Method and sources

The decoder does one thing: it applies each manufacturer’s published serial-number format to the serial you type and reports the date that format encodes. This page explains where the formats come from and where the limits are.

Where the formats come from

The site currently holds 39 serial formats for 41 brands. Each one is built from sources in this order of preference:

  1. Manufacturer documents. Support pages, technical bulletins and warranty help published by the company that built the equipment.
  2. US Consumer Product Safety Commission recall notices. A recall lists the affected serial numbers together with the dates the units were made, which confirms a format independently of the manufacturer’s own description.
  3. Established references used by home inspectors and service technicians. These are used to corroborate, and to cover older formats that manufacturers no longer document.

What counts as verified

A format is published only when one of two conditions is met:

  • Manufacturer: the manufacturer states the format. 12 of the 39 formats meet this standard.
  • Two independent references: at least two sources that do not copy one another agree on the format. 27 formats are published on this basis.

Formats that rest on a single source, or on sources that disagree, are left out until they can be confirmed. Every brand page lists the sources behind its formats and the date they were last checked.

What the decoder cannot tell you

  • It reports the manufacture date, not the installation date. Equipment is normally installed within a year of manufacture, sometimes later.
  • Some date codes repeat. A letter that stands for a year is reused after 10, 12, 20 or 30 years, depending on the brand. The decoder lists every year the code fits, newest first. The rating plate, the refrigerant or the installation record settles which one applies.
  • The brand on the cabinet is not always the builder. Store brands and several familiar names are made by other manufacturers, and the serial follows the builder’s format. Brand pages say so where it applies.
  • Formats change at the edges. In the year a manufacturer switched formats, both were in use. Week numbers follow each manufacturer’s own calendar, so the month shown for a week code is approximate.
  • A replaced or damaged label cannot be decoded. If the result looks wrong, read the serial again and check for the letter O against zero and the letter I against one.

The decoder runs in your browser. The serial number you type is not sent to this site or stored.

Model-number size layouts

The model number decoder reads the size of an air conditioner, heat pump or gas furnace from its model number. It holds 38 layouts for 14 brands. A layout is published when it meets one of three standards, and each brand page says which one applies:

  • Manufacturer document: a product data sheet or specification sheet from the maker shows where the size digits sit. 22 layouts.
  • Manufacturer listings and certified ratings: the maker’s own catalog or store gives the size for each model number, and certified ratings agree. 4 layouts.
  • Certified ratings: no document from the maker could be found, so the layout rests on the capacity each model is certified at. 12 layouts.

Certified ratings come from two public registries: the US Department of Energy compliance certification database and the ENERGY STAR product list. Every layout is run against both, whatever standard it was published under, and the brand pages print the result: how many certified models the layout reads and how many of those match the certified figure. The last run was on October 5, 2026.

A cooling size counts as a match when the middle of the model’s certified capacity range is between 80% and 112% of the nominal size in the code. A furnace input matches when the certified input is between 90% and 106% of the code. The size in a model number is nominal: the certified capacity of an air conditioner depends on the indoor unit it is matched with.

Lifespan figures

Typical service-life ranges come from published surveys and government guidance, and each lifespan page names its sources. They describe typical equipment. A given unit can fail earlier or run far longer, and age alone is not a reason to replace anything that works safely.

Sizing calculators

The sizing calculators use published reference tables and standard engineering formulas, which each calculator page states. Whole-house heating and cooling estimates use square-footage rules of thumb. They give a starting range only. The proper method for choosing heating and cooling equipment is a room-by-room load calculation to ACCA Manual J, which accounts for insulation, windows, air leakage and orientation, and it often arrives at a smaller size than a rule of thumb does.

Guides

The guides report what named sources say: government publications, codes and standards bodies, and manufacturers’ own documents. Each fact in a guide is tied to a passage in one of the documents listed at its foot, and a script checks that every passage is still in its document. The 4 guides rest on 295 passages, last checked on October 5, 2026. Where a figure is our own arithmetic on a published number, the guide says so.

Independence

Home Service Pros 247 is not affiliated with any manufacturer. Brand names appear only to identify the equipment a serial number belongs to. The site is free to use. It may carry advertising and links to service providers that pay a referral fee when a reader asks for quotes. Neither changes what the decoder reports.

Corrections

If a serial number does not decode, or decodes to a date you know is wrong, write to corrections@homeservicepros247.com with the brand, the model number, the serial number and, if possible, a photo of the rating plate. Confirmed corrections are published with a new “last checked” date on the brand page.

Page last reviewed on October 5, 2026.