Operating Underfloor Heating

[SpecialK]

I cant work out where the screed would have gone. Did it just fill from the insulation to the tops of the joists? Then the 18mm chipboard spanned over the joists?

With my system the boiler was sending water through the internal bypass valve rather than the UFH manifold. This made the boilers loop get up to temp very quickly. It then went into an anti-cycle mode for 5 minutes and in that time the UFH had sucked all the heat from the boiler and didn't heat the pipes properly.

How long does it take between 45 degrees being at the flow until 45 degrees appears at the return?

https://www.theunderfloorheatingsto...eating-for-between-joists-or-suspended-floors

@Nozzle the flow for both loops is set to maximum, the installer appears to have capped the temperature blender as it only turns to 4.5/6 which translates to about 48degrees on the flow. I've been requesting 21degrees on the room thermostat for days but it has never managed more than 19degrees in the room. The link you sent shows a higher temperature of 55-60 for timber! Over the screed we have 18mm chipboard, plywood (not sure of thickness) and then the karndean vinyl so I don't know if it should be in this higher range due to all the wood.

The red valve is only a quarter turn valve, I'm at a bit of a loss when it comes to reasons for a bypass / throttling etc.

@SpecialK our boiler is a newly installed Worcester Greenstar24ri, I've not looked at how it's behaving when the UFH calls for heat or what a cycling issue is I'm afraid. As mentioned above the screed is cement/sand I believe, then 18mm chipboard, the karndean installer laid ply and vinyl on top. From what I've seen the return temp and flow temp almost always read within a degree of each other which concerns me. I have tried reducing the flow rate to see if that changed anything but it didn't help. How would you normally increase heat drawn from the pipes?

 

[nirish]

@Exedon the ceiling peak height is 4.2m which runs the longer length of the room, it slopes down to 2.5m on the two longer exterior walls.

@SpecialK I didn't see the entire process but I did see them shovelling in the screed. I can only assume you are right as it went over the insulation/pipework but can only be enough to reach the top of the joists. Is this not normal?

As for the timing of the flow/return temps, I'll have to have a look after it's been off when I get a chance, but I haven't seen it where they are more than a degree apart anytime I've looked.

 

[Exedon]

Just looked at heat output at 200mm spacing at mean water temperature of 45c W/m2 = 65 x 28 = 1820w
Screed system generally have a 65 -70 mm thickness I've my doubts you have that.
Not got time to run heat calculations at moment but I wonder if you have enough output.

 

[nirish]

This is sounding grim! I wonder if heat loss calculations were ever done or if they just put in the standard amount of piping for a normal height ceiling. Nothing back from the builder yet.

If I am short of wattage output which I've been suspicious is the case for a while, are there any options in terms of adjustments? Simple temperature increase? I can't even contemplate having to rip it all up!

Assuming the screed layer is also too thin what's the effect? Flooring doesn't retain heat as well as it should?

 

[SpecialK]

You need to be slightly careful with increasing the temp as the LVT shouldn't exceed 27 degrees.
The pump - can you set that to the last setting? That should be for UFH although yours doesn't appear to have any pictures on it.

Is there any kind of flow indication on the manifold? Are they flowing about the same amount?

Any chance of running a radiator from the flow return at all?

What kind of insulation was put in the vaulted ceiling? 100m between and 40mm PIR over boarded?

This is sounding grim! I wonder if heat loss calculations were ever done or if they just put in the standard amount of piping for a normal height ceiling. Nothing back from the builder yet.

If I am short of wattage output which I've been suspicious is the case for a while, are there any options in terms of adjustments? Simple temperature increase? I can't even contemplate having to rip it all up!

Assuming the screed layer is also too thin what's the effect? Flooring doesn't retain heat as well as it should?

 

[nirish]

@SpecialK is there anyway to monitor the temp of the LVT? It feels lukewarm at best underfoot, there is chipboard and ply underneath!

What do you mean the last setting on the pump? Are you referring to the LED lights?

There are flow indicators at the top but are behind the wall in cavity so not in the photo. Both flow and return are turned fully anticlockwise and rates are at the bottom of the scales which is about 4L/min

I have no idea about how a rad would work in conjuction with underfloor, haven't got as far as considering that option!

Not 100% sure on ceiling insulation but they left behind some 70mm PIR so I assumed that's what they used throughout.

