Isolated ground

[hhsting]

Please see attached. I have trough with two service disconnects and main grounding electrode system. One of service disconnect feeds Panel M which feeds isolated receptacles.

Panel M has isolated ground bus but instead of ruining the isolated equipment grounding conductor thru conduit thru panelboards eventually to terminate in equipment grounding bus in main service disconnect, their is grounding electrode conductor from Panel M isolated bus bar to main service grounding electrode system.

Questions:

1. I find this strange but not sure if a code would allow such grounding electrode connection? If not then I cannot spot right code section which would not allow this.

2. Assume that isolated ground bus bar is connected to equipment grounding bus bar Panel M which has EGC to main bonding jumper service disco then can the grounding electrode connection be made at Panel M isolated ground bus bar?

 

[don_resqcapt19]

In my opinion it is a violation of 300.3(B).

(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1)through

(B)(4).

 

[infinity]

Why not run the IG in the conduit with the feeder? Otherwise you have an issue with 300.3(B).

 

[LarryFine]

In other words, it need not terminate wherever the feeder conductors do, but it should be run with them. One good reason is low impedance in case of ground-fault short circuits.

It should terminate on the neutral where the service's main bond is.

 

[tom baker]

Fro the answer to question #2 see section 250.24

 

[infinity]

Since the disconnect in your sketch is a service disconnect the IG should connect to the neutral or ground bus at that point not to the GEC as shown.