250.146(D) Isolated Ground

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ronmath

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Burnsville, MN
I am having a disagreement with an inspector about where this sections allows an isolated ground conductor to be terminated. He is stating that it must be run all the way back to the service ground. I say this section says "it shall be permitted" to do this, but it is not a requirement. I am stating that you can terminate it in the panel where the circuit originates and still provide a "isolated ground receptacle" (which as we all know is a misnomer anyway). Can I please have some other people chime in on this as well?

Thanks!
 
I agree with your interpretation but I would think that the value of the isolated ground is diminished when terminated at a sub panel.
 
Dennis,

I agree with you on the value of the isolated ground at a sub panel, but in this case which is a tenant panel with the main service 500' away and no existing isolated ground conductor, it does not pay to pull it in. It's really frustrating when someone misinterprets the code and will not back down in any way.
 
I just want to point that if the panel that supplies the IG protected circuit is from an SDS that it would be a violation to the run the IG to the service. It would have to go the EGC terminal of the SDS.
 
The isolated ground only needs to exist beyond the point of the common coupling/reference point for the circuit. The intent is to create a 'star' topology for the grounds versus a 'daisy-chain'.

There is nothing wrong with using a sub panel as the starting point.
 
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