How to read Lennox, Armstrong Air and Ducane serial numbers
This covers Lennox, Armstrong, Armstrong Air, Ducane, AirEase, Concord, Aire-Flo, Magic-Pak. The serial number is on the rating plate on the unit.
Reading it yourself
Nine or ten characters: four digits, a letter, then digits. The first two digits are the plant. The third and fourth digits are the year. The letter is the month: A is January, I is skipped, M is December.
Example:
5898G07568was made in July 1998.
This is the date the unit was made. It was usually installed soon after, but it can be later. If a serial doesn’t fit any of these patterns, look on the label for a printed manufacture date.
Sources
Checked in October 2026.
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