Originally Posted by
hghclsswhitetrsh
The only true way to know is a heat load calculation. It takes into consideration window sq feet, direction, sq footage, net wall, insulation in ceiling and walls, sq footage over unconditioned space etc etc etc. There are probably 40 factors that determine tonnage. The old saying "400-600" per ton" is primitive and asinine to say the least. It would also be silly to put an R22 system in instead of an R410A.
Oh yeah and too big of an AC can be worse than too small.