41 minutes ago, Adrian Clark said:

Thanks everyone, much appreciated, in response:

Situation.

Andeh. I too wonder if the scree is too thick, however, on a couple of occasions in the past the water temp has gone into the upper 30s and tiles have felt warm (there are no installation records with the house documents).

Radiators (just two upstairs) running efficiently.

Last photo, DP miller, from under white cap.

Second photo. GAC Pin under tcv is free and springs back.

Third photo. Manifold valve pins all free and spring back. A bead of water came through the middle valve when depressed (see photo).

Fourth photo. Flow meters 1.5 and responsive when pump switched from II to III.

Update. Water temp consistently 28 deg.

DP Miller, the boiler cycle is 1 min to bring from 40 degrees to 49.5 degrees and then 9 mins to drop back to 40. The pressure valve is in the green and just over 1 bar.

Welsh Nick. I'll buy a clamp-on IR thermometer and a volt checker. The boiler temp has been on min (40) for three days now (good luck against Japan).

Arigato.

2 hours ago, Adrian Clark said:

the boiler cycle is 1 min to bring from 40 degrees to 49.5 degrees and then 9 mins to drop back to 40

Sounds like the boiler is short cycling. You don't have enough of the heating open for the boiler to push heat into.

10 hours ago, Nickfromwales said:

Turned out to be the boiler flow temp was a little too high, causing the safety temp probe to shut the UFH manifold pump off; then it cooled down and came back on, then it got too hot and turned off again, and repeat, and repeat.

If your boiler is start stopping not sure you will be seeing this. But if you are you still don't have enough of the heating system engaged to keep the boiler happy and cannot move the heat fast enough away from the boiler.

Does your boiler have an error code 202 when you have the UFH on? if it does you are in a protection mode, which is effectively short cycling?

No error codes (and I have been keeping an eye on the boiler control panel). I've just turned the tcv on the radiators up to 4 to see if the additional demand makes a difference.

Edited Wednesday at 12:405 days by Adrian Clark
Additional information

38 minutes ago, Adrian Clark said:

No error codes (and I have been keeping an eye on the boiler control panel). I've just turned the tcv on the radiators up to 4 to see if the additional demand makes a difference.

You need tcv fully open on all radiators for now. Set thermostat high, so it doesn't get in the way and two way valves stay open. If rooms are getting too warm reduce boiler flow temperature.

Your boiler is just huge, especially at mild temperatures. Apology, your trying to boil an egg cup of water in you kettle currently, having everything open is more like trying to boil a cup and half. Ideally your system should be 4x the size for the boiler and then you would be trying to boil a full kettle.

Thanks Adrian, good that the pin is free, so a seized insert is less likely. A steady 28 at the floor while the boiler swings between 40 and 49.5 makes me think the mixing side is mostly pulling in cool return rather than boiler water. When the IR thermometer arrives, check the boiler flow pipe, the pipe into the manifold after that valve, and the manifold return at the same moment. If the boiler side is in the 40s and the manifold flow is still around 28 with the valve wide open, I'd look next at whether the manifold pump really runs all the time, like Nick said, and whether that mixing valve is actually passing boiler water when it is open (you already saw no flicker when you opened it fully earlier). The bead of water from the middle valve pin is worth keeping an eye on, but probably not what's keeping your floor cool.

@Nickfromwales if you've experience of these, what is that device under the white cap- might it be a strainer that is blocked or a lockshield that is strangling the flow?

4 hours ago, dpmiller said:

@Nickfromwales if you've experience of these, what is that device under the white cap- might it be a strainer that is blocked or a lockshield that is strangling the flow?

Usually just a lockshield / isolator.

Question is, has this been known to be working and has now failed post combi install, or longer term issues? @Adrian Clark ?

The TRV head (the adjustable white headed valve) is controlled by capillary wire > sensor probe, but I cannot see where this goes. Test this and rule it out, the head needs to be unscrewed and lifted off, then the pin that lives under it needs depressing to see if it moves freely and returns to its 'parked' position eg fully up / out. In that state the valve should allow full flow into the UFH loops, provided the flow from the boiler is hot and remains hot.

Check this and report back.

FYI, this is a dogshit UFH manifold, and after fitting the Vogel & Noot one, and seeing these issues, I never fitted another similar one ever again.

