Your HVAC serial number contains the manufacture date, plant location, and production sequence for your unit — you just need to know where to look and how to read it. The serial number is stamped on a metal data plate on the outdoor condenser unit (for AC/heat pumps) or inside the furnace cabinet door.
This guide covers serial number decoding for every major HVAC brand sold in the U.S. Find your brand below, match the format, and you'll know your system's exact age in minutes.
Where to Find Your Serial Number
Before decoding, locate the data plate:
| Equipment Type | Location | What to Look For |
|---|---|---|
| Outdoor AC/Heat Pump | Side or back panel of condenser | Metal plate or sticker with model + serial |
| Furnace | Inside the front cabinet door or side panel | Metal plate visible when front panel removed |
| Air Handler | Side panel or inside access door | Metal plate or sticker |
| Package Unit | Side panel of outdoor unit | Metal plate (all components in one) |
| Mini Split (Indoor) | Bottom edge or behind front panel | Small label |
| Mini Split (Outdoor) | Side panel | Metal plate |
Take a photo of the entire data plate. You need both the model number and serial number for accurate decoding. The model number reveals brand, size, and efficiency. The serial number reveals the manufacture date.
Carrier / Bryant / Payne
Carrier, Bryant, and Payne are all manufactured by Carrier Global and share serial number formats.
Modern format (2000s–present): A serial number like 3216E54321 decodes as:
| Position | Characters | Meaning | Example |
|---|---|---|---|
| 1st–2nd | Two digits | Week of manufacture | 32 = week 32 (August) |
| 3rd–4th | Two digits | Year of manufacture | 16 = 2016 |
| 5th | Letter | Plant code | E = Collierville, TN |
| 6th–10th | Five digits | Sequence number | 54321 |
More examples:
- 0122B12345 = Week 01, 2022 (January 2022)
- 2619F67890 = Week 26, 2019 (June/July 2019)
- 4825A11111 = Week 48, 2026 (November/December 2026)
Legacy format (1980s–1990s): The 3rd character is a letter representing the year. The code cycles every 20 years:
| Letter | Year Options |
|---|---|
| A | 1971, 1991, 2011 |
| B | 1972, 1992, 2012 |
| E | 1975, 1995, 2015 |
| J | 1980, 2000, 2020 |
| K | 1981, 2001, 2021 |
Cross-reference with the model number and equipment design to identify the correct decade.
For a complete guide, see our Carrier HVAC Age by Serial Number article.
Trane / American Standard
Trane and American Standard use identical serial number formats (both Johnson Controls brands).
Post-2002 format: Serial numbers typically start with a digit or digit pair representing the year, followed by a week indicator.
Common patterns:
- Year + Week format: First character = last digit of year, next two = week number
- Example: 523B456789 = 2015 or 2026, week 23
Legacy format (pre-2002): First character is a letter:
| Letter | Year |
|---|---|
| S | 2000 |
| W | 2001 |
| X | 2002 |
| Y | 2003 |
| B | 2004 |
| C | 2005 |
| D | 2006 |
| E | 2007 |
| F | 2008 |
| G | 2009 |
| H | 2010 |
| J | 2011 |
| K | 2012 |
| L | 2013 |
Trane has used multiple serial number formats over the decades, making them harder to decode than most brands. If the methods above don't work, contact Trane directly at 1-800-945-5884 with your full model and serial number, or use the AHRI directory lookup.
Lennox
Lennox serial numbers vary significantly by era. The easiest approach differs from other brands.
Best method: Many Lennox data plates include a clear "MFG DATE" or "DATE" field printed in plain text (e.g., "MFG DATE: 03/2019"). Always look for this first.
Serial number format (when date isn't explicit):
For units manufactured since ~2005, the serial number may follow patterns like 5821E04567 where:
- First two digits may indicate a product code, not a year
- Date information may be embedded in digits 3–4 or elsewhere
Model number method: Lennox model numbers are often more reliable for dating. The first few characters indicate the product line, and the data plate usually has an explicit manufacture date.
