Grounding of a 12.47/480 xfmr and switchboard

[RUWired]

However, this installation falls under 250.24 (not 250.30) through 250.28.

Smart $, Article 250.30 and 250.24 should get together and unify. There is a difference between the two and that is the point of service.I'll add the quote from the handbook to explain the difference between the two.

The power for ac premises wiring systems is either separately derived, in accordance with 250.20(D), or supplied by the service. See the definition of service in Article 100. Section 250.30 covers grounding requirements for separately derived ac systems, and 250.24(A) covers system grounding requirements for service-supplied ac systems.
According to 250.24, a premises wiring system supplied by an ac service that is required to be grounded must have a grounding electrode conductor at each service connected to the grounding electrodes that meets the requirements in Part III of Article 250. Note that the grounding electrode requirements for a grounded separately derived system are specified in 250.30(A)(3), (A)(4), (A)(5), and (A)(7).

 

[Smart $]

Smart $, Article 250.30 and 250.24 should get together and unify. There is a difference between the two and that is the point of service.I'll add the quote from the handbook to explain the difference between the two.

The difference between 250.24 and 250.30 is not the Service Point, but rather the Service Disconnect. A poco-powered, customer-owned transformer on the line-side of the Service Disconnect can never be a Serparately Derived System. It will always be a service transformer under current code.

 

[RUWired]

The difference between 250.24 and 250.30 is not the Service Point, but rather the Service Disconnect. A poco-powered, customer-owned transformer on the line-side of the Service Disconnect can never be a Serparately Derived System. It will always be a service transformer under current code.

I agree with you as far as utility supplied primary goes. i don't think the op stated where or not this is utility or owner supplied primary. My point about being unified was with primary supplied transformers. The rules are slightly different between the two, but are identicle in application. The difference being called a (service), but both are serving to the building.
Rick

 

[Smart $]

I agree with you as far as utility supplied primary goes. i don't think the op stated where or not this is utility or owner supplied primary. My point about being unified was with primary supplied transformers. The rules are slightly different between the two, but are identicle in application. The difference being called a (service), but both are serving to the building.
Rick

It doesn't matter who owns what on the line side of an NEC-defined Service Disconnect through which a utility supplies power, as it is all service equipment, raceways, and conductors. Transformers as such are "service equipment".

 

[RUWired]

It doesn't matter who owns what on the line side of an NEC-defined Service Disconnect through which a utility supplies power, as it is all service equipment, raceways, and conductors.

I said in my last post that i did agree with you on utility supplied primary.

Transformers as such are "service equipment".

There are are privately owned primary systems to transformers that do not fall under service equipment.In that case they are SDS's.
Rick

 

[Smart $]

There are are privately owned primary systems to transformers that do not fall under service equipment.In that case they are SDS's.
Rick

The source would have to be a privately-owned power generating facility.

And this is the case how often out of all services?

 

[RUWired]

The source would have to be a privately-owned power generating facility.

There are facilities where the poco comes into a switch yard or line-up and stops. They don't own or maintain past the main. Every thing down stream of that is a feeder. Because it's a higher voltage than secondary feeders does'nt keep it listed as service conductors.

 

[wirenut1980]

This is interesting to me. For example, if on a military base, the utility supplies/owns power/equipment up to the secondary of the substation transformer (stepping down voltage from transmission to distribution). From there the military base owns the equipment including the transformers supplying power to the buildings. Let's say they follow the NEC. Is the power supplied to the building a service or an SDS? I say it is still a service and is grounded by 250.24.

 

[Smart $]

There are facilities where the poco comes into a switch yard or line-up and stops. They don't own or maintain past the main. Every thing down stream of that is a feeder. Because it's a higher voltage than secondary feeders does'nt keep it listed as service conductors.

True... but 1) you are still basing your argument on who owns what, and 2) no matter who owns what, there has to be an NEC-compliant Service Disconnect if a utility company provides the power.

 

[RUWired]

no matter who owns what, there has to be an NEC-compliant Service Disconnect if a utility company provides the power.

Thats a true statement, but thats not what we were debating.

Privately owned sytems are feeders and could be treated as such. But i am all for installing the privately owned systems typical of service supplied systems. I have worked on plenty of privately owned campus type wiring systems and they are all wired the same as service supplied. Only on a few exceptions have i seen the grounding wire pulled with the neutral and the SBJ installed in the main gear.To keep the standard, is to wire it as a service.

Technically, it's a feeder and could follow the rules of 250.30. The exception in (1)(A) allows us to omit the grounding conductor and treat it like a service providing it meets the requirements.

 

[Smart $]

Thats a true statement, but thats not what we were debating.

...

Perhaps you were not debating that issue... but your posts did not explicitly refer to Separately Derived System transformers. Instead, you referred to ownership and service point, neither of which determines whether a transformer is service equipment or an SDS transformer.

 

[RUWired]

Perhaps you were not debating that issue... but your posts did not explicitly refer to Separately Derived System transformers. Instead, you referred to ownership and service point, neither of which determines whether a transformer is service equipment or an SDS transformer.

Maybe you missed my point in posts 25,27, and 30. My point is when a customer owns and maintains their primary systems, past the service disconnect, The transformers fall under article 250.30.

 

[Smart $]

Maybe you missed my point in posts 25,27, and 30. My point is when a customer owns and maintains their primary systems, past the service disconnect, The transformers fall under article 250.30.

No I didn't miss those posts. I even went back and reread them before making this post. Your most recent message (quoted above) is the first time you have mentioned the service disconnect location relative to the primary lines and equipment.