Avoid this if you still have to design your UFH

[Adsibob]

I thought my UFH design was pretty good. But now that I've lived through a couple of cold weeks, I've spotted an incorrigible flaw which I thought I'd write about here so others can avoid making it.

Our ground floor consists of the following zones:

1. Fairly wide entrance hallway with a WC under the stairs
2. Front room
3. kitchen and utility room
4. open plan lounge area off kitchen

 

I thought that was plenty of zones. Turns out I was wrong. The WC is in the middle of the ground floor, with the hallway and utility room to one side of it, the front room on the other side and the lounge behind it. Accordingly, although it's just made out of stud walls, being in the centre of the floorplan, it has no external walls and so probably doesn't lose much heat. The WC gets significantly warmer than the rest of the floor. Setting the thermostat on the zone (which is located in the porch on an external (brand new cavity wall) to 20C, gets the general area to about 20.5C but the WC to 22.7C. I think it's mainly because of the lack of external walls/windows, but there's possibly other factors I'm not aware of.

 

So I guess the lesson is if you have a space which has the unique characteristics that my WC room has, consider putting it on its own zone.

[ProDave]

Certainly on it's own pipe loop so you can reduce the flow in that room to ballance it?  do I take it one pipe loop does the WC and some other part of that zone?

 

Our last house, I made the "mistake" (actually the supplier that "designed" the system made the mistake) of a pipe loop and zone to the landing.  That NEVER turned on, there was always enough neat from downstairs.

 

Even the large entrance hall zone was questionable as that rarely turned on very little of that was an outside wall.

[Adsibob]

3 hours ago, ProDave said:

Certainly on it's own pipe loop so you can reduce the flow in that room to ballance it?  do I take it one pipe loop does the WC and some other part of that zone?

 

 

That’s a good point. I had assumed it will all be the same, but actually if the plumber has any sense he hopefully put it on its own loop. Particularly as the manifold which serves it only serves that zone and one other, both medium sized areas. I am not home now, but will check.

[Adsibob]

Ok, have checked. See picture below. From what I can tell (but grateful if someone could confirm) there are unfortunately only two loops.  

In picture to the left, under the orange pump are a pair of pipes, one with a blue sheath and one with a red sheath - I assume this is the hot water coming in to this manifold from my boiler and the cold water going back to get reheated by the boiler.

 

To the right, there are two pairs of pipes, representing the two loops. One supplying my front room and one supplying the hallway and WC. Real shame the installer didn’t think this through better. 
 

Am I right in thinking that I can only adjust pump speed and temperature? or is there a third adjustment available on each loop? @ProDave you mentioned something about balancing and flow, hire does that work?
 

I noticed that the water temperature was set to 45C which seemed high (the terrazzo in the hallway and WC gets pretty hot, not quite burning hot, but too hot really. And the wood parquet in the front room shouldn’t be exposed to that kind of temp, so I’ve turned down the water temp to 40C. 
 

Anything else I can do?

 

[ProDave]

To adjust the temperature, turn the white valve just below the pump.

 

You can adjust the flow rate through each loop, the flow meters are the two things on the top manifold, prise the red cap upwards and then you can turn the black part of the flow meter in it's thread to adjust the flow rate in each loop, so the one that is heating up too fast, reduce it's flow rate.  Be careful you can unscrew it too far and screw it right out, then you get wet.

[JohnMo]

I would leave pump speed alone, just adjust one variable at a time.

 

More flow is more heat, less flow less heat.

 

Interesting that your reading room has no flow, or very little in the photo?

[Adsibob]

6 hours ago, JohnMo said:

Interesting that your reading room has no flow, or very little in the photo?

The heating for that room was off at the time I took that photo.

 

I agree that to approach something scientific, I should only make one adjustment at a time. But I'm just interested to understand what is the difference between the pump speed and the flow. How would you describe their different roles in the UFH system?

[JohnMo]

Pump to supply enough flow to the UFH system to overcome the loop resistance in the highest resistance loop.

 

Flow meters to set flow rate through the loop, to give an appropriate rate heat transfer to floor.  Can also be used to balance temperature distribution through different rooms with different heat demands, by altering DT.

 

Mixer, work with the above, set the temp through the loop, to give an appropriate rate heat transfer to floor.