Odd breaker configuration

[Praxis]

I hope this is on topic:

Attached is an existing situation i am trying to figure out as i have not seen this before.


System is as Follows

600A 240/120v main panel with the following breaker sub-feeding a 208/120v panel (this situation is happening 3 times in the panel).

I have never seen a breaker configuration like this before and was curious if anyone could explain it to me.





thanks

 

[K8MHZ]

I hope this is on topic:

Attached is an existing situation i am trying to figure out as i have not seen this before.


System is as Follows

600A 240/120v main panel with the following breaker sub-feeding a 208/120v panel (this situation is happening 3 times in the panel).

I have never seen a breaker configuration like this before and was curious if anyone could explain it to me.


View attachment 6370


thanks

How can you have both 240 and 208 in the same panel without a transformer?

 

[Praxis]

This is what my survey person brought back to me to work with. From all the pictures and talking with them there was no visible transformer and the equipment was in a poured cement room.

That is why I asked the question about what could be going on as it does not make sense.

 

[jim dungar]

There is a typo someplace.

 

[CAPS]

Square D QO breakers larger than 100 A require 6 spaces and there is a requirement about the max rating of the opposite breaker in the panel. I can't find the documentation right now.

 

[kingpb]

Somebody didn't have, or didn't want to spend money on a 3 pole breaker. The SQ D QO style breaker in 150A does not come in single pole, only 2 pole and 3 pole. So, they used 3 x 2 pole breakers to get a 3 phase sub-feed. This size frame does not allow for a a breaker on the other side.

If you take off the cover you will most likely find that there is only 1 wire hooked to each breaker, to utilize a phase B, A, C ( as shown by the photo in that order)

Overall rating 5-stars for creativity :blink:

I would suspect that even though the handles are tied together, a trip on B or C would not result in all three phases clearing.

The fact that it is a 240V high leg delta feeding a 208Y/120V panel is just a labeling issue. No 208Y/120V exists.

Of course, that's just my guess:lol:

 

[jim dungar]

Somebody didn't have, or didn't want to spend money on a 3 pole breaker. The SQ D QO style breaker in 150A does not come in single pole, only 2 pole and 3 pole. So, they used 3 x 2 pole breakers to get a 3 phase sub-feed. This size frame does not allow for a a breaker on the other side.

If you take off the cover you will most likely find that there is only 1 wire hooked to each breaker, to utilize a phase B, A, C ( as shown by the photo in that order)

Overall rating 5-stars for creativity :blink:

I would suspect that even though the handles are tied together, a trip on B or C would not result in all three phases clearing.

Almost but not quite.
You are correct about a QO plug-on breaker, however Square D does sell a QOB bolt-on 3-pole 150A breaker with an internal common trip. These larger (>110A) breakers only allow a 20A maximum breaker to be installed opposite them.

This panel is most likely a factory assembled NQ panel. Based on the intended application of this panel the factory has decided the spaces opposite the large breakers should not be used.

 

[Praxis]

For added confusion on this, the transformer feeding the site is 300kva 120/208 (called the power company) and unless a second transformer is hidden in the first floor ceiling space(only place it could fit and there is no concrete chanel for one), then there is nothing between site transformer and the main disc in the basement elec room and this main panel being a 240v is being feed incorrectly.

 

[jim dungar]

For added confusion on this, the transformer feeding the site is 300kva 120/208 (called the power company) and unless a second transformer is hidden in the first floor ceiling space(only place it could fit and there is no concrete chanel for one), then there is nothing between site transformer and the main disc in the basement elec room and this main panel being a 240v is being feed incorrectly.

Square D does not make a panel with a nameplate of 208Y/120V, unless it was a very special order.
Any voltages listed on the nameplate are the maximum the panel has been tested for, this is in accordance with standard UL procedures.

 

[Sierrasparky]

Pull covers , check voltage, otherwise pure speculation!

 

[Joethemechanic]

Are they using the high leg 208V for some single phase loads?

I don't see any voltages marked in the picture. Are my eyes bad