How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
How can I tell the age of a Square D electric panel from the serial number?
Sunday, November 24, 2019
The alpha-numeric sequence is usually a stamp over the wiring diagram, as shown in the photo above. It would be more accurately described as a date-code system, since each panel box does not have a unique number. The diagram below is for panel manufactured from 1956 to approximately 2002.
So the date-code shown at the top of the page indicates that the panel was manufactured on December 15th of 1967 or 1988, by operator #924, on the first shift. Since the letter indicating year of manufacture can be one of several that are 21-years apart, you should evaluate the condition of the panel to determine which one that is most likely correct. Year of construction of the home, along with the year of any remodeling or electrical upgrades can further clarify it.
Here’s another example, below, that was manufactured on September 29th of 1952, 1973, or 1994, by operator #462, on the first shift. In this case, since we knew that the home was built in 1995, it was easy to establish that 1994 was the year of manufacture.
Panels from the late 1990s until the present most commonly use a five or six digit code, where the first two digits are the year, second two digits are the week. So “991731” would have been manufactured in 1999, on the 17th week of the year.
To get date-code sequences for panels manufactured before 1956, download the Schneider Electric pdf document from this link: SquareDDate.pdf.
Also see our blog post Which Square D electric panels were recalled in 2022? And for the age of another manufacturer’s panel, go to How do I determine the age of an electrical panel?
• • • • • • • • • • • • • • • • • • • • • • • • • •
Here’s links to a collection of our other blog posts about ELECTRIC PANELS:
of Blog Posts
Top 5 results given instantly.
Click on magnifying glass
for all search results.
Buying a home in North/Central Florida? for a team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.