Wet ufh. Not all rooms warming.

[JDAB]

Hi, hoping for a little advice.

 

After switching on my ufh I’ve discovered that two rooms in our bungalow aren’t warming. The system was installed before we moved here (just over 10 years ago) but we haven't altered anything in that time.

 

Upon closer inspection I found that the two actuators, linked to the thermostats in those rooms had stayed closed. I removed them, tested the pins (which all tested similarly to the others, firm but they do move) and re-attached. Voila! (I thought) as they slowly rose up. However, after several hours, no heat came to the rooms…

 

I’ve tried testing each non-working thermostat in isolation by turning them to max but no joy. I can’t feel heat coming from the supply pipes leading to those rooms either but the actuator tops do get warm. I’m wondering, is if this all sounds familiar to anyone? And is it something can resolve myself? Or am I in, call out a professional territory?

 

We did have a new boiler fitted around March this year. Though we haven’t had any problems with it.

 

We also had a small leak coming from the return area of the manifold. This was repaired shortly after boiler was fitted by the same person. I have no idea how long we had the leak but when I did find it, it was a single drip every 30 seconds or so.

 

Attached photos of the set up. And one (where i'm pointing) from when I noticed the leak.

 

From left to right on the manifold, the seven connected rooms are performing as follows:

 

O - NW - W - W - NW  - NW - W

 

(O = Off, W = Working, NW = Not working)

 

I do have Bosch AdvancedTemp Infrared Thermometer. Incase it help with fault finding.

Thank you for any help in advance.

[JohnMo]

Take the actuators off on the not working loops, does the flow meter move down (the red lines). Removing actuator opens loop, regardless of call for heat.  If this resolves issue you have an issue with electrics.  If nothing changes you have an issue with air in the system, get the plumber back to bleed the loops.

 

Takes all the junk off the UFH loop pipes. Look to box in, so they don't get damaged.

[Gus Potter]

32 minutes ago, JohnMo said:

If nothing changes you have an issue with air in the system,

Agree a bit of air can cause havoc. 

 

One way to purge this is to shut off the other loops and open the air vent. You'll need a bucket and a few towels to catch the water. 

 

Give it a good go and don't forget to top up the inhibitor once you have finished. 

[JDAB]

Hi, thanks for the replies. Really appreciated. Sorry for the late response, my daughter isn't well so I've been preocupied.

 

JohnMo, I've taken off the actuators and the red markers don't move. Should they start moving soon after removing, or should I leave them for a few hours to be sure?

One thing I have noticed is that, although the pins move, the part that surrounds them (sorry I don't know what that's called) is much lower down than the working ones. Photos attached.

Gus, I'm trying to find a manual on the system but finding that difficult. I haven't had to purge the sytem before so not sure what I'm doing.

The plumber that fixed the system is no longer available unfortunately. Trying to save myself a little money and fix myself if it's straight forward enough. Watching videos online it seems pretty easy other than re-pressurising.

Thanks again.

Edited Wednesday at 13:55 by JDAB

[vala]

If you need a guide for purging air out of the loops, we have done it using the method describe in this manual from Wunda.

Noticed a fair bit of air coming out even from loops we thought had been fully purged.

May be worth a try.

https://www.wundagroup.com/wp-content/uploads/2019/10/M07-generic-Wunda-premium-Manifold-25-4-2018.pdf

[JohnMo]

38 minutes ago, JDAB said:

JohnMo, I've taken off the actuators and the red markers don't move. Should they start moving soon after removing, or should I leave them for a few hours to be sure?

The red marker move down to. indicating flow had started. They move in response to water flow. 

 

The brass thread section with the pin at the centre sets your flow rate. Would assume screwing upwards increases flow. So it may be worth screwing outward (take note of how far you move in number of turns) watch the red marker if that starts to move that may be your issue.

 

If the red marker hasn't moved after a few of turns that isn't the issue. You are most likely looking at air in the loops.

 

To get things moving. Go round each room and turn off the thermostats (or set to lowest setting), once all are off the pump will stop. Now go to one problem room and set the thermostat on. Pump should start. Open bleed on manifold top rail (white radiator bleed thing - top left). It may spray water so slowly open have a towel handy. You may have to open and close a few times. Once the loop starts running, leave for 5 mins. Close the demand at thermostat. Repeat for each problem loop. Report back.

[JDAB]

Will report back. Just to quickly add. The pins that were moving (i'm sure of it) are now solid. I noticed because I was finding it very difficult to put the actuators back on.

[JohnMo]

35 minutes ago, JDAB said:

Will report back. Just to quickly add. The pins that were moving (i'm sure of it) are now solid. I noticed because I was finding it very difficult to put the actuators back on.

I would unscrew the brass bit and see if that frees things up the brass bit may be so far down they have fully closed off flow and pin has nowhere to go?

[JDAB]

You were correct about the pin. After I raised the height, the pin moves freely. I set it back to how it was calibrated. The red flow marker didn’t move though.

 

On 03/12/2025 at 14:46, JohnMo said:

The red marker move down to. indicating flow had started. They move in response to water flow. 

 

The brass thread section with the pin at the centre sets your flow rate. Would assume screwing upwards increases flow. So it may be worth screwing outward (take note of how far you move in number of turns) watch the red marker if that starts to move that may be your issue.

 

If the red marker hasn't moved after a few of turns that isn't the issue. You are most likely looking at air in the loops.

 

To get things moving. Go round each room and turn off the thermostats (or set to lowest setting), once all are off the pump will stop. Now go to one problem room and set the thermostat on. Pump should start. Open bleed on manifold top rail (white radiator bleed thing - top left). It may spray water so slowly open have a towel handy. You may have to open and close a few times. Once the loop starts running, leave for 5 mins. Close the demand at thermostat. Repeat for each problem loop. Report back.

