Secondary conductors from a feeder-tapped transformer- 240.21(c)(4)

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riverjig87

riverjig87

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Minot, North Dakota, USA
I have a utility transformer (500KVA- 480Y secondary) outdoors being fed from the utility pole. The secondary of the utility transformer feeds a CT Enclosure which is mounted within 30' and within sight of the transformer. (ALL OUTDOORS). From this CT enclosure, we are being instructed to use it as a tap for (2) 400A disconnects. According to 240.21 (C)(4), the secondary conductors from the transformer must "Terminate at a single circuit breaker (or a single set of fuses) that limit the load to the ampacity of the conductors". we meet the

According to the engineer, this CT Enclosure is "service rated" which allows this configuration to be installed in this manner. However, I do not see where this could be acceptable according to the NEC.

240.21(C)(1) does not apply being that the secondary is Y and not delta.

I would appreciate any input on this subject.

Thanks everyone.
 
240.21 (D) refers me to 230.91. This just states that "If the service overcurrent device is not an integral part of the disconnecting means it has to be immediately adjacent to it".

Could I get some clarification of your reference? I hope I'm not missing something obvious.
 

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riverjig87 said:
240.21 (D) refers me to 230.91. This just states that "If the service overcurrent device is not an integral part of the disconnecting means it has to be immediately adjacent to it".

Could I get some clarification of your reference? I hope I'm not missing something obvious.
Click to expand...

Forget 240.21.

Look at 230.70-230.95.
 
riverjig87 said:
240.21 (D) refers me to 230.91. This just states that "If the service overcurrent device is not an integral part of the disconnecting means it has to be immediately adjacent to it".

Could I get some clarification of your reference? I hope I'm not missing something obvious.
Click to expand...
Just that my original post said 240.21 does not apply to service conductors. I could have revised my original post to say 240.21(C) does not apply to service conductors, but instead I revised it to say what it says. There are no repercussions from me changing my original post.
 
david luchini said:
Forget 240.21.

Look at 230.70-230.95.
Click to expand...


So after looking through the mentioned sections, I am still finding some difficulty understanding. I cannot see where it is allowable to use this CT Enclosure to tap multiple disconnects from it.

230.82 specifies equipment that can be installed on the supply side of the service disconnect(s). None of equipment listed satisfies this. This enclosure has no disconnecting method. Its is simply pass thru lugs.

230.90(A) is the closest that I see that refers to this installation.

Maybe it is much simpler than this and I am over complicating. It seems odd to me that the secondary conductors from the transformer to this enclosure do not require protection before feeding additional disconnects.
 
Yes. That was it. I think I envisioned something else in my head for some reason. This exception also doesn't specify that it is limited to a certain occupancy either which is exactly what we have. The graphic does show that for an example.

Thanks for the help everyone!
 

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I was away from my desk, but I see others have you covered. For future reference may also want to note the following sections:

230.33
230.66
230.82(2)
230.82(4)

A CT cabinet qualifies under 230.82(4) automatically (CT's are instrument transformers) and depending use, possibly 230.82(2) because it comprises part of a meter. Could also potentially qualify under (7), (8) and/or (9)... but rather rare.
 
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