Trane uses alpha codes in their serial numbers to determine year of manufacture. They started this in 1987 with the letter B and skipped a couple of letters during the years........ The first letter of the serial number gives the year of manufacture as follows:
In 2002 they started their serial numbers with the year it was built. In 2002 the first character of the serial number is 2, in 2003, 3 and so on.