Isolated grounds

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billdozier 78

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Orlando
If you have 3 circuits in one conduit all calling for isolated grounds how many do you pull? To me I would pull one eg ground and one ig which would then pass through each box to individual duplex receptacles.1
 

texie

Senior Member
Location
Fort Collins, Colorado
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Electrician, Contractor, Inspector
Seen it done both ways. One could argue that a common isolated grould between the multiple outlets could set up ground loops between them. Also, keep in mind that in any event that the isolated grounds must pass thru (not connected to) any sub panels and connect at the service bonding point. In a commercial setting this can be a bit of a challenge. Other wise they are pretty much useless as isolated ground circuits.
 

Smart $

Esteemed Member
Location
Ohio
... Also, keep in mind that in any event that the isolated grounds must pass thru (not connected to) any sub panels and connect at the service bonding point. ...
Not an NEC requirement. In fact, the NEC don't require anything different than "regular" EGC's. The NEC just permits IG EGC's to not be connected to normally-non-current-carrying-metal parts along its route.
 
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texie

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Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Not an NEC requirement. In fact, the NEC don't require anything different than "regular" EGC's. The NEC just permits IG EGC's to not be connected to normally-non-current-carrying-metal parts along its route.
I did not mean to imply that it is a NEC requirement, just that if you don't they are pretty much worthless.
 

jim dungar

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Wisconsin
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Retired Electrical Engineer - Power Systems
Also, keep in mind that in any event that the isolated grounds must pass thru (not connected to) any sub panels and connect at the service bonding point.
This would be a design issue, only. The NEC does not describe where isolated grounds begin, or end.

Isolated grounds can be used to create a 'single grounding point' to minimize ground loops for interconnected equipment, as such there is no reason that a 'sub-panel' could not be that point.
 
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