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Grounding sub panel

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Isaiah

Senior Member
Location
Baton Rouge
Occupation
Electrical Inspector
I have a three phase 120/208V 4W panelboard that sub feeds another 3-ph Panelboard - MLO-located about 20’ away in the same building.
The first panelboard has a GEC at the 45kVA transformer mounted directly above it.
The second panelboard does not have a GEC nor are the neutral bus and ground bus bonded together. Also field did not run the neutral to the sub panel.



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Last edited:
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Isaiah said:
The second panelboard does not have a GEC nor are the neutral bus and ground bus bonded together. Also field did not run the neutral to the sub panel.
Click to expand...
The second panel would not require a GEC but it would require an EGC. If a neutral is not needed for the circuits within the panel one is not required to be installed with the feeder.
 
I

Isaiah

Senior Member
Location
Baton Rouge
Occupation
Electrical Inspector
infinity said:
The second panel would not require a GEC but it would require an EGC. If a neutral is not needed for the circuits within the panel one is not required to be installed with the feeder.
Click to expand...

Thanks Infinity.
Neutrals are required at both panel locations. Does the neutral and ground buss at the sub panel need to be bonded?


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augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Neutrals (grounded conductor) must be brought to the SERVICE panel (on grounded systems) 250.;24(C) and neutral and equipment ground bonded at the SERVICE panel 250.24(B).
At any panel fed from the service panel, the neutral and equipment ground shall not be connected (250.24(A)(5).
The neutral needs to be run to any sub-panel only if needed t supply the load.

The rules differ somewhat on panels in detached structures or panels fed from SDS.
 
I

Isaiah

Senior Member
Location
Baton Rouge
Occupation
Electrical Inspector
augie47 said:
Neutrals (grounded conductor) must be brought to the SERVICE panel (on grounded systems) 250.;24(C) and neutral and equipment ground bonded at the SERVICE panel 250.24(B).
At any panel fed from the service panel, the neutral and equipment ground shall not be connected (250.24(A)(5).
The neitral needs to be run to any sub-panel only if needed t supply the load.
Click to expand...

Fantastic feedback thanks Augie!


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