UFH manifold problem

[joe90]

Right I have decided how to plump the cylinder etc as per above, electrics next, I cannot find a diagram how to wire the manifold pump, the room stat on the Kingspan diagram is low voltage dc , mine is ac driving the manifold pump directly so I need to change that, but how do I power the manifold pump?, relay from the room stat? But if the DHW is activated at the same time then the manifold pump operates without hot water?

 

answers on a post card to joe90……..

[joe90]

Sit rep, studied the small print fir the ASHP/programmer and found there is a terminal fir an additional pump and a programming change to not power this if DHW is called fir. So it’s all go for later this week. Thanks to one and all for your valued input ? (I will let you know if it works ?).

Edited January 10, 2022 by joe90

[dpmiller]

It will work but you'll never know why as it addresses both points raised here- lack of flow in the supply loop to the manifold *and* @Nickfromwales's assertion that coils don't transfer heat in this situation.

In fact,  just increasing the LWT in heating mode a few degrees would likely cure it too, as I think on it...

[joe90]

1 hour ago, dpmiller said:

just increasing the LWT in heating mode a few degrees would likely cure it too, as I think on it...

Funnily enough when going through the programming I found the water temp (I only have one temp for both DHW and heating) was set at 40’ not 48’ like !!!! I upped it to 45’ and still the manifold fails to get hot and stay there. Interesting that at even 40’ the DHW was hot enough fir showers/bath/washing up , I may put it back down to give a better COP.

[joe90]

part 2.  after having a weekend away to clear my head I have come back to this. Thanks to @PeterW and @Nickfromwales I have replumbed the buffer tank to be a direct rather than indirect (using the internal coil) tank. The tank now heats up nicely but I am still not getting warm enough water to the UFH pipes. When the buffer tank is heating, the manifold (after the TRV, and pump) temp goes up to 40’ (the temp of water coming from the ASHP) but there is no flow because the manifold pump is not activated because the room stat is not calling fir heat. When the room stat calls for heat the manifold pump starts and the temp at the top rail (after pump and TRV) goes down to 25’. The TRV head has been removed at the moment to help diagnoses. I still believe the built in bypass valve from the return  rail to the pump is too weak and the manifold pump pulls water from the return rail rather than the buffer tank, if I reduce the pump speed I don’t get enough flow through the UFH pipes. I am tempted to ask Wunda what they propose as a solution. I cannot block the bypass again like I did before because when I re instate the TRV head again to control the temp the pump will overload when the TRV shuts. ?.

 

thoughts please chaps.

Edited January 18, 2022 by joe90

[joe90]

I heard back from Wunda very quickly…..

 

“What I think is happening here is the thermostatic assembly is mixing the temp down whereas with the preregulated flow temp from the heat pump we don’t actually want it to do anything.

 

Our advice would be to remove the assembly completely and mount the pump in line with the flow (top bar). Then, when the water returns to the manifold it is sent back to the heatpump for reheating.

 

This would require the left hand side of the return (bottom) bar to be capped off.

 

I would expect this to completely solve any issues that are occurring.

Kind Regards,”

 

then I asked them if they meant removing the TRV as well?…..

 

 

“What we are really looking for is to use the preregulation of the flow from the heat pump.

 

Then the floor limitation probes will be used to monitor floor temperatures and then switch the heating off accordingly to prevent damage to wooden floors and similar.

 

Kind Regards,”

 

I have no floor limitation probes, just a room stat. ? so they sold me the wrong stuff?  If the bypass was adjustable I could solve this.! What to do next?

 

[JohnMo]

You could use a pipe stat, close to the pump.  Set at say 45 degrees and wire the pump live through the normally closed connects.  If the flow temp goes above where it is likely to cause an issue the pump gets switched off.

 

[PeterW]

Ok  so they think their mixer isn’t up to it. And I don’t like those so I would do something really simple here. 
 

Remove the heads, and then mount the pump direct to the manifold (think these are 1 1/2”) and then from the return line remove the other end, blanking off the manifold so the flow goes back to the buffer. 
 

Then put one of these in the flow - to blend the correct temperature - and  use this to control the flow into the floor. 
 

 

[joe90]

47 minutes ago, PeterW said:

so they think their mixer isn’t up to it.

That’s been my thought all along, it more a relief valve than temp controlling. 
 

 

49 minutes ago, PeterW said:

Remove the heads, and then mount the pump direct to the manifold (think these are 1 1/2”) and then from the return line remove the other end, blanking off the manifold so the flow goes back to the buffer. 

The threads etc are different so can’t mount the pump directly, however I could mount the new blending valve in the feed 22 mm pipework and use cool from the return pipework ???, means blanking off the existing valve (like I did before to prove a point) and leaving the TRV valve but removing the head so it stays permanently open.

[PeterW]

Right. Leave the top connection as is, remove the bottom pump connection and the manifold connection and blank the manifold where the red lines are. 
 

Then use a standard pump valve to connect the hot from your new valve to the pump, remove the other valve from the other end of the manifold (one with a white cap) and then return that to the buffer. 
 

 

[joe90]

Hooray, it’s fixed. As I suspected the “bypass valve” built into the manifold is pants, it allowed way too much cold so the loops never got up to temp and it’s not adjustable. I have blocked the internal bypass and installed a separate blending valve and it all works. All I have to do now is play with the flows and temps. Many thanks chaps ?

