Find the manufacture year of any Lennox AC unit, heat pump, or furnace from the serial number.
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How to decode the serial number
Lennox uses a straightforward year-month date code at the beginning of the serial number. The format has been consistent since the early 1990s.
1993 to Present
The first two digits are the year, the next two are the week of manufacture.
5197A12345
Position
Meaning
Example
1–2
Year — 2017
17
3–4
Week — Week 23
23
5+
Sequence — Production sequence (ignore)
A12345
Where to find the serial number
On outdoor Lennox units, the data plate is on the side panel, usually near the refrigerant lines.
On Lennox furnaces, open the front access panel — the data plate is inside on the cabinet wall.
The serial number on Lennox units begins with two digits for the year followed by two digits for the week.
Serial numbers starting with 93–99 were made in the 1990s. Starting with 00–25 were made 2000s–2020s.
Decoded examples
2317A12345
→ Week 17, 2023
23 = 2023, 17 = week 17
1434B67890
→ Week 34, 2014
14 = 2014, 34 = week 34
9852C11111
→ Week 52, 1998
98 = 1998, 52 = week 52
Life expectancy
Expected lifespan: 15–20 years for Lennox central AC and heat pumps. Lennox is a premium brand — units often last toward the upper end of the range.
Common questions
The first two digits are the 2-digit year (93–99 = 1990s, 00–25 = 2000s–2020s). The next two digits are the week of manufacture. The rest is a production sequence number.
06 = 2006, 24 = week 24. That means it was manufactured in June 2006, making it approximately 18–19 years old as of 2025.
Lennox International also manufactures Ducane equipment. Armstrong Air and ADP (Allied Products) are separate companies but sometimes distributed through overlapping channels.
Lennox furnaces typically last 20–25 years. As a premium brand, Lennox heat exchangers and components are generally more durable than budget brands. Annual maintenance significantly extends lifespan.