Lennox Industries · Modern 10-Character HVAC Date Code
Lennox Serial Number Age Lookup
Find your Lennox furnace or AC manufacture date.
Lennox Industries encodes the production year in the 3rd and 4th digits and the calendar week in the 5th and 6th digits of standard 10-character serial numbers. Enter your serial number below for instant informational decoding.
Lennox Date Code Decoder
Enter your Lennox serial number.
Locate the rating plate on your Lennox gas furnace, outdoor AC condenser, or heat pump to decode its production week and year.
Enter your Lennox serial number above
Type the serial number from your equipment rating plate to decode the production week, manufacture year, and estimated age.
How Lennox Encodes Age in Serial Numbers
In modern 10-character Lennox HVAC serial numbers, the manufacturing date is encoded in positions 3, 4, 5, and 6:
Example: Serial Number 5821231234
- Digits 1 & 2 (
58): Manufacturing division / plant code. - Digits 3 & 4 (
21): Manufacture year = 2021. - Digits 5 & 6 (
23): Production week = Week 23 (early June). - Digits 7–10 (
1234): Unit sequence number.
Where to Find the Serial Tag on Lennox HVAC Units
Lennox Gas Furnaces
Turn off power, remove the upper burner access door, and locate the rating sticker on the inner left or right metal cabinet sidewall.
Lennox AC Condensers & Heat Pumps
Affixed on the exterior metallic cabinet near the electrical disconnect box or service refrigerant valve access panel.
Lennox Air Handlers
Printed on the front service panel or inside the blower compartment door.
Lennox Packaged Units
Located on the outer service access panel near the electrical line entry.
Frequently Asked Questions
How do I decode a Lennox furnace or AC serial number?
In standard modern Lennox 10-character serial numbers, digits 3 and 4 represent the year of manufacture, and digits 5 and 6 indicate the calendar week of production. For example, in serial 5821231234, '21' represents the year 2021, and '23' represents week 23 (early June).
Where is the serial number located on a Lennox furnace?
On Lennox residential gas furnaces, turn off power and remove the upper blower access door. The rating plate sticker is affixed to the inside cabinet sidewall near the burner assembly or gas valve.
How long does a Lennox furnace or air conditioner typically last?
According to the National Association of Home Builders (NAHB) and InterNACHI, residential gas furnaces have an average service lifespan of 15 to 20 years, while outdoor central air conditioners and heat pumps average 12 to 15 years.
Disclaimer: This HVAC serial lookup tool provides an informational estimate based on Lennox Industries date-coding documentation and third-party industry records compiled by the Building Intelligence Center. Because Lennox has used multiple serial styles across different production decades and commercial product lines, treat every result as an estimate. Never attempt gas valve, heat exchanger, or electrical service without a licensed HVAC professional.