Amendment No. 3 to BS 7671 – Regultion 421.1.201

Since January 2016 Amendment No. 3 to BS 7671 (421.1.201)IET Wiring Regulations states that within domestic (household) premises, consumer units and similar switchgear assemblies shall have their enclosures manufactured from non combustible material, or be enclosed in a cabinet or enclosure constructed of non combustible material and comply with product standard BS EN 61439-3.

Guidance from BEAMA (British Electrotechnical and Allied Manufacturers Association) who represent the UK manufacturers. The intent of regulation 421.1.201 is considered to be, as far as is reasonably practicable, to contain any fire within the enclosure and to minimise flames from escaping, caused mainly as a result of poorly installed connections.

Key Points:

1. What is a definition of non-combustible?

There is no published definition for ‘non-combustible’ that aligns with the intent of regulation 421.1.201. Ferrous metal is deemed to be one example of a non-combustible material that meets the intent of the regulation.

2. What constitutes a ‘non-combustible enclosure’?

A non-combustible enclosure includes base, cover, door and any components e.g. hinges, covers, screws and catches, necessary to maintain fire containment. See diagram 1. Blanks and devices are contained within the non-combustible enclosure.

3 How is account taken of cable entries into a ‘non-combustible enclosure’ with respect to
containment of internal fire and escape of flames?.

Good workmanship and proper materials must be applied by the installer. The cable installation entry method shall, as far as is reasonably practicable, maintain the fire containment of the enclosure. Account shall be taken of the manufacturers instructions, if any.

4. What is meant by ‘similar switchgear assemblies’?

‘Similar switchgear assemblies’ are assemblies used for the same fundamental application as consumer units.

5. Does regulation 421.1.201 apply to consumer units and similar switchgear assemblies installed in domestic (household) garages and outbuildings?

Yes, the intent of regulation 421.1.201 is that it applies to consumer units and similar switchgear assemblies to BS EN 61439-3 inside all domestic (household) premises including their integral/attached garages and outbuildings or those in close proximity.


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18th Edition IET Wiring Regulations – Guidance Note Books

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On-Site Guide (BS 7671:2018+A2:2022) (Electrical Regulations) – This publication has been further updated to include two subsequent amendments to the IET Wiring Regulations as BS 7671:2018+A2:2022