Unsure if wet UFH is working - advice on diagnostics needed please.

[Darkwind82]

Hi, I’m hoping someone can help – I need a bit of advice / help as I'm not sure if the recent cold spell is too much for the UFH in the main living space (it's a barn conversion so 25ft high vaulted area) and I've checked all I can think of. It's 15 degrees despite all looking to be OK to me (except flow indicators on the manifold), but cannot recall it being this cold inside before.

There are radiators in other rooms / a mezzanine area that are fed from the same boiler and they are working fine, so I used my limited knowledge to try and verify if the underfloor is actually working (I was a certified electricians some 25 years ago, and also been an electronics bench engineer – but have no direct professional experience with UFH or plumbing past tap washers!).

The UFH system is two-zone (dining and kitchen), controlled by a Honeywell Evohome HCC80R (which is working fine as I’ve tested and the respective UFH actuators receive 240v when the zone lights come on).

The pump is also working fine (after reading the manual I switched it to constant running briefly and heard / felt it run when on high), and the two port zone valve also operates (I’ve heard it operate, and also tried sliding the control leaver to manual).

The manifold under the flow indicators and under the caps of the actuators is hot to the touch (to the point where you cannot hold your finger on the metal too long), but the flow indicator balls never drop and remain at the top 0L/ min position. The PVC pipes going into the flow indicators are hot, but the ones below the actuators all remain tepid / cold to the touch.

This morning I also unscrewed the Uponor thermal actuators and depressed the pins manually (also tried with the pump and two-port on manual) - no change to the flow indicators.

I’m not sure what else I can test / check as my knowledge is pretty limited to the electrical side of things, but the floors feel cold and I cannot deduce if it is working and just struggling with the cold this year given the amount of space, or if I have a problem. It was working in the autumn as I remember the floors getting warm when I turned the heating back on after the summer, but in all honesty I paid no attention to whether the flow indicators moved or where they sat, sadly.

My wife is extremely reluctant to having anyone in at present unless it is an emergency so I have reached out to a few UFH engineers offering to pay for thier time if they can offer some insight / assistance to me remotely - sadly all have declined. Not knowing what else I could do I thought I'd try posting on this forum in the hope of some experienced insight / help. I have annotated some photos below in the hope that helps, and happy to try things / take pictures and answer any queries as needed....

Currently I'm left wondering if the flow indicators are just silted / stuck and it's actually working, or if the pipes have somehow frozen and so are blocking flow on all circuits - but I have no idea if either can / generally do happen, it's just guess work as I have checked things out as far as my knowledge / experience permits.

Many thanks to anyone that replies, as I really am between a rock and a hard place on this.

 

[Brambles]

I take it that the system has been modified post installation?

 

[Darkwind82]

Hi, in short no idea - we haven't done anything other than have the boiler serviced ans a zone valve replaced on the cyclinder a couple of years back, but don't know what the previous owners had done or when. I think the original install would have been 1998 so possible / likely I suppose. Nothing has changed or been done since it was heating the floors in the autumn, hence in part the mystery. Thanks for replying, happy for any input right now 🙂

 

[Gasmk1]

Is the pump. For the underfloor manifold working you will not get any heat through if it isnt

 

[Brambles]

The UFH pump is the Wilo pump on the left hand side of the manifold. I guess that is not working - normally the flow and return would enter on to the UFH pump side with the blending valve - with the right hand side of the manifold blanked off or for future expansion.

From your photo there appears to be a hole in the floor beneath the Wilo pump where the pipes previously entered.

I assume therefore that the original ( normal) configuration has been modified

In short if the flow gauges are not moving on all circuits you have no flow which is either the UFH pump ( which should be running and hot), pump controller or possibly (but unlikely) an airlock.

A decent heating engineer should be able to talk you through it on the phone if you don’t want a visit.

 

[Darkwind82]

Is the pump. For the underfloor manifold working you will not get any heat through if it isnt

The pump on the right is the one I assumed was the circulating pump (with the left one being some kind of pressure relief system???). The one on the right is a Grundfos Alpha2 L - Power light is on and when I use the > button to advance through the modes to III (which from the manual is constant on / manual rather than one of the automatic modes) I can hear and feel the pump operate, but still no flow on the indicators (even if I remove the actuator head and manually depress the pin). When on constant mode the pump makes a soft hum and you can hear the ticking noise from the pipes like when you open a TRV on a traditional radiator). Obviously cannot be 100% sure - but pretty confident the right hand pump is working.

 

[Darkwind82]

Sorry - was replying to the previous post - my assumption is clearly wrong based on that and it is the left side pump that is the circulation pump (the Wilo). It is a Wilo Yonos PARA 4524650 (RS15/6-RKA M) acording to the label. I'll go see if I can find a manual to see if there are any lights that should be lit, etc. - thank you.

