GE furnace age

I have a customer that wants to know the age of his furnace.
Mod-21LG, ser-26110246

I know it is old, guessing about 30ish, but he wants to be more accurate. Can anybody help me please? Thanks in advance.

Possibly 1972 or 1982 November based on your 30 year comment.

Someone with a Prestons can give you the dates for the GE 21LG series.

Hi to all,

Prestons show that as either a 1965 or a 1966



Thanks guys-BR

Hi Gerry. My info says the last three digits are the y(year) and mm(month)

I guess it not valid for a unit that old.:frowning:

Hi Mike, as you know I am not the expert on serial numbers, but it appears to me that few of the manufacturers back in the 60’s were encrypting the dates into the serial numbers, Maybe Russel can correct me on this but I thought that most of the dating info was added to serials in the 1970’s, although there is one that had plant#, Shift # and week# in the serial back in the mid 60’s



Makes sense. I’ll amend my notes.

I seldom report the age of HVAC equipment but I am asked sometimes and then I try to get decent information.

Same here, I only add the age of the components if it is to support a statement about the unit nearing or beyond its design life.



If there are no letters or digits missing from the serial number, including pre-printed or pre-stamped ones, then that does not appear to be a General Electric serial number. My guess would be that GE had a plant shut-down for some reason (strike, tornadoes, snowstorm, etc.) and that that unit was manufactured for them by someone else. The type of serial number, again presuming that nothing is missing from it, seems to indicate that it’s a February 1966/1976/1986/1996/2006 unit. Based on Gerry’s post, I have to go with February 1966.

Serial number date coding actually came about just after World War II ended. As my wise old grandmother told me (not really, but my wise old grandfather did, the ol’ 40-year proud member of the IBEW and AFL-CIO that he was), many service members came home from the war and brought their tracking and coding systems with them, which were then implemented with the companies that they got jobs with post-war. As the systems worked, more and more companies picked it up in all industries, and it continues to this day. See? We have something to thank the Germans, Japanese, and Italians for!

Gerry, would you mind looking in your Prestons for this GE furnace?

model 21LU105D202
serial 562261

You know, I tried to buy a Prestons online but they had no way to do that. That was probably a year ago and haven’t looked since. Maybe they’ve caught up to this century :slight_smile:

Anyway, I appreciate your help in this. It’s not critical, but I’d like to give her an answer.


Hi Bruce,

saw your PM before this post so answered there.

If the suspense is killing anyone else, the answer is 1965 through 1972



Thank Gerry,

The client told me the const. date of the home was 1964. I was willing to bet the unit was original to the home.

I appreciate you taking the time to look that up for me.