Using ducted aircon to heat the house

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25 Nov 2011 00:00 by carl9 Star rating. 136 posts Send private message

Hi everyone, I wondered if any of you have built in ducted aircon and use that as the primary heat source on your houses?

The house we are having built has pre installation for aircon with a ducted sysem installed. So I have the following questions:

1. Does the ducted heating system actually work? we have a two storey house and my fear is that heat will rise so the lounge will be cool and the bedrooms hot. Also the ducts are at ceiling level which is great for the cooling aircon but I guess not so good for the heating aircon.

2. How does cost of this work out? I've read that heating a house with aircon is actually very cost effective.

3. Given I've got the pre installation, typically what do i need to but to get the system up and running, and what is that likely to cost?

4. As an alterative for heating, we are looking at paying extra for underfloor heating and having either a ground source heating system or biomass (wood pellets) boiler to feed that. I like the Ground source heat option as for a few thousand more it can be made to cool the house in the summer via the underfloor heating pipes which work in reverve, and heat it in the winter via pulling in heat from the ground. it's not cheap but it does seem to provide options.

I guess it's all about initial cost versus savings over time, but was very keen to hear from anyone that has ground source heating installed, and anyone that uses a ducted aircon system to heat and cool the house to see what the pros and cons of each are.

Thanks in advance. This site is worth its weight in gold.

Regards, Carl




This message was last edited by carl9 on 25/11/2011.

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26 Nov 2011 09:55 by floella Star rating in SE Spain. 789 posts Send private message

 We have ducted aircon/heating and it is brilliant. You do however have to have a much higher potencia of kw. otherwise you will constantly blow the fuse. We have a potencia of 13.8 and for this privilage one has to pay a greatly increased standing charge. Our  bi-monthly charge is 82 euros.

Our house is single storey  with open plan living/dining/kitchen . Add into the equation that ceiling is double height  in the 7 x 5 lounge area.

We have separate 2 units where the ceilings have been lowered to accommodate the trunking and these feed the 3 bedrooms and bathrooms as well.

Heat rises and everyone was concerned, ...didn´t we realise just how cold it gets in Spain,... that without some other form of heating to back it up we would suffer from hyperthermia.

Fortunately this hasn´t been the case. We rarely need to switch on both units and the power of the units means within 15 mins we are very comfortably warm.

Downside is with anything electric once switched off the cooling is rapid.

Last winter when the temperature plummeted to a single number indoors most days and our electricity bill came to only 50 euros more a month than the cost of our normal usuage ( which is 330 bi-monthly) So on that premise we think it is successful.


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26 Nov 2011 10:45 by carl9 Star rating. 136 posts Send private message

Hi Floella, thanks so much for your feedback.

Cn I please ask when you talk about the standing charge, are you paying EUR 80 every other month before they even start to charge you for electricity?

Are you there all yeear around?

Our place is on two levels so I wonder if that will have the effect of keeping the upstairs hot and the dowenstairs cold as heat rises?

So your elcectic bill is EUR 165 per month? Is that all year around (takinga account you will be using both hot and cold depending on the season.

Finally, do you have a real fire or wood burner in the lounge?

Many thanks, Car

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26 Nov 2011 12:41 by xetog Star rating in Wiltshire/holiday ap.... 514 posts Send private message

This problem needs to be split into two main parts: a, heat/cool generation & b) heat emission system.

a) How are you going to generate your heat?

Do you have a choice of fuel?

Electricity : direct (Expensive & doesn't provide cooling)

                    heat pump ( air sourced 3x mere effective than direct, installation relatively cheap, ground sourced 4x as effective as direct but more expensive to instal, both will provide heating & cooling.

Gas: Natural (not often available in Spain outside cities)

         LPG ( expensive as it reflects oil price and has to be filled regularly)

Solid fuel: Coal (Is this available in Spain?)

                  wood (Logs, chips, pellets.  I don't know about this in Spain, but provides only heating & can be labour intensive although it's wonderful in winter to have a lovely roaring fire)

Your choice of fuel controls the heat generator you use

Electricity: direct (can be used in a boiler, which heats water,but rerely is.  Usually used in a furnace which heats the air directly)

                  Heat pump (is basically a refrigeration unit which can be reversed to provide heat which can either heat the air directly, via a refrigerant circuit or through a heat exchanger for underfloor heating)

 Gas & Solid:   Natural & LPG (can be used for refigeration, but rarely is, mainly used in a boiler to heat water or furnace as can electricity)

b) Emission system

Direct : Can be derived from any of the above, although solid fuel is generally stand alone. But effectively a furnace (or similar device) heats recirculated air which warms up the space.  Can stir up dust and also recirculates germs from room to room.

