Key Post: Underfloor Heating

Re: Users of Underfloor Heating: What Settings?

Spoke with Tim Cremin (MD of Oxyvent) he gave me 2 referalls. They swore by it. One guy was a Garda who also found he was burning oil big time, now he's not. I'm considering installing but price is putting me off, I reckoned about €1,500 !! One guy at work installed for an old radiator system in his house, his radiators never heated up properly, now they're hopping ! And he's a genuine legit guy !!

Re: Users of Underfloor Heating: What Settings?

Heinbloed - some clarifications
UFH = standard water filled pipe in screed above insulation.
Flow temp I can set to whatever I want digitally - I also have the outside air sensor.
I am most interested in the manifold adjustments. On the flow side of each loop there is a dial which is essentially a tap which as you say would adjust the litres per minute rate of flow. Each dial has a setting from 1 to 10 ( I dont assume its 1 to 10 litres?) I guess 10 = fully open.
The part of your comment I don't agree or follow is that the return temp of each loop should be the sames as the flow. Surely temperature is reduced in the return node because energy in the form of heat has been transferred from the water via the pipe, the concrete and floor covering to the room. Therefore the return temp could not be the same. I guess the lower the temp drop the more efficient your system is and probably a result of how well your system is designed vis a vis insulation below screed etc. In my early experience of running the system I see an 8 to 10 degree drop between flow and return - do you think it should be better? (I know this from a temp dial on the flow versus a temp dial on the return - although this is one dial for all the flow pipes and one for all the return pipes not individual measurment of each flow / return loop if you know what i mean )

To reduce the differential do I open or close the valve on each loop.
Open valve = faster flow - higher demand on the boiler - higher fuel use
Close valve = slower flow - lower boiler demand & fuel use

How does one judge if setting 3,4 or 5 etc is best for efficiency. My guess is that if you opt for an always on system (i.e maintaining constant 18/19'C) then heating response / reaction time becoms mostly irrelevant and the tap should be almost fully closed on each loop - do you agree?

Guys - on the Cremin tank i checked it out and saw the merits in principal but didnt do it re cost / complication etc. I think in my plumbing sytem I have vents which expel air anyway.....

Re: Users of Underfloor Heating: What Settings?

Hi Lakeview !

