Cold Radiators...

[Sonic]

Hi All, this is my first post and i hope you can help me overcome a really infuriating issue. I have a pressurised heating system, with drayton trv's on each radiator. recently i had to replace the pressure sensor on the boiler which was straight forward, but now i have an issue with the radiators in the bedrooms (upstairs) not warming very well (if at all). i have flushed and represurised the system 3 times, bled the rads, checked each TRV and none of the pins are sticking. i read somewhere that the trv's work better on the inlet side as the flow often helps to open the valve seat even if the pin is not sticking. the inlet pipe on the rads with the shut off valves get really hot, but the outlet with the trv's do not. i have tried turning of every other rad except the ones in the bedrooms and they show some signs of improvem$ent but do not get much above luke warm. the only other thing i have not done is take the TRV's off and clean then thoroughly. i am wondering if the valve seat could be stuck as they are on the outlet side of the rads? could this be the case or are there any other suggestions. thanks

 

[Sonic]

i did think this, but have flushed the system first with the valves closed on all rads, and then opened the valves on the problem rads to flush them through as well. i think it is a restriction on the return side somewhere, because when i turn off all the other rads in the house the problem rads get warmer but not hot like the other ones. the inlet pipes feel really hot, but outlet (with the TRV's) are almost cold or at best luke warm. this makes me think there is a restriction on the outlet side. i am wondering if the valve seat on the TRV's on the 2 x problem rads only opens partialy despite the pin being free and with them being on the outlet side, there is no pressure pushing the seat open. Hope this makes sense, i am going to drain the system again tomorrow and take the TRV's off and clean them thoroughly, if this does not work then i am at a loss unless anyone has any other suggestions worth trying??

 

[fuzzy]

take the rad off and test the valve

 

[Sonic]

I have removed and checked the valves and they are fine. i have now bought some system cleaner and had that running for 36 hours now. i think the problem is balance related or maybe my boiler is too small. if i turn the boiler temp to max and turn off all the other rads except the 2 problem ones, they do get hot now, but as soon as i turn on the other rads even a 1/4 turn, the heat drops off on the 2 problem rads and does not come back up again. could i fix this with a better circulation pump, or is my boiler too small? the boiler is fitted downstairs in the kitchen, and the problem rads are upstairs in the bedrooms. it also seems cooler when i am heating the water as well, i guess this is normal, but it does not seem to come back up hot afterwards.

 

[Sonic]

Woo Hoo fixed it. serious blockage in the return, had to use my compressor and blow air through at 100 psi and it cleared straight through. now have rads hotter than a hot place on a hot day.