One Radiator heating Intermittently

4 Mar 2014
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United Kingdom
Guys, I'm having issues with just 1 of 2 radiators in a single story extension room on ground floor.
One rad has no issues but the other has little or no heat. Valves on both ends of this rad are fully open and the flow pipe (comes down from ceiling) is warm but the return is stone cold, as is the rad.

Radiator has no air and the one bleed point in the loft above the room has been bled also. I took the dodgy rad off a few weeks ago and flushed through, connected the 2 valves together with a length of flex pipe (after draining a few litres from the flow valve) temporarily and the flow started and it all got hot (without rad connected). I then reinstalled rad and it all worked for a week (red hot) and now its stone cold again. flow pipe warm, return cold. So there is no flow for some reason.

Any advise please?
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Does the return pipe also go "up" into the ceiling? These types of setups are renowned for air locks in the pipes.
Yes it does...... in the loft above rad there are two short 6" vertical sections in the rad feeds (1 on flow and 1 on return) each with a bleed screw but no air in them, so not sure where the air is or how to get it out of the system
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Airlock indeed....

For the benefit of anyone else in the same situation... I used this method and now all is good


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