Radiators with or without TRV's

[Colin Noble]

I have 2 vertical radiators , when the TRV is fitted the radiators fail to get hot. I have replaced both TRVs for new and check the operation of the valve to confirm is correct operation but still no heat

If I removed the TRVs completely the radiators get hot, I would be grateful if someone could help

 

[ShaunCorbs]

Heads faulty maybe ? Have you tried new ones

 

[exedon2]

Not a one pipe system by any chance?