Rheem serial number lookup: age of a furnace, AC or heat pump
The serial number is on a tag on the back of the outdoor unit or inside the front cover of the indoor unit. In a Rheem furnace or air conditioner serial, the two digits after the last letter are the week and the next two are the year.
Decode a Rheem serial number
How to read a Rheem serial number
Plant letter, then week and year
Find the last letter in the serial. The two digits after it are the week and the next two are the year.
Shape: ends with a letter followed by nine digits. Older serials have a prefix of letters and digits in front.
W301745243 reads as week 30 of 2017 (around July).
Rheem does not publish its week calendar, so the month shown for a week is approximate. Rheem water heaters use a different code.
Where to find the serial number
A split system has two tags: one on the back of the outdoor unit and one on the inside of the front cover of the indoor unit.
A packaged unit has a single tag on an outside corner. An oil furnace has its rating plate on the left interior wall, just above the burner.
If the serial number does not decode
- Many Rheem plates also print the month and year of manufacture at the upper right, as in “MFD. 07/04”. Use it to check the decoded week.
- Rheem water heaters use a different code. Choose “water heater” for those.
- When the installation date cannot be verified, Rheem counts warranty from the manufacture date plus 90 days.
- Gas furnaces from the 1980s and 1990s print the year of the safety standard they were certified to, for example “Z21.47” followed by a year. The furnace was built in that year or a few years after it.
- The manufacturer can confirm the date from the serial: Rheem registration, warranty or serial lookup.
What the age tells you
| Equipment | Typical service life |
|---|---|
| Furnace | 15 to 22 years |
| Central air conditioner | 10 to 21 years |
| Heat pump | 15 to 16 years |
What size is it?
The model number on the same rating plate gives the size: the tonnage of an air conditioner or heat pump, or the heating input of a furnace. Rheem model number tonnage shows where the digits sit and reads them for you.
About Rheem
Rheem Manufacturing Company of Atlanta has been owned by Paloma of Japan since 1988. Rheem bought Ruud in 1960 and launched the Richmond water heater line in 1983. Rheem and Ruud share one serial code for water heaters and a different one for furnaces and air conditioners.
Brands that share this serial system: Ruud.
Questions and answers
Which characters in a Rheem serial number show the date?
Find the last letter in the serial. The two digits after it are the week and the next two are the year. This applies to units built since the early 1990s.
Sources
- CPSC recall: Rheem electric furnaces and air handlers sold 1992 to 1995, date code after the letter in the serial (US Consumer Product Safety Commission): https://www.cpsc.gov/Recalls/1999/cpsc-rheem-manufacturing-announce-recall-to-repair-electric-furnaces-and-air-handlers
- CPSC recall: Rheem and Ruud oil furnaces sold 2006 to 2008, date code after the letter M in the serial (US Consumer Product Safety Commission): https://www.cpsc.gov/Recalls/2009/rheem-recalls-to-repair-oil-fired-furnaces-due-to-fire-hazard
- Building Intelligence Center: Rheem HVAC age (independent reference): https://www.building-center.org/rheem-hvac-age/
- Rheem: how old is my equipment (sample serials) (manufacturer): https://www.rheem.com/how-old-is-my-equipment/
Formats last checked against these sources on October 5, 2026. Found a serial that does not fit? Send a correction. How formats are verified: method and sources.