How do TRV's determine the temperature of a room?

Lafleur_2

I've always thought that the TRV plastic control knobs placed over the top of the pin are used to set the desired room temperature only, although do they actually help TRV's to sense the room temperature as well? The Wikipedia article on TRV's is a bit hard to follow, it seems to suggest this.

Thanks

Nilrem

IIRC the plastic housing is just that a housing that holds the wax inner bit in place so it expands down on the pin when it reaches the correct temperature.

The plastic housing also turns (or at least the top half does usually) which controls at what point the expanding wax dohicky gets enough pressure on the pin to close the valve (I think it basically increases and decreases the starting gap between the pin and the bit that expands).

So basically the housing doesn't do anything to assist in sensing the temperature, but does allow you to set the point at which the pin is pressed down.

Biggles

TRVs don't sense the temperature of a room. They just sense the temperature within a few inches of the radiator. They are a crude device at best.

diywhynot

Danfoss has excellent explanations of heating controls.

Lafleur_2

Cheers guys, the explanation from Nilrem was very helpful, great that i can now have all radiators at full blast (when needed of course!)