Can someone help me on a Patriot oil fired furnace.
Age please?
Serial numbe 2491C3866 (1986)?

Also, water heater Glass Lined, 975081? Yes, the company is Glass Lined. (1981)
I haven’t seen either of these before.

I’m not familiar with either of those companies.

I suspect that they are a brand name manufactured by one of the biggies. With that suspicion, I would say 1991 for the furnace and 1997 for the water heater.

If you ever have to make an educated guess, a great supermajority of the time you’ll be right if you use the first four digits, with the first two being the week or month of manufacture, and the second two digits being the year of manufacture. Once you guess, put all the other clues together (dates inside toilet tanks, dates on electric panels, dates of construction, dates of other appliances such as microwave, condenser, range, dishwasher, etc.) and you’ll usually know whether or not you’re in the ballpark.

Thanks. Makes sense.

One can also use the ANSI date to get in the ballpark.

Most ANSI standards are updated every three years, and most manufacturers adhere to the latest and the greatest. So if you find an ANSI date, say, of 1988, manufacture date is usually 1988, 1989, or 1991.

On one of last week’s inspections, I did find my biggest discrepancy between the ANSI date and the manufacture date. The company used the 1988 ANSI date but the manufacture date was 1995. That’s extremely rare, though, but does happen with smaller companies that don’t have the money to update manufacturing processes every three years.

Patriot is a name owned now by State Industries