Our fire station had two new a/c units installed today.I have a question regarding one. I'm posting here because the station is more residential in style than commercial.

In our barracks side, which measure 30' x 18' qith another 10' x 10' room they installed a York 2 ton unit on the roof replacing the old 2 ton unit. We noticed tonight it doesn't want to cool below 72 degrees and it's in the mid 80's outside. We think the old return duct is too small at 13.5" x 15.5".

Could this be a problem and what should the proper size be? In the large room there's two 10" x 10" registers and in the small room a 10" x10". Just some general info would help us out a lot.