How To Read Lennox Serial Numbers?

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Lennox furnace and AC unit serial numbers contain important information about the unit such as the manufacturing date. Knowing how to decode a Lennox serial number can help determine the age of the unit and which parts may need to be replaced soon. Here's a breakdown of what each segment in a Lennox serial number means:

Example Lennox Serial Number

L5612341

First Character

The first character is always an "L" and signifies that this is a Lennox product.

Second and Third Characters

The second and third characters represent the product line. For example, "56" indicates this is from the SLP line of products.

Fourth through Seventh Characters

The fourth through seventh characters are numbers representing the date of manufacture. For example, "1234" indicates this unit was manufactured in the 12th week of 2004.

Last Character

The last character is a check digit used internally by Lennox for quality control.

With this serial number breakdown, you can easily determine the approximate age of a Lennox furnace or AC unit just by decoding its serial number. Contact a professional if your unit is nearing or past its expected lifespan.


Related tutorial videos:

How Old is My Lennox Unit?


How to Locate Your Furnace Model and Serial Number