Indirect: Usually by water which provides for radiators, forced convectors and underfloor heating.  The temperature of water is lower in underfloor systems so more suited to heat pumps and ground sourcing.

It is a matter of preference coupling a suitable heat source with a suitable emission system.  In the matter of heat, all heat rises, but only fires and radiant systems (radiators) heat bodies directly.  Other systems use convection which uses the propensity of heat to rise.  Forced convection does blow the air down before it rises again.

I am sorry if this seems complex and actually is not even complete and I could go on for several volumes, but it outlines some of the decision making process as the essentials are there.  Direct electric always costs more, but LPG comes a close second.



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26 Nov 2011 13:36 by floella Star rating in SE Spain. 789 posts Send private message


We have no other form of heating at all although will admit just to see an open fire or wood burner does make one feel warmer even if most of the heat goes up the chimney.   Yes, we do live permanently in Spain.

Our last bi-monthly bill states 13.856 x 63 dias x 0,095074 euro/kw dia = 82.99.. (this is the standing charge)

plus... energia consumada                 187.61

plus... Impuesto sobre electricidad     13.83

plus...Aquiler equipos de medida          3.24

plus...IVA @18%                                      51.78

TOTAL =   339.45  

Obviously people who are not totally electric have smaller bills BUT our local friends appear to spend as much ,if not more on gas bottles ,oil and logs.

We have 2 x power inverter units on either end of our property which are extremely efficient for both heating and cooling and have vents in all the rooms. 

Something else to take into consideration is that some ceilings have to be lowered to cover the extensive pipe work which re.reading your initial query I think the "pre instillation" only covers the buying and fitting of an individual unit per room and is nothing like our system.

However if you buy even this hot/cold system then you MUST increase the potencia of the electricity for which ,of course, there is a charge of 2-300 euros..













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26 Nov 2011 14:47 by carl9 Star rating. 136 posts Send private message

Many thanks Floealla.

Do you find the floor is much cooler than the tops of the rooms?

Sorry for all these questions but I need to get this right.

Regards, Carl

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26 Nov 2011 16:44 by floella Star rating in SE Spain. 789 posts Send private message

 The circulation of air appears to be very good. Whether you are standing, sitting or laying in bed you just feel warm or cooler all over within mins.

Floors here are aways cold so, like you, we did consider underfloor heating initially but the cost extortionate and being totally honest Spanish builders are not always au fait with these "modern" ideas that are now commonplace in UK. 

Am concerned, that this "being Spain" !!!  we have been fortunate with the system we have chosen so please investigate your options thoroughly and buy the best.


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26 Nov 2011 17:00 by carl9 Star rating. 136 posts Send private message

Will do Floella, many thanks.


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03 Dec 2011 11:17 by trish57 Star rating. 14 posts Send private message

 Hi Guys

I am anenglish refrigeration/air con engineer here in southern spain and have installed many systems of all types and makes. I can only answer the air con questions.

The pre installation will typically consist of the two refrigerant lines from the outside(where the condensing unitwill live) to the inside area where the air handling unit will live. usually this is in the ceiling of the bathroom. The preinsatll will provide the supply and return air ducting aswell as the flexible conduit for the electrics between the ahu and the unit. The drain from the ahu may be provided aswell but this does depend on the pre-installer.

Depending on whether the installer intends you to have one or two units(one for upper level and one for the lower level) will dictate the number and sizes of the unit to be selected. These are called stowaway units for obviuos reasons.

The modern units are inverters. These are electronically controlled to start the compressor very slowly and build up speed they will then run at full speed until they get to near the set point on the thermostat and then they will slow down and run at a slow speed until the the call for higher cooling or heating rate happens. As a result these systems are far more efficient than the the "on/off" units of yesteryear.

This type of ducted system are quieter in operation but a lot more subtle than the split systems that most apartments and houses have installed. A split is where the ahu is on the wall in the room at high level. These will deliver almost instant cooling or heating because the air delivery is far more direct than a ducted system. So where a split will cool or heat within minutes, a ducted systme will take longer to feel the actual cooling or heating effect, but the end result is the same in a short while.

