Consumer Unit Regulations Guide

Consumer Unit Regulations Guide

There has been a lot of confusion regarding changes to the wiring regulations and how they affect consumer unit regulations

Since the introduction of the 18th edition, there have been some new additions to particular regulations which affect the fitment of consumer units. 

In this blog post we are going to look over these regulations, and see exactly what they mean to you, whether you are installing a new consumer unit or completing an EICR

I’ll try and keep the individual sections short and to the point, however there is quite a lot to fit in here so the whole post is quite long.

It can help to use the contents section, this will break down each part into manageable chunks so you can find exactly which consumer unit regulations apply to the install you are completing/testing.

Consumer Unit Construction

Since AMD3 of the 17th edition was introduced in 2015, consumer units in domestic premises have been required to be constructed from a “non-combustible” material.

This generally means that all domestic installations must now have a metal consumer unit installed, unless the consumer unit is installed within a non-combustible enclosure.

Whilst there is no hard and fast requirement to upgrade older installations just because they have a plastic consumer unit, all new installations must now comply with this standard.

EICRs on older installations will come across plastic consumer units quite regularly.  These should only ever be coded as a C3 – IMPROVEMENT RECOMMENDED, there is no requirement in BS7671 to “fail” and thus upgrade these older plastic units

The particular consumer unit regulation relating to this in the 18th edition is 421.1.201

It should be noted that this regulation does not apply to commercial installations, where plastic consumer units can still be installed.

Not only that, but in domestic outbuildings, for example sheds & garages, you can still install plastic consumer units assuming that the outbuilding is not joined to the main building.

The reason these consumer unit regulations were updated is due to the amount of fires which had occurred in plastic boards. This isn’t a true causation though as the only reasons that they would catch on fire is either a fault within or else poor installation practices.

A non combustible consumer unit ensures that any fire is contained within the enclosure itself and cannot spread to the surrounding building materials.

Installing a metal consumer unit on a TT earthing arrangement system was always frowned upon prior to this due to the risk that the enclosure could become live and not disconnect the main OCPD.

This is a conumdrum that needs a whole other guide in itself, and we have done just that! Please check: Can I Fit A Metal Consumer Unit to a TT earthing arrangement system?

Division Of Circuits – RCD or RCBO?

This is a hotly contested debate amongst electricians. Dual RCD & split load boards were popular under previous versions of BS7671. Whilst these never really met the requirements for division of circuits, they were a safe compromise.

It should be recognised though, especially since RCBOs are so plentiful and relatively cheap, that an RCBO board is really the properly compliant with consumer unit regulations, specifically the parts of BS7671 related to dividing circuits to minimise inconvenience in the event of fault.

RCBOs not only minimise inconvenience to the end user, but they allow for much faster fault finding & rectification of issues as it obvious from the get-go which circuit is involved. Dual RCD boards do not allow this, each RCD can cover a multitude of circuits, thus complicating locating faults.

Maximum Leakage Current on RCD / RCBO

The 18th edition of BS7671 brought a new consideration for RCD equipped devices. Reg ????


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