UFH issue

[Lurchie]

Hi all,

 

Sorry for the long post,

 

I had a whole new system installed last year and I’m at my wits end in trying to get it working properly. At least I thought it was working fine last year but not so much this year.

 

The system installed was:

 

35kW Worcester Bosch Style System Boiler

300l Worcester Bosch Green Storage unvented cylinder

Ground floor underfloor heating 7 port manifold setup as:

 

Utility and Downstairs Bathroom - 2 loops but controlled as one zone (shortest runs)

Kitchen - 3 long loops controlled as one zone (longest runs)

Lounge - 2 loops controlled as one zone (medium runs)

 

Floor was dug up in all these areas so was redone as following layers, concrete, dpm, 100mm celotex, dpm and underfloor pipes installed on top with around 65mm of liquid screed.

 

Everywhere but Lounge has floor tiles.

Lounge has carpet with UFH compatible underlay.

 

Boiler is set to between 65 and 70 Degrees and setup as S plan with 4 Honeywell valves:
1 controlling radiators in loft conversion,

1 controlling 3 rads on ground floor and 9 rads on first floor

1 controlling hot water

last one runs through to the UFH manifold, which is then connected to a heatmiser UFH wiring centre and Hive stats.

UFH flow has been set more or less to design (1l for shortest runs, 2l for medium runs, 2.6l to 2.9l for longest runs) but have tried tweaking up, but a couple of them are stuck, one is currently stuck at 5l and is sticking there even when I fully close and open it.

 

UFH has a grundfos pump and mixing valve set to around 54 degrees and the flow and return temps don’t seem right to me. I’ve read people keep the mixer at around 40 degrees, but at that level nothing heats up at all for me. The flow and return temps are 48 degrees and 32 degrees according to the flow and return gauges, even though the mixer is set to 54 degrees. Actuators I have are wax actuators.

 

The main issue I’m having is the UFH is taking a long time to heat any of the rooms, I understand the carpeted room would take a while and that’s factored in but the kitchen would normally start heating up within 45 mins of switching on last winter but i’m having to switch on for 3 or 4 hours and even then I just about get up to between 18 or 19 degrees from around 16 or 17 degrees. Also, last year the kitchen floor was warm to touch, but not this year.

 

One issue I’ve noticed that I’m having is randomly the UFH makes a grinding noise and the flow gauges start bouncing around all over the place but can’t explain when or why specifically that is happening. It happened once last year and has happened several times already this year. Could that be air in the system?

 

I’ll upload pictures of the setup and a vid of the UFH pump going wild if possible.

 

I’d be extremely grateful if you all could help me understand what the bouncing flow and pump sound is and let me know your thoughts on whether think something isn’t quite right with my system. 
 

My plumber who installed it is not entirely sure what might be causing it and can’t get out to me for a while hence why I’m trying to see if I can identify the issue ahead of him coming out.

 

Thanks,

 

L

 

 

 

[Lurchie]

Links to videos of pump and flow gauges bouncing:

https://www.dropbox.com/s/rknzxfp35ky75y9/VID-20221130-WA0004.mp4?dl=0

 

https://www.dropbox.com/s/fihzsigz8g81jx1/VID-20221212-WA0005.mp4?dl=0

 

Additional picture of UFH manifold and setup:

 

 

Edited December 14, 2022 by Lurchie
Added videos of issues

[AliG]

Keeping it simple.

 

If the heating is off, do all the gauges return to 0?

 

If one stays at 5, I would guess it is stuck as its pretty much impossible for the water to be flowing with the heating off.

 

Is the "grinding noise" more of a groan. One of my blending valves has started to make that noise at it opens and closes. Does not affect the operation of the heating. Does turning the blending valve a bit stop the noise?

 

We run ours at high 30s-40, 54C is pretty high and the floor should definitely be warm.

 

I don't have a return gauge on mine, but a 16C drop seems excessive. Are your flow speeds maybe set too low. Mine pretty much just run at the maximum speed.

[Lurchie]

Thanks Ali,

 

when it is all switched off, all but one return to 0. The one that is stuck at 5l right now returns to zero, but the one next to it sticks at 1l. I’ve also had a dodgy flow gauge which opens up completely and shoots water everywhere If not careful, I think the threads on that have gone and it’s quite dangerous!

 

I’ve uploaded a a couple vids of the grinding or groaning noise in my 2nd post. Turning the blending valve doesn’t stop it.  First time it happened last year the vibrations were so loud, I thought the boiler or something was going to blow and so cut the power at the mains to the boiler. By switching off heating completely using Hive control stops it from bouncing and making that noise. It sounds like it’s trying to purge air but I’m no expert.

 

Images of flow and return temps on UFH included also. I thought the 16 degree differential didn’t seem right either but not sure how to fix all of this.

 

Appreciate your quick response.

 

Cheers,

 

L

[AliG]

@ProDavemight chip in, he knows a lot more about plumbing than me.

 

I think it is maybe air in the system, although maybe the pump is broken.

 

The pump is supposed to bleed automatically.

