Why does my electrical cable getting hot inside the wall when the cooker is on?
Quick answer
A cable getting hot inside a wall when the cooker is on almost always means the cable is undersized for the load, has a loose or corroded connection, or is being run through insulation that is trapping heat. This is a serious fire risk. Switch off the cooker circuit at the consumer unit immediately and do not use it until a qualified electrician has inspected and tested the wiring. Do not ignore this — overheating cables inside walls are one of the leading causes of house fires in the UK.
🏠Homeowner view
If you have noticed that the wall feels warm near the cooker cable route, or you can smell a faint burning or plastic smell when the oven or hob is on, this is a warning sign you should not ignore. Here is what is most likely happening and what you should do.
What causes a cable to overheat inside a wall?
The most common reason is that the cable is not big enough to carry the amount of electricity the cooker is drawing. A standard electric cooker in a UK home typically needs a 6mm or 10mm twin and earth cable depending on its rated load. If a previous owner or unqualified person fitted a smaller cable, such as a 2.5mm or 4mm, the cable can overheat under normal cooking use.
A second very common cause is a loose connection, either at the cooker connection unit, at the consumer unit, or at a junction somewhere along the cable route. A loose connection creates resistance, and resistance creates heat. Over time this can cause the insulation to melt, char the surrounding plasterwork, or start a fire inside the wall cavity.
A third cause is the cable running through or under loft insulation. UK Building Regulations and wiring rules require cables to be derated or run in conduit when they pass through insulation, because the insulation stops heat from escaping. If this has not been done, the cable can run dangerously hot even at normal loads.
What you can safely check yourself:
1. Switch off the cooker circuit at the consumer unit and leave it off.
2. Check the consumer unit for any sign of a tripped breaker or a blown fuse.
3. Do not touch or probe any wiring yourself.
4. Note any smell of burning, discolouration of sockets or switches, or brown marks on the wall.
When to call an electrician:
Call a Part P registered electrician straight away. This is not a fault you can monitor and come back to later. An overheating cable inside a wall can smoulder for hours before igniting. A qualified electrician will carry out insulation resistance testing, check the conductor size against the cooker load, inspect all connections, and confirm the installation complies with BS 7671. If you are a tenant, contact your landlord immediately and in writing so there is a record.