How to read a Trane, American Standard serial number (find the build date)

Decode a serial number now (works offline).

The rule

Characters 1–2 = year, characters 3–4 = week of the year (01–53). Example: 11241KADBB = week 24 of 2011. Applies to units made in 2010 or later; earlier serials use a different scheme that sources disagree on, so this tool does not decode them.

The maker doesn’t publish this rule where I could find it, so it rests on inspector and HVAC-guide sources and may be wrong for some units: Third-party HVAC guide (not the maker).

Worked examples

Applies to: Trane and American Standard furnaces and air conditioners (2010 and later). Always check the result against the label.