# Help Determining Age and Tonnage of AC

3477 Views 8 Replies 4 Participants Last post by  beenthere
Hello,
Have old GE unit likely original to the home. House was built in 1978. I am trying to determine the age and tonnage of this system. The current coding conventions that I can find online do not apply to this system. Perhaps someone who has access to Preston Guide or a significant amount of experience can chime in.

Model # BTB936A100B2
S/N 250542922 (thinking this is 22nd week of 1979 but maybe not)

Any help would be appreciated.
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You are correct on the age. Trane bought them out in 1987.
With the below info, I am going to guess 3 ton.

There are 12,000 Btus per ton of cooling, and air conditioners are sized by every ½ ton. Manufacturers often encode the approximate rating in Btus somewhere in the model number. Therefore it is often simple to scan the model number for a two-digit number that is divisible by 6 and to divide it by 12 to determine the capacity rating in tons. This number can be elusive, as it is not always exactly divisible by 6. Some manufacturer’s systems make this easier than others. To complicate matters, some manufacturers have changed their systems of encoding data over time.

General Electric
Capacity: Last three digits of model number indicate approximate rating in 1000s of Btus
Example: 21TC030A = 2.5 ton
Age: Last three digits of serial number indicate date of manufacture, where the first digit indicates the year and the second and third indicate the week
Example: xxxxxx241 = 41st week of 1982

http://www.localinspectioncompany.com/articles/acdata.pdf
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Yep, and built like a tank. They don't make new A/Cs as reliable as them anymore.
Actually they do, it is all about maintaining them. There are some out there that are over 40 years old still going strong.
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