Cold radiator in extension

[Staples1987]

I live in a 3 storey 5 bed house. Moved in beginning of March.
Every radiator is hot bar one - the double 2m wide 700 high one in extension. Had a heating engineer come out in May, clean system and fit magnaclean.
My system is a pressurised cylinder which is on the top floor.

I took that radiator off today and flushed with hose and clear water came out. Fitted rad back, bled system and put the pressure back up to 1.5. Every rad is still hot bar the one in the extension.

the pipe work is 10mm plastic and a new pump was fitted in May. I hope that helps

 

[exedon2]

Did you actually check there was water coming out of each valve? Could be as simple as a stuck trv

 

[Staples1987]

Yeah checked all that and was fine. I used to be a builder so I kind of know the basics.
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Sorry I also meant to say that the top gets like warm where the bottom stays cold

 

[Ben-gee]

Does it get hot if you shut down all other rads? If so - balancing issue most likely.
If not :

Check that it has a flow and a return, and that it doesn’t have two flows (or two returns) -you’ll need to trace the pipework back to where it tees in - I know it’s unlikely but I have come across it twice.