[joe90]

Bugger, just when I thought all was well, filled up with antifreeze/inhibitor and notice the flow gauges are less than they were. Wunda say 2 to 2.5 for a 100m loop, even with the pump at max (6) I can only get the loops up to 1.5. I tend to believe that the over blending that was happening with the original set up would not have caused the problem  with say a gas boiler chucking 60’ water at it. Now I am trying to feed it with 30’ water it’s failing to perform. I wonder if the TRV type valves at each end (left fully open) are causing a flow restriction. ?

[PeterW]

Bin the TRV at the return end - horrid things !!

[epsilonGreedy]

Given the cumulative diagnostic effort to get @joe90sorted I wonder if there is merit in the collective brains of this forum specifying a BuildHub no-frills UFH reference design? If it was uploaded to GitHub under a creative commons licence then future self builders could ask suppliers to quote for bits to install the reference design.

[Adam2]

Well this is most fortunate timing for me ? I've got my Wunda UFH pipes in + screeded with the manifolds (4 manifolds, 1 per floor) and am about to press the button on the Cool Energy ASHP package. Keen not to make any mistakes and have a friend as the plumber + an experienced  ASHP install company recommended by Cool Energy so feel should work out OK.

 

BUT - my plumber has suggested doing away with the blending valve at each manifold as he thinks this could be done more simply from the buffer so supplying all manifolds with ~35 degree water (will experiment of course with precise temp). I'm away at the moment, suffering 30 degrees in central america (someone has to) so have this suggested change from my wife but will try and chat with the plumber in the next day or so. My assumption is that the returns will go direct back into the buffer and the supply will be set to a common temp just after the buffer.

 

Given this interesting thread - is there anything I should be wary of in this simplification that's been suggested? 

[JohnMo]

My UFH heating started without blending valve, and without pump on the UFH manifold, had issues getting to work consistently well. So added pump and mixer at the UFH manifold and it then worked well all the time.

 

Having the blending valve at each manifold allows you to fine tune the flow temperature to the least temperature overshoot.  For what it saves you now to do without blending valves, I would just install for the added ease of tuning.

[JohnMo]

On 20/01/2022 at 22:23, epsilonGreedy said:

Given the cumulative diagnostic effort to get @joe90sorted I wonder if there is merit in the collective brains of this forum specifying a BuildHub no-frills UFH reference design? If it was uploaded to GitHub under a creative commons licence then future self builders could ask suppliers to quote for bits to install the reference design.

Sounds a good idea, however no brand or suppliers names.  Lots of people use Wunda trade, but they would only supply to my address for huge postage costs, so went elsewhere.

[PeterW]

7 hours ago, Adam2 said:

BUT - my plumber has suggested doing away with the blending valve at each manifold as he thinks this could be done more simply from the buffer so supplying all manifolds with ~35 degree water

Please go and beat your plumber to a soggy death with his blowtorch.  You can ask a lot of people on here about the difference and why you need pumps at every manifold along with a blending valve. The buffer will soon deplete and you won’t have 35°C water in it so you need to heat slightly higher and then let the valves do the work. 

[epsilonGreedy]

2 minutes ago, JohnMo said:

My UFH heating started without blending valve, and without pump on the UFH manifold, had issues getting to work consistently well. So added pump and mixer at the UFH manifold and it then worked well all the time.

 

 

Was the evolving design your own design from the outset or did you have the debug the initial pro installation?

[joe90]

45 minutes ago, PeterW said:

Please go and beat your plumber to a soggy death with his blowtorch.  

Now come on @PeterW, don’t hold back, speak your mind !!! I concur, with my recent problems I found the blending/bypass built within the manifold not fit fir purpose and as advised here i bought a “proper” blending valve and blanked the one in the manifold, yes the buffer does not last long at all when the UFH is on and it needs to be above the floor temperature a bit. I am still trimming mine and it’s working well now.

Edited January 22, 2022 by joe90

[JohnMo]

Started as my own design, using what the boiler manufacturers manual said was a sound design, based on weather compensation and huba high degree of boiler modulation.

 

But well insulated and airtight, throws conventional design, or the norms of, out the window.  It also confuses the normal plumber.

 

Our old house, not well insulated and not airtight (fairly normal), had UFH you could set the water temperature within a range of 10 degrees and just made no noticeable difference.  New house +/- 1 or 2 degrees makes a noticeable difference, of either under or over swing in temperature.

[JohnMo]

10 minutes ago, joe90 said:

@PeterWyes the buffer does not last long at all when the UFH is on and it needs to be above the floor temperature a bit. I am still trimming mine and it’s working well now.

But remember the buffer is there to stop short cycling.  Is it better for the boiler/ASHP, to run long and low for a longer period while there is heat demand?

[joe90]

1 minute ago, JohnMo said:

But remember the buffer is there to stop short cycling. 

Yes that is why I installed one, I was just pointing out that it’s does not last long before the stat calls for more heat.

[JohnMo]

That is sort of what I was saying, could you turn down the temp, run at lower temp and get a better COP? Run all the time while there is a demand for heat from the house?

Edited January 22, 2022 by JohnMo
Clarification

[joe90]

4 minutes ago, JohnMo said:

That is sort of what I was saying, could you turn down the temp, run at lower temp and get a better COP? Run all the time while there is a demand for heat from the house?

My heat pump only heats to one temp and that  I set at 45’ to cope with DHW. The buffer stat is set at 35’ (which calls fir heat from the ASHP), and the manifold blends down to 30’.