Appliage first identifies which structure the serial number follows and then calculates the manufacture month or production week. The Ducane serial number alone is enough for both formats, so the model number is optional.
Appliage decodes two Ducane serial number formats, and both are ten characters. In the letter format, digits 3 and 4 are the year and position 5 is the month letter, so 4605K23456 is October 2005. In the all numeric format, the published placement puts the year in digits 7 and 8 and the production week in digits 9 and 10, so 0183290431 is week 31 of 2004. Ducane Age Rules below covers both and an older reported variant.
Both formats span the same years, so go by shape. A month letter in position 5 means the letter format. Ten digits with no letter anywhere means the all numeric format.
Ducane Serial Number Lookup
The two Ducane formats are both ten characters long, but their date fields appear in different positions. First check whether the fifth character is a month letter or whether the entire serial number is numeric.
| Format | Example | Date fields |
|---|---|---|
| Letter format | 4605K23456 |
Positions 3–4: year Position 5: month |
| Numeric format | 0183290431 |
Published placement: positions 7–8 year, positions 9–10 production week. 1980s units built before Lennox bought the brand are reported with the year and week in positions 1–4 instead. |
Letter format serial number
The letter format example 4605K23456 separates as 46 | 05 | K | 23456.
| Positions | Characters in the example | Meaning |
|---|---|---|
| 1–2 | 46 |
Manufacturing plant code |
| 3–4 | 05 |
Last two digits of the manufacture year |
| 5 | K |
Manufacture month code |
| 6–10 | 23456 |
Sequence that identifies the individual unit |
The plant code identifies the factory, and the sequence identifies the individual unit. Neither field influences the manufacture date.
Ducane month codes
| Code | Month | Code | Month |
|---|---|---|---|
| A | January | G | July |
| B | February | H | August |
| C | March | J | September |
| D | April | K | October |
| E | May | L | November |
| F | June | M | December |
The month sequence skips the letter I. If the fifth character looks like I, compare it with a clear photo of the plate because it may be a faded J or the number 1.
What each year code means
| Format | Year code | Year Appliage uses |
|---|---|---|
| Letter format | 80–99 | 1980–1999 |
| Letter format | 00–26 | 2000–2026 |
| Numeric format | 80–99 | 1980–1999 |
| Numeric format | 00–26 | 2000–2026 |
Ducane’s documented records start in 1980, so earlier codes return no date in either format. Appliage does not assign a future year. A code outside the documented period does not produce an age from these rules.
Numeric serial number
The numeric example 0183290431 separates as 018329 | 04 | 31.
| Positions | Digits in the example | Meaning |
|---|---|---|
| 1–6 | 018329 |
Sequence that identifies the individual unit |
| 7–8 | 04 |
Last two digits of the manufacture year |
| 9–10 | 31 |
Production week |
| Week code | Meaning |
|---|---|
| 01–09 | Production weeks 1 through 9; keep the leading zero |
| 10–53 | Production weeks 10 through 53 |
| 00 or 54–99 | Not a valid production week for this format |
Older numeric serial numbers with the date up front
On Ducane units built before Lennox bought the brand in November 1999, home inspectors report the date at the start of the serial instead: positions 1–2 as the year and positions 3–4 as the production week. That front placement comes from field reports, not from the manufacturer’s published serial documents, so Appliage never uses it alone.
When a ten digit serial fits both placements inside the Ducane years, the result lists both dates with the published one first. For example, 8503740637 comes back as week 37 of 2006 from the published placement and week 3 of 1985 from the reported one. Check the older date against the unit’s installation paperwork before relying on either.
Ducane Serial Numbers Appliage Cannot Find the Age
Appliage cannot use these rules if the serial number has a different length or does not match either structure with ten characters. The letter format requires A–H or J–M in position 5. The numeric format requires a production week from 01 through 53 in positions 9–10.
- Make sure you copied the field marked Serial or S/N, not the model number or a service tag.
- Compare every character with a clear photo of the rating plate, especially 0 and O, 1 and I, or 5 and S.
- If the fifth character is a letter, remember that I is not used as a month code.
- If the serial still does not match, contact Lennox model and serial support with the model number, serial number, and a photo of the rating plate.
If the equipment plate says Lennox rather than Ducane, choose Lennox in Appliage instead.
Manufacture Date, Installation Date, and Warranty Date
The serial number provides an estimated manufacture date. The equipment may have been installed weeks or months later, and the warranty may begin on another date. A service sticker records a repair or inspection, not the age of the HVAC unit.
To find the installation date, check the invoice, permit, or registration paperwork. To check warranty coverage, use the official warranty lookup.
Sources
- Allied Air and Ducane serial number reference. Allied Air explains the two Ducane serial formats. Archived copy.
- Lennox serial number reference. The diagram labels the factory, year and month positions. Archived copy.
- Lennox warranty lookup
- Lennox model and serial number help
For other brands, see our appliance serial number lookup.
