Mixing Pressure Problems

Savdefriz · Nov 30, 2020

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

John.g · Nov 30, 2020

No, I don't think that pump is compatible with the controller, I wouldn't be too worried about the actual speed control just now, if you and your engineer thinks the mods may work then just do them first. It may be beneficial to install a ABV in the system.
When did he fit this Alpha??,

Savdefriz · Nov 30, 2020

I moved in to this house about 7 years ago. The UFH has never really worked since we moved in.

I think that as it wasn't working he swapped the injection pump about 5 years ago when he changed the boiler.

The system had a dutch boiler and Danish manifolds. Essentially each year we just swap the pieces bit by bit for things that are actually recognised in the UK.

To be fair to our hearing engineer, everything was pretty much non standard and so trying to pin down the problem was a nightmare.

My initial thoughts were that he had over pressurised the UFH when he replaced my downstairs manifold so a week ago I started doing my research. Then I thought it was the bypass valve, but I didn't know enough to be sure. I think my wife thinks I'm having an affair with the boiler as I've spent so much time in that room "fiddeling". Turns out I actually might have been right lol. Thanks once again.

John.g · Dec 1, 2020

Just re thinking suggested mods, suggest just relocating by pass and isol valve but do not remove the return loop to the boiler as high risk of too low circulation flow through the boiler if UFH only on.
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Back for more punishment, I think that rather than a PRV in the by pass that a two port Tapstat might give far better control, you can attach the sensor to the return (or the mixed flow pipe as desired) and it will/should then control to the requiredtemperature. If you install another isol valve in the by pass you can then isolate it and install/change to which ever device gives the best results.

Savdefriz · Dec 1, 2020

Evening John, It's the enigma that's more puzzling than a Rubik's cube.

I think that whatever you put in there, it's always going to be too close to the injection feed. I've been playing around with it today again and as long as I keep the Grundfos Alpha on it's lowest setting I do get hot water to flow just not enough. Problem is that I'll never get enough if I'm that close to the injector because more water will always equal more pressure which will inevitably mean feeding back into the injector loop. (Managed to get the mix feed up to 31 degrees today a new record, although it only stayed at that for half an hour).

Next enigma is trying to get a heating engineer to come and sort it out before the snow hits, and it's a bit of a trek from the south of Ireland to the North of England...

I'll keep you in the loop (Oh the puns!)

John.g · Dec 1, 2020

Any of the drawings refer to the bypass as just that..... a bypass and it would appear to be just that, ie, a bypass for the injector pump. If there were no injector pump fitted then now that we know there is no NRV fitted, that bypass IMO would supply almost ample flow from the boiler circ pump bearing in mind that it only has to supply only ~ 25/35% of the mixed flow. NO where is there any mention of cold water return to the boiler which is just as important as any injector pump or whatever so was something forgotten in the whole design.
Maybe at the end of the day thermostatic mixing is the real answer?. So, yes, heating engineer or magician needed.

exedon2 · Dec 1, 2020

I've watched this thread with interest im still sure only real cure is in essence to convert manifolds to standard pump/blender layout its done that way because it works!.
If its what you want flow temperatures double what our achieving would be possible

John.g · Dec 2, 2020

Just putting on my magicians hat but i think this will probably work.

Remove the return loop as there is no more risk of the boiler having insufficient flow with this proposal than with the pump/blender route.

So, remove return loop, leave existing by pass as is.(shut)
install new return piping Teed as far upstream as possible on the cold return and connect into the return to the boiler at the now broken loop with isol v/vs at both ends.
Install tapstat (injector valve) in this piping and connect sensor to the mixed water line or the cold water return as required.
I think this has a good chance of working as the hot water will be taken in by the manifold pump and the cold water return by the boiler circ pump via the controlling injection valve.?
You might even be able to run with no injection pump if on UFH only

The attachment shows the injector pump pumping into the manifold discharge unlike this set up.

Savdefriz · Dec 2, 2020

I was thinking that this might be the simplest fix. Just cut the bypass pipe, loop it out and put a t junction back in to the pipe pretty much directly above where it is at the moment. That will mean greater distance between the injector and the bypass returning the cold, meaning that less cold should flow back. I've left the Grundfos on (I) and the mix is heating up but it's a really big system (I think there's about 1600m of underfloor piping in the house). I'm hoping now that the answer might just be as simple as put the pump on a lower setting!
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exedon2 said:
I've watched this thread with interest im still sure only real cure is in essence to convert manifolds to standard pump/blender layout its done that way because it works!.
If its what you want flow temperatures double what our achieving would be possible

Glad that you've enjoyed the Craic... You may be right, but I'm never going to get that sorted before Christmas! I feel like I'm getting somewhere but as I said to John earlier, everything in this system is nonstandard and I'm just a man with no knowledge of plumbing trying to figure it all. Let's just say that if I was putting this in from scratch I probably would have chosen something a little more "standard". I'll invite everyone to come and have a look once things get back to normal!!!!🤣🤣🤣🤣

John.g · Dec 2, 2020

IMO, whatever else, you will definitely have to break the link between the flow and return.
Why don't you just switch off that injection pump just now and see if any improvement, there should be sufficient head from the boiler circ pump, the water will still flow through the stopped injection pump and it will now not tend to pull cold water back into the system.