The temperature at the RETURN , measured on the brass junction at the end each of the loop ( where they join the return manifold ) should be the same . Not the same as where they start at the flow manifold , that is logical as you have said . The temperature gets less when passing through the loops , of course .
The flow adjustment meters give indeed the number of liters per minute. The heating suplier/installer should have made a calculation sheet where the settings of these gadgets should be stated . But this calculation is never as correct as a meassurement done in vitro. During building the UFH a loop in a zone might not fit in or an extra one is put in because the fitters/installers find that there is plenty of room to do so - or not . The real site differs often from what is on the drawing . Also heat gains from the sun and ocupants behaviour (doors , windows opening i.e air exchange from cold droughts etc. ) can be of influence . So measure it .
As you said the flow and return temp.difference ( meassured at the boiler )should be around 8 degrees . To increase the efficiency of your boiler it is the best to have this difference gap as large as possible . BUT : and this is important : A difference to big could cause the screed to give off sqeeking sounds due to the higher expansion differences .It might even cause cracking , but that would be more the case with temperature differences of around 50 degrees depending on the concrete screed , hardly the case in a standard working UFH.
Back to the setting of the hydraulic pressure.
Each loop opens by the " demand sign " coming from the room sensor .
So the warm water can get in . But on deciding how long it stays there the flow reducer comes in . It allowes for the correct setting so the return temperature is the same for all zones .
Zones pipes have different sizes . Some are fully 150 meters long , some are just 30 meters long .
So sending IN the same temperature would result in different temperatures coming OUT . This shouldn't happen .
To adjust this dilemma the " standard " for adjusting is the largest i.e. the longest pipe . This is not necessary the one from the biggest zone , it could also be an average sized zone but in a far away place in the house . The lenght of the pipe decides .
When you have found this pipe you turn the reducer fully open by turning its base , not the looking glass itself . To make as much warm water passing through the zone as possible .The little float in the reducer shows how many liters are flowing through the pipe . Read always at the lowest point of the little floating ball .
Then you go to next longest pipe . Measure the temperature at the return as described above . If it shows a larger temperature as the first one then you close the return valve ( the thing with l/min. on it with the float in it ) by turning it's base until the temperature is equal to the one you have done first .
Then you go to the third longest pipe . Again the same story . Reduce the liters per minute that pass trough the zone untill the return temperature at this zone is similar to the two return temperatures you have meassured before .
And so on untill you have reached the return of the smallest zone/shortest pipe.
All return temperatures should be the same .
Job done .
Note : When adjusting the liters per minute then you will realise that the temperature and the flow rate ( the little ball will go up ) at the first return will increase more and more the more you " close " the other zones . That is fully normal. Nothing to worry about . The explanation is easy : The pump has only a certain capacity . The longer the individual pipe is the longer it takes for the warm water to pass through . And the water will flow faster when you close or reduce the flow of the other zones . So the longer the warm water takes to " get through " the colder it will arrive at the return manifold . And when closing /reducing the flow per minute of the other zones the more pressure (created by the pump ) will push the warm water faster through the one .
In easy words : The pressure has to be shared by the zones . The less the one gets the more the others get .
And the faster the warm water rushes through a pipe the warmer it will be at the outlet .
The fuel use of your boiler depends on the heat loss of the heating pipes/zones/radiators . Not in principal on the flow rate . If the boiler senses cold water coming back it fires . It does not sense the flow rate resp. it won't react to it .
In more advanced modulating boilers the pump in combination with the outside sensor will react , like an artificial intelligence the different parts communicate to give an optimum .But even at more modern boilers the pump quiet often is only fix set manually at differnt stages I,II and III . It depends on the minimum output of your boiler and on the minimum demand of your heating where to set it . In theory it should pump fast enough so the boiler does not overheat . A modern boiler has several features to prevent overheating , it simply shuts off the firing sequence until it has cooled down again .
When realising a " ping-pong " or "on - and - off " firing then the pump is not pumping fast enough or the difference between flow and return temperature is not set far enough apart . You could give it a try by setting the flow temperature at lets say 35 degrees and the return temperature at 36 degrees . Just to learn from it , not to run it in a standard mode ! The boiler would switch on and off , making it very uneconomical since during the start firing since it uses compareable much more fuel during the start frequence as during the modulated run .
Hey, when we are finished you are plumber !
Good luck !
The hydraulic adjustment as described above goes for any heating system , UFH or radiators .Every plumber should be able to do that , but most aren't . Many never heard about it .

Re: Users of Underfloor Heating: What Settings?

Heinbloed - that is possibly the best and most detailed response I could have imagined - much appreciated. Unfortunately I suspect that for all the people who chose UFH for comfort and economy the vast majority have not performed this kind of exercise and consequently have an underperforming system.

The only part I am unclear about is;

heinbloed said:

As you said the flow and return temp.difference ( meassured at the boiler )should be around 8 degrees . To increase the efficiency of your boiler it is the best to have this difference gap as large as possible . BUT : and this is important : A difference to big could cause the screed to give off sqeeking sounds due to the higher expansion differences .It might even cause cracking , but that would be more the case with temperature differences of around 50 degrees depending on the concrete screed , hardly the case in a standard working UFH.

Click to expand...

My understanding was that water only flows in the loop when a room stat calls for heat, when the room is at the desired temp then the flow valve shuts. If that is the case then when water flows in order to heat up the room if it returns at a significantly lower temperature then surely it means a lot of heat energy was consumed in transfer from pipe into floor screed. In other words had not the screed been allowed to cool too much ! if it required a large amount of energy to re -heat it. That would go against the principle of more constant and even level of heating and perhaps suggest an unresponsive system in terms of when the room stats see the need to call for heat ??

BTW - I dont have a device on the manifold with a floating ball - just one adjustable dial on the flow side of each loop only.

Re: Users of Underfloor Heating: What Settings?

