Heating coming on with hot water 

nice one

Thanks mate for explaining it.👍

Very informative guide thanks

Nicely explained. I think I may have this problem Dave. Could I just get round this problem to save on my gas bill by ensuring my radiators are turned off till I can afford a plumber?

Thanks dave well explained

Most of the time it's the return from the hot water tank has been 'tee' d in the wrong place

Could be reverse circulation

Cheers mate 👍🏽

After we bought our house, we realised both the heating and hot water came on at the same time. Could it have been designed like that? Or is it likely there's a fault?

Brilliant. I had issue when in winter I wanst getting heating on downstairs but upstairs was fine. Then engineer came n changed heating 2port zone valve, still no heating downstairs then flushed whole system, still no heating downstairs then changed the thermostat n it's main signal box. Slowly started getting heating everywhere. But now I'm getting heating on when I turn water on and getting water on when I turn heating on. I can't get anyone to sort this. As it was winter I never turned water on as I was getting boiling water with heating. But now its summer when I turn water on I'm getting heating and I just need both water and heating to work independently. Last year thermostat for timer has also been replaced as thot that may b the issue. Some one pls pls help and advice me. Ppl are saying the 2port zone valve replaced is faulty?

my central heating only works with hot tap running

Hi David …I have a Potterson boiler. Is it safe if we continue to use in this situation ie the radiator heats up time to time ? Will it affect the boiler functioning or can damage it? Just to add that room thermostat is off and boiler setting is set to OFF as well. Should the problem be fixed urgently ?

Hi Dave! I have recently got this issue where when using my shower / any hot water tap, the two rads closest to my combi boiler heat up quickly. Long story short, I do need to replace the whole boiler regardless, but as it'll take some time for approval / new boiler installation, is it still safe to use when the 3 port valve is faulty? I still get nice hot showers, just noticed the rads get hot too. My CH & thermostat are off. I can live without heating while waiting for the new boiler but not without hot water! So would like to continue using it for the time being. Thank you.

Are you around the south west London area pal?

What if your boiler does not have a 3 port valve? I have a Worcester 28i which does not have a 3 port but I have this issue