How to read Rheem and Ruud heating and cooling serial numbers
This covers Rheem, Ruud, WeatherKing. The serial number is on the rating plate. Some plates also print the manufacture date.
Reading it yourself
A letter, then nine digits. The first two digits after the letter are the week of the year, and the next two are the year.
Example:
W291013412was made in week 29 of 2010.Older 17-character serials: the first four digits after the last letter are the week, then the year.
Example:
CB5D302F099903346was made in week 9 of 1999.
This is the date the unit was made. It was usually installed soon after, but it can be later. If a serial doesn’t fit any of these patterns, look on the label for a printed manufacture date.
Sources
Checked in October 2026.
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