Yes residential Trane, how good is it?
If it's 15 years old and still going, pretty good. Is it a furnace or AC unit or both?
Either way, you could expect 5 mores years of service with normal maintenance. You may want to plan around that because the EPA keeps making them more expensive and less reliable. I'm not up to speed on the latest. I do know EPA messed up water heaters last year.