BS7671 18th Edition Changes

The 18th edition bs7671 guide contains a number of changes from the earlier 17th edition. Differences are varied in terms of degree and content. Although not all are huge, it’s essential to be aware of the information and consequences held within each one. In some cases, this will significantly change how an instalment should be approached. This is particularly important in the context of potential health and safety ramifications, as works may not completed to current compliance expectation levels if not abided by.Like previous editions, the introduction of the guide occurred some months before its official launch date in the trade. This enabled electricians and industry professionals to digest, learn, and practice regulation changes before their legal attribution. The book was released in July 2018, with formal industry monitoring commencing from January 2019.

This article intends to give an overview of the key changes between the 17th (and earlier) edition(s) and the latest book. The accompanying ‘on-site guide’, a strong referencing tool that compliments information contained in the 18th edition book, was also updated. However, this text will refer exclusively to the amendments made in the main guide.

Context and set-up

Electricity will rarely change in terms of its core principles. It will always flow the same way, attract similar equipment use, and demand appropriate attention to safety protocols. However, please ensure you’re across the relevant amendments in the guide. These will be important to working competently in the trade, and, as referenced, will serve to protect you from any newly realised hazards moving forward.

Lastly, before reading on, please ensure the copy of the bs7671 guide you’re using is an officially approved document. Untrustworthy copies are regularly seen in the industry, so make sure you have the correct documentation. If unsure, just check the inside cover, as it should have an IET (Institute of Engineering and Technology) endorsed hologram.

Where can I find the changes?

Handily, all updated changes are positioned at the front of the book, within the Introduction section. The list is relatively extensive, so leave adequate time to review these thoroughly. Nevertheless, the following narrative will provide the detail you need to acquire a firm grasp of the 18th edition’s variations, which may offer a more user-friendly way to understand the new regulations.

This version is slightly longer than the previous, 17th edition publication. There are an additional 64 pages included, which clearly demonstrates that the amount of content (and information surrounding it) has been increased. These are spread across all ‘parts’ of the guide, but are disproportionately concentrated in Part 4: Protection & Safety. Given that this alludes to worker and client welfare, it’s even more important than usual to get accustomed to the regulation updates.

What are the changes?

The notes below refer to which areas have been changed, and what general section of the 18th edition guide they correspond to (in sequence order). Remember, the numbering system relates to the line, section and ‘part’ of the book, so the following references should be easy enough to locate in the main body of the guide.

Part 1: Scope and Fundamental Principles

Regulation 133.1.3, within the selection of equipment guidance, relates to new equipment usage. Any recent tools made that don’t, by nature of their age, comply with standards set out in this book, must be recorded on the relevant certification on job completion.

Part 2: Definitions & References

No major changes. As mentioned earlier, explanations have been given more detail, and therefore this category will feel ‘fuller’ than earlier guides. Remember, this part does not cover new material as such, but serves to consolidate learnings and aid you on industry terminology.

Part 4: Protection & Safety

Again, as already referenced, this part contains the bulk of significant changes. These are the following:

Chapter 41: Protection against electric shock

In Section 411, there is a removal of the need to apply bonding on metallic pipes at point of entry, providing there is appropriate insulation in this area. This could be a plastic part, or other qualifying insulating product.

In table 41.1, which relates to maximum disconnection times, it should be noted that final circuits can be now powered up to 63A with one or more socket outlets, and those supplying fixed connected current-using equipment are allowed to reach 32A.

Regulation 411.3.3 now states that all sockets in a domestic context i.e., house/residence will require RCD (residual current device) protection. Within commercial properties, a risk assessment can be conducted on units to appropriately exempt them from this requirement.

Regulation 411.3.4 is new. However, given cabling applications in this space, it is unlikely that it will have a great impact on many installations. All lighting circuits will now require RCD protection. This development is already largely integrated into the industry-standardized approach. This is because the twin & earth style wiring used for this process carries this form of coverage already.

Regulation 411.4.3 demands that no switching or isolating device is to be used in a PEN (protective earth & neutral) conductor. This again shouldn’t trigger a huge change in approach.

There are some brief changes to regulations grouped under section 411.6, which correspond to IT (isolated earth) methods. However, as this is a fairly unusual system of install, it’s not worth addressing these developments in detail until times where such style of works arises.

The last amendment to Chapter 41 is pertaining to a new regulation group (419). This relates to where an auto-disconnection is not feasible, such as on equipment with a limited short-circuit current. Please read and digest.

Chapter 42: Protection against thermal effects

Within this chapter, there have been regulations introduced which allude to the recommendation of using arc fault detection devices. These offer mitigation against the risk of fire in AC final circuits in instances of arc fault currents. These pieces of equipment, which are sometimes abbreviated to ‘AFDDs’, are currently very expensive, and largely unknown in the UK context.

Although these devices are growing increasingly popular in North America, at this stage the guide is simply stating that they can be used to reduce risk, but are not a compulsory. Furthermore, UK-based circuits are designed to have low impedance and a high current, which lead to a disconnection of the circuit breaker anyway.

In reference to Regulation 422.2.1, conditions BD2, BD3 and BD4 have all been deleted.

Chapter 44: Protection against voltage and electronic disturbances

In this example, appropriate protection against instances such as lightning strikes or switching must be delivered. A defence against transient over-voltages has to be provided in cases where the impact of not doing so (to quote directly from the 18th edition guide):

  • Could result in serious injury to, or loss of, human life, or
  • Could result in interruption of public services/or damage to and cultural heritage, or
  • Could result in interruption of commercial or industrial activity, or
  • Could affect a large number of co-located individuals.

