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Correct flow rates for UFH?


Chriswills

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Hi, my first post in here. Hello all. 
I have UFH downstairs with 5 zone controllers. I have just cleaned all the plastic tubes to see what the flows are and had a play with them. Seems I can’t turn the flow up anymore than 2l/min and they are all fully open. Is this normal and what should they be?

 

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How old is the system?  Is it actually working adequately?

 

The usual (correct?) thing is the UFH manifold has it's own temperatuer blending valve and circulation pump.  for some reason a lot of systems are coming to light recently where they rely on just one circulation pump for everything which is not ideal.  Can you show a more zoomed out picture of the whole manifold?

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Any idea what temperature it is running at?

 

If you get a "proper" design for an UFH system you will be offered a manifold with a temperature blending valve and it's own pump.  I am guessing this was built by a developer who thought he knew better and could save £300 by not including these "unecessary" parts?  If the water is hot enough for radiators it is likely too hot for UFH and in any event because of the very different warm up times it would be preferable to have the UFH and radiators on separate time and temperature controls, which you could do with a proper system.

 

What do you know about the house re it's construction and levels of insulation?

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I know the property well I built it. Insulation is all good. Unfortunately I left the so called plumber to fit everything. It’s a long story !!

Rad temp is about 30deg but because of new build is ok and warms up rooms nicely. I have radfan on the cold room and works a treat. 
UF zones, 5 in total are set to 18

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51 minutes ago, Chriswills said:

Thanks Dave. Would you suggest fitting a mixer and pump type manifold or leave as is?

As it stands the actuators have no way of telling the pump to switch off. It’s mad really. 
My problem then I have only 1 pump so upstairs rad will go off too. 


Yes and .. yes..

 

So that needs re-fitting with a mixer if possible - you may have to take the manifold off the wall although it looks like someone removed the board with a spoon anyway ...

 

Depending on how far from the buffer that manifold is, the manifold pump may well pull the hot water into the system anyway. If you can move the “other” pump and make sure it’s before any tee to the mandifold even better. 
 

You could wire the rads to a zone valve - use that to switch the pump on only when the rads want heat and let the manifold pump be controlled by the actuators. 
 

All pretty easily doable

 

 

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My system has a similar setup. Circulator pump apart from the manifold and no blending valve, and I do not have any thermostatic control at the manifold. The circulator delivers approx 10 to 15 litres per minute, so with a 8 port manifold this is less than 2 litres per port on average.

 

In our case the controller built into the Ashp adapts the flow temperature according to the conditions. It measures external, room and set temperature and applies the appropriate amount of heat. On a very cold day flow temperature increases (max about 32C) and on a mild day decreases down to about 22C.

 

This works very well and keeps cop between 3.5 and 4 on average.

 

So before you make any changes suggest you check if your HP controller has any kind of adaptive control built in. If so I see no reason to change it, it is a perfectly valid setup and was recommended and commissioned by the Ashp's UK agent.

Edited by ragg987
tipo
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Thanks so much for the advice guys. I was beginning to think about changing the manifold so it does the job properly. 
any recommended components to use, eg, manifold with flow meters on lower, wiring centre etc. 
 

I did read in the supplier manual not to change the weather switch compensation to on if the unit was south facing. See pic. 
 

None of this has been commissioned, guy went bust and I had to pick up the pieces with other people. Although we had 10 years I’ve kind of just gone along with it as never had time, working away. Now I’m deep diving into it all. 
Max temps at 32 would do nothing for my rads either. 
This morning, after reducing the return temp on the ASHP to 35 (flow 40-always plus 5) the actuators are all open (bar 1) on the UFH and  HP running trying to get more heat in I guess. What if I started to reduce flows to try and force more water where needed as the hall is now up to temp.  
Turned up by 2 degrees now to see if I can get the UF up to temp. Bit of a trade off in my opinion. 
UFH room stats are set to 18. 

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Edited by Chriswills
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Solar gain for a heat pump is negligible but the air sensor on the back may be susceptible to solar warming. 
 

There is nothing intrinsically wrong with that set up. Emmeti are a decent brand, it just seems like it has been half installed ..! Depending on how “handy” you are then you can probably re-pipe a lot of that as it stands with some off the shelf components rather than use a new manifold and pump set. 


 

Couple of things to check though.

Is there a sensor or thermostat on the buffer tank ..? 
What triggers the circulation pump to run..?

What triggers the heat pump to run ..?

What timer / controller is installed ..?

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There is a temp switch on the buffer return tank which I can set. It works based on the  return temp to the HP. So for example it can be set to activate the pump only if the temp is 35 any lower then the grundfoss doesn’t come on. At the moment I have it switched off and the GP runs 24/7. 
 

HP runs when the return temp setting minus 3 is reached. Eg: return set to 37. Pump activates at 34. Pic shows 35 so unit is off. 

 

Timer is on 24/7 for UFH and from 6am until 12 pm for rads upstairs. Although most of the rads are off. 
 

Here’s some pics:

 

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8 minutes ago, Chriswills said:

It’s not plumbed in to. Solar cylinder is separate to buffer. I’m on about 40-50 kWh  a day now in winter at 12p a kw so not too bad. In summer it’s a lot less.

 
 

 

Is that the DHW usage?  If so that seems high.  I used 31kWh in the last week heating HW with the ASHP.

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I wouldn’t mind a go at trying the weather compensation option. Got the manual info but need a bit of plain English if anyone can help please?

 

Current settings are:

 

DS00 = 0 which is off, needs to be 1 to activate. 
DS02 = 22

DSO4 = 15

DS06 = -5

 

these are the factory sets I assume and here is the page from the manual:

 

 

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So for an increase of 15°C of outside temp (-5°C to 10°C) the heat pump will reduce the flow temperature set point by 5°C reading that. 
 

So if you set it at 35°C and it’s 10°C outside, then the HP will change it to 40°C when it’s -5°C or lower. 
 

I would possibly move the curve up slightly (although this looks linear ..!) and move the differential start (ds06)  to -2°C but make it -3°C on ds04 to begin with. 
 

Nice and simple this one to understand ..!

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3 minutes ago, PeterW said:

So for an increase of 15°C of outside temp (-5°C to 10°C) the heat pump will reduce the flow temperature set point by 5°C reading that. 
 

So if you set it at 35°C and it’s 10°C outside, then the HP will change it to 40°C when it’s -5°C or lower. 
 

I would possibly move the curve up slightly (although this looks linear ..!) and move the differential start (ds06)  to -2°C but make it -3°C on ds04 to begin with. 
 

Nice and simple this one to understand ..!


Glad someone thinks it’s simple  and Thankyou so much?

 Could you just run through the settings please to achieve best efficiency, DS02, 04 and 06?

 

 

 

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