Help find info on GE furnace, please?

Hi, I have an older GE furnace that I’m pretty sure dates to the early '60s, but would like more information on it, if anyone can help…

General Electric Gas Fired Warm Air Furnace
Model: 21LU080A2A
Serial: 764435 641

This is what I have:

**General Electric: **Age is the last 3 digits of the serial number. First digit being the year and the second and third digits being the month. Example xxxxx241 = 41st week of 1982, 92, 02 etc., xxxxx533 = 33rd week of 1985, 95, 05 etc…

Yeah, I was hoping there was some way to find the exact decade…

I THINK it’s from the '60s, but for all I know, it could be from the '50s or '70s.

I know it was made in mid-October of either of what? 1956? 1966? 1976? The house was built in 1920, and was heavily remodeled sometime in the '60s or '70s; we think… There are no permits filed with the city for the remodel (which was a complete ‘gut and rebuilt’, with none of the original 1920 ‘character’ left behind, other than a chimney that now only exists in the attic and the roof to make it LOOK like it has a fireplace.) But we’re not 100% certain when the remodel was. For all we know, the furnace could have even been installed in 1946 or 1986, it’s so generic looking.

Make sure you refer to HVAC company for evaluation.

Most of these I find have cracks in the back of the heat exchanger cells where they taper. At the front of the firebox the weld seams crack along the weld seams. These are hard to locate without doing a pentrant or water spray test. Also the dimples on the heat exchanger towards the top rust through.

Ed -

A simple way to aim you toward age IF the data was not known on the tag is:

Look at the gas valve OR fan/limit switch. One, the other OR both may have 4 digit numbers somewhere on them like:

7436 (the COMPONENT was made the 36th week of 1976 / the furnace could be OLDER than that but it won’t be newer than its parts).

1982 was last year of mfg for unitary products with GE / Sold to Trane and GE name dropped.

As Larry said use the last 3 numbers in the S/N (641). The 6 is the year (76 or 66, etc / while the 41 is the week of the year).

OR a simpler way may be to look in your copy of the PRESTONS GUIDE or CARRIER BLUE BOOK that most home inspectors carry - to reference the unit by Mfg, S/N and Model #.