Savdefriz · Dec 2, 2020

It's getting warmer.. I'm touching nothing.

Brambles · Dec 2, 2020

You have too many UFH circuits to feed to have any chance of an unconventional system to work well - unless you know exactly what you are doing. The UFH circuits take a high percentage of the boiler output - they need to be fed directly from the boiler - with the radiator and Dhw circuit in parallel.

The concept of using pumps for “injection” on low temperature heating systems is common in the world of thermal stores, but you need temperature sensors properly located and a control system to drive the pump. From what I can see on your photos, the pump you refer to as an injector is not plumbed in correctly and does not appear to have a temperature control loop or a limiting device to set or limit the flow temperature into the UFH loops. You don’t want 60 plus degree boiler flow temperatures entering the UFH loops.

On a system such as yours, the feed for the UFH circulation should come direct from the boiler to a pumped manifold with a mixing valve - relatively cheap and it will work.

If you had one or two UFH loops you may get it to work in an uncontrolled manner by tweeking it.

Savdefriz · Dec 2, 2020

Brambles said:
You have too many UFH circuits to feed to have any chance of an unconventional system to work well - unless you know exactly what you are doing. The UFH circuits take a high percentage of the boiler output - they need to be fed directly from the boiler - with the radiator and Dhw circuit in parallel.

The concept of using pumps for “injection” on low temperature heating systems is common in the world of thermal stores, but you need temperature sensors properly located and a control system to drive the pump. From what I can see on your photos, the pump you refer to as an injector is not plumbed in correctly and does not appear to have a temperature control loop or a limiting device to set or limit the flow temperature into the UFH loops. You don’t want 60 plus degree boiler flow temperatures entering the UFH loops.

On a system such as yours, the feed for the UFH circulation should come direct from the boiler to a pumped manifold with a mixing valve - relatively cheap and it will work.

If you had one or two UFH loops you may get it to work in an uncontrolled manner by tweeking it.

The system does have thermocouples and a control system. There is a temperature sensor for the boiler feed, and a temperature sensor for the mix. The injection pump is supposedly controlled by the processing unit to control the flow of water into the UFH system so that the temperature of the mix is appropriate to the outdoor conditions (which is measured by a third thermocouple on the north facing wall). It's just that the pressure on the UFH is hard to balance and I don't know enough about a Grundfos Alpha 2L to know what I'm doing!🤪
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Savdefriz said:
The system does have thermocouples and a control system. There is a temperature sensor for the boiler feed, and a temperature sensor for the mix. The injection pump is supposedly controlled by the processing unit to control the flow of water into the UFH system so that the temperature of the mix is appropriate to the outdoor conditions (which is measured by a third thermocouple on the north facing wall). It's just that the pressure on the UFH is hard to balance and I don't know enough about a Grundfos Alpha 2L to know what I'm doing!🤪

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Savdefriz said:
The system does have thermocouples and a control system. There is a temperature sensor for the boiler feed, and a temperature sensor for the mix. The injection pump is supposedly controlled by the processing unit to control the flow of water into the UFH system so that the temperature of the mix is appropriate to the outdoor conditions (which is measured by a third thermocouple on the north facing wall). It's just that the pressure on the UFH is hard to balance and I don't know enough about a Grundfos Alpha 2L to know what I'm doing!🤪
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The bluebox on the wall is a kanmor 361e controller.

Brambles · Dec 2, 2020

I am very familiar with Kanmor and the 361 - it does not (nor is it intended) to control the UFH flow temperature. For that you need a wax operated mixing valve.

The Kanmor 361 is intended to inject hot water from a controlled (known temperature balanced source ( plus or minus 8 degrees )) - and that is a thermal store not a direct fired boiler. The Kanmor has no capability to accept a return temperature so cannot adjust to any feedback from a fluctuating flow temperature.

The external temperature sensor feeds directly to the boiler and adjusts the flow temperature against a preset curve ( which you can adjust) - it has nothing to do with the performance on the UFH - it only adjusts the boiler flow temperature, it does not adjust mix - it has no control loop to do that.
It operates on what is known as proportional bounded adjustment - it takes the feed temperature and then applies a preset reduction to feed the UFH

Be very careful with an UFH if you have expensive floor coverings - you don’t need many (upward) temperature excursions to cause damage to engineered wood or fabric covered floors

John.g · Dec 2, 2020

What is the temperature now??.