Thanks . About the temperature difference "measured at the boiler " and the efficiency of it : I was talking/writing about the efficiency of the boiler only , not about the efficiency of the entire heating system .The boiler is only part of it , pump and manifolds, pipes and radiant surface are belonging to it as well.
So to run the entire UFH system on an efficient modus your system setting of 8 degrees flow/return difference is absolutly fine .
You are right about the reheating of a cold screed . For the efficiency of the heating system - and for comfort - this would be not desireable . The boiler would be working efficient but not the system as such . Compare it with motoring. Instead of wasting time in a bus one could take the private car and push down the pedal to get from A to B . That would make the private car in this case ( time-) efficient . But it certainly would not make the journey fuel efficient .
The boiler would work most efficiently when starting to fire and then puting out as much energy as wanted in one go - measured in kW . But having a hot floor for a few hours and the rest of the day a cold floor is not what an UFH is supposed to do .So spreading the kWs over the entire demand period of a day and tolerating some loss ( because of repeated boiler starting frequences ) is the way an UFH becomes effective . Or compare the A-bomb with a nuclear powerplant . The efficiency of the bomb is a better one then that of the power plant .....(stupid sample !)
To the flow meter : It is not so important what the flow meter/restrictor shows as such , they can be quiet inaccurate anyhow. What counts is the actual heat in the return pipe from the corresponding zone . This would be meassured and the restrictors adjusted to give an even temperature on all of them .The " float- in- a- window " flow meters are more for the installer of the UFH, for the handy man/women, to give a rough indication when installing the UFH . At the point of installing a lot of things aren't clear , for example the heating can't be tried out because the screed hasn't dried yet , the tiles (and their adhesive ) still to go on top of the screed would have different thicknesses ( U-values ) and so on. The fine tuning is done when everything is in place and the boiler is running for an hour or so. And check it again every heating season , the boiler maintenance company might be able to do that for you when servicing it. But as said: all you need is a thermometer that takes the temperature straight at the return pipes .
The neccessary adjustment can be done at the returns or at the flows , it doesn't matter .Compare it with trains entering a tunnel : no matter from what direction they come from they always have to push the same amount of air through the tunnel . And this moved air gives the same resistance .
So restricting the flow at the inlet or at the outlet makes no difference .

Re: >>Underfloor Heating

Hi,

Ive just bought an old house in Spain. An hour inland from Alicante in the mountains.

Can anyone give me information about Under Floor Heating and european suppliers/companies.

There is no mains gas available in my village so therefore we would have to run it on Electricity. Is this expensive?

Anyone have any experience of using solar powered energy to run UFH?

Geothermal heating system, good bad? We live in a townhouse with little outside space apart from a couple of terraces. So is geothermal system possible for me?

Any help/info would be greatly appreciated

Thanks

Re: >>Underfloor Heating

It is propably difficult and expensive to bring in staff and material from abroad . So contact the locals. Spain is destinated for solar heating , the gouvernment is subsidising the installment of solar heating systems as well as photovoltaic energy production . Their photovoltaic support system is the leading one in Europe , for every kW delivered to the grid the producer gets € 0.55 cents from the electric supplier/grid company.
Your first aim should be to save energy , by insulation for example. If your house is in the mountains then it could be a total different story compared to the coast . Again : talk to the locals .Spain has tree different climate zones as France as well .So there is no one-fits-all heating system . The first thing to find out is your heating demand , expressed in kilo Watts . Check you meter box when you arrive and again when you leave .
For a holiday home used only temporarly it might be worth it to use electricity , but for a sales point of view certainly not .Electric heating is cheap to install , but underfloor heating running on electricity is very expensive to install and to run . Night saver might be a thing of the past , the Germans are indicating that they won't replace the old power plants because of the CO2 emission trading . And it is the old powerplant that delivers for cheap - till it collapses . Spain is upgrading their old power production system , even the ESB is involved , incl. the IRA/ ETA to skim them off .

Re: Users of Underfloor Heating: What Settings?

Moderators

Can this be made into a key post ? I think it will be valuable for all u/f heating users.

Re: Users of Underfloor Heating: What Settings?

Hi JP,


I will merge it in due course with the key post on underfloor heating.

Considerations to Balance Temperatures at the Manifold

I tried to use the advide of Heinbloed in this post to balance the return temperatures of each loop on the manifold but found it was not so easy;

To measure the temperature I had a digital thermometer but it only had a sharp point (like a meat probe) so it was hard to get a good reading. I could not find in Maplins something which might clamp on.

In order to get warm water running through the loops (in order to check the return temperature) I had to put up the temperature request in each room to say 23 or 24 degrees (even though it would never each it) but now this is not like a real situation when I normally only look for 19 to 20 degrees.

