Three Related Questions: #1

[Smart $]

So in 240.21(C)2(1)(B) you would call the enclosure assembly "the device". (as a single load)

Perhaps... that's what I was thinking, but I cannot say with any certainty.

 

[charlie b]

Gee whiz, I walk away for one night and the details start flowing in. Many thanks for the input. But I am going to have to spend some time digesting your comments, before I can respond. I will say, in answer to someone's question, that a single enclosure (bigger than a bread box, but not quite as large as an SUV) contains the transformer, conductors from the secondary to bus bars, the bus bars themselves, and four breakers, and it is manufactured and listed as a single entity. That at least is my understanding. I have not seen it yet.

 

[charlie b]

1) How long are the wire conductors?

If you are refering to the conductors from the transformer secondary to the bus bars, I would say they are less than two meters long (yes, it is a metric job).

 

[Smart $]

Gee whiz, I walk away for one night and the details start flowing in. Many thanks for the input. But I am going to have to spend some time digesting your comments, before I can respond. I will say, in answer to someone's question, that a single enclosure (bigger than a bread box, but not quite as large as an SUV) contains the transformer, conductors from the secondary to bus bars, the bus bars themselves, and four breakers, and it is manufactured and listed as a single entity. That at least is my understanding. I have not seen it yet.

IMO, manufactured and listed as a single entity removes it from the purview of the NEC, except for 110.2 Approval.

 

[charlie b]

IMO, manufactured and listed as a single entity removes it from the purview of the NEC, except for 110.2 Approval.

That occurred to me as well.

Here (or so I believe) is a photo of the item in question. It was taken during a field trip by another engineer working on the project.

 

[charlie b]

OK, I have reviewed what several of you have been saying, and I think I see the issues. Let’s assume the NEC does apply here, and let me try the following approach.

? There is a set of “secondary conductors” that connects to the center of the transformer’s secondary windings. They are less than 3 meters long.
? The other end of these secondary conductors connects to a device that I will call a “switchboard” (i.e., what I have previously been calling "bus bars").
? The secondary conductors do not extend beyond this switchboard.
? Their ampacity exceeds the rating of the switchboard, and also exceeds the load current.
? I don’t need a raceway to enclose the secondary conductors from the location of the transformer to the location of the switchboard, as they in the same enclosure as the switchboard.
? I am now in a 240.21(C)(2) situation. Please note that that article does not require the secondary conductors to terminate at an OCPD.

Conclusion: This is code compliant. Whatcha tink?

 

[Smart $]

OK, I have reviewed what several of you have been saying, and I think I see the issues. Let?s assume the NEC does apply here, and let me try the following approach.

? There is a set of ?secondary conductors? that connects to the center of the transformer?s secondary windings. They are less than 3 meters long.
? The other end of these secondary conductors connects to a device that I will call a ?switchboard? (i.e., what I have previously been calling "bus bars").
? The secondary conductors do not extend beyond this switchboard.
? Their ampacity exceeds the rating of the switchboard, and also exceeds the load current.
? I don?t need a raceway to enclose the secondary conductors from the location of the transformer to the location of the switchboard, as they in the same enclosure as the switchboard.
? I am now in a 240.21(C)(2) situation. Please note that that article does not require the secondary conductors to terminate at an OCPD.

Conclusion: This is code compliant. Whatcha tink?

Sounds good to me...

 

[RUWired]

i agree as well now that i have been enlightend from Smart$ about devices.

Now that the secondary conductors are protected, have you solved the problem with protecting the secondary of the transformer. (1935 amps vrs. 1800 amps)

 

[charlie b]

Now that the secondary conductors are protected, have you solved the problem with protecting the secondary of the transformer. (1935 amps vrs. 1800 amps)

Still working on that one. If you look at the photo from post 45 above, and see the type of building served by this substation, it becomes a murky question as to whether this can be called a "supervised location," in the context of Table 450.3(A). But that is being discussed in another thread, here:
http://forums.mikeholt.com/showthread.php/138542-Three-Related-Questions-3.