Consumer Unit Types Explained
Consumer-unit selection is about containment, protective measures, future circuits and the condition of the existing installation — not just how many ways are available.
Main-switch, split-load, dual-RCD and all-RCBO boards arrange protective devices differently. The right choice depends on circuit segregation, required RCD protection, fault continuity, SPD/AFDD assessment and the installation's existing condition.
This is practical guidance for competent electricians. Assess the actual installation, follow the current edition of BS 7671 and manufacturer instructions, and stop where the work cannot be completed safely.
Key takeaways
- Agree the scope and make the installation safe before starting work.
- Use a controlled sequence rather than relying on a single reading or visual assumption.
- Record the actual result, limitation or action taken while it is still traceable.
- Check the result against the design, protective measures and equipment instructions.
- Issue the appropriate certificate or report when the work is complete.
Scope the work first
Main-switch, split-load, dual-RCD and all-RCBO boards arrange protective devices differently. The right choice depends on circuit segregation, required RCD protection, fault continuity, SPD/AFDD assessment and the installation's existing condition.
Method
Start with a full survey, identify circuits and demand, assess the earthing and bonding, then choose a board and device arrangement that avoids grouping unrelated essential loads behind one protective device where practicable.
Doing this on a job? Electrical Installation Certificate — part of TradePlanr. Free to start, no card needed.
Checks and common pitfalls
A consumer-unit change can reveal borrowed neutrals, low insulation resistance, inadequate tails or missing bonding. Do not treat it as a like-for-like accessories job: design, testing, certification and notification requirements all need planning.
Record and hand over
Document the circuit schedule, device types, protective-measure verification and any pre-existing limitations. Give the client circuit labels and an EIC with the completed schedules.
Keep the evidence with the job
Record readings, limitations and remedial actions as you work. A clear certificate or report protects the client and makes the next visit easier to manage.
From guidance to action
Frequently asked questions
Are all-RCBO boards always the right choice?
They often improve fault containment, but selection still depends on the design, compatible devices, budget and existing installation. Assess the complete board rather than choosing by a single feature.
Can I rely on a standard rule of thumb?
No. The installation method, supply characteristics, equipment instructions and the current requirements all affect the correct decision. Use the guide as a workflow, then assess the actual job.
What should be recorded?
Record the scope, results, limitations, observations, remedial work and the certificate or report appropriate to the work carried out.
Related guides
RCBO vs RCD vs MCB: What’s the Difference?
What each device protects against, why an RCBO combines both, and when to use each in a consumer unit.
Consumer Unit Regulations (BS 7671)
The regulations behind consumer units — non-combustible enclosures, RCD/SPD/AFDD provision and RCBO boards.
How to Price a Fuse Board Upgrade
A practical pricing method for consumer unit changes — survey first, then build remedials and certification into the quote.
