TRV with remote sensor

[Graham]

I often wonder how normal TRV's can work effectively, as their sensor is so close to the source of heat.

I have seen old ones like this

usually not in domestic situations.

Does a design with an external vial perform sufficiently better to make them worth considering, in spite of their aesthetic problems?

[John Stumbles]

I think the point is that _any_ TRV is a huge improvement over a non-thermostatic valve. The type in the example you show is usually specified where the TRV itself is likely to be covered by curtains or suchlike so as to make it almost completely ineffective.

For a remote sensor to give better control over room temperature it probably ought to be on the far side of the room. The Honeywell system with even more aesthetically-challenged motorised TRVs is a step in this direction.

[Cicero]

================================ Have you got a reference for Honeywell motorised TRVs? I'm interested to see what they look like and how they work.

Cic.

[Guy King]

The message from "Graham" contains these words:

Sod the aesthetics, that would last about five minutes in our house.

[Andrew Gabriel]

I fitted all mine at the bottom, and mostly on the return pipework (which is cooler). Positioning at the bottom means they are in the draft towards the bottom of the radiator, and so pretty accurately reflecting the room temperature. The thermal sensor is also well insulated from the pipework, so there's no heat conducted to it. I was also sceptical, but the scheme does seem to work surprisingly well.

I used the Drayton/Invensys TRV4. The instructions cover the remote sensor version too (which I didn't use). It says the sensor is ideally fitted at a height of 1.5m on the wall away from the radiator, or on the wall under the radiator.

Also the fragility of the capilliary pipe (probably unsuitable if small children around). The first 6" of capilliary pipe must not be clipped as it moves where it enters the valve head.

It probably does work better, but I'm not sure to what extent the extra accuracy matters. I used to have a proportional control gas wall heater (Drugasar). That used a vial which suffered from self- heating. I pulled it out to hang below the heater, and it then maintained the room accurate to 0.1C (which was the limit I could measure). Interesting though this accuracy was, it's not something you can "feel".

[John Stumbles]

Honeywell's web site?

Mind you I've no more idea where in that tangled web you'll find them. Last time I looked at their wibbles they were full of broken links from one part of their own sites to others.