underfloor heating

[Pat76]

Hi

I wonder if anyone can give me the benefit of their experience. We would like to install underfloor heating in the downstairs of the house we are renovating, and we hope to use geothermal heat to run it. Has anyone done this? I would be really grateful if anyone who has could let me know if they are happy with their system, and any problems they have had. We have enough land for the geothermal pipes, and we have to lift the floors downstairs and will be installing plenty of insulation. We are at the planning stage, and any help/advice  would be most appreciated.

Pat 

[crossy67]

There is loads of info on the net, I did a bit of reading up a while back.  It would seem in general most people seem to think the air source heat pumps are a much better option, cheaper to install and maintain.  It lends it's self well to under floor heating as it won't get rads piping hot, more it gives off a steady warmth throughout the day.  The inverter AC units (god I sound like an advert|)do the same thing only blow warm air, don't know if they could be used to warm under floor heating but can't see why not.

[Pat76]

hi Crossy67

Thanks for taking the time to reply, I'm very grateful.

I have done a lot of research on the net, and in books and magazines, and we have considered the air source as well. I was hoping there might be someone who has actually installed something like what we are considering (air or ground source) who could give me their advice. I recently read that the running costs can be quite high, in terms of electricity to run the pump - I wondered if anyone had experienced this.

 

Pat

[crossy67]

You need to think in terns of efficiency. 

If you have an oil boiler you might be getting around 80-95%, with oil being iro €0.80/ltr (and it will only go up) and yielding 35kbtu's.

Electricity costs €0.09/unit and yields 3.5kbtu/unit.  I would have thought electricity would be iro 99% efficient as there is no mechanical parts or chimneys to lose heat from.

Therefore it's easy to see that electricity cost is near as dam it identical to oil per btu unless you have either very inefficient elecrtic heaters or a very efficient boiler.

I don't know much about the ins and outs of the two heat source systems but the AC inverter systems (air source heat pump if you like) can be up to 400% efficient, this means you get 4x the heat energy out per electricity unit than you would using the electricity to warm a 100% efficient element heater.

The pumps might well be expensive to run but oil and gas are far more expensive.  You also have to think in terms of cost of installing the ground source system and maintaining it, if say some one digs through the pipe or there is a leak for what ever reason.  You also get air con in the summer if you go for a vented air source heat pump, bargain.

Have a bit of a read here.  http://www.energysavingtrust.org.uk/Generate-your-own-energy/Ground-source-heat-pumps

Didn't mean to sound like look in the net and stop asking questions by the way.

[just john]

I have no direct experience, though an acquaintance had a system installed a few years ago now, it was an old house, though the floors and roof had been modernised and insulated the walls were thick stone. His experience was frustrating in as much as the cost exceeded original estimate and was problematic on commission, the original heat pump failed during this and had to be replaced, and the size of the heat pump/water storage tank installation took up his utility room. Finally he was a little crestfallen to discover that whilst the heating was comfortable it was more background and required additional heating during cold periods.

Locally a local developer recently has completed a few houses fitted with 'state of the art' Reversible inverter system, capable of delivering either Air-Con or underfloor heating, based on what he describes as an 'efficient system that satisfies all Customer requirements'. Since installation costs is one of those requirements this seems to me the way to go. ie no need to bury a field full of pipe and as simply replaceable as a boiler system as and when it inevitable wears out.

[mint]

Hi, JJ, just wanted to greet you but I suppose I'd better comment on the topic or put a lot of people out.

Funnily enough, OH was only yesterday speaking to some friends about their geothermic dah-di-dah system and it now transpires that they have to supplement their system all day with a woodburner.

I suspect that underfloor heating is great for background taking off the chill but not what you'd call a full, comprehensive heating system.  The other thing is, I always worry about if it's put in kitchens as then your fridge, freezer, etc might have to sit on a warm floor!

Or have I misunderstood these things completely?[8-)]

[Pat76]

Thank you both for your replies. So, basically we would need additional heating throughout the house. We have a couple of woodburners, and we were hoping that with the underfloor heating they would be sufficient, but that seems unlikely (it's quite a big house)

Back to the drawing board.

