UFH stopped working

[H F]

Another stressful afternoon.

 

our ASHP is working... so are our rads. But the UFH has stopped working today (we’ve not touched or changed anything) and I’m stuck in trying to figure where the issue is - how can I diagnose why it’s stopped. 
 

Any help to point me the right direction would be massively appreciated.

[Ian]

The last time this happened to me it was the small 5amp fuse in the UFH wiring centre

[ProDave]

"not working" is a large target to aim for.

 

So lets start with some questions:

 

Is there a timer / programmer if so is it "on"

 

Are there any room thermostats? if so are they turned up?  If electronic ones and clues like "call for heat" symbols?

 

Look at the UFH manifold.  Can you hear the pump running?  Do ANY of the pipes feel warm?  Are there flow meters if so what do they show?  Some types of actuator have a tell tale when open do yours?  Any pressure or temperature gauges? If so what do they read?

[H F]

What do these things do?

[H F]

The reason for asking is because the pipe below it, leading the manifold was cool - above it very hot. It was on auto... when I moved it and hold it to open the pipe below hot instantly hot... 

 

can I leave it on open as opposed to auto?

Edited January 29, 2020 by Home Farm

[ProDave]

2 minutes ago, Home Farm said:

What do these things do?

That is a motorised valve.  When you turn on the UFH that should be energised to allow the hot water to flow to the manifold.

 

It also has a feedback microswitch that may or may not be used to tell other bits of the controls that it is open.

 

If it is not opening when it should, that can either be because the thing that turns it on is broken, or the motor inside it is broken.

 

Do you have a multimeter and know how to use it.?

[H F]

Can I leave it on open as opposed to auto? Do you think this could be the cause?

 

[ProDave]

Just now, Home Farm said:

Can I leave it on open as opposed to auto? Do you think this could be the cause?

 

Try it and see.  If that gets the UFH working then that is progress but is not the problem "fixed"

[H F]

20 minutes ago, ProDave said:

Is there a timer / programmer if so is it "on"

 

Are there any room thermostats? if so are they turned up?  If electronic ones and clues like "call for heat" symbols?

 

Look at the UFH manifold.  Can you hear the pump running?  Do ANY of the pipes feel warm?  Are there flow meters if so what do they show?  Some types of actuator have a tell tale when open do yours?  Any pressure or temperature gauges? If so what do they read?

yes, we have three controllers and our UFH is we be on 24/7. I can confirm they’re all on. All are calling for heat..

 

pipes are warm - as described with the motorized valve.

 

pump is running and all rads are hot.

 

no flow metre... I’ll take a photo of the manifold now...

[H F]

2 minutes ago, ProDave said:

Try it and see.  If that gets the UFH working then that is progress but is not the problem "fixed"

Agreed... how long can I leave it on open for? If that is the issue, does it mean the motorized valve needs replacing?

[H F]

[ProDave]

Those are your flow meters.  If they were full of nice clean water you would see a "float" that rises and falls to show the flow rate.

 

Now you have opened the motorised valve manually, do you feel warmth in the pipes heading off from the manifold down into the floor?

[H F]

I think it is...

 

these plastic pipes run out if the manifold and the UFH I’m assuming. None of the are warm... in fact they’re cool. I assume they should be warm.

 

also noticed only one light on the UFH - it’s really dirty in there.

[H F]

All the lights are back on and the temperature of the plastic pipes is warming up... underfloor heating in the first zone is warming up.

 

so we can assume it’s the motorised valve. Can we?

 

lastly, how long can I leave it on (not auto) until I can replace it? Can I replace it myself or us a plumber better suited for this? 

Edited January 29, 2020 by Home Farm

[ProDave]

You can get a new actuator head rather than changing the valve body.

 

But you don't know yet that is the fault. It could be the controls that are telling it to open are not working.

[H F]

Thanks Dave. Not sure I follow. Which controls do you not think are not telling the valve to open? 

[H F]

Sorry to keep asking, how long can I keep the valve open (not auto)?

[ProDave]

5 minutes ago, Home Farm said:

Thanks Dave. Not sure I follow. Which controls do you not think are not telling the valve to open? 

There are several ways this can work.

 

Sometimes it is the central heating programmer that turns on the UFH and avtivates the motorised valve.

 

Im my last house I had it wired so the central heating programmer energised the UFH control box.  Then IF any room was calling for heat, the UFH control box would open the motorised valve and then the feedback switch on it would call for heat from the boiler.

 

In my present setup, the UFH controller sends a heat demand to the ASHP and the ASHP controls the motorised valves.  This allows it when it wishes, to stop heating the floor and heat the DHW cylinder instead. (you don't normally do both at once with an ASHP because of the different temperatures)

 

I don't suppose you have any documentation how it is wired?

 

You won't break anything by keeping the valve manually opened, but in my case if I did that, then when the ASHP demanded hot water heating, it would potentially senf 50 degree water to the UFH (but the blending valve would reduce that temperature somewhat)

[Ed Davies]

4 minutes ago, Home Farm said:

Sorry to keep asking, how long can I keep the valve open (not auto)?

 

AFAIK, as long as you like but the thermostat won't be operating (you've overridden it) so eventually the room will get too warm.

[Nickfromwales]

5 hours ago, Ed Davies said:

 

AFAIK, as long as you like but the thermostat won't be operating (you've overridden it) so eventually the room will get too warm.

The rooms won’t get too hot because ( assumes ) the room / zone stats will close the actuators when the rooms / zones become satisfied. 
The problem will be that the primary pump and heat source will see the valve as open and keep trying to pump against a zero demand manifold. 
Boiler will short cycle through this but it won’t do it any serious harm. Get the valve changed, and el-pronto  

[dpmiller]

8 hours ago, Nickfromwales said:

 Get the valve changed, and el-pronto  

 

... once you've verified that it's failed and there isn't a supply/ control issue...

[Nickfromwales]

6 hours ago, dpmiller said:

 

... once you've verified that it's failed and there isn't a supply/ control issue...

Oops, should have said repaired not simply ‘changed’. Long day yesterday....  Thanks. 

[H F]

On 30/01/2020 at 07:19, dpmiller said:

 

... once you've verified that it's failed and there isn't a supply/ control issue...

Could you please elaborate on what you mean by supply/control issue?

 

With the valve set to open, everything’s working. On auto, it isn’t. It looks like an old valve. If it’s not the valve, what else should I be looking for that could be causing this?

[H F]

On 29/01/2020 at 23:12, Nickfromwales said:

The problem will be that the primary pump and heat source will see the valve as open and keep trying to pump against a zero demand manifold. 

At this time of year, due to the size of the ufh heating area, we won’t ever have a zero demand, so we’re ok on that front. We just want to solve the underlying cause. 

[dpmiller]

the valve works when it gets a supply of electrical power. You haven't yet confirmed that this is happening. Once you do this than you can confirm that either the valve (it's motor on top) has failed, or instead part of the control circuitry upstream (UFH wiring centre/ stats/ timeswitch/ ASHP controller even maybe)