Why is my electrical cable getting hot inside the wall cavity when the heating is on?

Finding that an electrical cable is getting hot inside a wall cavity when the heating is on is something you should take seriously, even if everything seems to be working normally. Here is what is likely happening and what you should do. Why cables get hot near heating All electrical cables produce a small amount of heat when electricity flows through them. Normally the surrounding air carries this heat away safely. But when cables are buried inside wall insulation, packed tightly together, or surrounded by spray foam or mineral wool, that heat has nowhere to go. The cable gets hotter and hotter. If this continues, the outer plastic sheath can soften or melt, which creates a serious fire and shock risk. The situation gets worse when the central heating is running because the cavity itself becomes warmer, adding extra background heat on top of what the cable is already generating. What you can safely check yourself 1. Feel any accessible sections of the cable near sockets, switches or the consumer unit. Warm is a concern. Hot to the touch is an emergency. 2. Check whether any cables pass through or near foam or mineral wool insulation in the wall, loft or floor. 3. Look for any discolouration, brown marks or a burning plastic smell near sockets or light fittings on that circuit. 4. Check whether the circuit has recently had extra appliances added to it, such as a new electric heater or additional sockets. What you should not do Do not open up wall cavities or pull cables yourself unless you are qualified. Do not assume the problem will go away once the heating is turned off. Do not ignore a burning smell. When to call a qualified electrician You should call a registered electrician if the cable is hot rather than just warm, if you can smell burning plastic anywhere in the house, if circuit breakers are tripping without an obvious cause, or if the property has had cavity wall insulation fitted recently. Any of these situations could indicate that the cables are already damaged and operating unsafely. A qualified electrician can carry out insulation resistance tests and check the installation against current wiring regulations to confirm whether the cable needs to be rerouted, replaced or derated.