MAS444 said:
Thanks for the responses everyone. I will ask for the actual calculations. And no, we don't have especially tall ceilings. Basically 10' down and 9' up.
Sorry this is happening to you. Just a heads up - brace yourself for pushback. The AC guy and the GC are now going to fight you on everything because this is a 14-20k problem. Also, the AC guy is most likely not going to have any real calculations to show you and they will accuse you of not knowing what you're talking about.
I would recommend you stand your ground and reiterate that the unit was not spec'd properly. The internal humidity speaks for itself. Usually what happens is the AC guy bumps up his rule of thumb calculations and its now officially oversized. A properly sized AC unit should run all day on the hottest day of the year.
And I misspoke earlier, ACCA owns Manual J not ASHRAE. Also, there's a web app called coolcalcac.com that can help you make your own determination for AC size. I have never used it, but just a quick google search makes it look like its simple enough for laymen to use and its geared for AC professionals.
As a side note, a general rule when getting into 'model fights' is that all models are wrong, some are useful. You're trying to figure out not only what your house should be, but also why you've got a 7 ton AC set up.