How do TRVs work

[icantbelieve]

I've looked at various websites and various AAM threads containing information on thermostatic radiator valves and despite there being many good recommendations on what type to use, where to buy, how much to install etc. I couldn't find anything explaining how exactly they work, do they switch off according to the temperature of the room or the radiator. So I'd appreciate it if someone could give me the definitive version.

 

[icantbelieve]

Found an answer to my question and a decent looking quote for getting the work done. Anyone ever used this site, if its reliable then it should possibly be added to the key posts as there are always people looking for plumbers and prices on this site.

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