Six-Disconnect Rule, Multiple structures

[nhee2]

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?

 

[charlie b]

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.

 

[david luchini]

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.

 

[charlie b]

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?

 

[nhee2]

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.

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]

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.

this is what I think as well.

 

[nhee2]

this is what I think as well.

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.

 

[electrofelon]

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, 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.