Mixing Pressure Problems

[John.g]

It may but last night I was looking at the system schematic and can't figure out why the injection pump inlet is taken from the boiler return (NRV in boiler flow), this means that if no demand for DHW or radiators that the injection pump, is fighting the boiler circ pump (which is on the return), very UNlikely designed that way, have another good look at the arrow on the injection pump which may be pointing upwards, the pump would then be returning cold water to the boiler but then there would need to be (probably controlled ) a hot water supply to the UFH main manifold somewhere, if you look at the schematic which includes the DHW cylinder you will see some form of controller that looks a bit like a pump but is probably a controller as it seems to be wired into the kanmor? high up in the drawing, can you identify this as well this evening.

 

[Savdefriz]

Right then John what do you want?

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The only thing missing from the schematic is the outdoor sensor which I think that the unit uses to calculate the flow need to keep the house at a certain temperature. I've also changed the alpha pump settings to lowest constant flow (I) and that seems to be letting the hot water flow through from the primary circuit.

As for the flow, here's my hypothesis:

The primary circuit has two junctions, the first is the intake and the second the return flow. I'm assuming that if the pressure of the return flow is greater than that of the primary the hot water will take the path of least resistance and flow downwards to the injector pump. This seems to be what's happening in practise, as if the return flow is too fast the hot water never gets to the t junction. If it's too slow, the injector doesn't allow any water to be injected which could be due to the incompressible nature of the ufh circuit, or just because the path of least resistance is forwards rather than down.... (I need a degree in fluid dynamics for this one!)

 

[John.g]

Pages 2, 11 & 16 to start with but have a quick look please at the injection pump orientation first before scanning.

 

[Savdefriz]

Arrow is definitely pointing down. Pages as requested, but I don't know what I've done but the mix temperature is going up. It's at 27 now and rising and it's never been above 21. Basically I put the alpha on (I) waited until primary was sending warm back to the boiler, changed to the pump up to highest constant and it seems like it's working
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Just checked again and it's back to 24 but progress.... I suppose it's proof of concept at least.

 

[John.g]

Thanks but can't read the attachments.

What do you mean by
" waited until primary was sending warm back to the boiler "

Is/was the CH or/and the HW on while taking these tests?

Can you see what that item is in the picture showing the cylinder, above. (post 21)

I honestly cannot see that system working as is with the NRV installed where it is and without the CH or HW on as well, at best then IMO, the injector pump will take some of the cooled water returning from the rads/cylinder coil and inject it into the manifold but that temperature is completely dependent on that return temperature which may be even lower than the required UFH temperature, also the "bypass" is stationed far too close to the injector pump to give any real temperature or contra flows separation.
Can you have a quick read through those pages and see what commissioning problems they had and a explanation of how the system is supposed to work.

Taking the injected water supply from between the NRV and the boiler would definitely make some bit of sense as it is then hot injected water at a set (boiler) temperature.

 

[Savdefriz]

I've tried to annotate the picture to label each item.

Hope this makes a bit of sense.

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Thanks but can't read the attachments.

What do you mean by
" waited until primary was sending warm back to the boiler "

I just meant that I restricted water flow through bypass so that the return to the boiler heated up.

Is/was the CH or/and the HW on while taking these tests?

I hadn't switched anything off

Can you see what that item is in the picture showing the cylinder, above. (post 21)

Wasn't sure what you meant so I annotated the original photo

I honestly cannot see that system working as is with the NRV installed where it is and without the CH or HW on as well, at best then IMO, the injector pump will take some of the cooled water returning from the rads/cylinder coil

No rads and cylinder coil has its own NRV as shown

and inject it into the manifold but that temperature is completely dependent on that return temperature which may be even lower than the required UFH temperature, also the "bypass" is stationed far too close to the injector pump to give any real temperature or contra flows separation.

The contra flow separation proximity is what I thought the problem was.

Can you have a quick read through those pages and see what commissioning problems they had and a explanation of how the system is supposed to work.

Taking the injected water supply from between the NRV and the boiler would definitely make some bit of sense as it is then hot injected water at a set (boiler) temperature.

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Here's the scanned pages.

 

[John.g]

Can you take a snapshot on the left around where I have continued the red line showing the pipework layout, in particular any NRV (the ones you showed are motorized zoning valves)

Read the Tap scanned pages, the most important item now is to see where (if) this NRV is.

 

[Savdefriz]

Hope that's clear enough as I had to shrink the file size down.

 

[John.g]

I think that's about as clear as you can get it, there isn't a NRV between the T off for the HW cylinder coil and the motorised UFH zoning valve so that means that the hot water is supplied to the UFH once its opened despite the original drawing showing one, I wonder why?.
So, as you said the proximity of the injection pump and by pass vale is the main problem although I find it inexplicable that a system would be designed this way... it may work if mods made as in attachment, I don't see any reason to have the hot & cold looped as this only creates a full fledged by pass once the UFH zone valve is opened, also the original injection pump was a standard pump which can be speed controlled.

 

[Savdefriz]

Thanks again John,

I've restricted the flow on the bypass valve and turned the Alpha down to constant setting (II). I'll see if that's enough flow to get at least a little bit of heat into the system. I was also wondering if an auto bypass valve might help.

As you know a bit about pumps do you think this one would be suitable as the documentation says that the original was a grundfos 15-50.

https://www.NoLinkingToThis/p/grund...5zoyb7cPKrGg5KEHDWkaAqQ8EALw_wcB&gclsrc=aw.ds

I just can't find out if it's controllable.

I'll speak to my heating engineer and see if he can make the relevant changes (although he's the one who put the alpha on!).

Thanks once again for your help with this enigma! One day I will get it to function correctly