One Radiator Not Working

[jiri5reg]

I had the system drain down in summer and now I cannot get one of the downstairs radiator works. It is warm but never hot. Seems to me its war up a bit if the boiler/ pump running for several hours. Radiator has been flush with water. RTV is working. In the hot water tank cupboard, after 3 way motorized valve, I found bypass valve fully opened. Should be this partly closed to stop flow circulate?
thanks Jerry

 

[ianmcd]

well shut it and see ? you can always open it again if it doesnt do anything

 

[jiri5reg]

If fully closed the boiler develop very loud noise as trap air bubble and the radiator is still cold. However if the rest of downstairs radiators are closed than it is heating up. Is the system not balance?

 

[ianmcd]

yes you need to balance the system , how to do this is extensively covered in the wiki on here