Service Terminology

[charlie b]

I have a somewhat-unusual setup, or at least one that I haven't encountered before. An outdoor service transformer has three circuit breakers within a enclosure that is shared with the transformer, and that is located on the same pad. That is, if you open doors on one side you see the transformer. If you open doors on the other side you see the breakers. Two of the breakers are small, and serve outdoor lights and a small picnic area. The third is much larger, and provides power to a main distribution panel inside the building. I put the N-G bond inside the outdoor enclosure, attached the GEC to the neutral bar, and ran an EGC with the conductors to the indoor panel. A client engineer who is reviewing the package is telling me that the N-G bond belongs inside the indoor panel, and that the GEC should run from there to the ground bar with the electric room. To my way of thinking, the “service disconnecting means” mentioned in 250.24(A)(1) is the breaker that sits two feet away from the transformer. My problem is the terminology: that same sentence speaks of “service drop” and “service lateral,” neither of which appears to apply to my situation. Any thoughts?

 

[Cow]

2011 NEC

250.30(A)1
250.30(C)

Does that help?

 

[jumper]

The indoor panel seems to be a sub panel at a separate structure, so it would seem that the GES at the pad is correct and an EGC needs to be run, but the indoor panel would need a GES also. No?

 

[texie]

I have a somewhat-unusual setup, or at least one that I haven't encountered before. An outdoor service transformer has three circuit breakers within a enclosure that is shared with the transformer, and that is located on the same pad. That is, if you open doors on one side you see the transformer. If you open doors on the other side you see the breakers. Two of the breakers are small, and serve outdoor lights and a small picnic area. The third is much larger, and provides power to a main distribution panel inside the building. I put the N-G bond inside the outdoor enclosure, attached the GEC to the neutral bar, and ran an EGC with the conductors to the indoor panel. A client engineer who is reviewing the package is telling me that the N-G bond belongs inside the indoor panel, and that the GEC should run from there to the ground bar with the electric room. To my way of thinking, the ?service disconnecting means? mentioned in 250.24(A)(1) is the breaker that sits two feet away from the transformer. My problem is the terminology: that same sentence speaks of ?service drop? and ?service lateral,? neither of which appears to apply to my situation. Any thoughts?

At first glance it would seem that you don't have a service drop or lateral, you have a feeder. This is not a POCO xformer but rather a campus type distribution, correct?
It would appear that you are correct, but you still need an GES for the building (without a neutral/ground bond).

 

[texie]

At first glance it would seem that you don't have a service drop or lateral, you have a feeder. This is not a POCO xformer but rather a campus type distribution, correct?
It would appear that you are correct, but you still need an GES for the building (without a neutral/ground bond).

I should have added see 250.32

 

[charlie b]

Thanks for the help, everyone.

250.30(A)1, 250.30(C)Does that help?

I think not, but thanks anyway. This is the service to a building, so I would not call it a ?separately derived system.?

The indoor panel seems to be a sub panel at a separate structure, so it would seem that the GES at the pad is correct and an EGC needs to be run, but the indoor panel would need a GES also. No?

That is how I see it. I will check the design to see if it shows a GES for the building as being a separate entity from the GES at the transformer.

At first glance it would seem that you don't have a service drop or lateral, you have a feeder.

Agreed. But my problem is in the wording of 250.24(A)(1). It tells me to connect the GEC anywhere I like, so long as it is between the service drop and the service disconnecting means. Do I simply infer that the secondary terminals of the transformer constitute the ?service drop??

This is not a POCO xformer but rather a campus type distribution, correct?

That is a surprisingly interesting, and difficult question. I believe it is a POCO transformer. But since it is a single enclosure, I would call it a unit substation, and I don?t think the POCO would own the breaker section within that enclosure. I will check into that. But I can?t just call up the POCO, because I don?t speak Japanese. :happyno: This is on a US military base overseas, and they want us to use the 2008 NEC as our design basis.

It would appear that you are correct, but you still need an GES for the building (without a neutral/ground bond).

Agreed, and as I said above, I will look into that.