Consumer Units
Installation · C&G 2365 Unit 305 · Full course section in Plus
A is not a box of breakers, it is a design decision made visible. Which circuits sit on which device, what happens to the rest of the house when one fault occurs, and whether the person standing in front of it in ten years can tell what is what — all of that is settled when the board is arranged.
Domestic in England and Wales must be in a non-combustible enclosure, which is why steel boards replaced plastic ones. Beyond the enclosure, the live choices are the protective arrangement: a split-load board with two , a high-integrity board keeping critical circuits apart, or an all- board where a single faulty circuit takes only itself out. Surge protection and arc fault detection sit in the same conversation.
Labelling is part of the installation, not paperwork bolted on afterwards. A circuit chart that matches reality, the warning notices a board is required to carry, and bonding connections marked so nobody removes them, are what make the next person's job safe rather than archaeological.
This guide is free to read. There is no public quiz specifically for this topic yet. Explore the key terms below without leaving the page.
Common questions
- Can I try Consumer Units free on this page?
- This guide is free to read, but there is no public quiz specifically for this topic on this page. Browse public practice samples for other subjects, or create an account for the learning path. The full course section requires Plus.
- Where does Consumer Units sit in the City & Guilds scheme?
- maps to Unit 305. On TradeTraining it lives in the Installation section as bite-size lessons with practice questions.
- Why must a domestic consumer unit be in a metal enclosure?
- Because a loose connection inside a board can arc, and a plastic enclosure can sustain a fire that a non-combustible one contains. The requirement applies to in domestic premises; the practical effect is that steel boards are now the norm.
- What is a high-integrity consumer unit?
- An arrangement that keeps circuits apart so one earth fault cannot black out the whole installation — typically two -protected banks plus ways for circuits you never want to lose, such as the freezer, the boiler or a socket in the hall.
Explore key terms
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Consumer unit
The distribution board of a domestic installation. A main switch, residual-current protection and a row of circuit devices on a DIN rail split the incoming supply into individually protected final circuits. Modern UK consumer units sit in non-combustible enclosures and increasingly give every circuit its own RCBO instead of sharing RCDs across banks.
Read the full Consumer unit glossary entryRCBOResidual Current Breaker with Overcurrent protection
A single DIN-rail device combining an RCD and a circuit breaker, so one module gives a circuit both residual-current protection and overload/short-circuit protection. The practical win is selectivity: a fault on one circuit trips that circuit alone, instead of dropping every circuit that shares a bank RCD.
Read the full RCBO glossary entrySPDSurge Protective Device
A device that diverts brief, high-voltage spikes — from lightning activity or heavy switching — safely to earth before they reach sensitive equipment. Usually fitted at or near the consumer unit, SPDs have moved from a luxury to an expected part of new installations as homes fill with vulnerable electronics.
Read the full SPD glossary entryAFDDArc Fault Detection Device
A protective device that recognises the electrical signature of dangerous arcing — the sputtering current of a damaged cable or a loose terminal — and disconnects the circuit before the arc starts a fire. Ordinary MCBs and RCDs cannot see these faults, because a series arc neither leaks current to earth nor draws obvious overcurrent.
Read the full AFDD glossary entry