A/C unit too small for the house?


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Old 06-30-10, 10:13 AM
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A/C unit too small for the house?

Just had a service man come out to check our system. House is 2863 sqft. There are two 3-ton units, on the ground outside, that cool the house, 8 years old. One unit handles roughly 65% of the home and the remaining 35% by the other unit. The 35% unit does quite well while the 65% unit has to run, run, run just to bring it to 80 degree on a 100 degree day outside. This a single story home and the ceilings are quite high at least 12'. The AC man said that the 3ton unit was too small to handle that kind of area and a 4ton would be a better unit. The builder of the home is well established and has a tremendous reputation for craftsmanship.
Any thoughts on this? Would the builder put too small a unit on the house. Should a 3ton unit handle ~1860 sqft?
 
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Old 06-30-10, 12:42 PM
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Have you thought about re-routing some of the cold air from the other unit ?
 
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Old 06-30-10, 01:09 PM
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Only way to know is to do a heat load on the home. This will take at least an hour to do.
 
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Old 06-30-10, 01:23 PM
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Those 12' ceilings mean you are cooling the equivalent of 4300 sq ft house with 8 ft ceilings. For your climate and volume of room air I'd say you are undersized. Some builders will "round down" in sizing if they are pressured to keep the sales price low.
 
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Old 06-30-10, 07:44 PM
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Can't go by size any more! You have to do a heat load!
 
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Old 07-01-10, 08:11 AM
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Originally Posted by airman.1994
Can't go by size any more! You have to do a heat load!
Ok airman. How do I do a "heat load"?
 
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Old 07-01-10, 08:19 AM
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My first thought as well - you have two identical units covering 100% of the home, can the airflow be changed to split the house 50-50 across the two?
 
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Old 07-01-10, 08:28 AM
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Originally Posted by bobed2121
Ok. How do I do a "heat load"?
Google "heat load calculator." Google is your friend.
 
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Old 07-02-10, 01:42 PM
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Not sure Google is always your best friend. Me and Sargent Schultz we know nothing!! But I have been lead to believe that this is the best calculator to use. JIm

Download Cooling Load Calculator Free Downloadr Software: Calculator Prompter, ComfortAir HVAC Software, Free Rent Or Buy Calculator, ...

It's not free but sometimes you get what you pay for.
 
 

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