Service panel GEC

[m sleem]

I believe the service panel needs a separate GEC as per 250.32(a), but if the transformer is located inside the building, thereby the GEC will be connected to transformer, for this case do we still need to connect GEC with panel? means that we would have two GECs one to transformer and the other one to the panel.
My first understanding that we have two GECs when the transformer is located indoor, but when i saw a forum discussing the IEC standard, i found post says the US uses TN-C-S AND TN-C systems where any of them has no connection from panel to grounding through the GEC.

 

[augie47]

I may find that I am mistaken, but I think you have a situation here that is a bit unusual in that a "service" transformer would be addressed a bit differently from a customer owner SDS.
If your panel is truly a "service panel" and the transformer belongs to the utility you might well have a GEC from each. If it is all customer owned, then you would follow 250.30 and establish one point for the GEC and system bonding jumper.

 

[Smart $]

First off, in referring to 250.32(a), we have to be talking about a building supplied by feeder or branch circuit. Therefore, nothing is referred to as "service" anything.

When a building is supplied by a feeder, the first connection must be a disconnecting means with ocpd at its entry, outside or inside near entry point. It cannot go directly to an inside transformer. There will be a GEC to the disconnecting means EGC. Grounded conductor and grounding system remain isolated.

When there is an SDS transformer inside this building, its grounding requirements are completely separate other than using a common grounding electrode. For a grounded secondary configuration, the GEC must be connected to the point where the system bonding jumper connects EGC to grounded conductor (either in transformer or system disconnecting means enclosure).

 

[m sleem]

From all opinions, if the transformer and the panel are owned by the customer, then the GEC must be connected to one point only ref to 250.30.

& if the transformer is located inside or outside the building & not owned by the customer & the access is limited by the utility only, then the GEC must be connected to the service panel.

 

[Smart $]

From all opinions, if the transformer and the panel are owned by the customer, then the GEC must be connected to one point only ref to 250.30.

& if the transformer is located inside or outside the building & not owned by the customer & the access is limited by the utility only, then the GEC must be connected to the service panel.

Around here, I very much doubt you'll ever see a POCO transformer inside a customer-owned building. Not sure what they do in downtown metropolis areas.

Regarding a service, a GEC can be connected anywhere along the grounded service entrance conductor. It is only the MBJ that is required to be in the service disconnect enclosure. If there is no grounded service entrance conductor, then a GEC will obviously have to be connected in the service disconnect enclosure.

 

[m sleem]

Around here, I very much doubt you'll ever see a POCO transformer inside a customer-owned building. Not sure what they do in downtown metropolis areas.............

That's normal in our place, the utility co. will occupy the transformer's room with lock (the access from outside only), they will supply and install the transformers up to #3 each 1mva, the maintenace and replacing through them only, maybe they give offers or promotion by reducing the kw unit price.