4 plumbers out and no fix. UFH not working downstairs. Return pipe cold

[Markca]

This one is driving me mad. I’ve had 4 different plumbers out and none of them have resolved the issue. 
 

issue:

 

underfloor heating has stopped working downstairs. The pipes into manifolds (top row) are hot. The ones on the second row are cold. Last year I was able to control the pressure on each individual manifold by turning them but this year the red gauge doesn’t move

 

system:

 

- thermostats via hive. Always has been and worked last year so nothing to suggest it’s this. 
 

- the pump is grundfos upm3 auto. 25-70 130 zzz

 

- manifolds are snug

 

- boiler is ideal logic max heat h30

 

- a 250L prostel unvented hot water tank is connected to the system. 

- I’m attaching photos of the system too. 
 

To note:

 

- this system worked perfectly fine last year (it was installed over the summer of 2022. Worked last winter but not working this year. 

- it’s fed by a boiler. The boiler isn’t showing any faults. 

- the boiler also feeds the upstairs UFH and this is working fine. 

- downstairs isn’t working. 

- there are several circuits for downstairs and none of them are working. So it suggests that the problem isn’t in one individual pipe. 
 

- One plumber has changed the pump as he thought it was this. No luck. 
 

- one plumber has used a hosepipe and changed all the water inside (I guess that’s checking / removing any potential airlocks or blockages). Still didn’t work. 
 

- todays plumber was convinced that it was the heat control to the left hand side of the manifolds as once turned down the pressure in the manifolds did move. But after several hours it’s still cold and the return pipes are cold. 
 

please help me get downstairs warm for Christmas! Thank you 
 

 

[Markca]

[Markca]

[Markca]

[Markca]

[Markca]

[PeterW]

Do the actuator heads actually lift or move (can’t see the brand) when the system is calling for heat ..? Whose wiring centre is it ..?  Don’t recognise the brand on it …

[ToughButterCup]

4 plumers eh? Lucky man. You try and get 4 plumbers out in West Lancashire. 

 

Thanks for the clear problem statement.

[Markca]

49 minutes ago, PeterW said:

Do the actuator heads actually lift or move (can’t see the brand) when the system is calling for heat ..? Whose wiring centre is it ..?  Don’t recognise the brand on it …

They do. You can take them off and push the top metal pin down too. One of the plumbers also did this. 
 

the wiring centre is also snug brand (same as the manifolds). The box for the wires says snug centre. 

[Markca]

10 minutes ago, ToughButterCup said:

4 plumers eh? Lucky man. You try and get 4 plumbers out in West Lancashire. 

 

Thanks for the clear problem statement.

😂 I mean 4 plumbers who haven’t fixed it? Surely that’s no better 

[ProDave]

No 1 thing to do is take all the actuator heads off the bottom manifold, keeping a note which one went where so they can all go back in the right order.

 

Do you get any water flow in the gauges?  (they measure water flow rate, not pressure)

 

Let us know the result of that.  Did any of the plumbers try that?

[Markca]

8 minutes ago, ProDave said:

No 1 thing to do is take all the actuator heads off the bottom manifold, keeping a note which one went where so they can all go back in the right order.

 

Do you get any water flow in the gauges?  (they measure water flow rate, not pressure)

 

Let us know the result of that.  Did any of the plumbers try that?

The gauges do have water in them but turning them does nothing. When the plumber yesterday turned the temp down on the system they did move down (they’re pretty much all stuck at the top) but twisting them still does nothing. 
 

all the heads on the actuator were removed and they’re just resting on top of the right head

[ProDave]

So when he turned the temperature down you got flow.  It sounds to me like a problem with the temperature blending valve then.  When it reaches the correct temperature it should stop drawing hot water from the boiler and instead just circulate the water in the loops until it cools down a bit, when it will then let a bit more hot in from the boiler.

 

I would be changing the blending valve as my next step.  Surprised none of them has suggested that.

[Markca]

1 minute ago, ProDave said:

So when he turned the temperature down you got flow.  It sounds to me like a problem with the temperature blending valve then.  When it reaches the correct temperature it should stop drawing hot water from the boiler and instead just circulate the water in the loops until it cools down a bit, when it will then let a bit more hot in from the boiler.

 

I would be changing the blending valve as my next step.  Surprised none of them has suggested that.

So we’ve tried having the temp lower as the gauges did move slightly but the return pipe remained cold and the floor didn’t get warm at all after several hours. I can definitely suggest it to plumber visit number 5

[Mattg4321]

I’m not a plumber, but I had a similar system in my old house and I’ve wired a load of these systems up. 
 

It sounds like either you’re getting no/not enough flow of water through the pipework, or that the water is too cold. 
 

As above, it could be that the blending valve is faulty and is causing the water to be too cold. 
 

What flow rate do the flow meters show when the system is running? If they’re all at the top showing at or near 0, then you don’t have any/enough flow. They usually flutter/move around very slightly all the time the system is running properly too in my limited experience. 
 

You say the top row of the manifold is hot, which makes me think it’s a problem with a lack of flow. Have you somehow managed to throttle back all the flow meters/turn them off? You mentioned you were fiddling with them last year. Once properly balanced they should be left alone really. 

[Markca]

3 minutes ago, Mattg4321 said:

I’m not a plumber, but I had a similar system in my old house and I’ve wired a load of these systems up. 
 

It sounds like either you’re getting no/not enough flow of water through the pipework, or that the water is too cold. 
 

As above, it could be that the blending valve is faulty and is causing the water to be too cold. 
 

