What ton a/c unit should I have for my house?

I have a split entry home and the evening summer sun kills us. Our 1.5 ton unit is obviously too small and can only cool the house down to about 82 degrees. We have about 1450 sq ft upstairs and 300 square foot downstairs. The builder put in the smallest unit he could obviously get away with. Thanks.

What ton a/c unit should I have for my house?
Have you considering using your existing AC downstairs and adding the new one upstairs?





Haven't a clue for size - don't know your location, details of house construction.


Suppose you'll need to find a local that's trustworthy...
Reply:3 ton unit will work fine for a 1750sqft house. Just keep in mind that your furnace needs to be able to handle a 3 ton unit. If it doesn't have enough air flow it will cause problems. If you get to big of a A/C unit it will put to much moisture in your house. Be sure and get a 13 seer unit, this will save you tons of $$$$$s in the long run. I'm not sure how the old the house is, but I sure would call the builder and discuss this with him, and if he doesn't want to correct the problem. turn him in to the BBB, and let him know your're going to do it.
Reply:Just to reinforce some of the other comments: tonnage is estimated by computer program. The program asks questions such as: square footage, how much natural shade is present, which way the windows and doors face (east and west exposure especially), insulation R-factor for walls, floors, and ceiling, etc. This information properly determines what size unit(s) are needed to properly heat and cool your home. But I can tell you what you already know, 1.5 tons is definitely not enough. A professional HVAC contractor can help you correct your problem.
Reply:You need to know more than just the square footage. There are many more factors that must be considered. What you need is called a load calculation. The process uses computer software to model the home to find the size of the equipment. For more info, check out my source.
Reply:Contact a HVAC contractor and they will size the home for you by doing heat/load calculations. Square footage alone is not enought to properly size a a/c to a home.


For a rough guess count the number of heat supplies in the entire house. Four heat supplies equal 1 ton of a/c. So if a house had 12 supplies it should handle a 3 ton a/c.
Reply:You cannot use just the square footage as a guide. There are inspections that need to be done which account for the number of windows and doors in the home. I would say you will be told a 3 ton unit as a guess based on sq. footage.
Reply:Seems like you answered your own question. 1-1/2 ton is definitely not big enough. I would suggest that you contact a local HVAC contractor in your area. Get recommendations if possible from family or neighbors. I just installed a 3-1/2 ton unit in a home about the same size. If you change the unit you will also have to change the A coil to match. Keep in mind also that bigger is not better in A/C cases. If it is too small it will run constantly and too large it will short cycle and kill the unit prematurely. I think a 3 to should do the job but no larger than 3-1/2.
Reply:We also have a west-facing house that lets in too much sun in the afternoon/evening. I'd suggest that you Google "air conditioning" and "ton unit" to get more of an idea of what you need before contacting AC companies; I really couldn't make a good guess.





Another thing I'd recommend, however, is to plant some bushes and trees on that side of the house to provide shade; it makes a bigger difference than many people realize, and reduces the strain on the AC system. Also try shades as window treatments that can be lowered when the sun gets to be too much, or some of the film that can be applied to the windows to block out the UV rays.

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