second electrode

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edleroy

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I have a 480/208-120v transformer supplying a three phase 120-208v panel for lighting and receptacles. At the transformer, xo is connected to an electrode and two conductors (neutral and grounding). the neutral and grounding conductors are connected to neutral and grounding bus in the panel. The bus's are not bonded in the panel. Also at the panel there is a second electrode connected to the neutral bus. All the equipment is located in a metal building, which is bounded to the second electrode.
Is this installation in violation of the NEC requirements?
 
Re: second electrode

Your wording is a little confusing. But it sounds like your grounded circuit conductor is bonded twice which is non compliant. Can you clear it up?
 
Re: second electrode

Originally posted by edleroy:
yes there are two electrodes, at the transformer xo and the panel neutral bus.
Click to expand...
If that second electrode at the panel is connected to the neutral buss then it is in violation of
(2) Grounding Electrode Conductor. The grounding electrode conductor shall be installed in accordance with (a) or (b). Where taps are connected to a common grounding electrode conductor, the installation shall comply with 250.30(A)(3).
(a) Single Separately Derived System. A grounding electrode conductor for a single separately derived system shall be sized in accordance with 250.66 for the derived phase conductors and shall be used to connect the grounded conductor of the derived system to the grounding electrode as specified in 250.30(A)(4). Except as permitted by 250.24(A)(3) or (A)(4), this connection shall be made at the same point on the separately derived system where the bonding jumper is installed.
Since there is no bonding jumper installed in the panel in question you cannot connect a Grounding Electrode Conductor (GEC) to the neutral buss bar. It would be permissible to connect a GEC to the Equipment Grounding Conductor Buss bar but that buss bar must be separate from the neutral buss and the EGC buss must be bonded to the panel cabinet.
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Tom H
 
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