About
Age by Serial Number helps homeowners, buyers and renters work out when a water heater, furnace or air conditioner was made, using the date code that manufacturers build into the serial number. Anders Myrmel edits the publication.
Where the facts come from
Date-code formats come only from the manufacturer’s own documents: its support pages and the installation or service manuals it hosts. Sizing guidance comes from the U.S. Department of Energy and ENERGY STAR. Recall information, where shown, comes from the U.S. Consumer Product Safety Commission. Contractor charts, forums and inspection-industry compilations are not used as sources. When a manufacturer publishes no format we can check, we say so instead of guessing.
Every page lists its sources with a link, the section we read and the date we read it. Facts are written in our own words.
What a date code can and can’t tell you
A serial date code tells you roughly when the equipment was manufactured. It doesn’t tell you when it was installed, whether it is still under warranty, how well it was maintained or how much life it has left. Warranty terms usually depend on the installation date and registration, so check with the manufacturer.
Safety
Reading a rating plate is a safe owner task. Gas appliances, venting, carbon monoxide and household electrical circuits are not. We don’t publish repair instructions beyond the checks a manufacturer tells owners they can do. If you smell gas, leave the building and call your gas utility or 911 from outside. Install and test carbon monoxide alarms, and call a licensed professional for anything beyond the owner checks on a page.
Independence
This site is not affiliated with, endorsed by or sponsored by any manufacturer, contractor or home warranty company. We don’t sell leads or pass your details to installers. Brand names are used only to say which equipment a page covers. No logos are used.