Why do the radiators in my home heating system get extremely hot?
A lot depends on the type of system you have. If you have a system or combi boiler, it could be the diverter valve which is faulty. This will be in the boiler itself. If you have a Y-Plan system with a three port valve, it could be the three port valve which is faulty. These are usually found in your airing cupboard or in your loft.