Underfloor heating weirdness

[azgarciadeniz]

We have underfloor heating on ground and first floor and radiators on second floor.

The underfloor heating manifolds have mixer valves to drop temperature down. There are two manifolds, one on each floor

Heating on ground floor is fine no issues at all

Heating on second floor with radiators is also fine.

The problem is on the first floor where the heating is somewhat erratic.

It worked fine for about 1 year to maybe 18 months and then it's been suboptimal.

All the loops were set to about 2 litres/minute and one of the rooms (my kid's bedroom) got progressively less heat.

At some point I set the loop that goes into that room to about 3 litres/minute, which seemed to solve the issue for a bit but then it seemed to make no difference.

Sometime later, I decided to drop the flow to 1 litre/minute on the spare room and then I stopped the flow (I actually tried to get it to about 0.5 litres/min but it seemed to actually mostly stop), the odd thing is that for about a week the spare room was still getting warm.

I thought that there might be air on the loop on my kid's bedroom but I talked to a plumber, who said that it was unlikely, though he didn't offer an explanation and then never turned up.

Any ideas?

Thanks

Picture of the manifold on the first floor with the heating OFF. Loops from left to right are: spare room, hallway/bathroom, kid's bedroom, home office.

 

[Madrab]

Does the flow pipe to that room actually heat up and then the floor? If not and you shut down the other circuits does that room/floor then warm up? I presume you have one set temp for the whole zone as there are no actuators, one valve/stat controlling the whole floor?

 

[azgarciadeniz]

oops, tried to quote the previous message and failed

 

[azgarciadeniz]

Does the flow pipe to that room actually heat up and then the floor? If not and you shut down the other circuits does that room/floor then warm up? I presume you have one set temp for the whole zone as there are no actuators, one valve/stat controlling the whole floor?

It does heat up and it does heat up the floor, just not very efficiently. I think with all running at about 2l/min and temperatures hovering around 0 C (outside) the room struggles to reach 20 C, whereas the spare room comfortably reaches 21 C

There is a single thermostat for the whole floor

 

[Sucker69]

Try to increase the temperature control mounted just below the pump.
Also unscrew the blue cap on the third circuit and make sure the pin underneath is moving freely.
Use a tool to press down on the pin. Maybe it is stuck closed and not allowing hot water to flow.

 

[azgarciadeniz]

Try to increase the temperature control mounted just below the pump.
Also unscrew the blue cap on the third circuit and make sure the pin underneath is moving freely.
Use a tool to press down on the pin. Maybe it is stuck closed and not allowing hot water to flow.

I think it does move as I can tighten/loosen it and the flow rate changes.

I'll have to try the temperature control, see if that makes a difference. I do think I bumped it up ages ago but not sure now

 

[Johntheo5]

Can you measure the manifold flowtemperature (mixed) or just feel it?.

 

[Sucker69]

I think it does move as I can tighten/loosen it and the flow rate changes.

I'll have to try the temperature control, see if that makes a difference. I do think I bumped it up ages ago but not sure now

As you press down on the pin the corresponding flow meter will move to a closed position.
Is this happening?

 

[SpecialK]

Are those blue caps on the bottom rails screwed down tight? On some they should be unscrewed? Does the top manifold get hot?

 

[azgarciadeniz]

Can you measure the manifold flowtemperature (mixed) or just feel it?.

So I got a cheap IR thermometer and ran the heating for 15 minutes. Measured on the pipes just below the blue manifolds

Numbers are for loops from left to right.

1 and 2 are almost off
3 is 3L/min
4 is 2L/min

So not sure what's going on here

	1	2	3	4
Heating Off	21°	21°	21°	21°
Heating for 15 minutes	24.3°	24.2°	35.2°	30.0°

 

[Johntheo5]

Can you measure the manifold flow temp just above the pump and also the manifold return temp on the pipe coming out of the thermostatic mixing valve on the bottom?

 

[azgarciadeniz]

So I decided to treat myself to an IR camera, which helped me to find out what the issue was.

Essentially, the zones don't match up to the rooms, so by lowering the flow for my office (Zone 4), I was also lowering the flow for my little one's room, which spans Zone 3 and 4 as can, hopefully be seen on the picture.

 

[azgarciadeniz]

thanks for the help

 

[Madrab]

Not sure what the pic is showing us? Is that the loop spanning 2 rooms?

The issue that I can see there though is the way the loops has been laid - in essence it has been laid in a snake pattern whereby as the loop progresses the water gets colder, really bad layout design. It should have been laid in a reverse return pattern whereby the loop turns back on itself so the heat is evenly distributed across the whole space.

Best shown here - yours looks like the diagram 3.

Is the UFH encased in screed? Or is it overlaid/floating floor?