Water heaters, furnaces and air conditioners
How old is it? Find the age by serial number
Most manufacturers hide the build date inside the serial number. Pick the brand on the rating plate and we’ll decode it using that manufacturer’s own published format, or tell you plainly when it doesn’t publish one.
Water heater age by serial number
AllDecoders for each water heater brand’s serial date code, built from the manufacturer’s own documents.
- Bradford WhiteDecode the two-letter date code at the start of a Bradford White serial number. The letters give the year and month the water heater was made.
- A. O. Smith, State, AmericanRead the year and week of manufacture from an A. O. Smith, State, American, Reliance or U.S. Craftmaster water heater serial number.
- WhirlpoolWhirlpool-brand water heaters are made under license by American Water Heater. See what the serial number shows and how sure that reading is.
- Rheem and RuudDecode Rheem, Ruud and Richmond water heater serial numbers in both the older month-year layout and the plant-week-year layout used since 2012.
- LochinvarRead the build date from a Lochinvar tank water heater serial number, in the two-letter layout used until 2011 and the 11-character layout since.
Furnace and AC age by serial number
AllDecoders for furnace, air conditioner and heat pump serial date codes, from each manufacturer’s published nomenclature.
- Goodman and AmanaGoodman and Amana warranties say the first four digits of the serial number are the year and month of manufacture. Decode yours and see what it can’t tell you.
- LennoxRead the plant, year and month from a Lennox serial number like 5921C05716, using Lennox’s own serial numbering documents.
- CarrierCarrier serial numbers start with the week and year of manufacture. Decode a Carrier air conditioner, heat pump or furnace serial and see what Carrier does and doesn’t confirm.
- Trane and American StandardTrane and American Standard don’t publish a residential serial decoder. Here is how they tell owners to find the manufacture date instead.
Water heater and furnace status light codes
AllWhat blinking status lights mean, restated from manufacturer manuals, with safe owner checks only.
- Rheem water heater lightsWhat the blinking status light on a Rheem gas water heater means, including seven blinks, which points to different faults on atmospheric and PowerVent models.
- Goodman furnace lightsWhat the blinking LED on a Goodman GMSS96 or GCSS96 furnace means, including three flashes (pressure switch stuck open), with the only owner check Goodman allows.
Water heater calculators
AllWater heater sizing based on U.S. Department of Energy and ENERGY STAR guidance.
Before you decode
- Find the rating plate. The serial number is printed on the manufacturer’s label, next to the model number. Don’t remove panels to reach it.
- Manufacture date isn’t install date. Equipment can sit in a warehouse before it’s installed, and warranties usually run from installation.
- Age alone doesn’t mean replace. Condition, maintenance and safety checks by a licensed professional matter more than a date.
- Smell gas? Leave the building and call your gas utility or 911 from outside.