Six-Disconnect Rule, Multiple structures

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nhee2

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A site with single utility pad-mount (2500 KVA), CTs and meter at the pad-mount, has an existing 3000A switchgear in one area of the facility. It has 3 other, 100A disconnects in other areas of the facility feeding process loads at other skids/structures. The smaller disconnects are fed from their own conductors off of the secondary of the utility transformer.

- In this case, is the service point the secondary lugs of the xfmr?
- Is each set of underground conductors feeding the 4 service disconnects considered individual sets of service conductors per 230.40?
- Supposing they want to add 3 more skids tapped similarly off of the transformer, is it correct that the six-disconnect rule doesn't apply, since we are dealing with separate structures, even though everything is coming off the same CTs/meter?
 
If I understand your description (not a certainty), I would answer that,
  1. The "service" ends at the transformer (could be either primary or secondary terminals, depending on the utility rules), and that everything downstream is a feeder.
  2. No. Article 225 applies, not 230.
  3. The six disconnect rule is not the issue. Note 2 in both tables 450.3(A) and 450.3(B) say that you can protect the secondary of a transformer using up to six devices. But all six must be grouped at the same location. So I think this installation is already in violation, and doing what you suggest would only aggravate the violation.
 
I would say yes, you have multiple sets of service conductors. You could add three more skids, each with it's own set of service conductors from the transformer.
 
David, doesn't that depend on the location of the "point of common coupling," where the utility company's property (i.e., primary conductors, transformer, secondary conductors, meter, etc.) ends and the owner's property begins?
 
charlie b said:
If I understand your description (not a certainty), I would answer that,
  1. The "service" ends at the transformer (could be either primary or secondary terminals, depending on the utility rules), and that everything downstream is a feeder.
  2. No. Article 225 applies, not 230.
  3. The six disconnect rule is not the issue. Note 2 in both tables 450.3(A) and 450.3(B) say that you can protect the secondary of a transformer using up to six devices. But all six must be grouped at the same location. So I think this installation is already in violation, and doing what you suggest would only aggravate the violation.
Click to expand...

Thanks Charlie b.

The xfmr is utility owned. I would say 450.3 does not apply. Even if the service point were at the secondary terminals, 450.3 would not apply. I believe 230 applies, but trying to determine if the arrangement of service conductors and disconnects is compliant.
 
nhee2 said:
this is what I think as well.
Click to expand...

I think I have changed my mind.

Single service is at the transformer secondary.

All Service disconnects have to be grouped. I don't see anything that lets me have them distributed about the site, from a single service.
 
david luchini said:
I would say yes, you have multiple sets of service conductors. You could add three more skids, each with it's own set of service conductors from the transformer.
Click to expand...

David, I see it as multiple services, not a single service. Is that what you mean? How the sets are fed is up to the POCO. They can feed all from one transformer or provide a transformer for each. There is no exception in 230.40 covering this so it must be separate services.
 
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