Hi, I've noticed that a couple of radiators become hot even though the central heating is off when I'm using a hot water tap for some time. I have an old glowworm combi bolier if that's of any use. Can someone explain how this is possible? Thanks. Regards Rick
Sounds like the diverter valve which changes the boiler water flow from CH to DHW isn't closing fully, allowing a small amount of water to flow into the CH side when it should all be flowing to the heat exchanger to heat the DHW.
I don't think Glowworm boilers had valves 30 years ago, (like my reliable antique). It could be circulation round the CH caused by convection when the gas is burning a lot and the boiler water is very hot. My hot tank water is done by convection from the right side of the rectangular boiler and the CH by a pump from the left side, hence four pipes to the boiler altogether. It is possible that there is some interaction of the flows in the boiler.
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