Consumer Unit Regulations (BS 7671)
A modern consumer unit has to meet several BS 7671 requirements at once — enclosure material, additional protection, surge protection and, increasingly, arc fault detection.
The consumer unit is where most of the protective devices in a domestic installation live, so BS 7671 places specific requirements on it — from the material it is made of to the protection each circuit gets.
This guide pulls those requirements together: the non-combustible enclosure rule from Amendment 3, RCD and RCBO provision, surge protection under Chapter 443, and where AFDDs now apply.
Key takeaways
- Consumer units in domestic premises must have a non-combustible enclosure (metal) or be in a non-combustible cabinet.
- Most final circuits require 30 mA RCD additional protection, which an RCBO board delivers per-circuit.
- SPDs are required unless a risk assessment shows they are not needed — in practice they go in on most jobs.
- AFDDs are required for certain higher-risk premises and recommended more widely.
- A consumer unit change is notifiable work under Part P and needs an EIC.
Non-combustible enclosures
Since Amendment 3 to the 17th Edition, consumer units and similar switchgear in domestic premises must have a non-combustible enclosure or be installed within a non-combustible enclosure. In practice this means the familiar steel consumer unit replaced the older plastic boards.
The requirement came from fires linked to loose connections in plastic units. If you find a plastic consumer unit on an EICR, it is not automatically a defect, but the reason it was changed is worth understanding.
RCD and RCBO provision
BS 7671 requires 30 mA RCD additional protection for socket outlets up to 32 A for general use, cables buried in walls at low depth, and circuits in special locations. A dual-RCD split-load board or, better, an all-RCBO board delivers this.
All-RCBO boards are increasingly the default because they avoid the nuisance of a single RCD taking out half the installation on one fault, and they make fault-finding cleaner.
RCBO vs split load
An RCBO board isolates a fault to one circuit, keeps the rest of the house live and speeds up fault-finding — usually worth the extra device cost on a change.
Surge protection (Chapter 443)
Chapter 443 requires surge protective devices where a transient overvoltage could cause serious consequences, and otherwise unless a risk assessment shows the low cost of the equipment is not justified. Because the assessment rarely rules them out for a dwelling, SPDs are fitted on most consumer unit changes.
The SPD is installed at the origin, as close to the main switch as practical, with short connecting leads to keep it effective.
AFDDs and certification
Arc fault detection devices are required by BS 7671 for socket-outlet final circuits in certain higher-risk premises such as HMOs, care homes and purpose-built student accommodation, and recommended more widely. Amendment 4:2026 revisits their scope.
A consumer unit change is notifiable under Part P and is certified with an Electrical Installation Certificate, recording the board, the devices and the test results.
Paperwork done on the board
TradePlanr's EIC captures the new board, every RCBO/RCD/SPD and the test schedule, so the certificate is ready to sign before you refit the cover.
Frequently asked questions
Do consumer units have to be metal?
They must be non-combustible or in a non-combustible enclosure. In practice that means a steel consumer unit for domestic installations, following Amendment 3.
Is a plastic consumer unit a fault on an EICR?
Not on its own. A plastic unit installed to the standards of its day is usually a C3 (improvement recommended) unless there is an actual defect such as thermal damage, which would be coded more seriously.
Do I have to fit an SPD?
Chapter 443 requires SPDs unless a risk assessment shows they are not justified. For most dwellings the assessment does not rule them out, so they are fitted as standard on a consumer unit change.
From guidance to action
Related guides
Consumer Unit Upgrades Explained
What a consumer unit change involves — assessing the existing installation, RCBO boards and paperwork.
SPDs: Surge Protection Devices
SPD types, the BS 7671 risk assessment, and how to install surge protection correctly.
RCD Types: AC, A, F and B Explained
The difference between Type AC, A, F and B RCDs and when each one is required.