For Lennox units, skip the serial number and look for the manufacture date printed on the data plate. It's almost always there and gives you an exact month and year. This is the most reliable method for Lennox.
Goodman / Amana / Daikin
Goodman, Amana, and Daikin residential units have the simplest serial number format in the HVAC industry.
Format: First four digits = YYMM (year and month)
| Serial Number | Year | Month |
|---|---|---|
| 1605123456 | 2016 | May |
| 2003456789 | 2020 | March |
| 2209111111 | 2022 | September |
| 2512654321 | 2026 | December |
| 2601345678 | 2026 | January |
That's it. No letter codes, no cycling, no ambiguity. The first two digits are always the year, the next two are always the month.
For more detail, see our Goodman AC Age by Serial Number article.
Rheem / Ruud
Rheem and Ruud (sister brands) encode the date in the first two characters.
Format: First character = month (letter), Second character = year (last digit)
Month codes:
| Letter | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| J | September |
| K | October |
| L | November |
| M | December |
Note: Rheem skips "I" to avoid confusion with "1."
Examples:
- K4F2345678 = October 2014 (or 2024 — check model era)
- A6B1234567 = January 2016 (or 2026)
- F2C9876543 = June 2012 (or 2022)
The third character is the plant code. Use the model number's design generation to determine the correct decade.
York / Johnson Controls
York serial numbers use a letter + digit code for the year:
Year code (recent):
| Code | Year |
|---|---|
| W0 | 2010 |
| W1–W9 | 2011–2019 |
| X0 | 2020 |
| X1 | 2021 |
| X2 | 2022 |
| X3 | 2023 |
| X4 | 2024 |
| X5 | 2026 |
| X6 | 2026 |
The month is encoded in the third character using a letter code (A=January through M=December, skipping I).
Example: W7G1234567 = July 2017.
Heil / Tempstar / Comfortmaker (ICP Brands)
These International Comfort Products brands (now part of Carrier Global) share a serial number format.
Format: First character = year (letter), Characters 2–3 = week number
Year codes:
| Letter | Year |
|---|---|
| A | 2006 |
| B | 2007 |
| C | 2008 |
| E | 2009 |
| F | 2010 |
| G | 2011 |
| H | 2012 |
| J | 2013 |
| K | 2014 |
| L | 2015 |
| M | 2016 |
| N | 2017 |
| P | 2018 |
| R | 2019 |
| S | 2020 |
| T | 2021 |
| U | 2022 |
| V | 2023 |
| W | 2024 |
| X | 2026 |
| Y | 2026 |
Example: N163456789 = Week 16 (April) of 2017.
Mitsubishi (Mini Splits)
Mitsubishi encodes the date in the second and third characters of the serial number:
| Position | Meaning |
|---|---|
| 2nd digit | Last digit of manufacture year |
| 3rd character | Month (1–9 for Jan–Sep, X=Oct, Y=Nov, Z=Dec) |
Example: 84X00001 = October 2014 (or 2024).
Fujitsu (Mini Splits)
Fujitsu uses letter codes for year and month in the first two characters:
Year codes: R=2013, T=2014, U=2015, V=2016, W=2017, X=2018, A=2019, B=2020, C=2021, D=2022, E=2023, F=2024, G=2026, H=2026.
Example: G3456789 = 2026.
Bosch
Bosch HVAC serial numbers typically contain the manufacture date in YYWW format (year and week) within the first four digits.
Example: 2318456789 = Week 18 (May) of 2023.
Daikin (Commercial/Ductless)
Daikin ductless units manufactured in Japan may use a different format than Daikin-owned Goodman/Amana units. Check for a letter-digit combination in the first characters similar to Fujitsu, or look for a plaintext manufacture date on the data plate.
