Rads not getting hot

[handful]

I recently changed 3 radiators and have had trouble getting all rads hot since. I drained the system down to put inhibitor in and repressurised to 1 bar. I've tried balancing the rads, I have 12 in total and 7 are working fine (including the 3 new ones), 2 are getting warm but not hot and 3 are stone cold. I have a Worcester Bosch 28cdi combi boiler. I have tried everything I know (which is not a lot ) but can't seem to get over the problem. I have had problems with rads previously but have normally resolved it by playing around with the balancing. All rads have been bled by the way. Any suggestions as to what I could try next? Thanks!

 

[yerino]

Turn off all the hot/warm radiators (on the thermostatic valve) in your house and turn up the heating to full.. It sounds like an air lock and this will push it out and should heat up all the other radiators. Once they are warm turn everything back on.

 

[spraggo]

You may have an airlock in the pipework so try turning of all the radiators that are gatting warm or hot and try the heating for about 30 minutes with just the cold radiator turned on, make sure that both valves are opened on this radiator. If this works do the same with the other radiators that only get warm.


Hi yerino, great minds think alike. You beat me to it.

 

[handful]

Thanks gents, will try that now....if you both said the same thing you must be right!! Will update later.

 

[handful]

Ok, I think I'm on the right track, have done as suggested and now the rads that were stone cold are now luke warm apart from one. I've tried opening up all the lockshield valves all around the system and this also helped slightly. I have a feeling the TRV on the cold one may be faulty as the pipe to this is warm but nothing is getting in at all. I also have another rad that is piping hot and won't turn off so possibly another TRV issue there. This shouldn't be influencing my other issues though should it?

I'm now trying to do it one at a time, closing all rads off apart from one and see if that works.

 

[boilerbeasty]

You can check the TRV on the cold radiator by unscrewing the top part from the valve body. On top of the valve body there should be a small brass pin sticking up, and you should be able to push it down a few mm with a screwdriver handle or similar, and see it pop back up into position. Avoid pulling the pin upwards with pliers etc as you may damage it.

Sometimes these pins get stuck 'down' which means the valve always stays closed.

 

[handful]

Thanks boilerbeasty, I have been trying to read up on that but as yet can't find out how to remove the valve body on the TRVs. I have discovered that the ones I have fitted to the existing rads I had when I moved in are cr@p Tower ones and both the suspect ones are of this type. I can't see how they come off though. There is a small grub screw which appears to be what holds them on but removing this hasn't helped and I don't want to break them. I think I may have to bite the bullet and buy some new Honeywell or Drayton ones to replace the Tower ones.

If anyone has any knowledge of Tower TRVs and can tell me how to remove the valve body it would be appreciated.