Air conditioner, heat pump and furnace age
To find out how old an air conditioner, heat pump or furnace is, read the serial number on its rating plate: almost every brand codes the year, and the month or the production week, into it. Central air conditioners, heat pumps, furnaces and air handlers share one serial layout per brand family, so a single page covers the outdoor unit and the furnace of the same maker. Each family page decodes the serial number and, where the manufacturer publishes a nomenclature, the model number as well: the nominal cooling size in tons, the furnace input and, for some lines, a refrigerant code.
An indoor and an outdoor unit installed together were often made months apart, and either may have been replaced since. Decode both plates if you want the full picture.
- Carrier and Bryant
Brands: Carrier, Bryant
Decode Carrier and Bryant serial numbers (week and year, documented since 1993) and model numbers: cooling tonnage, furnace input and refrigerant prefixes.
- Trane
Brands: Trane, American Standard (inferred), RunTru (inferred)
Decode Trane serial numbers from 1980 to 2029 with Trane's own date table, plus capacity and refrigerant codes from Trane, American Standard and RunTru models.
- Goodman, Amana and Daikin
Brands: Goodman, Amana, Daikin
Goodman, Amana and Daikin serials start with the year and month on most products. Decode yours, plus tonnage and refrigerant codes from the model number.
- Lennox
Brands: Lennox
Decode Lennox serial numbers: location code, year and month letter in the current and older layouts, plus tonnage and furnace input from the model number.
- Nortek (Nordyne) brands
Brands: Frigidaire, Gibson, Maytag, Westinghouse, Tappan, Intertherm, Miller
Nortek (Nordyne) serials for Frigidaire, Gibson, Maytag, Westinghouse, Tappan, Intertherm and Miller: plant, year and month, plus model size codes.
Weeks, months and fiscal calendars
Carrier, Bryant and Trane count production weeks on a fiscal calendar, so their dates are exact to the year and close to the month. Goodman, Amana, Daikin, Lennox and the Nortek brands print a month, so their dates are exact to the month. Either way the decoder states which kind of number it read.
Size from the model number
For split air conditioners and heat pumps the model number usually contains the nominal cooling capacity in thousands of BTU per hour: 24 or 024 is 2 tons, 36 or 036 is 3 tons, 60 or 060 is 5 tons. Furnace models contain a heating input code, and here the brands differ: Lennox lists code 070 as 66,000 BTU/h, not 70,000. The decoder therefore translates furnace codes only from the manufacturer's own values.
Refrigerant
The date of manufacture does not settle the refrigerant question. EPA rules changed what could be made and installed in 2010, 2020 and 2025, and units built from older stock may be installed later. The refrigerant and EPA dates guide explains the milestones and where the refrigerant is printed.
HVAC brands we do not decode yet
- Rheem, Ruud and WeatherKing: Rheem documents its HVAC serial layout in parts lists, but we have not added a Rheem HVAC decoder to the site yet. Rheem's water heater rule does not apply to HVAC.
- Heil, Tempstar, Comfortmaker, Arcoaire, KeepRite and Day & Night: A manufacturer catalog documents the serial only for the newest R-454B variable-speed units; the classic layout is described only by third parties.
- York, Coleman and Luxaire: We found no manufacturer document that explains the serial number.
- Armstrong Air, AirEase, Ducane and Concord: Their documents explain model numbers but not serial numbers.
- Payne: Payne is made by Carrier, but no Payne document decodes its serial number.
Page updated . Decoding rules last checked against their sources on the date shown with each source.