Newest radiator (most recently added)virtually never heating

[JC_DCFC]

Suffering massive frustration with this.

Our eldests bedroom is above a garage, we think this is a later extension amendment to the building, but for the time weve been here the radiator nearest his bed has been mostly cool or not worked, the other radiator in his room works perfectly. The radiator im talking about was changed as it was that full of sludge....Likewise a number of others, we are still having renovation work done around the house.
anyway long and short two or three days ago this radiator was warm to touch nearly hot, now its cold again*, its 22mm pipework where as the rest of the system is micorbore either 8mm or 10mm (another reason we think this was the most recently added). Currently the pipework up to the radiator is cold too - is this likely to be an airlock?
Ive just changed upped the thermostat to 23 and also changed the pump speed to the middle setting, this has now bought the feed pipe hot to the Trv and the body of the TRV is hot but the radiator still not heating....
*a small radiator in our conservatory had stopped heating properly, i know that has airlock issues so sorted that.

 

[denso13]

Turn off all other radiators except the problem one and see if it heats up properly.

 

[terryplumb]

Remove thermostatic rad valves actuator head ,and see if the pin in the middle of the valve is moving up and down freely.

 

[JC_DCFC]

Turn off all other radiators except the problem one and see if it heats up properly.

Yep done that and it does....will probably go thorugh this again tomorrow

 

[terryplumb]

Your system is probably not balanced.

 

[kidgreen61]

Begs the question, has it ever worked properly?

 

[JC_DCFC]

Begs the question, has it ever worked properly?

Yeah, think it was put in (the replacement) last year but we are changing lots round the house so the heating has been drained down a couple of times. weve still got a radiator to add in the downstairs toilet so whilst its sort of balanced it will change again when thats put in next week.

 

[kidgreen61]

The reason I ask is because builders are often guilty of DIY plumbing, & they'll tee off an existing pipe for an extension, using miles of 10mm pipe and wonder why it won't work.

 

[JC_DCFC]

The reason I ask is because builders are often guilty of DIY plumbing, & they'll tee off an existing pipe for an extension, using miles of 10mm pipe and wonder why it won't work.

As works have progressed, this is what we've found - the new radiator was teed off an existing one with copper pipe (cant remember the size now but think 15mm or suchlike) however the feed was microbore... so that appears to have been the issue all along....hopefully once extension is complete this will work properly as it has now been re-piped from/to the manifold!!!