Helpful video reference. We use John Ward's tutorial "Cooker Circuits Diversity, 15kW load, 32A circuit breaker" as the video reference here. John is a UK electrician based in Dorset and one of the most thorough electrical educators on YouTube. This video explains why a 15kW cooker can legally run on a 32A circuit under the diversity rule in BS 7671 Appendix 15 — a point that catches a lot of people out when they are specifying a new cooker.
1. Find out what you already have
Look for a double-pole switch plate — usually a white plate with a red or amber indicator lamp — mounted within 2 metres of the cooker position. That is the cooker connection unit (CCU). If there is no CCU, or only an ordinary socket nearby, a qualified electrician needs to install a proper circuit before any cooker can be connected.
Check the rating on the CCU: most are 45A. Check the cable behind it too if you can see it — 6mm² twin and earth is correct for most domestic cookers. Older properties sometimes have 4mm² which may not be adequate for a modern range cooker.
2. Understand the diversity rule
A large range cooker might be rated at 13kW or more, yet BS 7671 allows it to be wired on a 32A circuit using the diversity rule. The logic is that the oven and all four hob rings are never simultaneously on at full load for sustained periods. The formula in Appendix 15 produces a "design current" significantly lower than the nameplate total. John Ward's video explains this clearly if you want the numbers.
The practical upshot: a standard 6mm² radial circuit protected by a 32A MCB is correct for most domestic electric cookers and separate oven-plus-hob combinations up to around 14kW combined.
3. Isolate the circuit
Switch off the cooker MCB at the consumer unit. In homes with a rewireable fuse box, remove the fuse and keep it with you. Use a voltage tester on both sides of the CCU switch — with the CCU switch both on and off — before you touch any terminals. Dead in all positions? Good.
4. Disconnect the old cooker
The cooker connects to the outlet side of the CCU. There will be three conductors: brown (live), blue (neutral) and green-and-yellow (earth). Some older installations use red, black and bare — if you see those colours, photograph them carefully before touching anything. Loosen each terminal, withdraw the old cooker tails or flex, and keep the conductors separated until the new cooker is ready.
5. Prepare the new cooker's connection
Most cookers come with a short length of 6mm² heat-resistant flexible cable already attached. If yours does not, connect a 6mm² heat-resistant flex — at least 1.5 metres long — to the cooker's own terminal block following the manufacturer's instructions. Strip about 10mm from each core and check the ends are not frayed before insertion.
6. Make the connections at the CCU
Connect brown to the terminal marked L (or Line Out), blue to N (Neutral Out), and green-and-yellow to E or the earth symbol. Tighten each terminal firmly. Give each conductor a gentle tug to confirm it is secure. Fit the CCU cover back on before restoring power.
7. Restore power and test
Switch the MCB on at the consumer unit. Switch the CCU on. Test at least one hob ring and one oven function. If the MCB trips immediately, switch back off and check for a pinched or damaged conductor inside the CCU. Do not keep resetting a tripping breaker.
When to call us
Reconnecting a new cooker to an existing, correctly rated CCU is a simple job. The moment it involves work at the consumer unit, upgrading the cable, or installing a new circuit from scratch, that is Part P notifiable work. Richard covers kitchen rewiring and new cooker circuit installation across east Kent — contact us for a fixed price before any work starts.
Need a cooker circuit in Sandwich or east Kent?
New cooker circuits, CCU upgrades and consumer unit work carried out to BS 7671, Part P certified on completion.
Contact Richard