I've continued to monitor the system:

Report. The temp coming into the system is a consistent 36 - 38 degrees (either side of the trv). The temp on the manifolds and ufh pipea is consistently 26 - 30.

When I reduced the pump from two to one there was a brief increase in the temperature of the first return valve and a half degree increase in water temp. With flow pump remaining at one the temp settled at 30.

I dont see a boiler cycling problem because the two radiators upstairs consistently maintain temperatures (no discernable fluctuation).

Summary.

The actuator is new, the trv tested and working, the flow meters showing correct flow.

The boiler is providing water to temperature.

The return manifold is introducing cooled water lowering the water temp in the under floor pipes.

Question. What can be done?

does seem like there's not enough hot flow into the UFH. I'd be focussing on that doo-dah with the plastic cap. If it's an iso or lockshield I'd be opening it a bit and if unsure I'd probably drain down and remove it to investigate or replace.

Look at the set up. The 2 port valve is on the flow in to system and the white capped valve is on the outlet back to boiler.

So my theory on how test and set up.

Your temp sensing element (for TRV) is on the upper manifold section and so is your temp gauge.

The TRV is sensing temp of mixed water before it flows in to the UFH pipes and open/closing to maintain a set temperature, using the sensor element to gain the reference temperature. It adds new hot water to the return water from the UFH pipes.

The covered valve on top manifold ultimately determines how much fluid is allowed to escape the system back to the boiler. This in turn limits how much hot water can enter the system.

If the temperature in the flow pipes is to low either the TRV isn't responding to a required increase in heat (the thermal sensing element is kaput), or the covered valve isn't allow enough water to escape the system to be refreshed with hot water.

To test

Remove TRV head, this will allow the valve to fully open or maybe fully close, but generally fully open. With the TRV removed the flow gauge should increase in temp over the next few minutes. If it doesn't remove the white cap from the upper manifold and to need to open up the valve, I would open until you see about 45 degs on the temp gauge. If that has zero effect reset to last position and order a new sensing element and TRV.

Reattach the TRV (original or new) and set to 35 degs and see if it modulates flow temp.

The white cap removed provides the means to bleed the system (there was no trapped air).

The trv removed made no difference to the ufh water temperature.

I wouldn't be surprised if that was a screw down valve with a leaky gland tbh...

For comparison, here are the readings from my underfloor heating this evening. The heat pump is sending about 34.4 °C, the manifold flow is about 33.6 °C and the return is about 26.8 °C, with the room holding around 22 °C on a 6 to 9 °C day. (The main pump at 100% is normal at my house, I inherited quite the piping runs 😅 here's my home: https://heatlosspro.cloud/s/YAzppFumRwF3TzRGRBaV0g)

Could you measure your manifold flow and return at the same time? A clamp probe or an infrared thermometer on bare pipe would do.

As a quick test, since your incoming water is only 36 to 38 °C, I'd set the mixing valve fully open, if your manifold allows it, and put the underfloor heating pump on maximum speed. On some manifolds, you pull the knob out and turn it fully open. Within about 5 minutes, you'd expect both manifold flow and return to start rising. If they don't, that points more towards hot water not getting through to the loops.

If the numbers do respond, you could then reduce the pump speed until the return settles about 5 °C below the flow. Something in the 5 to 7 °C range is usually fine for underfloor heating.

How is your underfloor heating pump controlled? Is it on a fixed speed setting, or controlled by a signal from the boiler or controller? You mentioned a slower setting briefly helped, so it would be useful to know which setting it normally runs on.

3 hours ago, Adrian Clark said:

The white cap removed provides the means to bleed the system (there was no trapped air).

No, it is not a bleed / vent. It is an isolation valve aimed at commissioning the flow rate of water through the system. It is basically an Allen key operated gate valve.

The T off at the very top of this arrangement has a brass bottle (automatic air) vent, for releasing air out of the system automatically. It is possible that this has failed and the system has air trapped in it aka air locking it.

Does the system sound 'gurgly' and can you confirm the cap is loose on the bottle vent? It operates like the float valve in a carburettor, with a pin on a float.

2 hours ago, gac said:

I'd set the mixing valve fully open, if your manifold allows it, and put the underfloor heating pump on maximum speed. On some manifolds, you pull the knob out and turn it fully open.

