208/120 single or three phase panel?

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greenspark1

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That is the question. This is fed from a 3 phase switchgear, any way to tell without taking off the cover? I believe Square D type QO panels can be either three or single phase.

DSCN1466v2.jpg
 
LOAD CENTER COVER QO, Load Centers, Indoor, 1 phase 12-42 CKT, NEMA1Mfr. Part#: QOC24US


This is what I found if the door matches the interior??
 
QOC24US

QOC24US

look up the cover cat number...the catalog says "cover with door is suitable for QO142M200, QO140M225, QO142L225G load centers".
And those are single phase panels.

that would be my guess
 
raberding said:
look up the cover cat number...the catalog says "cover with door is suitable for QO142M200, QO140M225, QO142L225G load centers".
And those are single phase panels.

that would be my guess
Click to expand...

Ah, perfect. I didn't know how to read the compatible load center product codes. Thanks!!!
 
I decided some firsthand investigation was in order so took off the cover and was surprised to find a three phase panel!

DSC01843v2.jpg

I'm not sure how this is possible since the trim says it is for single phase panels. I am very surprised.

The other thing I noticed was the phase bus bars don't extend down all the way. You can see this in the photo. Doesn't this mean that poles 21-24 are un-usable since there is no bus there?! Not sure why they would make panels like this.
 
Now the question? Is the bus rated for the tandem breaker you installed on the bottom left? Now have to figure out what interior you have!!
 
greenspark1 said:
I decided some firsthand investigation was in order so took off the cover and was surprised to find a three phase panel!

I'm not sure how this is possible since the trim says it is for single phase panels. I am very surprised.

The other thing I noticed was the phase bus bars don't extend down all the way. You can see this in the photo. Doesn't this mean that poles 21-24 are un-usable since there is no bus there?! Not sure why they would make panels like this.
Click to expand...


I think that the only difference between the covers for single phase panels and the covers for three phase panels is in the diagrams and compatible parts lists pasted to the cover.
So if somebody happened to have a single phase cover assembly it would fit just fine on some three phase panels.
There might be a difference in the size of the knockout for the main breaker if one is used, but that does not apply here.
 
raberding said:
look up the cover cat number...the catalog says "cover with door is suitable for QO142M200, QO140M225, QO142L225G load centers".
And those are single phase panels.

that would be my guess
Click to expand...

It is also listed for QO320L125G and QO324L125G 3-phase main lug only load centers.

I think they only have around 8 cover sizes for their entire line of QO loadcenters.
 
You do not have same branch breakers installed in the two different photos

First photo does not have any tandems or three pole breakers installed, second one does - I say it is not the same panel in both pictures or something changed after removing the cover:blink:

Any QO panel that is installed in that same size cabinet uses that same cover - exception would be a main breaker three phase panel as the main on those has a different sized opening/position then the single phase main breakers do. This also generally applies to the over 100 amp main breaker panels - 100 amp or below three phase main breaker panels typically use a back fed main breaker and hold down kit in positions 1/3/5.

QO142M200, QO140M225, QO142L225G - I don't know where that information come from those panel interiors are all too long to fit in a cabinet that uses the 24 space cover.

I had a job a couple years ago in a school building where we were converting single phase service (that was relatively new) to three phase. I purchased new three phase panels and swapped guts in existing cabinets - carefully selecting proper panels so that they fit in existing cabinets - all we did was unplug breakers, remove feeder/replace with three phase feeder, swap panel interior and snap breakers back in same positions and even kept covers as they were already marked with circuit information. Did this for the sake of balancing existing load across all three phases - three phase loads that were added came from different panels that were added.
 
Yes a different panel, but same label on the door. This is from a college campus, 3 separate buildings with 3 similar panels. Good eyes :)

Are these all 100A main bus, and how can you tell. Per NEC don't panels need to be labeled with their rated voltage/current?
Any insight on why the main bus doesn't extend down to all the poles? :?

Thanks for the feedback.

PS: here's this panel's label:
DSC01841v2.jpg
 
greenspark1 said:
Yes a different panel, but same label on the door. This is from a college campus, 3 separate buildings with 3 similar panels. Good eyes :)

Are these all 100A main bus, and how can you tell. Per NEC don't panels need to be labeled with their rated voltage/current?
Any insight on why the main bus doesn't extend down to all the poles? :?

Thanks for the feedback.

PS: here's this panel's label:
View attachment 12333
Click to expand...
But there is no guarantee the other panel isn't a single phase panel as that same cover fits multiple loadcenters both single and three phase. Had there been at least one three pole breaker in the first panel then you can fairly safely assume you have a three phase panel without removing the cover.

As you can see in the one pictured with the cover removed you have a 24 circuit opening cover but only a 20 circuit interior in the cabinet, there likely is a 24 circuit interior in both single and three phase that fit that cabinet, and use same cover.
 
greenspark1 said:
Per NEC don't panels need to be labeled with their rated voltage/current?
Click to expand...
The actuall supply voltage labeling is a responsibility of the installing electrician, not the manufacturer of the panel. The manufacturer just needs to list the maximum rated value.
greenspark1 said:
Any insight on why the main bus doesn't extend down to all the poles? :?
Click to expand...
The purchaser of the equipment wanted the lowest possible price, so they only wanted bus bars space for 20 circuits instead of 24.
The manufacturer wanted to save cost by using one box and cover for multiple interiors.

Over the years I have seen more than 1 contractor get burned by using the number of circuits shown on a cover directory versus the determining the number of spaces on the bussing.
 
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