I’m going to try this next. Couple of questions (sure they’ll sound daft):

 

You say I may have to open and close the bleed a few times. Will it be obvious when to stop? Guessing it’s when the water stops?
 

Regarding the loop starting running. How will I know? Because the actuator is already warm & lifted. Am I looking to the flow marker?

 

Also, I’ve attached a top down photo of the bleed. I've turned the plastic white part left & right 360 degrees but nothing happened, so I assume I need to turn the brass part shown instead?

 

Edited Thursday at 14:56 by JDAB

[JohnMo]

47 minutes ago, JDAB said:

Guessing it’s when the water stops?

No when it starts, air will come out first. It should collect at the high point.

 

48 minutes ago, JDAB said:

How will I know

The flow indicator will start to move 

 

49 minutes ago, JDAB said:

I've turned the plastic white part left & right 360 degrees but nothing happened, so I assume I need to turn the brass part shown instead?

You need a screwdriver turn the brass bit. Water/air will come out the plastic bit - there should be hole.

[JDAB]

Sorry, I meant 'water starts'. 🫠 I see the little hole (photo attached). Will try and find time to test later, if not tomorrow. Still in nursing mode.

Thanks again for the help.

 

Edited Thursday at 15:53 by JDAB

[JDAB]

Reporting back.

So I shut off all thermos except for a problem room. Waited around 10 minutes. Turned on a problem room thermo and waited for its actuator to rise.

Using a radiator key I began the bleed. Warm water began slowly coming out of the little hole. I turned it a little more until it lifted to an arching stream and then closed it. I didn't hear any air. And the stream of water didn't splutter at all. It was a steady. I closed it after each bleed within about, 5 seconds.

Results:

 

Problem room (1) Bedroom.

Flow marker didn't move.

Supply pipe warmed to around 26 °C

Actuator rises and warms.

Pin moves.
Tried increasing flow by two full turns.

Termo gun reads the floor temperature between 13-15°C which is the same as a similar room with the heating turned off.

 

Problem room (2) Living Room (Thankfully we have a wood burner in here!)

Flow marker did move a little. From 0>2 Also noticed it bobble when I powered off/on the ufh system & boiler.

Supply pipe warmed to around 26 °C

Actuator rises and warms.

Pin moves.
 

This room did warm, but after I wasn't calling for heat! This really threw me. I can only assume that the pin hadn't been pushed down properly by the actuator (which was closed). Rather ironically at this point I was worried I wouldn't be able turn it off. I removed the actuator. Called for heat so it rose. Replaced it and turned the thermo off again. This closed it and the floor eventually cooled.

I haven't tested the living room again yet as I wanted to be sure it was cooling fully. The floor (laminate with underlay) warmed to around 19/20°

=======

Things i'm wondering:

 

Could the flow makers be stuck? If I understand correctly they only display the flow level but have no effect on the actual flow. This is set by turning the brass 'bit' under the actuators. Even if I power everything off they flow markers stay in the same position.

Is it safe to spray the pins with a little WD40? Just to be sure they are moving freely.

 

Could the thermostat in the bedroom be faulty even though it clicks when I turn it up. And its actuator rises?

Does the pressure reading confirm there is enough water in the system?

Am I correct in thinking that the further a pin moves, the more flow a room is getting?

Sorry for all the extra questions. I'm trying to ask the right things to help rule things out.
 

Edited 18 hours ago by JDAB

[Nickfromwales]

These are the ‘stems’ around the pins, and the square head of the stem allows you to rotate the body of the valve; further down = less flow > no flow if fully seated.

 

 

How old is this setup? 

[JDAB]

System was installed around 2010. before we moved in.

[Nickfromwales]

15 minutes ago, JDAB said:

System was installed around 2010. before we moved in.

After 16 years of constantly moving / doing its thing, don’t discount the possibility that the components (which don’t last forever) are nearing / at “end of life”.

 

Stripping and cleaning / servicing will likely just start these stems and flow gauges leaking, as they all rely on tiny rubber O-rings which eventually just go D-shaped and give up.

 

If you want trouble free motoring, judging by the multiples of issues arising, I think it’s time for an upgrade and a new manifold / pump set. 
 

You may be able to retain the actuators as these are all pretty standard fitment.

 

Depends on budget, and whether you’re happy to just keep putting band-aids on this to get through winter.

 

Cheap option: LINK

 

Best option: LINK

 

Up to you if you want to spend time / money (good after bad) treating a terminally ill bit of equipment. 

 

Ask Santa maybe 👀🤞

 

Also, just to cheer you up a bit more in early December, if your room stats ‘click’ are they rotary dial type (Honeywell?) basic stats? These are quite crude for use with UFH (huge hysteresis), so you may want to consider upgrading those too if over/under-shoot is an issue; rooms get too hot then too cool instead of one steady temp for eg? 

[JDAB]

Thanks Nick. Hoping to band aid things for now as Santa's already starting to feel the pinch 😆

Cheers for the links though. They will come in handy i'm sure.

The Thermostats are rotary, yeah. Damfoss. Except the living room which I replaced with a google nest-e a year ago. They've performed fine since we've been here. But it has been on my mind to upgrade them.

My thoughts were that perhaps the bedroom one had died. It is talking to its actuator. Thought that perhaps it wasn't reading the room temp though?

Whats confusing me is that the temperature of the supply feed to the bedroom, is the same as the temperature to the bathroom, which is warming just fine. All the others are off at the moment, so a much cooler.

 

Thankfully it's a little milder outside this evening.

 

Edited 16 hours ago by JDAB