Lennox serials start with two digits for the plant, then two digits for the year, then a letter for the month (A is January through M for December, with I skipped). 1606B13871 was built in February 2006. Five more digits follow. Enter yours below to get the age.
| Serial | Built |
|---|---|
| 1606B13871 | February 2006 |
| 5819C12345 | March 2019 |
Armstrong Air and Ducane are Lennox brands and use the same format. The month letters skip I so it isn't confused with the number 1.
Codes based on a week number give the month only approximately. If the plate prints a manufacture date (often labeled MFG or MFD), trust that over the serial.
| Equipment | Typical service life |
|---|---|
| Gas furnace | 15–25 years |
| Central air conditioner | 7–15 years |
| Heat pump | 10–15 years |
Source: InterNACHI Standard Estimated Life Expectancy Chart. Maintenance, water quality and climate all move these numbers.
Age doesn't mean a unit has to be replaced; it tells you when to start planning. A replacement you schedule costs less than one you buy the night it fails. If it's near the end of its range, write down the model, serial and capacity now, so a contractor can quote the right replacement without a trip just to read the plate.
Scan the nameplate and Answer3 Vault reads the serial, works out the age, saves the model and the maker's parts list, and reminds you before the unit reaches the end of its life.
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