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08-03-2009, 05:23 PM #1
Sizing Low temperature rads for Daikin Altherma
Hi all, i would like some info on the calculation to size low temp rads ( Jaga ) to a Daikin Altherma.
I am sizing a house at the moment in Spain, i am familiar with heat loss calcs but with flow temperatures of 55 and a return of 45, are the calculations different.
For example i have a room with a heatloss of 2100watts, now the rads required would be 2 X 1050watts and the physical size of these are 1.2 meters long. But a heating company has given me their calculations based on surface area X 115w psm and their heatloss calc is more or less the same as mine but they have given me 2 X 788watt low temp rads, which is 600 watts short for the room.
Now i know Low temp rads convect the heat but does that have any bearing on the output of the rad.
I look forward to any replies.
Debonair Spain
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08-03-2009, 06:43 PM #2
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Re: Sizing Low temperature rads for Daikin Altherma
They should be almost double in size than normal radiators for 75/65°C temperatures.
So radiators for your system should have catalog power output (75/65°C) of about 2100W to get 1050W at 55/45°C temperatures.
Why not use fan-coils? They have much better temperature distribution and better suited for low temperature aplication.Last edited by nike123; 08-03-2009 at 07:02 PM.
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08-03-2009, 07:46 PM #3
Re: Sizing Low temperature rads for Daikin Altherma
Hi Nike123 thanks for the quick reply fan coils is not an option because the people prefer central heating.
I just cannot understand why the heating supplier of the Jaga rads has undersized the whole house.
I will need to consult further before i submit a price.
Many thanks
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08-03-2009, 10:15 PM #4
Re: Sizing Low temperature rads for Daikin Altherma
Hi all i would appreciate some more comments please.
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08-03-2009, 11:00 PM #5
Re: Sizing Low temperature rads for Daikin Altherma
Is it too late to fit underfloor heating to take advantage of the lower temperature available?
edit: Some data relating to the change of radiator sizes is given in this papr....
http://www.mas.bg.ac.yu/istrazivanje...ac_129-134.pdf
However, I believe your figures are correct, whatever the radiator is it still needs to output the required design heat loss.Last edited by Brian_UK; 08-03-2009 at 11:13 PM.
Brian - Newton Abbot, Devon, UK
Retired March 2015
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09-03-2009, 07:35 AM #6
Re: Sizing Low temperature rads for Daikin Altherma
Hi Brian thanks for your reply, they were considering underfloor heating and i did suggest that the Altherma would work better with this system
But as usual money if a factor and it would mean concreting and tiling the whole house, which would put the price up considerably.
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09-03-2009, 09:02 AM #7
Re: Sizing Low temperature rads for Daikin Altherma
When we were all down there, I'm sure the chain smoker said any rads would only need to be 20% bigger...?
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09-03-2009, 09:05 AM #8
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09-03-2009, 02:11 PM #9
Re: Sizing Low temperature rads for Daikin Altherma
Hi all yes i believe Multisync could well be right that the Spanish size to 17 degrees c which is not good for the times when you really need it especially when their houses have a tremendous heatloss.
Thanks for all your help, this site has a wealth of knowledge.
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20-04-2009, 10:21 PM #10
Re: Sizing Low temperature rads for Daikin Altherma
try visiting www.altherma.co.uk
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