In this balancing exercise it is also not like real life usage because from 9 return loops on the manifold at different time zones of the day the settings on the thermostat could request different temperatures which means some zones are open and some are closed. Furthermore even if the temperature request was the same the valve could be closed for a looop supplying a sunny room but open to heat a loop in a shaded room perhaps with a north exterior. Therefore different combinations of 9 loops could be open or closed at any one time - so what is the point of balancing 9 open loops which probably rarely ever happens?

Finally I find a contradiction in general with my underfloor heating. In theory it is more efficient to keep the floor slab warm all the time. It is also in theory better to conserve fuel by not overheating the house and setting just a 19 degree living temperature for example.

So the contradiction is in a well insulated house with also some passive solar gain the general temperature without heat could be close to 19 degrees indoor without heating at all. Or with heat for an hour or two the house can retain its pleasant temperature easily for a long time. In the time then when the heat is maintained or already 19 degrees then the stats don't call for heat and no warm water flows in the loops so the floor gets a good chance to go cold all the time !!!

In the instance where I feel cold and push the stats to 20 or maybe 21 degrees then the system is starting off from zero with an entire cold floor slab to heat up which is slow to happen and hard on fuel usage !!!! (see my other post today on costs of LPG so far included in a post about litres of oil used in 5 weeks by another poster)

Anyone else tried this 'balancing act' or have similar undefloor heating issues - I t

Re: Users of Underfloor Heating: What Settings?

You haven't understood the idea of adjusting the loop return temperature. See also http://www.heizungsbetrieb.de/en/index.html , it's done worldwide.
If one loop closes then the flow rate on all other open loops increases, therefore as well the return temperature at each of them. Because the hot water hasn't got that much time to reduce/give off it's energy.
But this will happen similar, at all loops at the same rate.Take the sample of a fountain in the park with four jets spraying water: If you close one of them the other three would blow the water higher, further-at a similar rate in liters per minute. Close the second jet as well and the remaining two open ones will spray even higher/further. At a similar rate.
Provided they are adjusted.
Use an infrared thermometer, read the manual of it before adjusting the return temperature, the instrument you've described gives mostlike no compareable results.
This should be the job of the installer, but it's easily done.
The difference between floor temperature and ceiling temperature should not be higher then 2 degrees with UFH. If it is more then the floor is badly insulated. Use the thermometer.
The room temperature should hold the floor temperature at it's level, if not then the floor is not good enough insulated. Why should it be colder? The actuall room temperature is controlled by the thermostats, if it gets warm then they close off all further flow in the UFH untill they sense a room temperature drop and open the valve again. That is normal with any room/zone thermostat.
One other point: The room thermostat does NOT set the flow temperature. This would be done by the boiler.
The thermostat opens and closes the loop, not more.
One question: Do the floor buildups differ between the different zones? For example do you have timberfloor fixed on concrete screed?

Re: Users of Underfloor Heating: What Settings?

I am going to look for an infrared thermometer and start again!

Yes the floor build up's do vary - it is solid timber (17mm) glued down to a concrete screed on top of insulation layer in many rooms (bedrooms & living areas) but it is tiles in other places (utility, toilets, hall, landing etc).

Downstairs insulation was Kingspan TF70 at 65mm and the same product upstairs with 25mm thick. I think this is more than minimum required but of course like all insulation it could be more, even double!

My flow temperature is set by the boiler and currently 43 degrees but perhaps in my case this is not high eneough to penetrate the timber / glue layers?

Re: Users of Underfloor Heating: What Settings?

It looks to me that your UFH was installed in an amateur manner. Get a heating engineer in to write a report. Your UFH seems to be better insulated from above then from below. 65mm under the UFH downstairs is less then the legal min., check the SEI homepage for their min.recommendation (10cm). 25mm under the upstairs UFH is only good if you want to heat the ceiling below when turning on the heating upstairs.The tiles and their adhesive (glued to what actually?) propably have a better insulation value(U-value) then the Kingspan board below.
When having this report bring the architect/UFH installer to the courts.
If you increase the temperature too high then the tiles might come off, as well as the timber floor might get demaged.
I run my UFH at the moment/ the last few days at 32 degrees, but it was turned up to 39 degrees when it was minus 5C a few weeks ago.
Sorry for not having better news, good luck.

