SD QO loadcenter number of spaces

[olc]

Square D Cat. No. QO20-24L125WGF
Does it have 20 spaces or 24 spaces (for branch circuit breakers)?

 

[kwired]

sure you have the right number? Their loadcenter numbers usually would be QO120.... for single phase 20 spaces, or QO320 for three phase 20 spaces, I have never seen the suffixes you have in your number either besides the G which likely means it comes with an equipment grounding bar, - unless it is maybe a Home Depot or other big box store product. I guess the F probably means a flush cover is included but not sure about the W.

Otherwise the 20-24 likely means there are 20 bus connections, but four of them are designed to be able to accept tandem breakers meaning there can be up to 24 poles available for branch circuits.

The number you posted is not in the Digest but as I said could be a model made specifically for some big box store.

 

[Jraef]

Yes, you are missing a digit in there, the "1" or "3" after the QO that designates 1 phase or 3 phase. But be that as it may, the 20 means it has 20 single pole spaces, the 24 means you can have up to 24 circuits, by using 4 tandem breakers. In the QO system, tandem breakers have a special clip arrangement, so they can only be installed in spaces that are set up for them. In the case of this panel, there are only 4 spaces which can accommodate both the single pole and those tandem breakers. So you get to 24 poles max. because you take the 20 pole spaces, minus the 4 which will accept tandems, for 16 single pole breakers, then in those 4spacrs you can put 4 tandems for 8 more poles, 16+ 8 = 24 poles.

Oops, sorry kwired, took me too long to pull the trigger on that...

 

[jim dungar]

The first number is the quantity of 'full size' spaces.
The second number is the maximum quantity of circuits when using 'tandem' breakers.

For almost 4o years, Square D single phase loadcenters did not use the "1" digit prefix to denote single phase. There are definitely a lot of panels still service using this old numbering method.
During that same time the prefix "4" was used for 3-phase panels with 100% neutrals (back when QO was introduced, the industry allowed 50% neutrals).

More recently (maybe less than 20 years) the prefixes 1 and 3 began being used on the later generations of loadcenters.

 

[Jraef]

...

For almost 4o years, Square D single phase loadcenters did not use the "1" digit prefix to denote single phase. There are definitely a lot of panels still service using this old numbering method.
During that same time the prefix "4" was used for 3-phase panels with 100% neutrals (back when QO was introduced, the industry allowed 50% neutrals).

More recently (maybe less than 20 years) the prefixes 1 and 3 began being used on the later generations of loadcenters.

Well that explains it then. I even worked for Sq. D 20+ years ago (albeit a different division) and probably knew that at the time, but forgot that detail and relied on the almighty Google. Just shows to go ya, there is no substitute for experience... :thumbsup:

 

[kwired]

More recently (maybe less than 20 years) the prefixes 1 and 3 began being used on the later generations of loadcenters.

I don't know when this change was made but pretty sure it has to be closer to 25 years then it is to 20 years. I've been in the trade about 27 years and the design they use now with the QOM mains and nonmetallic frame for the panel interior was introduced sometime right around when I started in the trade, and I think that series brought with it the current model numbering system.

 

[jim dungar]

I don't know when this change was made but pretty sure it has to be closer to 25 years then it is to 20 years. I've been in the trade about 27 years and the design they use now with the QOM mains and nonmetallic frame for the panel interior was introduced sometime right around when I started in the trade, and I think that series brought with it the current model numbering system.

Digest #170 dated 1994 lists single phase loadcenter part numbers; QO20-40M200 and QO24M200 among others.