 

To bleed the pipes, if you look at the manifold, there is a small black plastic cap on the RHS at the end of the manifold. Open this up until water comes out just like bleeding a radiator. The pump will need to be running. Depending on the make the cap should be left open as it might auto bleed.

 

[ProDave]

Is it doing that "bouncing" all the time?

 

I've not seen anything like that it is too regular and too harsh a noise for it to be air passing through, so my though is a mechanical failure with the pump.

 

@Nickfromwales is the proper plumber around these parts, I wonder if he has seen this before?

[Lurchie]

Thanks both,

 

Ali - when you say small black plastic cap, do you mean the little bleed valve on the image you’ve cropped? I did open that up the other week as my plumber mentioned that, but it didn’t seem to do anything, I didn’t get any water come out of it, but I can’t remember if I opened it up whilst pump was on or not, so I’ll try it again.

 

ProDave - it doesn’t happen all the time, it happens randomly and I can’t find a pattern, which is frustrating. First time it happened last year was when I’d switched the heating off at the end of the evening after it’d been on for a couple hours, but couldn’t explain what it was to anyone as it caught me by surprise. The times it’s happened this year are random but I managed to capture a few vids, it’s happened when the Lounge UFH zone was on for around 20 mins andI could hear the vibrating noise from upstairs so went and checked.

 

It’s also happened when the kitchen zone was on for an hour or two and I went and increased the mixer valve temp up slightly because it was taking an age to heat.

 

It’s happened other times on other days but not always captured recordings. It also depends on whether I hear the vibrating sound coming from the utility where it’s all housed to make me go and have a look at what’s happening. For all I know it could be happening at other times but I may not have noticed.

 

I have to have the UFH on for about 8 hours to try and reach a reasonable temp of 18 - 19 degrees. 4 hours for the kitchen and and around 4 hours for the lounge almost separately. It struggles to do both together and so it’s costing me about £15 - £18 per day in gas alone, when you include the upstairs rads too, although I appreciate it’s a lot colder right now, but I’m certain it didn’t need that long last winter and it reached much higher temps than 18 or 19 deg.

 

Would air or a faulty pump cause it to struggle to heat? Is that a reason for such a big differential between flow and return? Is the boiler temperature set to 65-70 degrees fine? Trying to work out if it’s all one linked issue or a separate issues.

 

Appreciate the help so far.

 

Sorry, I’m not very technical with heating systems so just picked things up as the system was being installed and using it, so I don’t fully understand the deep workings of the pump, mixer valve, flow and return temps etc.

 

My plumber doesn’t look to have come across this issue either and I’ve asked a few others and they’ve not come across it either, so doesn’t look like a common fault.

 

Cheers,

 

L

[AliG]

My guess is that the water is no longer properly flowing around the UFH loops hence it takes too long to heat the rooms and the massive drop in temperature whilst it is in the loops.

 

Sounds like you have bled the loops already so not air.

 

As @ProDave says it sounds like the pump is trying to turn and hitting something so maybe bouncing back.

 

Does it ever run now without this happening?

 

I did find a thread somewhere where someone said a broken flow valve like you seem to have was causing issues and replacing it fixed things, but I don’t see how it would affect the pump.

[Nickfromwales]

Just watched the videos!! Never seen that before, something seriously wrong here. 
Credit to the plumber, it’s a neat conscientious installation, but maybe technical / hydraulic issues are at play.

Firstly, I would not have put all these segregated heating loads ( a couple are very small ) onto a gas system boiler without proper hydraulic separation. The 4 zone valves will all be sucking water at massively different L/p/m flow rates, and the UFH pump will be getting ‘pushed’ by the pump in the boiler. It’s all very hydraulically unbalanced. Yes there’s a bypass, but it’s not designed to be used in such an adverse way imo. 

 

Your plumber will need to install, firstly, a small buffer tank or large low loss header ( LLH ) to allow the boiler to fire > pump to that hydraulic separator > return back itself without ‘seeing’ any of the heating circuits directly. That will remove the push / pull factor here which I think is the start of the issues.
 

In the boiler installation guidelines, most will state that the appliance shouldn’t be installed; where it would be subject to / unless measures have been taken to avoid, short cycling. With the segregation you have here, you’re on the borderline or just the wrong side of it. 
 

Next thing to do is to remove all the actuators and run the system again without them fitted. With the actuators removed the loops will be free flowing. The thing causing the water hammer ( loops and pumps to ‘jump’ ) will be the actuators ( I believe ) so I’d like to see them out of the picture to see what effect that has. So, @Lurchie, please do that and run the UFH on its own and report back. Turn all UFH stats to maximum and tell us what happens. 

Edited December 15, 2022 by Nickfromwales

[ProDave]

15 hours ago, Lurchie said:

I have to have the UFH on for about 8 hours to try and reach a reasonable temp of 18 - 19 degrees. 4 hours for the kitchen and and around 4 hours for the lounge almost separately. It struggles to do both together and so it’s costing me about £15 - £18 per day in gas alone, when you include the upstairs rads too, although I appreciate it’s a lot colder right now, but I’m certain it didn’t need that long last winter and it reached much higher temps than 18 or 19 deg.