 

[Mr Chibs]

In light of some of the info, think possibly it’s a culmination of a few issues you seem to have.

We all guessing you might not have enough screed, as already mentioned you need around 70mm to be effective, then you’ve got a covering of plywood and chipboard & lvt flooring.

perhaps the insulation is also on the thin side. I had 100mm on the floor, and a total of 140 in the ceiling (from memory) all celotex.

Hope you get it sorted

 

[nirish]

@Mr Chibs yes indeed, unfortunately it all feels like issues I can't do anything about retrospectively.

The potential screed situation is the most frustrating as that looks potentially well below standard amount, although difficult to judge how much from pics I have. Insulation again could maybe be better but can't change it.

We've also spent a relative fortune and flooring and fitting to even contemplate ripping it up for a more conductive solution.

Feel like it's a lot of dead end solutions unless the installer has any tricks up his sleeve .... if I ever get him back out!

 

[nirish]

Hi everyone, can I come back and revisit this. The plumber has unlocked the blending valve to allow an increase in the flow from 45deg to 55deg. This is now successfully heating the room to 21deg when it's mild outside.

However this past week with cold conditions outside it seems incapable of heating the room above 18deg and despite running it overnight the room dropped to 16deg overnight.

So as it appears I'm stuck with a system which for whatever reason can't cope with the rooms heat loss what are my options going forward? I guess there is little I can do to improve insulation, token gestures such as thermal curtains perhaps.

I suspect I'll need another heat source, I do have an electric fireplace with an output of 1500W. I hadn't planned to use this for heat, but only for it's visual aesthetic. Should I attempt to make up the difference with this or will it be too costly? Alternatively get a rad plumbed in or other solutions please!

 

[Mr Chibs]

Hello again


Sorry to hear the news is still not good.

I think the easiest solution will be to add a decent rad to the room.
I know it’s slightly defeating the idea of ufh, but the other options will be much more costly.

 

[Exedon]

Really bad news but in truth not unexpected you just don't have enough tube in floor that simple.
Did you ever get to see heat loss calculations? Or underfloor design layout or did they just guess it?
Nice design rad supplied and fixed by heating installer at there cost would look to be best option at end of day what they installed is not fit for purpose.

 

[nirish]

@Exedon I've enquired of my builder and he just replies saying the installer is an expert who does major installations etc. but no, I've not seen any calculations so I assume it was eyeballed! As tempting as it to start firing out blame I can't actually see it helping to be honest.

I've had it suggested in another thread to run a large rad off the underfloor system as it's having to run at a high flow temp of 55-60° to get a 22-23° surface temp.

 

[muggles]

Hi everyone, can I come back and revisit this. The plumber has unlocked the blending valve to allow an increase in the flow from 45deg to 55deg. This is now successfully heating the room to 21deg when it's mild outside.

However this past week with cold conditions outside it seems incapable of heating the room above 18deg and despite running it overnight the room dropped to 16deg overnight.

So as it appears I'm stuck with a system which for whatever reason can't cope with the rooms heat loss what are my options going forward? I guess there is little I can do to improve insulation, token gestures such as thermal curtains perhaps.

I suspect I'll need another heat source, I do have an electric fireplace with an output of 1500W. I hadn't planned to use this for heat, but only for it's visual aesthetic. Should I attempt to make up the difference with this or will it be too costly? Alternatively get a rad plumbed in or other solutions please!

It's not up to you to pay to sort out the installer's error. Whoever specified the system should have carried out the required calculations to achieve the desired temperature in normal Winter conditions. This isn't hard to do. If the UFH installer was a subcontractor for your builder then go after your builder. They need to pay to put it right, not you

 

[nirish]

@Exedon did you ever get time to run those calcs to get a ballpark figure of what output you think I need vs what I have?

I found out I've got two underfloor loops which are about 55m each apparently and flow temp has now been increased and can be anywhere from 55deg to 60deg.

@muggles if only life was so simple, I can get no acceptance that anything at all has been done incorrectly from anyone!

 

[muggles]

@nirish if it's not heating up to a comfortable temperature then someone has definitely done something wrong. A higher flow temperature is just more likely to cause damage to your floor surface. There should be a thermostat with a floor temperature limiting function to protect the Karndene.

https://www.gov.uk/make-money-claim is an option if they don't want to sort it amicably. I think you have a good case for claiming costs to pull up and re-lay the floor, plus any other work required to make it work correctly