Under Floor Heating

[Norcon]

This port facing the camera is the cold supply of an ufh tempering valve I've fitted a few times. I think its Itailian. Rehau use the reliance valve afaik.
The design allows for quite an unrestricted flow.
Its quite constricted with about 1.5mm of clearance between the piston and valve seat when fully open where the arrow is pointing.
I didn't think this would work fitted across a low loss header. At the very best its bound to under perform imo.
Of course the OP's valve may be different but given what JG show in their schematic with a primary circulator and by-pass arrangement (looks to be in the wrong place) then I wouldn't deviate from that.

 

[Onetap]

This port facing the camera is the cold supply of an ufh tempering valve I've fitted a few times. I think its Itialian.

Caleffi, maybe?
It would work on a low loss header. You're relying on the secondary pump, downstream of the blended outlet port, to draw water from both H & C inlet ports. The two inlet ports are at equal pressures. The zone valve wouldn't be necessary.

JG's schematic would allow the primary pump to force water through the TMV and the pump, so the zone valve is required. It is a variable flow rate system' which might cause problems with the boiler' hence the need for the by-pass.

I think the bypass is in the wrong place too; it doesn't inspire much confidence in the mixing system recommendations. Their system could be operating with the rads shut off by the zone valve. All the primary pump pressure would then be applied to the TMV hot inlet port. The TMV could be using only a tiny part of the hot water supplied by the boiler.

I think the OP's problem is due to his confusing his pipes.

 

[Norcon]

The two inlet ports are at equal pressures

Yes I would agree "equal pressures" but surely the constricted port (hot) would have a much higher pressure drop across it in comparison to the cold port at the same flowrate.
But how could an equal flowrate ever be acheived on a valve that only regulates on one port which is connected across a low loss header?

Which leads me to think convention needs to be applied with the primary circulator/by-pass arrangement remaining the driving force, achieving the correct mix through this particular valve.

Rehau's technical manual 864.602EN does give some information relating to their tmv valve .....

in certain cases the TMV can fully open the main system port (Hot) and fully close the return flow port(Cold)

Which would lead me to think this particular valve regulates on two ports. But have no experience of this valve so cannot say for certain.
ESBE are the only other manufacturer I can think off who make tempering valves which regulate on both inlet ports.

 

[Rhondo]

JG state minimum 0.2 bar dynamic on the hot port for it to blend effectively.
You wouldn't acheive that across a low loss header.

 

[Onetap]

JG state minimum 0.2 bar dynamic on the hot port for it to blend effectively.
You wouldn't acheive that across a low loss header.

Where does it say that? Please provide a link.

If the primary pump is capable of supplying the required 0.2 bar across the TMV, why would you think that the secondary UFH pump can't do that?

If you need 0.2 bar on the hot port, don't you need 0.2 bar on the cold port?

You keep on trying, sonny. All hat and no cattle; you're giving cowboy plumbers a bad name.

 

[Onetap]

Yes I would agree "equal pressures" but surely the constricted port (hot) would have a much higher pressure drop across it in comparison to the cold port at the same flowrate.
But how could an equal flowrate ever be acheived on a valve that only regulates on one port which is connected across a low loss header?

Which leads me to think convention needs to be applied with the primary circulator/by-pass arrangement remaining the driving force, achieving the correct mix through this particular valve.

Rehau's technical manual 864.602EN does give some information relating to their tmv valve .....

in certain cases the TMV can fully open the main system port (Hot) and fully close the return flow port(Cold)

Which would lead me to think this particular valve regulates on two ports. But have no experience of this valve so cannot say for certain.
ESBE are the only other manufacturer I can think off who make tempering valves which regulate on both inlet ports.

I do not think a TMV would only regulate the hot port. Surely it would need to be able to regulate both H&C inlet ports inversely to each other to give the required outlet temperature? H open, C closed and vice versa. I don't think the pressure difference across the hot and outlet ports would be different to that across cold and outlet ports for a given flow rate.

