Do TRVs have to be fitted on Flow?

[reg091]

Does it matter if the TRV is fitted to the Flow side or the Return side of a rad? Logic suggets that it should be on the Flow side but how do you identify which is which anyway?

Secondly, are all TRVs ok for a pressurised system or do you need special ones?

 

[Charnwood]

Most TRVs are bi-directional nowadays. Some can be fitted as a vertical valve or a horizontal valve to facitate fitting on either flow or return, Pegler Terrier, for instance.

 

[rego]

turn on heating and whichever pipe on rad gets hot 1st is the flow,
all new trvs these days will be ok for sealed system

 

[Agile]

The best place for sensing room temp is on the cooler return.

Although the valves are stated to be bi-directional I always find them better on the flow and perhaps less likely to judder if the system is not correctly installed/balanced.

Tony

 

[reg091]

Thanks for the info folks.

 

[namsag]

Although trvs are bi directional a properly designed and installed system will have the trv on the flow .

As for Agiles comment that the best place is on the cooler return what utter nonsense . Somehow i think the manufactures have actually designed them to function on a properly designed system and the heat that is generated

 

[Agile]

So what feature do you imagine they contain to enable them to ignore locally generated heat from a radiator?

 

[doitall]

And if they Judder 99/100 it's nothing to do with balancing but the system pressure Differential is too high for the valve spec.

Bad install or incorrectly adjusted by-pass.

 

[namsag]

Agile the feature that the actual designer of the valve had an idea that the valve would be fitted to a pipe carrying water at upto 82 degrees and fitted to a radiator.
Also do you not understand the basics of balancing FLOW fully open and lockshield on RETURN adjusted to give correct flow through the rad for temp differential to be achieved .
This cannot be achieved correctly with the valves reversed

 

[Agile]

This cannot be achieved correctly with the valves reversed

I have to disagree with that.

Also most people would say from a common sense point of view that a TRV will better sense the room temp away from a source of heat like a hot pipe.

There were even some early attempts to fit remote sensors.

Tony

 

[D_Hailsham]

And if they Judder 99/100 it's nothing to do with balancing but the system pressure Differential is too high for the valve spec.

But if the system has not been correctly balanced there is a fair chance that the pump has been set to max, so the differential pressure will be high.

Agile the feature that the actual designer of the valve had an idea that the valve would be fitted to a pipe carrying water at upto 82 degrees and fitted to a radiator.

Drayton's TRV4 Spec says that the water temperature influence is 0.8K.

Also do you not understand the basics of balancing FLOW fully open and lockshield on RETURN adjusted to give correct flow through the rad for temp differential to be achieved. This cannot be achieved correctly with the valves reversed

It doesn't matter which end you put the LS valve or the TRV. All you are doing is controlling the flow through the rad: what goes in must come out!

Drayton TRV4 and Honeywell VT200 have integral balancing systems, so the LS valve is left fully open.

There were even some early attempts to fit remote sensors.

Still available from Drayton.

 

[doitall]

As the valves start to close the pressure builds up to a point where the spring in the valve cannot hold the plunger in position so it bounces.

If you read the MI's it will give you the pressure differential, and an auto by-pass valve correctly adjusted will open as the TRV's close and so avoid the problem in the first place.

 

[D_Hailsham]

As the valves start to close the pressure builds up to a point where the spring in the valve cannot hold the plunger in position so it bounces. If you read the MI's it will give you the pressure differential

Drayton TRV4 quote max diff of 1 bar to ensure valve will close; but only 0.2 bar to ensure low noise.

A diff pressure of 1 bar would be virtually impossible in a residential property. After all the largest pump normally used (15-60) can only provide a diff pressure of 0.6 bar, and that's when there is no flow. In normal circumstances the diff pressure across the valve will be less than 0.1 bar.

 

[doitall]

If I think about it when I get back I'll get the MI's out for a TRV and scan it in the thread.

 

[namsag]

Dhailsham you have clearly never worked on CH systems .

A venturi allows the same amount of fluid to leave it as enters it but reverse the venturi and it completly changes what a venturi is actually designed to do this is the similar principle on how balancing rads works .And was one of the first things we where taught, perhaps you wont find that on google


Anyone who regularly works on heating will have come across lockshields on flow closed down and they will not even allow air to pass through them change it about and the rad heats as it should strange that when you say it doesnt matter