You have to determine the size that can be handled by furnace . 30000 BTU is required to handle 01 ton ( roughly ) So say your furnace is 100,000 BTU it means that you can safely chose 3 or 3.5 ton AC . Furnace is sized according to the house size . So chosing the right AC should be suffice without going in too much calculations .
Lot of people chose for bigger AC for peace of mind which will give you trouble . AC is better to be undersized than oversize as it removes humidity while giving you cooling effect .

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Originally posted by Aashu


Ok Ashwani G, so to start how do we determine what capacity we need ?

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Growing Old Is Mandatory ..Growing UP is Optional

Hi Ashwani,

How do I know what size of furnace is needed for my house.. Is there a sqft to BTU relation.

Thanks,

I see the calculation here,
http://www.wikihow.com/Calculate-BTU-Per-Square-Foot#Determining_How_Much_to_Heat_or_Cool_sub

As per the above site it's (40 - 50)*(area of house in sqft) BTU

Thanks Ashwani G, once we find what we need, do you have any suggestions as to where ? which ?

I got the number 35000 from a door to door AC installer guy ,....

KR

As a rule of thumb you got with the same Input as installed by builder .
Otherwise an air test can be performed to determine the correct size .
There are other factors that should be considered as roof age and condition , no of windows and most importantly direction the house is facing .

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Originally posted by lemon925

Hi Ashwani,

How do I know what size of furnace is needed for my house.. Is there a sqft to BTU relation.

Thanks,

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Growing Old Is Mandatory ..Growing UP is Optional