Helpful video reference. Gary Hayers at GSH Electrical — a UK electrical training channel run from Tresham College with more than 170,000 subscribers — illustrates what you should see on a correctly labelled consumer unit in "Labels and Descriptions on Consumer Units". The video covers the regulatory requirement for circuit identification and the specific warning notices the regulations require. Worth watching before you start so you know what the finished result should look like.
1. What BS 7671 requires
Regulation 514 of BS 7671 (the IET Wiring Regulations) requires that every circuit in an installation is clearly identified. In practice, for a domestic consumer unit, this means:
- Each MCB, RCBO or fuse has a label identifying the circuit it protects — "upstairs lights", "kitchen ring", "shower" and so on.
- A circuit schedule is provided, either affixed inside the consumer unit door or stored nearby, listing each position, its rating and the circuit it serves.
- Mandatory warning notices are displayed where required.
Consumer unit manufacturers include labelling strips and pre-printed warning notices in the box when the unit is new. In an older property, or after someone has made changes without updating the labels, all of this can be missing.
2. Warning notices
Two warning notices are particularly common in domestic consumer units:
- RCD test notice: Where an RCD is fitted, BS 7671 requires a notice telling the occupier to test the RCD by pressing its test button every quarter. The wording and format are specified in Appendix 2 of the regulations. Replacement notices are sold by electrical wholesalers for a few pence and are self-adhesive.
- Dual supply notice: Where the installation has more than one source of supply — for example, a property with rooftop solar panels connected to the consumer unit — a notice is required to warn anyone working on the installation that there may be a second energised source even with the main switch off. If your property has solar, check this notice is present.
Some older consumer units also carry a notice warning that the conductors may be hot under normal operation. This is a hangover from early designs rather than a current requirement, but there is no harm in leaving it in place if it is already there.
3. How to identify each circuit
If your consumer unit has unlabelled MCBs, the only reliable way to identify circuits is to switch them off one at a time and note what stops working. This is a two-person job: one at the consumer unit, one moving round the property checking what has lost power.
Work through a methodical checklist:
- Lighting circuits: Switch off and note which rooms go dark. Most properties have upstairs and downstairs lighting circuits; some also have a separate circuit for a kitchen or extension.
- Socket ring circuits: Use a plug-in socket tester (the kind with three indicator LEDs that plugs into a 13A socket). Switch off one MCB at a time and note which group of sockets loses the green light.
- Dedicated circuits: These usually have a higher-rated MCB: 32A or 40A for a shower or cooker, 16A for an immersion heater or electric vehicle charger. They often serve a single appliance with an obvious physical connection to the consumer unit.
Write each result down as you go. It is surprisingly easy to forget which circuit you have just identified if you are switching back and forth between the consumer unit and the rooms.
4. Dealing with multiple RCDs or RCBOs
Modern consumer units either use two RCDs (each protecting half the circuits) or individual RCBOs on every circuit. If the unit uses RCBOs, identify the circuits the same way — switch one RCBO off at a time. If it uses two RCDs, you can identify which half of the board each circuit is on by resetting one RCD at a time and testing.
Note on your schedule which circuits are protected by RCD 1, which by RCD 2, and which (if any) are on RCBOs. This is useful information if an RCD trips in future: only the circuits on that RCD will be affected, so you can restore the other half of the board while you trace the fault.
5. Write the circuit schedule and fit the labels
A circuit schedule need not be complicated. A handwritten list on a piece of A4 card, sealed in a polythene sleeve and slipped inside the consumer unit door, is perfectly acceptable. If you prefer a printed template, consumer unit manufacturers and electrical wholesalers supply blank schedules in the right format.
Each row in the schedule should record: the position number (1, 2, 3 from left to right), the type and current rating of the protective device, and the circuit description. Add the cable size if you know it — 1.0 mm² for lighting, 2.5 mm² for socket rings, 4 mm² or 6 mm² for shower and cooker circuits typically.
Once the schedule is written, cut individual circuit labels to fit the label strip on the consumer unit face and press them firmly in. If the consumer unit is an older type without a label strip, self-adhesive tape labels work well. Use permanent ink and make sure every label is readable at arm's length.
When to call us
Labelling and circuit identification is safe work that any careful homeowner can do, provided you stay out of the live parts compartment. If what you find raises questions — unlabelled circuits that do not map to any obvious appliance, signs of overheating, or a consumer unit that looks like it has been modified in an ad hoc way — call an electrician to investigate properly before you assume everything is in order.
Consumer unit concerns in Sandwich?
Richard can inspect your consumer unit, identify all circuits, label everything correctly and let you know if anything needs attention — often as part of a small local visit.
Contact Richard