Water heaters with confirmed manufacturer and numbering family; unrelated devices using the same name are outside these date-code rules.
Explore a sourced example:
Choose the equipment family
Knight serial numbers by device type
Match the product, manufacturer and documented serial layout before interpreting a date. The model is a separate label field; a date code alone does not identify capacity, installation date or warranty entitlement.
Knight historic Lochinvar tank water heaters
This name appears as a historic Lochinvar tank trade name in the supplied chart and a regulatory manufacturer/model list. Apply only the confirmed tank-family letter-year/month or year/week system that matches the actual label and era. The name alone does not establish a current boiler model or a universal serial format.
Confirmed KNIGHT and KNIGHT XL boiler families use the equipment-specific pre-May-2015 month/year letters, the 2015 reversed week/year layout or the later year/week layout. These are separate from the historic tank trade-name systems. The model on the boiler plate establishes the family.
Manufacture date is different from installation, purchase and warranty start dates.
Enter the separate model number from the rating plate to search for the correct manual. These date positions do not establish a full model, capacity, fuel type or warranty entitlement.
The historical inspection chart is secondary evidence of listed brand relationships, not proof of the manufacturer, product family or date system on a particular unit. Confirm the actual label and select the matching system explicitly.
A missing match does not establish age, authenticity or condition. Unsupported eras and device types require the manufacturer or model-specific documentation.
Knight is a Lochinvar product-line name and an unrelated equipment badge elsewhere. Confirm the Lochinvar water-heater label before selecting a historical system.
Research reviewed October 16, 2026. This independent tool applies published rules and retains unresolved years and model candidates.
Only Lochinvar PDF page age 2 listed legacy tank families; the exact printed year map 1993–2012, not an assumed repeating cycle.
The chapter heading lists families ending 2011, but its printed year table includes J=2012. Both facts are disclosed. Older 1979–1992 units are within some family headings but their year mapping is not proved by this table. No 1964/1984 cycle extrapolation is applied to Lochinvar. Six/seven numeric suffix positions are production identifiers, not quantity.
Select only after confirming the water heater or boiler family and numbering system described here. Brand ownership alone does not establish this system.
Lochinvar tank-family YYWW/plant system 2011 onward
Only the 2011-onward tank-family list on Lochinvar PDF page age 2.
The manufacturer chart explicitly lists weeks 01–52 and a fifth-character manufacturing-plant code. It does not publish plant geography or an exact Gregorian date. Do not borrow the other manufacturer group’s week 53 allowance for this chart.
Select only after confirming the water heater or boiler family and numbering system described here. Brand ownership alone does not establish this system.
Lochinvar confirmed equipment families before May 2015
Only PDF page age 3 list: Custom Hi-Power, qualifying jacketed tanks, Copper-Fin, Energy Rite, Power-Fin, Mini-Fin, Copper-Fin II, Efficiency+, Intelli-Fin, Solution, Knight/Knight XL, Armor, Shield, Sync, Crest and FTXL; each family’s actual introduction/end dates still apply.
This month alphabet includes I=September, J=October. Do not apply tank/Standard Hi-Power skipped-I months. The source calls E 07 H 00123456 June 2007, but its explicit table maps E=May; the decoder follows the table and exposes the example-caption error. The strict reviewed shapes are the printed 7-character numeric-suffix and 12-character fourth-letter examples. May 2015 is transitional and not automatically assigned to the earlier system.
Select only after confirming the water heater or boiler family and numbering system described here. Brand ownership alone does not establish this system.
Lochinvar confirmed 2015 reversed WWYY system
Only the equipment-family list on PDF page age 3 and production year 2015.
In 2015 the manufacturer says the first four characters are WWYY; 2016 onward is YYWW. The prose says 13 characters but both worked serials contain 12, so this source-qualified rule accepts the two documented lengths 12/13. The exact first production week after the May transition is not established; no ISO date/month/day is manufactured from the week.
Select only after confirming the water heater or boiler family and numbering system described here. Brand ownership alone does not establish this system.
Lochinvar confirmed equipment YYWW system 2016 onward
Only the equipment-family list on PDF page age 3; 2016 onward YYWW prefix.
The source says 13 characters while its 2016 example has 12. Both documented lengths are accepted only after family confirmation, with opaque suffix preserved. Week 01–52 is read literally; no plant/model/quantity or exact Gregorian date follows.
Select only after confirming the water heater or boiler family and numbering system described here. Brand ownership alone does not establish this system.
Reading your result
Knight lookup questions
Why does the year code match more than one year?
Some systems reuse letters or only encode the last one or two year digits. Every supported interpretation is retained. A decade supplied from reliable records can narrow the reading; the tool does not automatically pick the newest year.
Does the serial identify my exact model?
Usually the model is a separate plate field. Where published serial ranges actually identify a model, the result shows model candidates and links to their manuals. Overlapping ranges remain ambiguous.
Can I share the result?
After a lookup, the address includes the serial in a fragment beginning with #serial=. Use “Copy share link” to share the serial and selected context. Opening the link runs the same lookup. The fragment is not a query-string result page.