I'm about to upgrade my central heating system, and will be fitting new TRV's to the existing radiators - I seem to remember reading somewhere, thats it better to leave one radiator with standard valves on it - presumably so the boiler can never be pumping against a dead head - ie with all TRV's closed?
You need to have one rad without a TRV in the room where the wall mounted thermostat is located.
If you have a TRV on this rad one of two things will occur:
If the TRV is set to to lower temperature than the wall thermostat, the radiator will shut of when it reached the TRV set temperature so the wall thermostat will never reach temperature. Result is the boiler will run and run.
If the TRV is set to a higher temperature than the wall thermostat, the boiler will shut down when the wall thermostat reaches temperature, so the radiator will never reach the TRV set temperature.
You must have a wall thermostat to meet building regulations.
If you have TRVs on all rads but one, you also need an automatic bypass valve.