Quick Reference Table
| Brand | Date Location | Format | Example Decode |
|---|---|---|---|
| Carrier/Bryant/Payne | Digits 1–4 | WWYY (week, year) | 3216 = week 32, 2016 |
| Trane/American Standard | 1st character(s) | Varies by era | Check multiple formats |
| Lennox | Data plate MFG DATE | Plaintext date | "MFG DATE: 03/2019" |
| Goodman/Amana | Digits 1–4 | YYMM (year, month) | 2205 = May 2022 |
| Rheem/Ruud | Characters 1–2 | Letter+digit (month, year) | K4 = October 2024 |
| York | Characters 1–2 | Letter+digit (year code) | X3 = 2023 |
| Heil/Tempstar/ICP | Char 1 + digits 2–3 | Letter (year) + WW (week) | N16 = week 16, 2017 |
| Mitsubishi | Characters 2–3 | Digit+char (year, month) | 4X = October 2024 |
| Fujitsu | Character 1 | Letter (year code) | G = 2026 |
| Bosch | Digits 1–4 | YYWW (year, week) | 2318 = week 18, 2023 |
How to Decode Model Numbers for System Specs
Beyond the serial number, the model number reveals specifications:
Common Model Number Elements
| Element | What It Tells You | Examples |
|---|---|---|
| Tonnage code | System capacity | 024=2 ton, 036=3 ton, 048=4 ton, 060=5 ton |
| SEER indicator | Efficiency rating | 14, 16, 18, 20 |
| Fuel/type code | System type | G=gas, E=electric, H=heat pump |
| Refrigerant | R-410A vs R-454B | 4=R-410A in many brands |
Model Number Examples
Carrier 24ACC636A003: 24A=product line, CC=Comfort series, 6=16 SEER, 36=3 ton, A=revision, 003=config.
Trane 4TTR4036L1000A: 4=R-410A, TTR=cooling, 036=3 ton, L=14 SEER.
Goodman GSXN403610: GSX=AC condenser, N=series, 4=R-410A, 036=3 ton.
Why Knowing Your System's Age Matters
| Decision | Why Age Matters |
|---|---|
| Repair vs. replace | Systems 15+ years old usually aren't worth major repairs |
| Home purchase | Age reveals remaining useful life and upcoming costs |
| Insurance claims | Age determines depreciation and replacement value |
| Warranty claims | Confirms whether equipment is under warranty |
| Efficiency assessment | Pre-2006 systems run at 10 SEER or less |
| Refrigerant type | Pre-2010 systems likely use R-22 (phased out) |
| Maintenance priority | Older systems need more frequent service |
Real-World Decoding Examples
Home purchase scenario: Sarah was buying a house listed as having "newer HVAC." She found the outdoor unit data plate and decoded the Carrier serial number 2217B34567 — week 22, 2017. The system was 9 years old in 2026, not "newer." She negotiated $3,000 off the asking price.
Warranty claim: Tom's 7-year-old Goodman had a compressor failure. Serial number 1908567890 decoded as August 2019 — within the 10-year warranty. Goodman covered the $1,800 compressor; Tom paid only $700 for labor.
Repair decision: Maria's Carrier was leaking refrigerant. Tech quoted $1,200 to fix. Serial number 1209C99999 decoded to week 12, 2009 — the system was 17 years old. She replaced instead of repairing.
Refrigerant identification: James found a Goodman serial starting with 0806 — June 2008. This confirmed the system used R-22 refrigerant (phased out, now $80–$150/lb). He prioritized replacement to avoid increasingly expensive refrigerant charges.
Key Takeaways:
- Your serial number is on the metal data plate on the outdoor unit or inside the furnace cabinet
- Goodman/Amana is the easiest: first four digits = YYMM (year, month)
- Carrier/Bryant/Payne: first four digits = WWYY (week, year)
- Lennox: look for "MFG DATE" printed on the data plate — it's the most reliable method
- Always photograph the entire data plate for reference
- Pre-2010 systems likely use R-22 refrigerant (phased out, expensive to recharge)
- Systems 15+ years old are approaching end of life regardless of brand