I remember the old days when i was told to stand across the street on the oposite curb hold my hand out a foot from my body and raise my thumb.I your thumb blocks out the entire house it's a 1 ton,two thumbs is a two ton ect LOL.I was in that trade for 10 years and rarely seen load calculations done properly.It's very important that the a/c unit be slightly undersized rather than oversized as too large a unit will short cycle reducing life expetancy.Most electronic thermostats will force the a/c to run a minimum of 10 minutes and lock it out for 5 if someone fools with it for this reason.Most newer units with mechanicaly siezed compressors are oversized with cheap thermostats.
