What size central air unit for my home???

[setterguy]

My wife and I recently moved into a new home and declined having the builder install our central air unit as I know someone who can do it for about 1/2 the price...I now have to decide what size unit to get and am getting conflicting answers. Our home is about 1900 sq feet not including the basement. One source is saying a 2.5 ton unit and the other is saying 3 ton. I have heard that going too big is almost as bad as going too small...anyone have any advice?

[looking 4 a 30]

you need to have a load calc. done on your house. If somebody is going to guess of go off square footage your unit could end up being over-under sized. to many factors to give you a correct size. hope this helps.

[backlash 1]

Personally, i'd rather be a little over than a little under,(size wise ) Had a house one time where the AC wasn't big enough, not a good deal.

I would ask the installer. If he is qualified to put one in for you he sure should know what size you need.

Good luck

[Ryan Berger]

Quote:

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Personally, i'd rather be a little over than a little under,(size wise ) Had a house one time where the AC wasn't big enough, not a good deal.

I would ask the installer. If he is qualified to put one in for you he sure should know what size you need.

Good luck

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actually being to big is way worse than being a bit too small, too big will cool the air to quick without taking all the moistuer out of the air it will short cycle and never totally condition the air in your home. The general rule for ac is 1 ton per 600 cubic foot so the 2 1/2 ton would be great, just have them put in a 3 ton A coil (you can oversize your A coil but only half a ton is reccomended) and that will make the unit have more superheat improving your efficiency quite a bit, take the money that you would have spent on the 3 ton and maybe a bit more and get yourself the highest SEER (seasonal energy efficiency rating) rating you can afford at the time, I would definatly go 13 seer or higher

[setterguy]

Wonderful advice, thank you guys. We are getting a 13 seer rated unit. And we are buying our unit from someone other than the person that is installing it, and he is saying 3 ton but the place that we are buying it from is saying a 2.5 ton would be suffeicient...I will keep investigating.

[SDHNTR]

Just to add to what everyone else was saying. Oversizing is worse than undersizing. Undersizing only requires that the unit will have to run longer each cycle. I agree with the statement that an oversize unit will cool the air to fast and not remove enough of the moisture in the air. From what I was told by the AC guys that I work with, a 2.5 ton AC unit should be large enough for you, even though a 3 tons would probably work fine too.

[one more]

as long as they both did heatload calcs. the differance between 21/2 tons and 3tons will not be much of an issue. there most likely will be a TXV installed (13seer) to meter the refrigerant, which will give you a little "wiggle" room with the humidity issue. you need to have a GOOD heatload calc. done, DO NOT use "rules of dumb" to size it.

[End of the Line]

Anyone not doing an actual heat calculation should probably not be installing your system unless someone else figured it out for you. I once had a house that was 1700 sq. feet with a full basement too(3400 total). I heated the house here in Duluth with a 3 ton (36,000 BTU) heating system. Calculated to only 2 ton (24,000 BTU) but they didnt make anything smaller in the heating/cooling system for my house. It's not the size of the house its the construction; and the old 'rule of thumb' will probably work, but should not be the accepted method for determining what you need. My two cents.