hot radiators when HW turned on

[KCK]

I would like some advice please. Used to have an old gravity hot water/pumped central heating system, which was changed to a Vaillant ecoTec 624 with a hot water cylinder last October. Switched off the heating and and left HW on , but radiators continue to heat up. Called plumber back and he changed brass (3 part )gadget. Called plumber back again with same problem now he says he needs to lift up tiled floor in bathroom to look at pipework. My question is, is there any other way to solve this problem other than to tear my bathroom apart. Boiler is in kitchen and bathroom directly above.

 

[SortedPlumbing]

sounds like Ur pipework between HW and CH is connected at some point.
did it just start to happen when you changed boiler?

 

[LUNAT]

HI

if it was done recently it might have been piped incorrectly.and if it is then floorboards need to come off.

 

[KCK]

Yes. This started after new boiler was fitted.