Has it worked well in the past? How old is it?

Is there a way that you can get in touch with the owner of the apartments? When the apartment was built they go by guidelines called a Manual J calculation for that apartment's HVAC needs. Even though you are renovating, the square footage isn't changing. It seems odd you would have to increase your unit with the same footage. If you get talked into an overcapacity unit you will end up with short cycling, low efficiency, high humidity and high bills. Also, forget all those calculations of 400 sq feet to a ton. Every situation is different depending on where you live and your load.

If your owner of the unit doesn't have it or the condo association doesn't have standards for your unit, then you most likely can get the Manual J calculations at the building department for your unit. It's public record in most municipalities (permits, plans etc too). The last a/c unit installed would have had to have a HVAC permit too. In my area there is a records department at Building and Zoning where you can get a copy of all the building records pertaining to any property. It is a public records request that doesn't take long at all to fulfill. Some of the records are online, not everything.

Hi,

I consider a 3.5 ton capacity air conditioner to be a very large unit for a new 1,600 SF single family home (i.e., no common walls) even in the south. Since your space is an apartment, I imagine you have some shared walls with adjacent units, and you may even have a unit above/below you--all of which would decrease the heat load for your apartment. I suggest you have a good mechanical contractor run the calculations for your apartment to determine the size unit needed as well as the duct design. If your A/C system is 10 or more years old, replacing it with a more efficient, properly sized system will both improve your comfort and reduce your utility bills.

Good luck.

Don't forget to take into account your window area and exposure. We have seen far too many systems get sized based on some formula that doesn't account for the heat gain/loss through the windows. As much as 40% of the AC load can be attributed to the glass in your apartment. Window film can be a fix for this and allow you to use a smaller capacity system. Visit www.enerlogicfilm.com to learn more.