Similarly, in certain cases the TMV should be able to fully close the main system port (Hot) and fully open the return flow port (cold).

The Rehau manual you mention is here;
http://www.rehau.co.uk/files/8179_REHAU_BA_Controller_864602_UK.pdf

The diagram on P13 is similar to the JG schematic ( posted on the previous page) but with the by-pass in the 'right' place. The compact mixer unit schematic on P11 uses a 2-port thermostatic valve to control the UFH flow temperature (injection mixing).

 

[Rhondo]

Where does it say that? Please provide a link.

You can scour the net all you want as you won't find that info.
When you can claim to have some experience installing ufh then I might listen.
And speaking of links have you any to back up your flawed design?

 

[Onetap]

Where does it say that? Please provide a link.

You can scour the net all you want as you won't find that info.

You lied then. Tool.

And speaking of links have you any to back up your flawed design?

Yes. Fig 5-66b here.

http://books.google.co.uk/books?id=...&resnum=4&ved=0CCkQ6AEwAw#v=onepage&q&f=false

Or Figs, 1,2 and 3 here;
http://www.pmmag.com/Articles/Column/69285e1f0bfc7010VgnVCM100000f932a8c0____

Stick some emoticons on that, boy.

 

[Rhondo]

No I didn't lie but you obviously must think it astonishing that I have that info.
And your link is irrelevant to the OP's situation and of course many other valve designs which each have their own requirements.
But keep on peddling your duff advice. I'm sure there's plenty out there who will listen.

 

[Norcon]

Caleffi, maybe?

Honeywell Sparco.
I recognised it in the last link you gave. It definately only regulates the hot port. With tight shut off when you close it down to 1 on the 1-10 knob setting.
http://tinyurl.com/33erez6

Diagram 2.1.1 single loop. Normal practise is the primary circulator between A and H which serves radiators also.

Possibly would need a regulating valve on the cold supply similar to a termovar loading valve with this arrangement.

 

[Onetap]

It definately only regulates the hot port. With tight shut off when you close it down to 1 on the 1-10 knob setting.
http://tinyurl.com/33erez6

Diagram 2.1.1 single loop. Normal practise is the primary circulator between A and H which serves radiators also.

Possibly would need a regulating valve on the cold supply similar to a termovar loading valve with this arrangement.

It must regulate the cold port, giving a tight shut off when the outlet temperature is less than the set point.

I don't think 2.1.1 would work with the pump between A and H. The recirculated water wouldn't flow into the TMV against a higher pressure.

The arrangement I suggested is shown in 2.3. The advantage is that the primary flow through the boiler remains constant. The system in 2.1.1 could draw only a tiny part of the boiler's minimum flow rate. It would need a by-pass, as Rehau's diagram.

 

[Onetap]

No I didn't lie but you obviously must think it astonishing that I have that info.

No. It's incredible though. Not credible. You're a liar.
Still no technical input from you to explain why the cross over header won't work. Siegenthaler, Spirax, Esbe, etc. say it does. I know it does.

But keep on peddling your duff advice. I'm sure there's plenty out there who will listen.

Pathetic, child.

 

[Rhondo]

Not credible. You're a liar

Chris Nash@JG technical wrote

The UFH mixing valve has a minimum working pressure of 0.2 BAR which is 2 metres in terms of static head. Therefore the hot port of the mixing valve will require this minimum amount to blend and perform correctly

 

[Norcon]

It must regulate the cold port

Nope. I've tested it,stripped it, examined it , rebuilt it and retested it etc. The arrow in the image points to the only valve seating which is on the hot port.
It definately is incapable of shutting off the cold supply or acting as a diverting valve.
Maybe an older model or different spec.

 

[Registered Gas Man]

Dont really want to get dragged into mud slinging! OP is moving your PF pump to under the boiler from the airing cupboard an option?