How effective are TRVs?

[PaulAH]

Had a chat in Plumb Center yesterday with the Drayton rep. I asked him something that has been puzzling me: How do TRVs accurately measure the room temperature when they sit so close to the rad?

"That's been compensated for in their design" says he.

How can this be? OK, the TRV shuts off when it reaches a certain temp but as soon as the rad cools this must have a dramatic cooling effect on the TRV. A very hot body a couple of inches away going cold will surely affect it more than the small drop in air temp that it's trying to stabilise.

Has anyone done any practical tests on their characteristics, or have further advice?

Thanks. Paul

 

[AnonymousImport]

I am not a plumber, but my guess is that they act as a switch (on or off, with a large temperature differential), they are not temperature marked. It is therefore trial & error to find the setting, but once YOUR setting is found they will operate, the temperature of the radiator is therfore irrelevant

 

[masona]

TVR's sense the room temperature and not the radiator temperature.

 

[oilman]

A very hot body a couple of inches away going cold will surely affect it more than the small drop in air temp that it's trying to stabilise.

The only significant heat source is by conduction through the metalwork, the "very hot body" is really pretty cool and wouldn't pass much heat directly until it gets into the near infrared. The sensor is a wax capsule that expands and pushes a plunger shut, and the connecting bits don't pass much heat. I suspect the manufacturers have done masses of development on this, and while I wouldn't trust a sales rep as far as I could thow him, the valves are not too bad. With everything else though, anything that works is working its way to its next breakdown.

 

[PaulAH]

Masona, were you that rep? You need to develop Oilman's sense of scepticism - and his powers of observation.

 

[PaulAH]

Sorry for that. Write out 100 times 'I must not be intolerant of people trying to help'.

Oilman, a block of ice gives off infrared. The rad must produce enough radiation to heat a neighbouring body several degrees - more than the change in air temperature (calculations required here). You only need to hold your hand near a hot rad to feel the effect.

So... the unavoidable question: Do TRVs perform better when mounted horizontally?

 

[ChrisR]

I too was sceptical so have doen some tests - air in the room, surface temp of the rad valve etc. Yes they work pretty well - better than I'd expected.

Radiation works both ways. Its energy transfer is proportional to the FOURTH power of the absolute temp, so it gets very much more significant with bigger temp differences.

 

[PaulAH]

That's interesting, Chris. Thanks.

Boy, you must need them in Antarctica.

Paul

 

[masona]

Masona, were you that rep? You need to develop Oilman's sense of scepticism - and his powers of observation.

Sorry just re-read your post, maybe I'm just tired.

Then you said "Sorry for that. Write out 100 times 'I must not be intolerant of people trying to help"

Why didn't you edit or deleted it then ?

If you want to have ago at people then that's up to you.

 

[PaulAH]

You were tired. I was ****ed. Sorry.

 

[oilman]

Masona, you may notice PaulAH rarely posts between say 6:00pm and several hours later. There is a discernable diffrerence in attitude between his daytime posts and the late evening posts.

.... I was p****d.....

sums it up. Take no notice of late evening posts, if the Saffron Walden bobbies were a bit less thin on the ground we would probably only get "early next morning posts"

PaulAH, as you now have a tame OFTEC brain in the pub, he would be able to give you loads of info about these things.

 

[PaulAH]

Unlikely. He'd either be ****ed or contemplating how to write an algorithm to substitute stars for rude words in plumbing forums.

11.45pm

 

[oilman]

See what I mean?
Another "post-pub" timed posting.

 

[masona]

But what gonna happen when the pub open 24 hrs

 

[oilman]

Don't know, but the last reply looks to have taken just over an hour, except the clock must have been going backwards, or vision was defective.