I think the high cost is the weather, not a "fault"

 

If the UFH is failing to deliver enough heat to the rooms, then it will use less gas.  If it is burning a lot of gas the heat has to be going somewhere.  Don't confuse the higher cost of gas per unit with thinking it is burning more gas.

[SteamyTea]

12 minutes ago, ProDave said:

I think the high cost is the weather, not a "fault"

There is quite a difference this year from the long term averages.

 

[Nickfromwales]

North of £6k for gas points to a poorly insulated home, and an in efficient system. 
Nothing wrong with the boiler choice here, and assume radiators are modern convector radiators? 
Trickle vents on windows open? 
What insulation is in upper floors? 

[Lurchie]

Thanks all for your help so far.

 

So the system does run and works to an extent, the bouncing flow gauges or water hammer as Nick has called it happens randomly and when it does happen, the system won’t work. The times I’ve seen it happening after a minute or two of watching it, I’ll switch if off and let all the actuators close and then try and switch it back on again. I’ve never let it just play out fully to see what if it just continues or stops. Switching it off and waiting and trying again usually sorts it out. It’s so far not yet happened consecutively from what I can remember, but it’s happening almost daily now.

 

Ali - that stuck flow gauge at 5l is stuck there now since yesterday. It wasn’t stuck before yesterday but after you asked, it’s been stuck in that position when the heating is on and off, even if that zone is on or off, or any other zones. 

 

Nick - thanks for your suggestions, I’ve let my plumber know about the need for a buffer tank or low loss header. The hydraulic separation part is starting to get a bit too technical for me, but will try and read up some more. I will try everything you’ve mentioned and come back to you with the outcome once we’ve tested it.

 

Radiators are K Rad Aspen double sided designer radiators. We checked the btu output were right for each of the room sizes.

 

No trickle vents on windows, we’ve got some air bricks and the standard vented fans in the bathrooms.

Walls are solid brick but had insulated plasterboard on external walls.

 

I had mineral wool insulation placed between the joists of all the rooms when ceilings / floors were open, not sure if that would do anything but had it done anyway. Kitchen extension has 100mm celotex in the ceiling and cavity slabs in the walls. Above all the ground floor rooms are heated rooms except for the the kitchen extension part which doesn’t have a room above, just an insulated vaulted ceiling, but should be well insulated to building regs.

 

Loft is insulated but was done years before we bought the house and probably needs topping up.

 

Loft conversion ceiling is insulated, builder had checked, but it was the only ceiling we didn’t open up fully. Again this was done when previous owners had the loft converted 15 or 20 years ago, so might not be to current standard.

 

Despite all of this, it still feels cold to me, but that might just be me as a person or the fact I struggle to heat the house in a reasonable amount of time. In this current cold spell I lost about 2.5 degrees of heat (measured by first floor hallway stat) in 5 hours last night after the heating switched off at 9pm (9pm to 2am), but it was somewhere between minus 5 and minus 7 last night. Kitchen lost about 2 degrees in that time and Lounge lost around 1.8 degrees. Not sure if that’s good or bad or if that helps but doesn’t seem too bad to me, it’s just getting it up to the right temperature which is killing me.

 

Might be a how long is a piece of string question, especially with variations in how well insulated homes and floors are and floor finishes etc. but roughly how long should UFH take to heat up? When speaking to friends who tell me their floors heat up in 15 mins and rooms are warm withinabout an hour, my 4+ hours seems excessive. It makes it difficult to control, as I need to plan well in advance if I am going to sit in the lounge that evening or not. For example right now I’ve had the lounge on for 3 hours so far this evening and I’ve gone from 16.3 degrees to 17.5 degrees in that time.
 

Since we’ve moved in last September the 2 largest UFH zones (kitchen and lounge) don’t like to be on together, the flow gauges drop from around 2.5l where most are set on average, down to 2l or 1.5l and heat up time takes even longer, which again doesn’t feel normal to me but I have zero experience or anything to compare against.

 

Uploading a plan of the UFH design if it helps as more information. Just ignore the dining room tag, that’s actually the hallway, I assure you I haven’t got a dining table right in front of the front door!

 

Thanks again for all your help and apologies for yet another lengthy post!

[AliG]

UFH can take a long time to warm up depending on many factors. Insulation levels sound ok based on the temperature drop you are seeing.

 

Looking at my house rooms with tiled floors see very quick response to the UFH, but rooms with wooden floors can indeed take hours to heat a few degrees, they easily take 5x as long. However my flow temp is only set at around 40C.

 

If the pump was broken it would likely not reset by switching it off for a while so it seems @Nickfromwales is likely correct.

 

There is definitely something wrong with your system if it doesn’t like the kitchen and lounge being on at the same time. Again it suggests some issue with flow not being sufficient in the loops. I’m not sure but I doubt there is much benefit from trying to optimise the flow to the minimum level necessary.

 

My system with multiple manifolds as well as heating the hot tank and a pool has a low loss header.