Central heating problem.

[Hopgood]

Hi. My central heating system consists of an extension with wet underfloor heating (3 zones) and the original part of the house standard pipes and radiators. With just the underfloor heating on and the rest of the system turned off, the radiators get warm. Any idea what the problem might be. My current plumber is unable to find a solution.
Many thanks
Paul

 

[SJB060685]

Has this always been the case? Are the radiators off their own zone valve?

 

[Deleted member 120897]

Does your boiler have a preheat function?

 

[Timmy D]

Pics of boiler/pipework/underfloor manifold please. Shouldn’t really be difficult to diagnose.