TRVs - A Theory and a Question

[Goldberg]

Well there's 6 inches of bare pipe below the valve (no real gap in the floor), and as long as that pipe's filled with hot water it will send up warm air by convection and the valve fitting itself will get hot by conduction.

Yes, BUT you seem to be ignoring the fact that if the valve is closed then the hot water in pipe will quickly become cold water.

Can't do anything about the conduction, but convection is lessened if the valve is to the side of the pipe.

Maybe so, but there are tens of thousands of installations just like yours that don't give the problems you're seeing.

Of course the problem would be solved if I could find TRV with a fully open setting as well as a fully closed one.

Not sure what you mean by this, as all TRVs have a maximum setting - why do you think that doesn't represent being fully open?

Have you removed the head yet and looked at the pin?

 

[Biggles..]

TRV's even when closed under operation are still open to prevent freezing. the only way to fully close a TRV is to fit the decorators cap or manually wind the head down to off,even then some will still pass with the head right down.

Doesnt help your problem but lets you know why water still flows.

 

[Goldberg]

TRV's even when closed under operation are still open to prevent freezing.

No. They are not.

You're confused by the 'frost protection' position on the TRV head, which opens the valve if the air temperature drops below 8°C. Above that temperature, when the head is turned to the lowest setting the valve will be closed.

the only way to fully close a TRV is to fit the decorators cap or manually wind the head down to off,even then some will still pass with the head right down.

Absolute nonsense - unless in freezing conditions, a TRV that won't shut off has debris under the seat.

Doesnt help your problem

That was the only correct part of your post.

 

[D_Hailsham]

This is the key to it - the radiator is going cold but the in-pipe which is underneath the valve is staying very hot. I think this is keeping the valve warm and thus closing the thing up.

That argument really does not stack up. The water temperature is about 75C, which is considerably higher than room temperature. If the influence of the heat from the pipe was so great, it would be exerting that influence all the time, so the TRV would be permanently shut.

The valve are designed so the temperature of the water and metalwork has a minimal influence on the performance of the TRV. Drayton state that the "water temperature influence" for a TRV4 is 0.8K.

One cause of poor TRV performance is incorrect balancing.

 

[Goldberg]

Please note rule 1 (Abusive or unhelpful posts are not welcome.) - See here for the forum rules.
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abusive post removed

Presumably you don't regard this post as abusive or unhelpful:

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• BingoBongo
• 1 Nov 2009
• 2

 

[kevplumb]

ooooh diddums

View media item 14413
add that to your list

 

[namsag]

If that picture is upsetting you softas/goldberg etc etc etc you should see what they are saying about you in th CC

 

[kevplumb]

nothing i wouldn't say on here

 

[bengasman]

If that picture is upsetting you softas/goldberg etc etc etc you should see what they are saying about you in th CC

And why not, it is all true.
Coldberk has no experience in the industry, nor does he have any relevant qualifications.
All he does, is trying to create havoc and antagonise people; I have yet to read his first useful post.
What does that make him? Indeed.

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• bengasman
• 1 Nov 2009
• 2

 

[namsag]

No reason at all but it will be grating on him

 

[Agile]

Hi

Living in an old and energy inefficient house, I've noticed something of a problem with TRVs. Just wondered if anyone would like to comment on the semi-baked theory I've got to explain it.

Ian

I think there are two aspects to be taken into account.

But I have not seen anything to say what make/model/age your TRVs are.

Nor have I seen anything saying what the flow temperature is.

Firstly, some older TRvs seem to exhibit a degree of hysteresis, i.e. a gap between turn off and turn on temperatures.

Secondly, your flow temperature seems to be far too high!

The normal mode of control for a TRV is proportional and they ease the flow back to the point that the flow provides exactly the required heat input to provide the required temperature.

They are NOT designed to turn on/off every 10-30 minutes.

If you can state the flow temperature then thats useful but anyway try turning it down about 10°C.

I tell customers their rads should be hot enough to be able to hold the top firmly for just 2-4 seconds. Thats usually about 70° C. Of course its more efficient if it provides enough heat at a lower temperature.

Tony

 

[muggles]

Please note rule 1 (Abusive or unhelpful posts are not welcome.) - See here for the forum rules.
-
abusive post removed

Presumably you don't regard this post as abusive or unhelpful:

Untitled

• BingoBongo
• 1 Nov 2009
• 2

How can something which is entirely true, and which can help the OP to identify the Troll, be unhelpful?

Incidentally, just remind us what you do for a living? It seems some of us have forgotten...

 

[Goldberg]

How can something which is entirely true, and which can help the OP to identify the Troll, be unhelpful?

I suggest that you ask the moderator who deleted the abusive posts.

Incidentally, just remind us what you do for a living?

Sure - I keep your wife busy while you're at work.

 

[bengasman]

Sure - I keep your wife busy while you're at work.

Ha! Told you.
He did get booted from his council job, and now he is going door to door with The Big Issue.

 

[bengasman]

Come to think of it, it could be worse; this berk is the type to be a jehova's witness.