Odd you should suggest this, as the pictures clearly show the type of manifold and the lack of mixing valve. Are you not able to see these?

7 hours ago, Nickfromwales said:

No, it is not a bleed / vent. It is an isolation valve aimed at commissioning the flow rate of water through the system. It is basically an Allen key operated gate valve.

If the OP has screwed this fully closed, he will get no water or maybe very little water leaving and therefore entering the system, and a flow temp cooler than expected, which is what they are seeing. If when open partly or fully it leaks water the valve needs to be replaced, spare available here

https://underfloortradesupplies.co.uk/product-category/manifold-spares/uponor-manifold-spares/uponor-tm-manifolds/

9 hours ago, Nickfromwales said:

Odd you should suggest this, as the pictures clearly show the type of manifold and the lack of mixing valve. Are you not able to see these?

I was assuming it's upstream, as we don't see the complete system? Because that could be a factor in the issue we're trying to diagnose remotely, not sure if anyone specifically asked for it?

Edited 4 hours ago4 hr by gac

19 minutes ago, gac said:

I was assuming it's upstream, as we don't see the complete system? Because that could be a factor in the issue we're trying to diagnose remotely, not sure if anyone specifically asked for it?

Thanks. Photos, the whole system. And the pump speed contol.

3 minutes ago, Adrian Clark said:

Thanks. Photos, the whole system. And the pump speed contol.

Is the Allen head valve fully open?

2 hours ago, JohnMo said:

If the OP has screwed this fully closed, he will get no water or maybe very little water leaving and therefore entering the system, and a flow temp cooler than expected, which is what they are seeing. If when open partly or fully it leaks water the valve needs to be replaced, spare available here

https://underfloortradesupplies.co.uk/product-category/manifold-spares/uponor-manifold-spares/uponor-tm-manifolds/

10 hours ago, Nickfromwales said:

No, it is not a bleed / vent. It is an isolation valve aimed at commissioning the flow rate of water through the system. It is basically an Allen key operated gate valve.

The T off at the very top of this arrangement has a brass bottle (automatic air) vent, for releasing air out of the system automatically. It is possible that this has failed and the system has air trapped in it aka air locking it.

Does the system sound 'gurgly' and can you confirm the cap is loose on the bottle vent? It operates like the float valve in a carburettor, with a pin on a float.

Is this the component to which you referred. The pin is loose and comes out with no effect. There was no gurgling just water when I opened the white capped valve. Are we now at the point of replacing one component at a time until the system operates normally?

52 minutes ago, Nickfromwales said:

Is the Allen head valve fully open?

which is the allen head? (the allen head screw in the photo for the pump control coveris tightened)

1 hour ago, Adrian Clark said:

Is this the component to which you referred. The pin is loose and comes out with no effect. There was no gurgling just water when I opened the white capped valve. Are we now at the point of replacing one component at a time until the system operates normally?

That is the air bleed valve, put the screw removed back in.

This valve is the allen screw valve, it is a flow regulator. This is the one I have mentioned above (copied below). This valve needs to be open.

15 hours ago, Adrian Clark said:

The white cap removed provides the means to bleed the system (there was no trapped air).

See above statements, this IS NOT an air bleed its flow regulator

3 hours ago, JohnMo said:

If the OP has screwed this fully closed, he will get no water or maybe very little water leaving and therefore entering the system, and a flow temp cooler than expected, which is what they are seeing. If when open partly or fully it leaks water the valve needs to be replaced, spare available here

https://underfloortradesupplies.co.uk/product-category/manifold-spares/uponor-manifold-spares/uponor-tm-manifolds/

2 hours ago, JohnMo said:

That is the air bleed valve, put the screw removed back in.

This valve is the allen screw valve, it is a flow regulator. This is the one I have mentioned above (copied below). This valve needs to be open.

See above statements, this IS NOT an air bleed its flow regulator

Got it. The screw is back in. By "open the valve ", do you mean use the alen key through the top?

Thanks again for your patient advice.

Is it time to start replacing components?

4 minutes ago, Adrian Clark said:

The screw is back in. By "open the valve ", do you mean use the alen key through the top?

Thanks again for your patient advice.

I would take out to middle position see how everything responds, if still net meeting temperature expectations, screw it another turn etc.