Rheem Serial Number: How to Read the Build Date
Rheem's 2023 guide says the first two numbers after the letter in a Rheem serial number are the week the unit was built. The third and fourth numbers are the year. The letter sits “in the middle or beginning of the serial number.” The serial number is the unit's own ID number; the model number names the product.
How Rheem Lays Out the Date
| Part of the serial | Meaning, as Rheem prints it |
|---|---|
| A letter, in the middle or at the start | Marks where the date starts |
| First two numbers after the letter | Week of manufacture |
| Third and fourth numbers after the letter | Year of manufacture |
Where the Serial Is
Rheem's model and serial number page says two model and serial tags identify split system equipment, and one tag identifies package equipment. A split system has an outdoor unit and an indoor unit; a package system is a single cabinet.
Reading your Own Serial
- Copy the serial number from the tag exactly, letters included.
- Find the letter in the middle or at the start.
- Read the two numbers after it as the week and the next two as the year.
A date code is the build date. It is not the install date. The same tag gives the unit's size: AC tonnage from the model number. Heat pump or air conditioner: how to tell from the label.
Sources
- Rheem, What to Know Before Meeting with an HVAC Contractor (May 16, 2023): https://www.rheem.com/air-conditioning/articles/what-to-know-before-meeting-with-an-hvac-contractor/
- Rheem, Model Serial Numbers page (published 2025-07-03): https://www.rheem.com/rheem_model_serial_numbers/