I'm looking at a Trane set-up that utlizes a 2 speed fan on a 13 SEER AC unit and a 4 speed fan on a 80% 2 stage furnace. At least that's what's on the Trane website. I still have to see if these units are rated to be used together.

I've read a few posts concerning fan types. Some of the professional members have indicated that variable speed (ECM) fans are the way to go, while other inidcate that multiple speed fans (2 speed, etc.) are sometimes less reliable than a single speed fan.

So if the professional members were buying for their own home (and had to pay retail) what would you buy as far as fan types, and what are the important issues?