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AIR CONDITIONING


A et K
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We are thinking of installing air conditioning to heat our barn , does anyone have any views as to if this would be a problem...it doesnt seem to be very common in France , is there a reason for this???
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Do you mean Heat/Cool units or a full plant?

Heating with electricity is neither economical or comfortable. Unless your barn was unbelievably well insulated, you could use the aircon units as back up or supplementary to another background heating medium. As far as the cooling side, you would need plenty of capacity, and why would you need to aircon in the first place, one wonders.

Typical unit prices in GBP here:

http://search.ebay.co.uk/air-conditioning-split_W0QQsofocusZbsQQsbrftogZ1QQfromZR10QQsacatZ-1QQcatrefZC6QQsargnZ-1QQsaslcZ3QQga10244Z10425QQftrtZ1QQftrvZ1QQsadisZ200QQfposZPostcodeQQfsopZ1QQfsooZ1

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Heating with electricity is neither economical or comfortable. Unless your barn was unbelievably well insulated, you could use the aircon units as back up or supplementary to another background heating medium. As far as the cooling side, you would need plenty of capacity, and why would you need to aircon in the first place, one wonders.

Help me to understand this bit about not being economical please, cooling I understand the need for.

If you pay for 1.38kw of electricity and obtain 4.2kw of heat is that not a good deal? Especially at 0.553 cents a kilowatt most of the time.

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The electricity rate is Tempo day rate for 300 days of the year.

I have a heat pump for the pool which uses 2.55kw to produce around 12kw of heat into the pool, the 1.38kw to produce 4.2kw is for an inverter type air con unit unit currently on sale at Auchan.
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Even the most inept school physics student will be able to confirm that electrical energy cannot be converted to produce MORE heat energy.

Quite the converse. All energy conversion has an efficiency less than 100%. In the real world.

I think someone has misinterpreted the sales blurb claims. They talk about "comparative equivalents".

And soon the car that fills it's own tank due to an efficiency > 100%?

Only on eBay!

 

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Now, firstly I will admit that even the most inept school physics student, so kindly mentioned by Opel Fruit, knows more about physics than I do, so please bear with me.

The sales blurb gives a figure of 2.55kw consumption for the equivalent of 12kw of heat being put into the pool at maximum efficiency . Opel Fruit questions this as being impossible under the laws of physics and challenges the manufacturers blurb.

A quick Google search for “how things work” found this under a page entitled “Explaining the physics of everyday life” :

“I can think of three important energy-efficient household electric devices: (1) heat pumps, (2) electric discharge lamps (including fluorescent lamps), and (3) microwave ovens.

A heat pump is a device that transfers heat against its natural direction of flow. If you use one to heat your home, the heat pump uses electricity to transfer heat from the colder outside air to the hotter inside air, so that the inside air becomes even hotter and the outside air becomes even colder. The electricity that the heat pump uses also becomes thermal energy inside your home. Since both the electric energy and the thermal energy pumped from the air outside end up inside your home, a heat pump provides more heat than a simple space heater can provide with the same electricity. The energy efficiency of a heat pump decreases as the temperature budifference between inside and outside becomes greater, but it typically provides 4 or more times as much heat to your home as a normal electric space heater would provide with the same amount of electricity. Incidentally, when the heat pump is reversed, so that it pumps heat out of your home, it is then an air conditioner.”

So come on all you physics A students, do heat pumps work or not?

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ermm blimey !!!

quite simply we are considering air conditioning units purely because we know someone who fits them!! and he has installed them in his house and finds them an extremly efficent  source of instant heat..

I do understand that we probably, unless we have a scorchning summer wouldnt use them to cool our barn, but he seemed to think that it would be an alternative to other methods,,

We were curious to know if air conditioning units were an extremly bad idea as they didnt seem very common in france, as some of you said it may be due to the fact electricity is expensive...

Please dont laugh but our friends live in spain , yes they need the cool air there, but in winter he uses his to heat his quite large villa, which air conditioning does very effectivly there.

 

 

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[quote]Now, firstly I will admit that even the most inept school physics student, so kindly mentioned by Opel Fruit, knows more about physics than I do, so please bear with me.The sales blurb gives a figure ...[/quote]

Of course heat pumps work, they produce heat from 2 sources of energy; electricity and geothermal, which is energy from the sun, stored in the ground (they are basically a big fridge in reverse, but that is for another lesson).

A/C units use electricity to remove heat and water, they produce heat outside the house in return for "cool" inside. They have no other source of energy. They cannot put more energy into the "cool" than they use from the mains, because there is no other source...

Pay attention! I shall be asking questions later.

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[quote]Of course heat pumps work, they produce heat from 2 sources of energy; electricity and geothermal, which is energy from the sun, stored in the ground (they are basically a big fridge in reverse, but t...[/quote]

Thanks Nick, that, of course, is my understanding too.

I was trying to find out what our learned friend Opel Fruit was on about, as he states "electrical energy CANNOT be converted to produce MORE heat energy", in a thread about ac and heat pumps.

Until Opel Fruit comes back and gives us the benefit of his wisdom and enlightens us as to why they don't work - well, they still seem like a cost effective solution to many heating and cooling requirements to me.