Pat

[just john]

[quote user="sweet 17"]  OH was only yesterday speaking to some friends about their geothermic dah-di-dah system and it now transpires that they have to supplement their system all day with a woodburner. I suspect that underfloor heating is great for background taking off the chill but not what you'd call a full, comprehensive heating system.  The other thing is, I always worry about if it's put in kitchens as then your fridge, freezer, etc might have to sit on a warm floor! Or have I misunderstood these things completely?[8-)][/quote]

Not entirely Sweet, (nice to get your greet, greetings to you too). Underfloor heating is fabulous, had it in the last house on a water system, the girls loved it, no slippers or thick towel dressing gowns, nor cold tiles in the mornings, just like the ad's, and a friend had electric similarly wonderful. Although it is meant to be installed 600 mm away from walls, specifically not under kitchen units or where appliances or solid furniture will sit and of course Fridge/Freezers are insulated anyway but have to cope with ambient temps etc.

However wonderful, geotherm systems can't get up to those sort of temperatures, about 20degrees max I believe, so ok in bedrooms perhaps and spring/autumn in loungers ok too, but supplementary heating is required when temperatures drop and you want to sit comfortable.

Whereas the 'State of the art' inverter systems can be made to pump it up hot or cold, whether a specialist installation or single unit systems like Quillans, (electric underfloor below tiles in bathrooms is good too[:)])

[Quillan]

Some people seem to think that geothermal heats the water ready to use, it does not. It simply raises the temperature of the water that you are going to heat. For example, if the heat in your ground is say plus 10 deg and stays much the same at that depth then to heat your water for your heating to 20 deg you only have to raise the temperature by 10 deg thus saving money. I am not quoting actual figures by the way just trying to keep it simple. Now when the outside temp goes right down normally you have to raise the temp but quite a bit without a heat pump but because of the medium in which your heat-pump is working the inlet temperature stays the same. Think of it this way, ever noticed how much colder the cold water runs out of your tap in the winter than in the summer, if the water pipe was around a metre lower in the soil it would probably come out the same temp in both winter and summer also why don't water pipes in the soil freeze (normally). You don't actually have to put the pipes in the ground apparently, bottom of  big river, down a well or on the bottom of a pond/lake will get similar results. So you still need a boiler of some sort but you don't need to use so much power to heat the water as it arrives preheated.

Rather than dig up the garden and the costs involved an air-source heat-pump may be worth looking at, Brico Depot sell one for 3,400 Euro's. It'as basically a clim unit that heats water and not air but as you can see from the drawing it still requires a boiler, it's COP by the way is 3.76 hot to 4.27 cold (a COP of say 4 means for every 1kw of electricity used you get 4kw of heat/cold out).

http://www.bricodepot.fr/carcassonne/chauffage-production-deau-chaude/pompe-chaleur-aerothermique-air-eau 

Two things,  have no clues about this kit, how it performs in real life but I am very happy with my inverter clim units, same sort of thing but they heat/cool air not water. The second thing is I don't have a clue what the COP on geothermal units will be and how expensive the digging up of the garden, supplying and laying the pipe and the cost of the actual heat pump will be. If it's going to be say over 4k Euros then perhaps the unit above is a better bet.

[Pat76]

Thanks for that, Quillan.

We are having a serious rethink - much as we would like underfloor heating, the geothermal idea is not going to work for us, it would not be cost effective based on the quotes we have had. We will check out the air source which will undoubtedly be cheaper. Do you know if the air source unit is noisy to run? A friend has the individual air source units and they are quite noisy, but they are a few years old.

 

Pat

[pachapapa]

[quote user="Quillan"] it's COP by the way is 3.76 hot to 4.27 cold (a COP of say 4 means for every 1kw of electricity used you get 4kw of heat/cold out).[/quote]

A heat pump is a heat engine and the performance is governed by the Second Law of Thermodynamics, consider a diagram of the Carnot Cycle. The COP of a heat pump requires the application of temperatures on the Kelvin Scale. A cursory play with a slide rule, inputting typical ground temperatures and ambient temperatures in the bathroom, will quickly reveal that all you are likely to get are large quantities of heat in the transfer medium at a temperature just and only just warm enough to thaw the balls on a brass monkey.