Re: Users of Underfloor Heating: What Settings?

My boiler output varies from min. of 60 Celsius to max. 90 Celsius. Is this ok with UFH. Just read some Lakeview's post where he mentions 45C

Re: Users of Underfloor Heating: What Settings?

heinbloed said:

65mm under the UFH downstairs is less then the legal min., check the SEI homepage for their min.recommendation (10cm). 25mm under the upstairs UFH is only good if you want to heat the ceiling below when turning on the heating upstairs.

Click to expand...

Obviously I will check what you are saying (didn't find it on SEI first attempt) BUT I believe insulation requirements are not met by a function of thickness only but the thermal properties (U value) of the boards. I believe the U value of the board I used delivered at least (if not more) than the minimum requirement !!

Re: Users of underfloor heating: what settings?

To 10to1:No, your boiler is not suitable for UFH without adjustment. This would be the job of a heating engineer, most plumbers wouldn't be able to do this.It would be more energy wise to get a new,modern modulating condensing boiler with a very low min.output. I think the lowest output is aroud 2-3kWh with some types.
And to Lakeview: The legal requirement for floor insulation is about the amount of insulation that you have in place. But the legal requirement is not good enough for UFH, this would demand an extra layer of insulation material.The "Technical Guidance Documents" of the building regulations do not take care of UFH, the U-values given there are for the standard heating i.e. radiators and the like. Check the SEI page's search box for "floor insulation" or a similar word.

Hi, does anyone know or can recommend which is better for underfloor heating... QPL in cork or Unitherm? We are trying to make a decision on it and need a few opinions??

I am also interested in the answer to Floman2008's question.

And have more questions: Has anyone ever dug up existing floors to install underfloor heating?

We have bought a 10 year old house which we are extending on either end. The existing radiators are corroded and need replacing and we're considering replacing all the pipework too. It was initially suggested that we put underfloor heating in the extensions but then told that the pipework has to come through the existing part of the house to the hotpress/central control unit so we might consider doing underfloor heating in the whole house. This means digging up the floors.

I'm the kind of person that jumps from bathmat to carpet and into slippers to avoid touching cold floors. I can't imagine anything getting too hot. I'm mostly concerned about the cost of running the system after the extra cost of installing it.

Can underfloor heating be run off renewable energy (not considering geotherm, too expensive to install)?

Re: Key Post: Underfloor Heating - Can I use vinyl and carpet flooring?

Hello, may I ask advice here please? I am putting underfloor heating in house and wanted to ask if it is possible to use vinyl flooring (karndean/good quality lino) and carpets with this type of heating system as I am not keen at all on tiles (except for bathrooms). I have visited several floor shops and some of them tell me that vinyls can be used with underfloor and some say that it cannot.....who is right?? (I understand that carpet can be used with underfloor heating). Has anyone out there used vinyls (i.e. lino/amtico/karndean etc.) or carpet with their underfloor and if so, has it worked out fine for them? There is a wonderful array/choice of vinyls/lino's out there now. Thanks very much.

I am trying to follow Heinbloed's guidance above

Zones pipes have different sizes . Some are fully 150 meters long , some are just 30 meters long .
So sending IN the same temperature would result in different temperatures coming OUT . This shouldn't happen .
To adjust this dilemma the " standard " for adjusting is the largest i.e. the longest pipe . This is not necessary the one from the biggest zone , it could also be an average sized zone but in a far away place in the house . The lenght of the pipe decides .
When you have found this pipe you turn the reducer fully open by turning its base , not the looking glass itself . To make as much warm water passing through the zone as possible .The little float in the reducer shows how many liters are flowing through the pipe . Read always at the lowest point of the little floating ball .
Then you go to next longest pipe . Measure the temperature at the return as described above . If it shows a larger temperature as the first one then you close the return valve ( the thing with l/min. on it with the float in it ) by turning it's base until the temperature is equal to the one you have done first .
Then you go to the third longest pipe . Again the same story . Reduce the liters per minute that pass trough the zone untill the return temperature at this zone is similar to the two return temperatures you have meassured before .
And so on untill you have reached the return of the smallest zone/shortest pipe.
All return temperatures should be the same .

Click to expand...

. My question is: Should all the reducers be fully open when starting off this process, or should I open the reducer for the longest loop first with the other loops closed and opening them one by one?