How old is my HTP boiler?
Serial number age decoder for HTP boilers: 3 format eras, the decode rule in plain English, transcribed tables, and the official lookup.
Type the serial from the data plate, not the model number. Nothing is sent anywhere; the tables are in this page.
Format example: I21M28666
- HTP boiler serial numbers in the 1994 to 2011 format encode the year as letter 2 (4th char) (table below) and the month as letter 1 (A=Jan..L=Dec, I=Sep, 12 consecutive letters); day of month as digits 2-3 (source: htproducts.com).
- Example: serial I21M28666 decodes to September 2006.
- HTP boiler serial numbers in the 2011 to 2021 format encode the year as digits 5-6 (20YY) after dropping a 2-digit prefix when the serial is 16 digits and the month as digits 1-2, day as digits 3-4; the letter = production line (source: htproducts.com).
- Example: serial 112116E2054485 decodes to November 2016.
- HTP boiler serial numbers in the 2021 to present format encode the year as digits 10-11 (20YY) and the day of year = digits 12-14 (045 = Feb 14) (source: htproducts.com).
- Example: serial 3251200U4220450000188 decodes to day 45 of 2022.
- HTP's official lookup at htproducts.com returns warranty / registration lookup.
Format eras
- 2021 to present VERIFIED
#######A#############digits 10-11 (20YY) - 2011 to 2021 VERIFIED
######A#######digits 5-6 (20YY) after dropping a 2-digit prefix when the serial is 16 digits - 1994 to 2011 VERIFIED
A##A#####letter 2 (4th char): A=1994 B=1995 C=1996 D=1997 E=1998 F=1999 G=2000 H=2001 I=2002 J=2003
How to read the serial
2021 to present formatVERIFIED
Shape #######A############# · example 3251200U4220450000188 · confidence high
- Year
- digits 10-11 (20YY)
- Week or month
- day of year = digits 12-14 (045 = Feb 14)
- Plant
- chars 8-9 = Ariston factory code (e.g. U4, 02, 35)
Example: serial 3251200U4220450000188 decodes to day 45 of 2022.
2011 to 2021 formatVERIFIED
Shape ######A####### · example 112116E2054485 · confidence high
- Year
- digits 5-6 (20YY) after dropping a 2-digit prefix when the serial is 16 digits
- Week or month
- month = digits 1-2, day = digits 3-4; the letter = production line
Example: serial 112116E2054485 decodes to November 2016.
1994 to 2011 formatVERIFIED
Shape A##A##### · example I21M28666 · confidence high
- Year
- letter 2 (4th char): A=1994 B=1995 C=1996 D=1997 E=1998 F=1999 G=2000 H=2001 I=2002 J=2003 K=2004 L=2005 M=2006 N=2007 O=2008 P=2009 Q=2010 R=2011
- Week or month
- month = letter 1 (A=Jan..L=Dec, I=Sep, 12 consecutive letters); day of month = digits 2-3
| Year code | Year(s) |
|---|---|
| A | 1994 |
| B | 1995 |
| C | 1996 |
| D | 1997 |
| E | 1998 |
| F | 1999 |
| G | 2000 |
| H | 2001 |
| I | 2002 |
| J | 2003 |
| K | 2004 |
| L | 2005 |
| M | 2006 |
| N | 2007 |
| O | 2008 |
| P | 2009 |
| Q | 2010 |
| R | 2011 |
| Month code | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| I | September |
| J | October |
| K | November |
| L | December |
Example: serial I21M28666 decodes to September 2006.
Where the data plate is on a boiler
On the jacket: a plate or sticker on the front or side of the boiler casing, sometimes behind a removable front panel next to the gas valve or control.
General guidance, not brand-specific: the owner's manual or the installer can point to the exact spot. See the data plate guide.
For scale only: the InterNACHI Standard Estimated Life Expectancy Chart for Homes lists Boiler at 40 years of expected service (nachi.org). That chart is a guideline, not a prediction for your unit.
Open the official HTP lookup takes serial number; returns warranty / registration lookup; URL verified live
This site is a reference built from published tables. The manufacturer's own lookup wins whenever the two disagree.
What we could not confirm
- Official PDF 'UnderstandSerialNumbers-2-2024.pdf' fully documents 3 HTP eras + 2 Ariston formats. Warranty Wizard (htp.my.site.com) takes a serial number; 'Find Serial Numbers' PDF gives label locations.