Technical FAQs

Ask a Question

Where is the date code on a QO,QOB and HOM circuit breaker?

Product line:
Circuit Breakers

Applies to QO(B) and HOM Circuit breakers

The method of showing the date code of QO and HOM breakers has varied somewhat over the years. The following explains the difference:

Older QO and HOM breakers
The older method of displaying the date code involved using a 2-letter date code stamped in red ink on the small white label on the end of the breaker.
  • The first letter indicates the month.
  • The second letter indicates the year. The letters reset every 21 years, therefore the same letter can indicate multiple years. (Letters "I", "O", and "Q" are not used, and "Y" and "Z" were only used during certain years.)
The complete list of this method is in document 0110PD9201. See page 2.
As an example, the picture below shows a breaker with date code LW. Using the information at the above link, the breaker was manufactured in either November 1969 or November 1990.

Newer QO and HOM breakers
The newer method of displaying the date code involves laser etching it into the front face of the breaker, near the toggle handle. It appears as 4-digit number, and might have a single letter after the number. 
  • The first two letters indicate the year
  • The second two letters indicate the week of that year (any following letter is not related to the date code)
As an example, the picture below shows a breaker with date code 0925. The breaker was manufactured during the 25th week of 2009.

Newest version of Date Code
Implemented the first week of August in 2016 (starting date code 16341), the date code on CAFI, GFI and DF breakers was changed to include a 5th digit. This will be laser etched, like the example above. The 5th digit now included will indicate the day of the week the breaker was manufactured, with 1  = Monday and 7 = Sunday. Dual Function (DF) breakers also had a 6th final digit added to the end of the date code (letter "H"), but on 1/1/2017 the 6th digit was dropped, and the date code for DF breakers went back to 5 digits.
Was this helpful?
What can we do to improve the information ?