What flow rate do the flow meters show when the system is running? If they’re all at the top showing at or near 0, then you don’t have any/enough flow. They usually flutter/move around very slightly all the time the system is running properly too in my limited experience. 
 

You say the top row of the manifold is hot, which makes me think it’s a problem with a lack of flow. Have you somehow managed to throttle back all the flow meters/turn them off? You mentioned you were fiddling with them last year. Once properly balanced they should be left alone really. 

Hey!

 

when I say fiddled with them last year I meant that I had to increase the flow to a couple of rooms as they weren’t getting warm. This was under the advise of the original plumber. It wasn’t a regular occurrence, but they definitely easily moved up and down when twisting unlike now. 
 

the flow rate metres are all at the top yes - so zero and they’re definitely not fluttering about. 
 

the water has been made really hot by other plumbers and this didn’t resolve it at all. 
 

the in pipe is really hot and it does change temperature when you lower the blending valve / temperature dial. 
 

Did you find a way to improve the flow rate? 

[Mattg4321]

For some reason you’re not getting enough flow of water through the system. Hopefully someone with a plumbing background can offer some further advice. Something is throttling it, perhaps even the blending valve as fiddling with that is the only thing that has slightly improved things (the flow meters moved)
 

Can’t be pump as that has been changed. 

[Jenki]

My two pence worth.

If you've took the actuators off, and your not getting flow then the problems are either:

1, Pump 

2, Valves closed( 2port valve not working, or isolation valves closed)

3,Air lock in the system 

4, faulty blending valve

 

You've changed the pump, I assume you've manually opened the 2 port valve.?

If none of this get results then blending valve or air.

So for me, I would

Close the return manifold isolation valve, attach hoses to the return manifold bleed / drain,

Close all flow meters, open the drain cock and fill the system, opening and closing the flow meter loop by loop ensure there is no air lock. You should also see a flow through the meter.

If you don't get any significant air then the blending valve is #1 culprit.

 

[Mattg4321]

It sounds like plumber has already flushed it through, which if done properly would eliminate an air lock hopefully. 
 

It also seems weird to me to have an air lock in underfloor heating (a low point in the system) when nothing has been worked on and it was previously working well. Sounds like something has gone faulty or been fiddled with and is severely restricting the flow. 

[JohnMo]

So everything did work👍

 

Now it doesn't, so step through the system logically.

 

Upstairs is fine, you are heating the cylinder, so basically nothing wrong with boiler producing heat.

 

I notice the UFH circulation pump is running, if the circulation pump is connected to the wiring centre, it shows the wiring centre is receiving a signal to heat floor.

 

The wiring centre should also open the zone valve (white actuator on second photo - bottom left) does this open and close as required ? Check by selecting all thermostats lower than room temp, valve should close and pump go off. Then select a room thermostat higher to check opening is no issue, pump should start and zone valve open

 

While doing the above the small actuators on the manifold should open and close, so verify, led flashing and slight noise.

 

If all the above are ok the only other thing is the system is mixer valve and it has stuck in a position, you may or may not be able to strip the mixer and clean. If can't you will need to get a new mixer

 

 

[MikeGrahamT21]

The zones which are working upstairs, they show flow yes? If so how many litres per min are they showing? Also this is assuming it’s a single manifold for all zones?

 

id remove all of the actuators, ensure all zones are open to some degree, then turn down the zones which have flow, this should transition to flowing round the remaining open zones which would be the non working ones, and in theory it’ll either shift whatever is stopping it or just travel through the bypass valve.

 

also should this be turned on?

 

Edited December 20, 2023 by MikeGrahamT21

[Mattg4321]

I’m willing to bet the upstairs heating is on a separate manifold and is unrelated to the problem. 
 

I’m also willing to be that the 20amp isolator you’ve pointed the yellow arrow at is for the immersion heater. 
 

The blending valve has to be the thing to try next. 

[TonyT]

No heat= No flow of hot water in the circuit.

 

turn  the upstairs that is working off/pit thermostat to a temperature lower than the room temperature and put thermostat for other circuit up a few degrees than room temp, no weather compensation just heating on full and get all the energy from the boiler/pump working on that circuit.

 

at The boiler is that an a brass air vent?

getting any air from that?

 

who’s to say there is sufficient water in the UFH, might be best to blast mains water into the UFH one loop at a time to also remove air locks

 

 

 

Edited December 20, 2023 by TonyT

[Markca]

Everyone you’re all being amazing with all these ideas. I appreciate it a lot. I’ve actually had to go to my parents for a few days a couple of hours away so can’t do any of this for the time being. (at least their heating works, unless im a bad omen!)
 

im also convinced it’s probably the blending valve. 
 

in answer to other questions here:

 

- yes that switch is for the immersion heater. 
 

- yes the upstairs is on a separate manifold, just fed from the same boiler. 
 

- yes that is a brass air vent and there’s only water that comes out of that. 
 

 

[PeterW]

@Markca You say the top manifold gets hot ..?

 

OK - take the actuator off the first circuit, and on the far right of the lower manifold there is a white manual cap. Attach that to the circuit where you have removed the actuator, and then fire up the system.

 

If you’re getting a call for heat then the pipe into the bottom of the blender will get hot, the pump will run and the top manifold should get warm.

 

Now turn the white cap in the ‘+’ direction and see if the flow gauge moves. If it doesn’t, turn the cap all the way open, then slowly move the flow gauge - it shouldn’t need much as it is the only circuit that is taking heat.

 

Now check if the pipe is getting warm below the flow gauge, and if it is, you’ve got a flow issue with either the actuator or the flow gauges. If it isn’t, and the manifold isn’t getting warm, you’ve got a  blender valve issue.

 

Check and report back !!