Ducted systems have to be selected slightly bigger in performance to take into account the amount of extra space they have to cool or heat IE the ducting and the distance the air has to travel before it reaches its destination (your lounge etc)

With regards your questions of the warm air rising, this is an obvious fact but the diffusers at the end of the ducting have vanes to allow you to direct the air to where you want it, so in the winter you will point the vanes downwards and in the summer you point them upwards.

I think thats as much info I can give you for now but if you feel I can be of further assistance either PM me or send me an email and I will pick it up from there.

Best regards

Pete Gillam

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03 Dec 2011 13:14 by Sallyshaw Star rating in Alicante city. 9 posts Send private message

Sallyshaw´s avatar

Hi Floella,

I have just moved into a house with Daikin ducted aircon (inverter). Year 2005 model RXS60B2VMB. We have 2 units on the solarium, one for each floor. I was interested to see how much you pay a month for electricity as I am unsure if our system will use a lot of electric or not.

The "potencia contradada"  (contracted power) is 9.21 kw and the standing charge for this are €16,12  per month. There seems to quite a bit of difference in standing charges even though yours is 13 kw. (higher) around €40 a month? We are with Iberdrola.

My last electric bill was 70 euros for one month (no use of aircon or heating) so I'm trying to calculate how much the bill will rise to when and if we use the aircon system for heating.

Could I ask you how many hours per day you have the heating on?  Do you use the upstairs unit to warm just before you go to bed for the bedrooms?

I tried it out one day but found that it took a long time to heat our living room (it's quite large 45 square metres) yet the kitchen and the downstairs office room heated very quickly. What I find annoying is that I can't control (switch off heating in kitchen and office) or at least divert all air to lounge, this is probably due to the fact the model is 5 years old. There is only one control panel for each floor.

Many thanks

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03 Dec 2011 16:37 by floella Star rating in SE Spain. 789 posts Send private message

Hi Sally,

We are with Iberdrola as why the enormous difference in standing charge  for a few extra kw  I wonder !!

Our 2 double units are Mitsubushi and they are about the same age as yours.

We have a bungalow with approx 77sq.m of open plan living/dining/kitchen space plus a double height ceiling in the lounge. Some of  the ceilings were artifically lowered for the ducting. The total size of build which is being covered by these units is about 180 sq.m

Must admit they are for us very efficient and within 15 mins the house is comfortably warm or cool everywhere and we have to turn off one of the units. Plus the only time you hear any discernable noise from them is when the aircon is initially blasting through. 

Last year was very cold and the Jan bill for 66 days was 386e  and the March bill 59 days was 351e when a normal bi-monthly bill would be about 320e. Must admit our first year here the January bill was over 700 euros because the house was new and so very cold or perhaps I am getting more canny !!.

How long do we have the heating on for now ? On average about 3 hours everyday.  An hour in the morning and a couple of hours  in the evening.  

All I can suggest is to monitor your usage and finger crossed there will be no nasty shocks. 








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03 Dec 2011 18:04 by MANXMONKEY Star rating in Channel Islands. 81 posts Send private message


Ouch.  How expensive is the electricity in Spain!!?  I rented a place in Valencia last winter and I'm glad it included all costs because I had the heating on for at least 7 hours a day, as I would have in my own home. I feel guilty now.

However I have had properties with both individual split units and ducted so here goes:-

There is of course as always swings and roundabouts.  If I was building new I would go for a ducted system but ensure that you don't have a long run - try to centre the unit rather than having it at one side so that it will be less efficient at the end of the "run".  It is quieter and aesthetically nicer.  Modern set ups can be controlled separately so you could have upstairs cooler than downstairs etc. With a well designed ducted system you won't be worried about it being cold in areas - or lower in the room - because it gently flows the heat or chilled air to be even.  Make sure you choose a guy with credentials; references NEVER take their word for how brilliant they are ask and seek references from ex-pats who have been clients.  Don't let the builder say he can do it, he can't, you know he can't!  Use a heating / aircon engineer and if you don't speak fluent Spanish ensure he speaks fluent English, or try to find an ex aussie or a yank where ducted systems are two a penny and they've installed zillions of them.

