cold radiator in living room!

[cozmo]

Hi, can anyone help with some advice?!
i have 2 radiators in living rm, 1 works very well and 1 of which has never worked since moving in 2 years ago. 3 radiators upstairs work well. Replaced dodgy rad with new one, also replaced both valves. Rad now only very slightly warm. some heat at flow/inlet pipe but cold at return pipe even when all other rads turned off and new rad turned on full. 8mm microbore pipe used in system. Any thoughts? Any advice would be most helpful! cheers!

 

[Whitespirit66]

Maybe blockage in one of the 2 pipes. Try this;

20 ) Checking Flow through Heating pipes - The "BUCKET TEST"

This is used to check the flow through pipework on either radiator valves, or pump isolation valves.

You turn off both valves and undo the valve union connection (collect water contained between the valves) then remove the radiator or the pump ( or usually just the pump head! ).

You then place the bucket under the valve and open the valve and see if a good flow of water runs freely into the bucket.

Its best to run at least half a bucket from each radiator valve in turn.

With a pump its only necessary to check that the flow rate is good and that the pump valve is indeed opening.

This test will often clear a blockage on a radiator feed pipe as there is far more pressure than the pump head provides.

Pump valves sometimes shear off and dont open or they can become blocked by dirt.

Sometimes after using DS40 it loosens calcium based dirt which then becomes mobile and blocks at a pump valve on the inlet to the pump volute.

Tony Glazier

Last edited by Agile on Thu Feb 19, 2009 1:51 am, edited 1 time in total

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Agile

 

[cozmo]

Hey, thanks for your reply. Just to say, im new to this type of DIY and hv very little knowledge or experience with radiators! Anyways, hv tried 'flow test' as suggested, although only at radiator. Havnt touched pump yet. Seems to be good flow at return pipe by opening lockshield valve, not sure about flow from inlet pipe. with TRV opened full and central heating on, doesnt appear to be alot of pressure or flow through radiator, also no difference with radiator removed. Should I check pump? should I just replace both feed and return pipes and if so, how easy is it to do, and how likely will it be that it'll sort the problem?! thanks for your patience and advice on this one!!

 

[jackthom]

If other radiators are working well you can probably forget about the pump.

The most likely culprit is the 8mm pipework to the radiator which the bucket test (boiler switched OFF and radiator removed) should have shown up.

If the TRV side is barely squirting that's the place to start replacing pipe (preferably not with more 8mm if you can avoid it) and at the same time checking the TR valve when it's removed.

 

[cozmo]

Great, thanks for that. Will try heavier gauge piping. Is there a need to replace both pipes to keep them the same or is it ok to leave the return pipe at the 8mm type? Cheers!