Friend bought a house with a Bryant Plus 80 gas hot air furnace, installed probably within the last 10 years. Installed horizontally in crawl space so I can't get at serial #. Manual sitting there says either 373 or 376 LAV or CAV. Anyhow, here's the Q: I have an unused 3ton Trane condenser; was wondering if that is compatible to add to furnace for central AC?

3 ton,, get a manual J calculation done,, is it big enough for your home (in BTU`s)
You don`t want one to big,(will cause more problems)