide protection for single dwelling units in certain situations.

Chapter 46 Devices for isolation and switching – A new Chapter 46 has been introduced.

This deals with non-automatic local and remote isolation and switching measures for the prevention or removal of dangers associated with electrical installations or electrically powered equipment. Also, switching for the control of circuits or equipment. Where electrically powered equipment is within the scope of BS EN 60204, only the requirements of that standard apply.

Chapter 52 Selection and erection of wiring systems

Regulation 521.11.201 which give requirements for the methods of support of wiring systems in escape routes, has been replaced by a new Regulation 521.10.202. This is a significant change.

Regulation 521.10.202 requires cables to be adequately supported against their premature collapse in the event of a fire. This applies throughout the installation and not just in escape routes.

Regulation 522.8.10 concerning buried cables has been modified to include an exception for SELV cables.

Regulation 527.1.3 has also been modified, and a note added stating that cables also need to satisfy the requirements of the CPR in respect of their reaction to fire.

Chapter 53 Protection, isolation, switching, control and monitoring

This chapter has been completely revised and deals with general requirements for protection, isolation, switching, control and monitoring and with the requirements for selection and erection of the devices provided to fulfil such functions.

Section 534 Devices for protection against overvoltage

This section focuses mainly on the requirements for the selection and erection of SPDs for protection against transient overvoltages where required by Section 443, the BS EN 62305 series, or as otherwise stated.

Section 534 has been completely revised and the most significant technical change refers to the selection requirements for the voltage protection level.

Chapter 54 Earthing arrangements and protective conductors

Two new regulations (542.2.3 and 542.2.8) have been introduced concerning earth electrodes.

Two further new regulations (543.3.3.101 and 543.3.3.102) have been introduced. These give requirements for the insertion of a switching device in a protective conductor, the latter regulation relating to situations where an installation is supplied from more than one source of energy.

Chapter 55 Other equipment

Regulation 550.1 introduces a new scope.

New Regulation 559.10 refers to ground-recessed luminaires, the selection and erection of which shall take account of the guidance given in Table A.1 of BS EN 60598-2-13.

Part 6 Inspection and testing

Part 6 has been completely restructured, including the regulation numbering to align with the CENELEC standard.

Chapters 61, 62 and 63 have been deleted and the content of these chapters now form two new Chapters 64 and 65.

Section 704 Construction and demolition site installations

This section contains a number of small changes, including requirements for external influences (Regulation 704.512.2), and a modification to Regulation 704.410.3.6 concerning the protective measure of electrical separation.

Section 708 Electrical installations in caravan/camping parks and similar locations

This section contains a number of changes including requirements for socket-outlets, RCD protection, and operational conditions and external influences.

Section 710 Medical locations

This section contains a number of small changes including the removal of Table 710, and changes to Regulations 710.415.2.1 to 710.415.2.3 concerning equipotential bonding.

In addition, a new Regulation 710.421.1.201 states requirements regarding the installation of AFDDs.

Section 715 Extra-low voltage lighting installations

This section contains only minor changes including modifications to Regulation 715.524.201.

Section 721 Electrical installations in caravans and motor caravans

This section contains a number of changes including requirements electrical separation, RCDs, proximity to non-electrical services and protective bonding conductors.

Section 722 Electric vehicle charging installations

This section contains significant changes to Regulation 722.411.4.1 concerning the use of a PME supply.

The exception concerning reasonably practicable has been deleted.

Changes have also been made to requirements for external influences, RCDs, socket-outlets and connectors.

Section 730 Onshore units of electrical shore connections for inland navigation vessels

This is an entirely new section and applies to onshore installations dedicated to the supply of inland navigation vessels for commercial and administrative purposes, berthed in ports and berths.

Most, if not all, of the measures used to reduce the risks in marinas apply equally to electrical shore connections for inland navigation vessels. One of the major differences between supplies to vessels in a typical marina and electrical shore connections for inland navigation vessels is the size of the supply needed.

Section 753 Floor and ceiling heating systems

This section has been completely revised.

The scope of Section 753 has been extended to apply to embedded electric heating systems for surface heating.

The requirements also apply to electric heating systems for de-icing or frost prevention or similar applications, and cover both indoor and outdoor systems.

Heating systems for industrial and commercial applications complying with IEC 60519, IEC 62395 and IEC 60079 are not covered.


The following main changes have been made within the appendices

Appendix 1 British Standards to which reference is made in the Regulations includes minor changes, and additions.

Appendix 3 Time/current characteristics of overcurrent protective devices and RCDs

The previous contents of Appendix 14 concerning earth fault loop impedance have been moved into Appendix 3.

Appendix 6 Model forms for certification and reporting

This appendix includes minor changes to the certificates, changes to the inspections (for new installation work only) for domestic and similar premises with up to 100 A supply, and examples of items requiring inspection for an electrical installation condition report.

Appendix 7 (informative) Harmonized cable core colours

This appendix includes only minor changes.

Appendix 8 Current-carrying capacity and voltage drop

This appendix includes changes regarding rating factors for current-carrying capacity.

Appendix 14 Determination of prospective fault current

The contents of Appendix 14 concerning earth fault loop impedance have been moved into Appendix 3. Appendix 14 now contains information on determination of prospective fault current.

Appendix 17 Energy efficiency

This is a new appendix that provides recommendations for the design and erection of electrical installations including installations having local production and storage of energy for optimizing the overall efficient use of electricity.

The recommendations within the scope of this appendix apply for new electrical installations and modification of existing electrical installations. Much of this appendix will not apply to domestic and similar installations.

It is intended that this appendix is read in conjunction with BS IEC 60364-8-1, when published in 2018

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