Are branch circuit grounds required to land on the ground buss in the panelboard? Or can they land on a ground buss in a panel that the grounds pass through. My feeling is that 1) the branch circuits should not be passing through a panel on the way to another panel in the first place. And that the grounds are required to land at the panelboard, not another electrical equipment even is that equipment is connected through RMC. I couldn't find a reference though. Thanks.
Branch circuit grounds back to panel
- Thread starter spsnyder
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peteo
Senior Member
- Location
- Los Angeles
It is a design issue whether to pass through another panel if there is no box fill issue and less than 600 V by 300.3(C)(1). 250.134(A) permits any customary (250.118) method. I've seen some requirements for an unbroken, continuous ground wire, for example within panels and for swimming pool equipment. I believe this would then be called an isolated ground once it enters the feeder, which 250.134(B) permits.
It appears more robust to me to use a continuous, separate EGC in this case as well, mainly in case there is a ground loop created either unintentionally or later, from modifications to what's in the 'midway' panel. Also, if anyone ever needs to work on that final branch circuit it will be simple, i.e., good. This issue has come up before but I can't speak for a consensus and hope more knowledgable words will be posted.
It appears more robust to me to use a continuous, separate EGC in this case as well, mainly in case there is a ground loop created either unintentionally or later, from modifications to what's in the 'midway' panel. Also, if anyone ever needs to work on that final branch circuit it will be simple, i.e., good. This issue has come up before but I can't speak for a consensus and hope more knowledgable words will be posted.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
The SOLE purpose of the EGC is to provide a path back to the source so that in the event of a ground fault, the OCPD will be able to clear the fault.
Since there is not supposed to be any current flow on an EGC except for the short period of time it takes the OCPD to clear a fault, there is no ground loop issue.
As long as you have a path back to the source that is low enough impedance so that the OCPD can clear a ground fault, it is perfectly adequate.
Since there is not supposed to be any current flow on an EGC except for the short period of time it takes the OCPD to clear a fault, there is no ground loop issue.
As long as you have a path back to the source that is low enough impedance so that the OCPD can clear a ground fault, it is perfectly adequate.
- Location
- Illinois
- Occupation
- retired electrician
If you run an EGC upstream of the panel that contains the branch circuit OCPD, you have a violation of 300.3(B) and 408.40, unless the ground is an insulated (isolated) grounding conductor.
Don
Don
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