In calculating the coefficient of performance of a heat pump, or any other heat-engine related quantities, the temperatures must be the values in Kelvins.

[Quillan]

I have to say I am no mathematician or thermal engineer but I can tell you from experience, which includes using a thermometer, that with an air temp outside of around -5 deg the air coming out of the internal unit is about 26 deg (I am missing out the points of degrees to keep it simple) and the unit is using about 970W of electricity (measured using a clip round current probe). How that actually equates to the Carnot calculation I don't know but I suspect that things may have changed just a bit since the early 1800's. I can only report what I can see physically.

[Quillan]

[quote user="Pat76"]

Thanks for that, Quillan.

We are having a serious rethink - much as we would like underfloor heating, the geothermal idea is not going to work for us, it would not be cost effective based on the quotes we have had. We will check out the air source which will undoubtedly be cheaper. Do you know if the air source unit is noisy to run? A friend has the individual air source units and they are quite noisy, but they are a few years old.

Pat

[/quote]

I have one outside the window and with the windows open I can of course hear it but with the window closed I have to try and listen for the noise. If I were going to use one of these water heating units I would place it where I would get the least noise and then box the side and top in to reduce it further. It is a fan and a motor so it's not going to be dead quiet.

[Chancer]

The laws of thermodynamics havn't changed since the 1800's Q, and wont ever either!

Like yours mine chucks out heat even during minus temperatures but there are very long periods when it gives out nothing but is still pulling power, I am not convinced that all of them are degivrage cycles. Its interesting to know what current is being used though, its something i wanted to measure.

I think at those type of temperatures the COP is close to unity, certainly when you take int account the dwell periods I reckon when its that cold mine only puts out an average of 1kw. They say as much in the tech specs.

The cynic in me would say that perhaps they take their mesurements for the heating COP at 10 or 15 degrees ambient, if that is so then maybe the COP for refrigeration is taken at a lower temperature as well.

So from hereonin to save the planet, the whales and that polar bear if he is still on his ice floe I am going to use my clime for air con in winter and the heating in summer [:P]

[Quillan]

Is yours an 'inverter' type or does the compressor simply switch on and off? Mine take about five to ten minutes to get started when it's really cold. Also, they do not seem to go through a de-icing cycle, they simply slow down a bit, still producing heat, then speed up. Are yours from Brico Dept?

[pachapapa]

[quote user="Quillan"]I have to say I am no mathematician or thermal engineer but I can tell you from experience, which includes using a thermometer, that with an air temp outside of around -5 deg the air coming out of the internal unit is about 26 deg (I am missing out the points of degrees to keep it simple) and the unit is using about 970W of electricity (measured using a clip round current probe). How that actually equates to the Carnot calculation I don't know but I suspect that things may have changed just a bit since the early 1800's. I can only report what I can see physically.[/quote]

Well lets see then; that gives an input temperature of 268.15 K and an output temperature of  299.15 K.

Resulting in a COP of 9.65. 

STOP STOP !  CLOSE THE PLACE DOWN!  DONT LET ANYONE NEAR IT! APPLY IMMEDIATELY FOR A BREVET IN PARIS!

THE ENERGY NEEDS OF MANKIND FOR THE FUTURE ARE SOLVED.  A VERITABLE SCIENTIFIC BREAKTHROUGH.

POSSIBLE MODIFICATION TO PHILOSOPHERS STONE ROLE TURNING LEAD INTO GOLD.[:D] 

[just john]

You really should take a little more water with it PPP[:D]  sarcasm is like a small beer lost in it's own froth[B]

[pachapapa]

[quote user="just john "]You really should take a little more water with it PPP[:D]  sarcasm is like a small beer lost in it's own froth[B][/quote]

Heat pumps and underfloor heating are a bit of a laugh, but promoters dont get the humour so a lapse into a satirical nuance is difficult to avoid..

I always visit friends with underfloor heating after a hard frost to lie on the floor of the kitchen.[:)]

[Quillan]

Anyone interested in plans of a cold fusion generator that I nicked from Stan Pons and his mate? Size of a packet of fags and can run a whole street on 0.5W of electricity and a bucket of water.

