Equipment grounding conductor definition

[kwired]

Do not confuse the connection of the GEC to the Grounded Conductor (neutral) with the Main Bonding Jumper...

I don't think I was.

 

[Smart $]

I don't think I was.

Regardless, a GEC can be connected at any accessible point along the service entrance grounded conductor [250.24(A)(1)]

 

[kwired]

Regardless, a GEC can be connected at any accessible point along the service entrance grounded conductor [250.24(A)(1)]

That is what I always understood, but wasn't finding where it was stated when I was posting earlier in this thread, thanks for finding it.

 

[cppoly]

Ungrounded systems still need all non current carrying metallic components bonded together to form and equipment grounding system and needs to have a grounding electrode at the service, separately derived source or first disconnecting means. This is to provide a reference to ground on all these bonded items and prevent having any voltage between those items.

See 250.24(E) for the requirement to have a grounding electrode system for an ungrounded service.

One last question here. For ungrounded systems with EGCs and a GEC, is the utility transformer grounded or ungrounded?

 

[kwired]

One last question here. For ungrounded systems with EGCs and a GEC, is the utility transformer grounded or ungrounded?

The utility transformer is likely not covered by NEC.

That said any source transformer that is covered by NEC still has to have the metal frame connected to the equipment grounding conductor and grounding electrode system. (it needs to be connected to same potential as all other non current carrying metal components to eliminate voltage potential between those metal objects.)

 

[ggunn]

One last question here. For ungrounded systems with EGCs and a GEC, is the utility transformer grounded or ungrounded?

Yes.

 

[ggunn]

Question, if it's an ungrounded system we're talking about, why would there be a GEC in the first place? Wouldn't that mean there wouldn't be a connection of the EGC to the GEC?

No. All it means to be an ungrounded system is that there is no circuit conductor connected to the GEC, i.e., a grounded conductor. There still needs to be a GEC to connect the EGC(s), and thereby all metal parts not part of the active circuit to a grounding electrode.

 

[cppoly]

Something isn't right here. See the attached image. The ungrounded system is grounded through a GEC and EGCs. Now if the utility transformer is also grounded, that creates a dangerous situation.

 

[ggunn]

Something isn't right here. See the attached image. The ungrounded system is grounded through a GEC and EGCs. Now if the utility transformer is also grounded, that creates a dangerous situation.

View attachment 9427

If the primary of the transformer is grounded but the secondary isn't, the secondary voltage is not referenced to ground and there is no return path.

 

[cppoly]

Yes, but as someone else mentioned the utility transformer grounding is not a part of the NEC scope. How is this coordinated?

 

[ggunn]

Yes, but as someone else mentioned the utility transformer grounding is not a part of the NEC scope. How is this coordinated?

To what are you responding?

 

[cppoly]

The utility transformer is likely not covered by NEC.

That said any source transformer that is covered by NEC still has to have the metal frame connected to the equipment grounding conductor and grounding electrode system. (it needs to be connected to same potential as all other non current carrying metal components to eliminate voltage potential between those metal objects.)

ggunn, I'm responding to this post

 

[kwired]

Yes, but as someone else mentioned the utility transformer grounding is not a part of the NEC scope. How is this coordinated?

When I said NEC doesn't apply to the utility transformer what that means is whether or not the frame of the transformer is grounded or not is not of concern of the NEC. If a secondary conductor is grounded - you do not have an ungrounded system period.

 

[cppoly]

Thanks kwired.