In other cases, an appropriate risk assessment is to be performed to determine whether the same level of protection is required.

Chapter 46: Isolation & Switching

Although the book suggests this is a new chapter, it is actually a re-addition from the 16th guide. It was exempt from the 17th edition. These regulations detail actions needed for non-automatic local and remote isolation and switching measures. One to definitely re-visit in detail given its absence from the previous guide.

Part 5: Selection & Erection of Equipment

A number of changes are present in Part 5.

Chapter 52: Selection & erection of wiring systems

Regulation 521.10.202 replaces 521.11.201. This is a significant change. Previous guidance dictated that fire resistant support of wiring systems was only required in locations where emergency escape routes were situated. This was to mitigate against the risk of cabling dropping due to fire damage, and subsequently blocking access and egress routes for the public and emergency services.

However, this regulation has been extended to whole installations, and therefore, for example, plastic fittings are no longer valid.

Chapter 53: Protection, Isolation, Switching, Control & Monitoring

This update alludes more to the re-location of content. As previously documented, isolation and switching have been moved into Chapter 46. There is a small amount of adjusted information, but largely presents nothing new of note.

The changes in section 534 mainly relate to the selection and erection of SPD’s (surge protection devices). At the time of writing the guide, these were not abundantly common, but are perpetually on the rise given our forever increasing use of electrical equipment in commercial and domestic spaces.

Chapter 54: Earthing arrangement and protective conductors

Two new regulations have been introduced in this field, which correlate to earth electrodes.

Chapter 55: Other Equipment

This is a very specific reference to changes in scope for ground-recessed luminaires. These are usually skyward facing, perimeter lights, situated on domestic drives or pathways.

Part 6: Inspection & Testing

Although content remains overwhelmingly the same, there is a slight tweak to the numbering format. This has been delivered to comply with the CELENEC (European) standard. As a by-product of this, Chapters 61,62 and 63 have been moved into Chapters 64 and 65.

Part 7: Special Installations or Locations

There are a small number of changes within Section 704: Construction and demolition of site installations. However, most adjustments relate to differences in approach to specific locations, such as Camping Parks, Medical locations etc.

One particular update which will become more and more relevant as time moves on are changes connected to Section 722, involving installations of Electric vehicle charging stations. Use of electric cars has spiked dramatically in recent times, as car manufacturers seek more environmental friendly solutions to power their vehicles. Therefore, a robust understanding of the contents of this section is advised.

When installing EVs, in relation to the use of a PME (protective multiple earthing) supply, the book has deleted out the exception titled when ‘reasonably practicable’. Therefore, the guidelines must now be followed in all cases. There are also some more general, wholesale changes to the full installation journey.

There is a brand-new section (730) for guidance on inland navigation vessels. These are for water-based vehicles located at a docking point or marina rather than out at sea.

Section 753 (Heating Cables and Embedded Heating Systems) has been completely revised. However, these are largely uncommon due to their expensive nature. These systems are usually used on airport runways or large real-estate properties to clear ice. So, please don’t immerse yourself too much on this detail unless specifically relevant to planned works.


Lastly, there are some small changes to the appendices. Remember, these should be deployed to clarify and supplement learnings taken from the main body of the book.

Appendix 1: Has been updated to reflect the current British standard.

Appendix 3: Content from Appendix 14 has been re-located here. This alludes to time/current characteristics of overcurrent protective devices and RCDs.

Appendix 6: Some minor changes to wording on certification. Testing & Inspection of circuits remains exactly the same however.

Appendix 8: Some tweaks to rating factors for current-carrying capacity in busbar trunking and powertrack systems.

Appendix 14: As referenced, content switched to Appendix 3. This line has been replaced with information on determination of prospective fault currents.

Appendix 17: This appendix was originally a full ‘part 8’ of the 18th edition guide, and was featured this way on the book’s initial draft. However, it was decided that this was too hastily drawn up, and therefore just features as a recommendation in the Appendices. This focuses on ‘green’ factors such as length of cabling and optimizing energy efficiency. Again, this is simply asserted as best practice, not a compulsory measure. This area will undoubtedly hold higher status in the next edition.


As discussed, no fundamental changes occur to how we both understand electrical systems to operate, and general industry ways of working. However, there are some clear and critical updates to specific areas of electrical installation. These require your full attention. So, please ensure therefore you allocate appropriate time to digesting these changes, and feel confident in applying them in real-world scenarios.

The introduction of the 18th edition does not mean that work carried out aligned to previous wiring regulation versions are instantaneously obsolete. Therefore, no efforts need to be made to re-hash or undo any historical work conducted, unless this fails testing & inspection sequencing, poses a health and safety risk, or differs wildly from current regulations (although this should never be the case).

Some manufacturers and retailers will brand certain equipment as compliant to ‘18th edition’ regulations, do not feel compelled to purchase this! So long as the equipment is safe and practicable, there is no requirement to update toolboxes as well as knowledge!

So, familiarize yourself with all of the key changes in this article, using your 18th edition guide as a referencing point. As with any application of the book, there is no requirement to learn the detail off by heart. Its content is designed so that you can seamlessly transfer learnings to real-life situations, so just make sure you read, digest, and consider the on-the-job practicalities of the changes.

Thanks for reading, and, as ever, if you are ever unsure on a piece of information or specific regulation, consult your course convenor or industry professional accordingly.