Split systems are just as expensive to do a whole house BUT also have benefits. For instance most units will only serve two header units so you can use maybe only one unit if you are not using all of the house.  They are easy to repair (but they are very reliable, my Daikin units in Australia work really hard and have never even been serviced in 10 years!)  Would I also go for underfloor heating?  - On a new build it is tempting, on a refurb no way. If you want to walk around in socks on warm tiles then go for it - spoil yourself.  If you will be happy with cold floors but a comfortable ambient heat then don't bother, throw down some  nice rugs when the winter starts!

Ground source heat pump system - how old are you? It'll take 20 years to pay for itself in fuel savings but I do feel good at just the IVA saving I make on my solar panels so if you hate giving money to the power companies and the EU bandits then the self satisfaction is sometimes quite a nice little investment AND of course, fuel prices will never come down!

Good luck with it - enjoy the project but make sure you make the builders know they are working for you - not the other way around.





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03 Dec 2011 18:16 by trish57 Star rating. 14 posts Send private message


Good advice re the credibility, there are loads of people that can install but when they go wrong due to an incompetent install they havent got a clue what to do.

Re your mention of 10 years without a service. I take it that you dont mean that literally!!! By now the condensors on the outside units and the air filters on the ahus would be clogged solid and costing a fortune to run.

regards Pete

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03 Dec 2011 18:20 by Sallyshaw Star rating in Alicante city. 9 posts Send private message

Sallyshaw´s avatar

Thank you for the information Floella. There seems to be a big difference in the price per unit, the price for rental too. Very weird! Our house is also 180sq.m not including the garage.

I have copied and pasted my last bill for 2 months. (there was an estimated one before this of 20€)

Here is my last bill: 30th of September to 31st of October. (No use of aircon or heating) Gas for cooking.

Potencia contratada 9,2 kW x 31 días x 0,056529 €/kW día 16,12  (standing charge for 1 month)
Energía consumida 570 kWh x 0,142319 €/kWh 81,12  (energy used 2 months)
Impuesto sobre electricidad 4,864% s/97,24 x 1,05113 4,97  (extra tax on amount of energy used) it goes up after 500kw)

Alquiler equipos de medida 31 días x 0,01874 €/día 0,58  (rental cost of meter 1 month)

IVA 18% s/102,79 €18,50

Maybe the price per unit will rocket when we use heating! Bit of a mystery. I will give it a try for a month and wait for the shock!

Many thanks.

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13 Dec 2011 00:21 by seleco Star rating. 1 posts Send private message

Congratulations on buying in Spain,

Air Con ducted systems are fine and the heat they produce usually surprises new users. I'm based near Alicante in Spain and normally the builders include an internal ducted pre-installation on each floor, usually the indoor units are situated within the false ceilings of the kitchen or bathrooms. Builders usually charge an arm & leg for this simple service but there's not a lot you can do. They should also provide the power supply to the unit as it needs a seperate circuit so the tariff should be sorted. 

Basically, in Spain,  the Summer heat is unbearable in July & August and so you most certainly need a/c fitted, therefore you might as well take advantage of its heating in winter.

If you treat it like central heating you won't go far wrong.

The main disadvantage to ducted systems is the lack of individual control to each room ie. to cool a downstairs bedroom overnight you will end up cooling the lounge as well, or cooling a main upstairs bedroom, you may have two other bedrooms that you dont need but are also cooled.  You can fit seperate dampers which close off the individual vents to the rooms but they add to the initial installation cost.

For  a very approximate price for a lounge and one bedroom or three average bedrooms, your looking at something from around €1120 per unit, €2240 per dwelling.

** EDITED - Against forum rules **






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13 Dec 2011 09:15 by floella Star rating in SE Spain. 789 posts Send private message

 Sallyshaw,  your potencia charge won´t alter unless the heating keeps tripping the system and you need ask Iberdrola to up the kw and then I guess they think of a number and double it !!.



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13 Dec 2011 10:05 by Sallyshaw Star rating in Alicante city. 9 posts Send private message

Sallyshaw´s avatar

Hi Floella,

At the moment no tripping but I think this is because we have a double circuit , (upstairs and downstairs) so I reckon that they are 4.4 each floor or something. I have been in many flats in Spain before where the circuit has tripped though, I remember one Christmas eve cooking dinner (nochebuena) as my family are Spanish and it was impossible to have the roast on (electric oven) have a hot shower and dry my hair all at the same time. LOL!

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