How Old Is My Lennox Furnace?
Characters 3 and 4 of a Lennox serial number are the year and character 5 is a letter for the month. Type the serial number from your furnace's data plate below.
Where the serial number is on a furnace
Take off the front lower panel (turn the power off first). The data plate is a metal or foil sticker on the inside of the door or on the side of the cabinet, next to the blower. The serial number is usually labelled "Serial No.", "S/N" or "Ser. No."
How to read a Lennox serial number
Characters 3 and 4 of a Lennox serial number are the year and character 5 is a letter for the month.
10 characters, 1974 to today
PP YY M #####
- Characters 1 and 2 are the factory.
- Characters 3 and 4 are the year: 98 means 1998, 10 means 2010.
- Character 5 is the month as a letter.
Example: 5898F06044
Month letters: A = January, B = February, C = March, D = April, E = May, F = June, G = July, H = August, J = September, K = October, L = November, M = December (there is no I).
Units made before 1974 use an older code that we do not decode yet.
How long does a furnace last?
Most furnaces last 15 to 20 years. Yearly servicing, the local climate and how hard it works all move it within that range. Past 15 years, it is worth getting a replacement price before the unit fails, so you aren't forced into a rushed decision.
Furnaces made before 1992 were built before the federal 78% efficiency minimum. If yours is that old, a new 95% furnace could cut your heating fuel use by a quarter or more.
Questions
How do I find the age of my Lennox furnace?
Characters 3 and 4 of a Lennox serial number are the year and character 5 is a letter for the month. You'll find the serial number on the data plate. Take off the front lower panel (turn the power off first). The data plate is a metal or foil sticker on the inside of the door or on the side of the cabinet, next to the blower. The serial number is usually labelled "Serial No.", "S/N" or "Ser. No."
How long does a Lennox furnace last?
Like most furnaces, a Lennox typically lasts 15 to 20 years with regular servicing.
Related
How sure are these dates? Checked against official records (recall notices or data plates with printed dates). How we test the decoder.
Keeping an older furnace going
- Furnace air filter: Change it every 1 to 3 months. Check the size printed on the old filter.
- Carbon monoxide detector plug in: Any gas furnace, and especially an older one, should have a CO alarm nearby.
- Smart thermostat: Cuts run time on any system, old or new.