Got two different quotes to replace HVAC system for the upper level of my house. One installer recommended a 4 ton Amana AC unit and a 95% efficient Amana furnace. The second installer recommended a 3.5 ton Trane AC unit with an 80% efficient Trane furnace. The second installer said that they don't install furnaces greater than 80% efficient in attics because the condensation can freeze in the dead of winter (live in Atlanta). Not sure about Amana vs. Trane and not sure about the right efficiency level for the furnace in the attic. Thoughts?

If you have 2 systems, the upper unit probably does not run half as often as the downstairs. 80% should work fine. Water in a unheated space always has a chance to freeze. Your call, is the unit being removed a 80% or 90%

Thanks for your quick response. Current system is 80%, but would like to move up to variable speed. Actually have 3 systems in house (2 floors plus basement). Having more issues with AC than heat, so will likely stay with 80% given risk of freezing, as you suggest. Any thoughts on the Trane XV series vs. the Amana AMV or AMH series?

Current AC is 3 tons. Never been great. Like a cool house-- 73-75 degrees in summer when 85-95 outside. Struggles to deliver 78-80. Just converted two-story open family room to one-story to create an upstairs bonus room. New room is about 300 sq ft and total upstairs is ~2500 sq ft. 4 bedrooms, large master bath and walk-in closet, bonus room. Now the upper AC unit is really struggling. One installer suggested going up to 3.5 tons, the other going up to 4 tons. Thoughts on what's needed to do the trick? Happy to pay for what I need, but don't want to pay more for no reason. Would a four