We built our home in 2005 and had Polar Foam insulation put on all exterior walls, attics and between 1st and 2nd floor.

Is anyone aware of the effects of polar foam on air handlers in attics? Two of three Trane units have had thus far in 7 years, each 2 new evaporator coils. Coils completely rusted out and leaking all refrigerant within 24 hrs. The 2.5 ton has required 2 new fan motors as well. The latest replacement on the 2.5 ton is an aluminum evaporator coil, but very pricey! The other unit, 2 ton for upstairs, had a burned up fan motor and completely rusted evaporator coil. Fan also completely covered in mold. It was recommended to replace the air handler and condenser. Thought it would be more cost effective. We did, but with a Broan. Now we can't get the air cool and humidity down unless we drop the thermostat to 72 degrees. Can't wait for my next electric bill.
The upstairs is 1108 sq ft with a 2 ton 14 seer rating (cooling), and cooling capacity (Btuh) 24000. No clue if this means anything.
Our third unit is in a closet on the main floor with no coil or fan issues whatsoever.
All three Trane units have always been set at 77 degrees for cooling in the past, with cooling and humidity control excellent. Pretty good for Florida during the hottest time of year.

It was also recommended to have two attic vents placed in the roof where the new Broan is located. Other than cutting into the foam and creating a hotter attic, this has not improved our situation. So far they have no other recommendations for us, other than slowing down the fan speed for better humidity control? I don't even feel the blower as it is, at the speed it is set at.

Today we told the rep and installer that this unit is unacceptable as it is and to come up with a solution or removal and refund.
Any ideas what the problem could be with the Broan?
Any thoughts on foam insulation and air handlers in attics?