I have a 16 y/o Carrier packaged heat pump that I am replacing due to a coil leak that can't be located or fixed (recharging leaks out too quickly), so this is a concern of mine too. I am in the process of pricing both a Trane and a Carrier as a replacement and I wonder if the coil currently needs to be a major concern? Trane emphasizes their solid aluminum vs the tin covered copper (or whatever it is). I see where someone posted that Carrier's coils are pretty much ok now. Is that correct? Is there a significant difference between the coils performance? To me this is a pretty important decision point. I'm looking at a Trane XL14c 14 Seer and a Carrier 50XT 15 Seer two stage and need to make a choice quickly.