I've had a couple of rooms which have had the rads turned off for over a year, as i dont use them.

 

I've turned one of them back on, and it's not getting hot whatsoever.

 

At first i thought i'd unbalanced the system, but i've turned off all the rads now except that one, and it's still totally cold. The pipework going into the TVR is warm up until about 10cm before it reaches the TVR valve.

 

This seems like a blockage in the rad itself.

 

Any thoughts?

Have you bled it ? ( forgive if that’s obvious ) . You then might need to re pressurise the boiler ( assuming a combi ) 

Sometimes the plunger on the trv valve sticks. Try removing the TRV and manually manipulate the plunger, should free up if stuck.

 

Edit: The TRV can be removed without opening the water circuit. Shouldn't require tools.

Edited December 4, 20241 yr by -rick-

The pin on the radiator control valve was indeed stuck! Fixed. Thanks