Key changes from the 18th Edition that you need to know

January 21st 2021

Months of anticipation and speculation has come to an end as the 18th Edition of the IET wiring regulations has now been published.

BS7671:2018 was released on the 1st July 2018 and will become effective from 1st January 2019, but the new edition can be used immediately. 

There are lots of changes in the 18th Edition. These include new and revised regulations, new chapters and restructured sections.

So with the big blue book now available where do you look to discover these changes? Hopefully these headlines will make your task a little easier.

(This is for information only.  For the full details designers & installers should purchase a copy of BS 7671:2018 IET Wiring Regulations 18th Edition and follow the requirements & recommendations therein, this information does not constitute design advice)

Extended Scope

The scope has been extended to include an extra category (section 730 catering for electrical shore connections & inland navigation vessels).  Section 730 contains the particular requirements for this added special location.

Chapter Changes

Chapter 46 is new and Chapter 53 has been rewritten. Part 6 is restructured & the regulations for inspection & testing move to new chapters and get new regulation numbers.


There are several new definitions, and a few existing definitions that have been amended. For example, “Departure” is a new definition.

Departure is explained as an intentional decision to not fully comply with BS7671.This must be accompanied by a declaration from the designer that the safety levels achieved are not less than full compliance with BS7671 would provide.

Energy Efficiency

A new appendix on energy efficiency is included within the 18th edition. Appendix 17 makes recommendations for the design construction & assembly of the installation for optimising efficiencies in the use of electricity.


Only Use Approved Parts

Devices & components used in low voltage assemblies e.g. Consumer Units, Distribution Boards etc. shall only be those that have been declared suitable for that purpose by the manufacturer of the assembly.

If in doubt ask the manufacturer of the assembly to confirm compatibilities. 

Note; if a deviation from manufacturer instructions is introduced then the person introducing the deviation becomes the manufacturer.

Arc Fault Detection Devices

AFDDs have been included in Chapter 42. These devices provide additional protection against fires that are caused by arc faults in AC final circuits.  

Arc fault detection devices (when used) should be installed at the origin of each final circuit that is are being protected, AFDDS should be installed in consumer units and/ or distribution boards.

Discover more about Arc Fault Detection Devices here.

Appendix 6

In the schedule of inspections, under the section dealing with consumer units & distribution boards there is a reference to check for the AFDD six monthly test notice, similar to the requirements for RCDs & RCBOs.

Also in the schedule of test results form there is a new tick box for AFDDs which allows the installer to record operation of the manual test button on the AFDDs, again this is similar to RCDs & RCBOs.

Surge Protection

Within the 17th Edition of the Wiring Regulations, the requirements of surge protection were determined through risk assessment methods. Now, overvoltage protection is required in certain circumstances.

For example, where there is risk of serious injury or of loss of life,  where many co-located people are affected, where there is an interruption to public services, or commercial / industrial activity. Other requirements are contained in 443.4.

For circumstances where overvoltage protection is not required, a risk assessment can be carried out. If a risk assessment is not carried out, overvoltage protection must be provided.

You can find out more about surge protection here. 

Get the lowdown on the 18th Edition

Looking to get more pointers on the 18th Edition?

From Arc Fault Detection Devices, Transient Overvoltage Protection to RCDs, we've got you covered.

Visit our 18th Edition Area and check them out.

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