You can set the temp to "...but since it took so long to finish the house the air conditioner has actually been installed for awhile."

- Check your filter and inside coil. They may be dirty from all of the construction dust and dirt. A freezing-up coil means either a low charge or restricted air flow across the coil.

I am not a pro but I would think that a 5500 square-foot home would require at least 2 separate systems. You do not say what area of the country you live.

My new 3 ton unit will cool my 1800 square-foot home in Baltimore to 72 easily even at >95 outside. It is a little oversized for a/c, but I need the sizing for the heat pump in the winter time.

Ask the builder to see the Manual J (heat loss/gain) and Manual D (duct sizing) calculations for the new home. I bet the calcs weren't done.

Best of luck to you.

5 tons for 5,500 sq ft?? Wow. I have 5 tons for 2,550 sq ft. Location may make the difference, I'm in Texas.

A/C's are asked to do a job that sometimes is impossible. Remove humidity and cool the home no matter what the outside temperatures and humidity. A system large enough to create comfort in the home at 90-100 degrees, doesn't do well when it's 78 outside and runs only a few minutes to reach comfort levels. A system only removes humidity when it's running, so during the cooler days it may feel warmer in the home because the system runs little. On hot days it runs a long time creating a dry an more comfortable home. Finding a system that is somewhere in between these two areas is hard to do. Now since systems are, by standards, designed for 75 degrees inside, setting the temperature at 72 may, in some cases cause problems on the hottest days- relative to humidity conditions.
If the system needs to overcome heat built up in some homes structure during the day and run a long time in the night, it could possibly ice up if the outdoor temps fall into the 60's, but that is rare.
During the hottest months, leave the thermostat set within 2 degrees of the temperature you want it in the home, or it may not be able to recover in the evening and over run.
The system could have been low on freon without a leak.
I went to a newer home and had to add freon to the system. I found no leaks, but did find that the downstairs a/c was low on freon too. I found out that the Goodman heat pumps were started up during the winter and the facts sheet informed me that the system could only be charged properly in the a/c mode. I concluded that this was the problem.
5,500 sq ft and 5 tons seems small- what area of the world are you? We would use a 5 ton for about 3,000 sq ft and a 2.5- 3.0 ton for the 2,500 sq ft.- Depending on windows and structure placement ect.

Thanks for all the helpful comments! Actually there are two 5-ton AC units, one for each floor - sorry for the confusion. But I'm glad it sounds like the size of the units I have is in the right ballpark. I'm in the Upper Midwest, so we don't get too many long stretches of high temps, but lately it's been pretty warm. I'm going to check over the filters and coils, and also have the freon level checked again - hopefully it's just a maintenance thing or a small leak. Thanks again for all the help!

I'd like to have that be a federal law--no non-specialized (i.e., the chocolate shoppe) building should be colder than 75 degrees in the summer.

If it's colder than 72 in the winter, I want a sweater!

(sorry--this has nothing to do w/ your problem; just my pet peeve)

There should be a law requiring no building be above 60 in the winter.

Actually, if its my building or my lease then I should be able to set in on any temp I want as long as I pay the electric bill.

No building should be cooler than 75° in the summer? That's definitely a matter of opinion. haha! Our climate doesn't use much air conditioning, but if my home stayed at 75° at any point in the year, I think I'd melt. And despite living in Alaska, I still find 60° indoors during the winter to be too cold. (Although my Aunt would certainly disagree.)

yeah, I'm mostly joking--if it's your building, of course you should be able to set it.

I'm just so darned cold--in July!!

I wear two sweaters at work. I shiver almost uncontrollably in some stores.

I just wish it would be "cooler" inside, and not frigid.