Savdefriz · Dec 2, 2020

I'll bow to your greater knowledge, but my system does look like the one that I found in the manual.

tekmar 361 Mixing Control - Manual (Page 4) - https://www.manualsdir.com/manuals/594646/tekmar-361-mixing-control.html?page=4

Temp has dipped to 30 at the mo but not too worried as DHW has just been on for kids baths. The house feels a bit better, but there's a lot of concrete that needs heating so I'm not expecting to see any significant rises for days (if I'm lucky enough to get any at all)

Brambles · Dec 2, 2020

I will say no more. Look at the schematic on page 1 of the manual on the link you have posted.

That is not the system you have shown in your photos. Also note the inputs ( 3 no to the controller) and then reread my earlier posting

John.g · Dec 2, 2020

can you just feel the pipe just to the left of the T for the injection pump, it should be very hot....at boiler temperature, now feel the pipe on the inlet to the inj pump.....that too should be at the same temperature, if not and only lukewarm (30C) then you are simply pulling in cold water from the by pass and the system will never work, you have a good chance if you break the flow/return loop.

Savdefriz · Dec 2, 2020

Brambles said:
I will say no more. Look at the schematic on page 1 of the manual on the link you have posted.

That is not the system you have shown in your photos. Also note the inputs ( 3 no to the controller) and then reread my earlier posting

I don't know enough about this stuff but I'm learning. Here's the schematic of my system from the book. (Although I've no radiators). As I said I'm just a science teacher trying to warm up his house.
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John.g said:
can you just feel the pipe just to the left of the T for the injection pump, it should be very hot....at boiler temperature, now feel the pipe on the inlet to the inj pump...that too should be at the same temperature, if not and only lukewarm (30C) then you are simply pulling in cold water from the by pass and the system will never work, you have a good chance if you break the flow/return loop.

Pipe to the left is hot, injector pipe is hot, pipe to the right is hot but cools once it gets to the relay. Pump is hot and temp is rising again.
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John.g said:
can you just feel the pipe just to the left of the T for the injection pump, it should be very hot....at boiler temperature, now feel the pipe on the inlet to the inj pump...that too should be at the same temperature, if not and only lukewarm (30C) then you are simply pulling in cold water from the by pass and the system will never work, you have a good chance if you break the flow/return loop.

Pipe to the left is hot, injector pipe is hot, pipe to the right is hot but cools once it gets to the relay. Pump is hot and temp is rising again. I've got pump set to lowest setting which seems to help.
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Savdefriz said:
I don't know enough about this stuff but I'm learning. Here's the schematic of my system from the book. (Although I've no radiators). As I said I'm just a science teacher trying to warm up his house.
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Pipe to the left is hot, injector pipe is hot, pipe to the right is hot but cools once it gets to the relay. Pump is hot and temp is rising again.
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Pipe to the left is hot, injector pipe is hot, pipe to the right is hot but cools once it gets to the relay. Pump is hot and temp is rising again. I've got pump set to lowest setting which seems to help.

Even the pipe directly under the pump feels hot..... Oooohhhh such excitement

John.g · Dec 2, 2020

Didn't realize you had no rads so if no demand for HW then is the boiler running constantly now or cycling on/off?.

Savdefriz · Dec 2, 2020

John.g said:
Didn't realize you had no rads so if no demand for HW then is the boiler running constantly now or cycling on/off?.

Cycling. It seems to kick in to push the temp up then falls back. I think it's kicking in when the boiler temp sensor falls below about 52. It pushes it up to about 72 and switches off.
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Savdefriz said:
Cycling. It seems to kick in to push the temp up then falls back. I think it's kicking in when the boiler temp sensor falls below about 52. It pushes it up to about 72 and switches off.

Now it seems to be constant..... I need to spend less time with my boiler and more with my wife!

John.g · Dec 3, 2020

OK, thanks.
Picasso has had a good drop of Jamesons tonight so sketching not up to his usual standard but this is the way I would go if you don't want to modify to a 3 way thermostatic mixer, there isn't much involved, as I said previously, you can leave the existing by pass if you wish (less work)

and just do the other changes.

Savdefriz · Dec 3, 2020

John.g said:
OK, thanks.
Picasso has had a good drop of Jamesons tonight so sketching not up to his usual standard but this is the way I would go if you don't want to modify to a 3 way thermostatic mixer, there isn't much involved, as I said previously, you can leave the existing by pass if you wish (less work) View attachment 46533and just do the other changes.

Looks good, the only downside to that would be that (from what I've read) the system would be less efficient as the control system wouldn't be able to regulate temp. But at this point in time I'd take an inefficient system that works over an efficient cold one that doesn't.... I'll keep you up to date with temps as they fluctuate, and have a drop for me!

John.g · Dec 3, 2020

I wonder just how sophisticated UFH systems really need to be as the system is a big thermal store in itself and runs 24/7, so very slow to respond to any tweeking, also your boiler will be running with a very low return temperature (no rads) so will be quite efficient.
Even though I would like to see if the proposed mods will work I think the sensible way to go would be with a 3 way thermostatic mixing valve as you will be making pipework changes anyway and will just re use the existing manifold pump.

Savdefriz · Dec 3, 2020

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