In response to A&K I have noticed that a number of new builds locally have ac heat pumps fitted to them.

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When the canicule was at its height in 2003, we decided to have air conditioning installed in our bedrooms. It was quite expensive to install, but we divided the cost by four, the number of our children, and decided that if they inherited that much less each it would be no great loss.

For us, because this is only a holiday home, it's not a huge expence. To be honest we didn't look into it very deeply, we just wanted a decent night's sleep ! Our electricity bills are not huge because we don't use it all the time although we can and do use it for heating too. The set up we have  suits our cirumstances. Obviously everyone's are different.

What is physics ?

Hoddy

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Heat pumps do work, but one has to be careful about the claims. The "blurb" makes wild claims, based on perfect operating conditions and environmental conditions.

The best you can expect in the real world is about 200% heat gain, and even then this is subject to seasonal performance factors.

The point I was trying to make is the huge heat output claims made by those selling these are not real. And of course, the principle applies to heating and cooling cycles only.

The best heat pumps work on either solar or geothermal sources. The former being rather variable in our northern part of the world, the latter being rather more stable. Air/Air heatpumps are nowhere near as good.

The other thing to take into account is the payback. The capital outlay for ANY heatpump system is very high, comparatively. The less you use the installation, the more adverse the payback period. For someone with a low occupancy home, heat pumps make little sense.

In terms of energy conversion, my original waftings stand. Energy CONVERSION cannot exceed 100%, in most cases one form of energy converted to another would rarely better 80%. A car engine converts chemical energy into various other forms of energy, the mechanical energy being about 25% of that.

Heat pumps are not pure energy conversion. They use electricity to extract heat energy from a natural source. The common fridges and freezers use heat pumps, in reverse.

One technology to keep an eye on is the Peltier effect devices. They should proved a greater heating/cooling efficiency with less noise.

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oh ye of little faith

air/air heat pumps

for every euro you spend on running the unit in heating mode you will get UP TO €4 OF HEAT Please NOTE up to  the reason for this is as the ambient outside temp drops so does the heat gain ratio, the claims you see are not wild but true at a given temp you do get a large heat gain, a bit like...... the sun always shines on our gites!!!!! ......enjoy glorious sunny days at our cottage.

the big question is HOW BIG IS YOUR BARN ? AND IS IT TOTALLY OPEN PLAN ?

Hope this helps

Stephen

p.s Refrigeration & Air Conditioning Engineer 

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[quote]oh ye of little faith air/air heat pumps for every euro you spend on running the unit in heating mode you will get UP TO €4 OF HEAT Please NOTE up to the reason for this is as the ambient out...[/quote]

Stephen,

 

Very interested in your comments.  We have spent six months trying to get quotes for under floor heating (seems the Aude is a pipe too far...) and have ended up with a quotation from Multibeton.  (http://www.multibeton-france.fr/)  They are offering Solar, Geothermal, Solar/Geothermal and air heat extraction.  How do the sources compare and any thoughts on back-up fuels.  (We have no mains gas, so its oil or electricity I suppose.)  We will be using our full SHON allowance of 250m2.  ‘Surface Habitable totale’: 217m2.

 

Many thanks.

 

Brian 11500

     

‘He of little faith but looking forward to being converted….. ’

 

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[quote]We are thinking of installing air conditioning to heat our barn , does anyone have any views as to if this would be a problem...it doesnt seem to be very common in France , is there a reason for this?...[/quote]

Has anyone tried the mobile air conditioning units or air coolers, we are thinking of this as we have attic bedrooms that can stay very warm at night and disturb sleep.  As stated in another post, we use only as holiday home, and dont think the running costs would be that high, as only used on a "need" basis. Air coolers in B&Q run from £50 upwards with the conditioners from about £200 and wondering if the investment would be worthwhile.  Any advice?
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Hi Brian

I have only installed and worked on air/air systems (I believe in sticking to what you know) but common sense says geo would give you a more constant heat gain, it would also be much more expensive to install and I guess (and it is a guess) the system would be a one off, designed for your property no doubt a good system but who would carry out any repairs and how soon could they get to you if in the middle of winter if you have a problem?

As a ball park figure you will need 25/30kW output from the system

Hi Sallyb

the £50 coolers use water as the cooling medium which means you will be putting water into the air in the room you are trying to cool which in turn will give you a very humid room.

The £200 mobile unit will need to be vented to the outside (you cannot destroy heat only move it from place to place) is liable to be noisy as the compressor and both fans will be inside the room a fixed split system has the compressor and one fan outside the indoor unit has the cooling block (evaporator) and a tangential fan (very quiet)

you pays your money and makes your choice

Hope this helps

Stephen

 

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One of the cheap water evaporation units run during the day cools our guest bedroom enough to make it pleasent at night. The guests room is the only one without cross ventilation.  We are in the Haute Vienne, with the befit of hindsight I would have cut a second window in the guestroom.
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[quote]Hi Brian I have only installed and worked on air/air systems (I believe in sticking to what you know) but common sense says geo would give you a more constant heat gain, it would also be much more e...[/quote]

Thanks Stephen and Anton, 2 differing views will have to see how this summer pans out and how hot/humid it gets.
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