The 'hole' in the floor is actuall paint on the tile - so just the photo BTW 🙂

 

[Brambles]

If the UFH is set to on and the room stat to a high temperature, the Wilo pump should be working ( if it is working it will be hot) - if it is not working, check for a 240v feed. If it is not present “bell” back to the control unit to determine what is blocking it (overheat stat, room stat et al).

If you have an electrical feed and the pump is not working - it may be seized.

If you are not confident with a multimeter on live circuits get a heating engineer in

 

[Darkwind82]

If the UFH is set to on and the room stat to a high temperature, the Wilo pump should be working ( if it is working it will be hot) - if it is not working, check for a 240v feed. If it is not present “bell” back to the control unit to determine what is blocking it (overheat stat, room stat et al).

If you have an electrical feed and the pump is not working - it may be seized.

If you are not confident with a multimeter on live circuits get a heating engineer in

Hi - thanks so much for the help - thankfully the time as a bench engineer and my electrician's training (albeit years ago now) have the one thing I am happy with being a multimeter and OI still have a decent Fluke from way back.

I have scoped out the connections, essentially I have a hot 240v supply coming out of the switched spur, but 0 volts at the pump (that accounts for the cold feet lol!). I've sketched up what I have in the image below, so it seems (B) is killing the supply (would that be the overheat stat or pressure sensor of some kind??).

The image shows the pressure, so would it be safe / OK for me to try bypassing (B) just as a test for a few minutes to see if the pump lights?

Thanks again - I hate things I don't understand!!

 

[SJB060685]

B is an overheat stat to prevent excessive heat and damaging of screeds/floors. For testing purposes yes you can link out to see if pump runs but only for testing purposes. Afterwards you should reinstate it.

 

[Darkwind82]

Fantastic and understood - test only. Thank you!

 

[Brambles]

What is the temperature of the pipework around B in its current state - ie before you start to loop out the thermostat?

 

[Darkwind82]

I happen to have an IR / laser gun thermometer - I am getting between 28 and 30 degrees C on the brightwork below (B), the upper manifold (under the flow gauges) and the exterior of the copper infeed pipe to the upper manifold.

 

[Brambles]

The obvious answer is that the overheat thermostat or the thermostatic mixing valve (TMV) has failed. The overheat stat operates to prevent water of more than 55 degrees C entering the UFH system - but the flow temperature limit setting is adjustable at the controller so could be significantly lower.

The TMV limits flow temperature by blending the incoming flow temperature.

However, from the description of your first post you seem to be getting flow across the manifold when the UFH pump is off - you said that the top branch of the manifold is hot but the lower branch is cold. That seems to indicate that the control valve is passing and that you are getting a secondary reverse flow of unblended boiler flow water. If that is the case you could get water at a higher temperature than 55 degrees (or whatever the overheat stat is set at) reaching the overheat thermostat, which could / would trigger it to operate.

The control logic for your system to operate correctly is that the control valve on the lower right of the manifold opens to allow the boiler flow to enter, it passes through the thermostatic mixing valve with the external temperature sensor and blends with the return water from the UFH, it reaches the pump, is pumped and passes though the overheat thermostat (limited by its setting - see above) then enters the UFH system - which can be seen by the balanced flow valves, after the last balanced flow valve has been satisfied the flow becomes the return, which should be direct, back to the boiler.

In essence if you are getting seepage from the control valve, with the Wilo pump not running, the lower part of the manifold should be hotter than the upper part.

In your case there appears to be an installation configuration issue that may be allowing a secondary reverse flow when the UFH pump is not operating

If everything is operating correctly, when the Wilo UFH pump is off ( after a reasonable period of time) the top and bottom of the manifold should be cool.

You have probably not got complete hydraulic separation between the two pumps - replacing the thermostatic mixing valve and reconfiguring using an injector valve would resolve that.

Hope this all makes sense

 

[Darkwind82]

Hi Brambles, thank you so much for taking the time to post all the replies - I have never really understood the flow and now I do (OK, it took me a couple of reads, but it's crystal now and what you've suggested regarding seepage also makes complete sense).

I have tested with the hi limit stat bypassed; the Wilo energised and we got good flow. The external temps on all pipework did not exceed 32 degrees during the 10 minute test, and the pressure gauge remained within 10-15% of the pointer's original position. I have since reverted the connections so the stat is back inline with the Wilo, and as expected the pump / flow has ceased.

I've ordered a new stat this morning as swapping it out seems the easiest / quickest way to see if it is actually faulty.

If the new stat allows the pump to run then the plan currently is to run it for now, but keep eye and still get a specialist / engineer in to check for the issues you suspect / do a general check or service later in the year (when hopefully circumstances are a bit better). If the new stat still prevents the pump from running then clearly the issue is more urgent and we will have to decide whether we try to find someone to look at it right away, or manage without the underfloor for a bit.

A big thank you to everyone that replied, it's a huge help and aside from the issue I am much more at ease just having a far better understanding of how it should function and what the various bits do in the system. Everything south of the controller was a bit of a mystery until yesterday!!

 

[SJB060685]

@Brambles I had spotted the piping by the system pump and was a tad confused to be honest.