Rad going cold after two hours

[Jon20279]

Evening, my radiator at the end of my chain of radiators heats up for two hours before going cold. Thermostat have been changed within the house recently and all set to five.
The pipe leading to the rad is no longer warm after two hours and rest assured the room is not at temperature.
The guy who fitted them has been out twice and still not resolved the issue. Any help would be gratefully accepted, many thanks

 

[cross thread]

Could it be the cool rad is feed of another and when that rads shuts its cutting the supply to the rad you are concerned about.

 

[Jon20279]

All the other rads stay red hot so I’m unsure if that would be the problem or not?

 

[terryplumb]

After going cold ,does it then start to heat up again ,or remain cold ?
Try removing the TRV actuator head ,see if it makes a difference.

 

[Jon20279]

I’ll give it a go thank you. It stays cold until I turn the heating off all together and back on shortly after

 

[terryplumb]

Did this radiator ever work properly ,before TRV's were fitted ?

 

[Jon20279]

It would stay on yes but never really get to temperature

 

[terryplumb]

System needs balancing ,and if the rad heats after removing the TRV actuator ,the TRV is duff.

 

[Jon20279]

Cheers Terry much appreciated