Just another comment. The old unit was a 3.5 ton, new unit proposed is 4 tons. Would this be the reason for an extra return? i'm guessing they do not make any more 3.5 ton units.
Every manufacturer that I know of has a 3.5 ton unit unless its a two stage. The extra return is usually a good idea because there is not to much of a downside for having to much return air as long as they are proportional for the space they are supposed to cover.
Do you know why they sized you up to a 4 ton unit? Did the old 3.5 unit not cool? 90% of the time I see oversized units only about 10% or less are undersized(although just had this yesterday on a sales call 2 ton when they the load calc said they needed 2.75 tons, had a 40 amp breaker installed for a max fuse 25 on their two ton, somebody made a mistake 18 years ago and they just lived with a hot house.)
sorry, actually looked at the specs and it is in fact a 4-ton. and it did cool when the r22 was recharged in march. now it's taking a good 3-4 hours (first time to turn on during the day) to drop from 87 to 82. hence the reason i was asking how long it usually takes to cool. Is this common? since during this time the air blowing is cool but not cold.
another question do the installers need to be authorized dealers for that manufacturer? and i did have a question about trane labor warranties, can you buy them from somewhere else or do you need to buy them through the installer?