central heating

[natedodd]

just moved into a new house with an attic conversion and the radiators up in the attic never get that warm the valve and thermostat are fully open and the boiler is only running 7 radiators. they dont need bleeding either.....

[stuelwell]

your pump may not be strong enough to pump as high as the attic. would recommend to get a heating engineer out to check it

[parkesquay]

I had a similar problem on one or two of my rads despite bleeding them. It was suggested that I remove the temperatur control setting bit(the piece that you turn to select heat number(1-5) and then press in the pins a couple of times and replace the control. With one of them it was sufficient to turn the controll to *(frost setting)and then push the cap area at the end a few times. The cap end should press against the levers/pins
Hope this is clear enough to follow.

[buildersmate]

If all the other radiators are hot, this suggests the system needs BALANCING. This means forcing enough water through all the pipes that lead to the rads. The very act of doing this may lead to the need for a more powerful pump as Stuelwell suggests.
I haven't a clue what Parkesquay is referring to, but it doesn't seem relevant to me.
To balance the rads to adjust the lockshield valves on the opposite end of the rads to the adjustment (normally TRVs these days). It is behind the scope of this site to explain in a few words how to do it.

[terence7556]

parkesquay is suggesting the radiator valves are sticking because of a buildup of muck on the valve stem and not allowing the hot water to get into the rad to warm it up.
i have come across this problem on 3 jobs and on each occasion cleaning the valve stem worked and the customer was amazed that the rad was heating up again
it does,nt do any harm to try it but i agree with the others that height is a problem here especially if the rads in the conversion are new and have not really had enough time to gat that dirty

[gucciman]

you can quickly test to see if the system needs balancing by shutting off the radiators on the lower floors and seeing if the ones on the top floor then get hot. if that works and you then dont want to pay a heating engineer to balance the system properly then you open up the return flow valve (this is the valve that has a smooth cap and is designed for the installer to adjut not the houseowner, you will need to take out the screw, remove the cap and adjust the valve with pliers) on the downstairs rads(having previously closed them for your test) a turn at a time until those radiators get hot without the top floor ones losing too much heat.
you can also see which speed your pump is set to and turn it up to number 3 if it isn't aleady and see if that makes a difference. or you could try a higher head pump which would push the water around the system to the the top floor better.
you can also see if the trv pins need oiling s previously suggested but i doubt it.