Isolated ground

hhsting

Senior Member
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?

 
Last edited:

don_resqcapt19

Moderator
Staff member
Location
Illinois
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

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Why not run the IG in the conduit with the feeder? Otherwise you have an issue with 300.3(B).
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
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.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
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.
 
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