About this site and our method
HVAC Label Guide answers two label questions: the real size of an air filter, and the manufacture date in a serial number.
Rules we follow
- Makers' sources only. Each size and each date rule comes from the maker's own page or PDF. We do not copy from retailers, lookup sites or other compilations.
- As printed. We copy figures in the maker's units and format. Where we do arithmetic, we say so.
- Dated. Every source shows the date we read it. Every page shows a “last checked” date.
- Every possible reading. If a code could mean more than one date, we show all of them.
- Manufacture date only. A date code is not an install date and says nothing about warranty status or the unit's condition.
- No advice on repair, replacement or safety. We do not tell you whether to repair or replace anything, and we make no safety claims. Ask a licensed professional about your equipment.
How we keep it current
We save a copy of each source with a checksum when we read it. We plan to re-open every source on a schedule and compare it with the saved copy. If a source changes or disappears, we re-read it before we keep the figure.
Makers we have not added
- Carrier and Bryant: Carrier's FAQ explains where the serial plate is but not how to read the date.
- Trane: the Trane page we found covers light commercial units only, and parts of its year table look inconsistent.
- Nordic Pure and Filtrete sizes: the maker pages we read did not show an actual size.
Corrections
If a maker publishes a different figure, we update the page and the date.