[Chancer]

[quote user="Quillan"]Is yours an 'inverter' type or does the compressor simply switch on and off? Mine take about five to ten minutes to get started when it's really cold. Also, they do not seem to go through a de-icing cycle, they simply slow down a bit, still producing heat, then speed up. Are yours from Brico Dept?[/quote]

I have one, from Brico-depot but the old ungreen refrigerant gas and not an invertor type, but at €129 I was dead chuffed, the longer it carries on working the more chuffed I become.

Your comments on the invertor type are interesting, even if the energy savings are marginal the way it works seems much more acceptable in the heating cycle, come to think of it that would also apply to the aircon cycle although the pauses arent so noticeable unless its a humid day. I twould alsoavoid the lights dimming whenthe motor cuts in, I think the capacitor(s) is drying out.

[Quillan]

Rather than sit and type an explaination you might find this http://en.wikipedia.org/wiki/Inverter_(air_conditioning) useful in explaining how they work and why they are better than the older units like you have. It will also confirm some of your thoughts.

[PaulT]

Can't add anything to the technical debate but in a house I once owned the heating pipes ran under the kitchen floor and were not lagged. It was bliss on a to stand in the kitchen on a freezing cold morning in bare feet

Paul

[nemltd]

12 to 18 months ago I researched all of the 'green' and 'cheap-running' heating options. If you talk to a specialist on Heat Pumps about underfloor heating, he will advise you that a secondary form of heating will be neccessary. Unless of course he is advising AND selling it to you!

Looking to the forceeable future, "You are feeling the cold and want to turn the heating on to warm you up" Forget the heat pump and underfloor heating! A good oil boiler such as 'Chappie' will get you feeling toasty very quickly, and you will soon be turning the thermostat down because its too hot! In this context, forget about Heat Pumps and Underfloor Heating, they just will not create the same temperatures. 

The COP boasts of geothermal/air pumps sound good on paper, 1:4 energy ratios etc., etc. But the bottom line is this, when you are cold, then you want heat, quickly. The Chappie range of boilers are very effiecient at doing this, Heat Pumps are not.

By the way, I don't sell Chappie boilers, I have just spent hours researching both sides of the coin. Our Chappie oil boiler heats our water and radiators in the winter, in the summer we turn it off and use an electric hot water balon. This system gives you maximum comfort and convenience and also, the running costs are no more than the Heat Pump when the secondary heat source is included in the costs.

Consider also the proven track record of the conventional oil systems, and they are also more friendly to the environment than they were. Maintenance is another consideration, try to find an expert to come and fix your Heat Pump/Underground system..............Much easier to find a conventional heating engineer. I think the fact this subject is discussed so many times on this forum is evidence enough that the boffins are not quite there yet when it comes to replacing the good old boiler.

It may seem a little selfish, but I would leave the Heat Pump systems to the 'Rich-Guinea Pigs' for now.

Good luck.

Tony

[Quillan]

[quote user="nemltd"]

The COP boasts of geothermal/air pumps sound good on paper, 1:4 energy ratios etc., etc. But the bottom line is this, when you are cold, then you want heat, quickly. The Chappie range of boilers are very efficient at doing this, Heat Pumps are not.[/quote]

Well I have one, well a couple to be precise (heat pumps that is and their air pumps to be exact). They are very economic giving on average 3kw for 800w or energy burnt. Whilst I agree in extreme temperatures like -17 deg C they can take up to 10 minutes before they produce heat they do produce heat and work fine. When I think about my gas central heating system in the UK which was quite modern that's about the same time from a 'cold start'.

My question is however have you personally installed these 'other systems' and speak from actual first hand experience?

[Pat76]

We looked at air units in Brico Depot when we were in France last week, but the ones we saw said something along the lines of  " effective at temperatures above 5 degrees" which seems a bit odd, but perhaps we misunderstood.

As to oil heating, we have been put off oil by the cost, which goes up and up. When we move to France we will be living on a fixed income, so we are hoping to keep our outgoings as predictable as possible.

Basically, we have a couple of woodburners, and are looking for a form of background heat so that when we get up on cold mornings, we are not freezing while the fires get going. We are now looking at night storage heaters, which run on cheaper overnight electricity, and give an even background heat in the morning. Does anyone have experience of these?

Thanks for all the replies,

Pat