Combi boilers, should they have an open radiator, ie one you can't turn down?

[Madmog]

Our new house has a combi boiler with nine radiators. All have thermostat valves fitted. In our last property one of the valves was constantly set high and you couldn't turn it down, think it may have been called an open radiator, but our new house hasn't got one. Should we have one? What is the benefit?

If they all have TRVs, then it is possible for all the radiators to turn off, while the boiler is still trying to produce heat and pump it round. This is wrong. It is usual for the radiator in the room where the wall thermostat is fitted, to have no TRV, and a lockshield valve at each end to prevent anyone turning it off.

When the house is warm, the wall thermostat turns off the heating.

It's not just combi boilers, BTW.