Why is my electrical cable getting hot inside the wall cavity when the heating runs – Advice from Electriman, North London Electricians

Finding that an electrical cable is getting hot inside a wall cavity when your central heating is running is genuinely concerning, and you are right to look into it. The good news is there are a few common reasons this happens, and understanding them will help you explain the problem clearly to an electrician.

The most common cause is thermal insulation. When wall cavities are filled with insulation — whether that is blown-in mineral wool, foam, or rigid boards — electrical cables that run through those cavities can no longer shed heat the way they are designed to. Every cable is rated to carry a certain amount of current, but that rating assumes the cable can cool itself by radiating heat into the surrounding air. When insulation wraps around the cable, that cooling effect disappears, and the cable runs hotter than it should.

The heating system itself can make things worse in two ways. First, if your heating pipes run near or through the same cavity, they warm the air around the cable. Second, if your heating system is drawing more electrical current than usual — perhaps a pump or boiler controller is working harder — the cable carrying that load will naturally generate more heat.

Other causes worth knowing about include:

A cable that is undersized for the load it carries, meaning it was not correctly calculated when installed.

A loose connection at a junction box, socket, or consumer unit, which creates resistance and g

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Electriman covers Mill Hill, Barnet, Finchley, Edgware, Enfield, Watford and surrounding areas. All work is Part P certified and fully insured.