I've looked through the sections in the Nec on grounding conductors how they can splice and placement and attachment of electrodes . I'm installing a meter socket disconnect combo making my main load center inside a sub panel. What is unclear to me is if I can run my sub panel grounding conductor to the same grounding electrode as my service disconnect is being attached effectively making a grounding " splice" ( I know it's not a splice) between the sub and main conductors instead of running my sub conductor into the main and right back out onto the grounding electrode. Would it be a problem if in a ground fault situation the energy is getting sent to ground potentially instead of back to neutral or would it bypass the electrode anyway to seek the neutral path.

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    What are you using for the feeder wiring between the meter-main and the sub-panel? – ThreePhaseEel Feb 18 at 4:03
  • I suggest embellishing "grounding conductor" to be either "ground" or what its momma calls it when it's in trouble, equipment grounding conductor. That way you avoid confusion with "groundED conductor" which is the lawyer name for neutral (WTH right?) . – Harper - Reinstate Monica Mar 19 at 18:18

The feed from the new main panel / meter to the inside sub panel is 4 wire from the main panel. Inside the sub the neutral is isolated from ground. Are you thinking that the sub ground comes directly from the ground electrode? I think this would be a code violation for a new system as 4 wire feeders have been code since 99. Since the sub is in the same building a separate ground electrode is not required and if a grounding electrode conductor is added would create a parallel path.

Now if you want to sink a new grounding electrode at the panel and connect it to the sub that would be code compliant. But your feed from the main is required to be 4 wire and a parallel grounding conductor would violate code.

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  • I was asking if you were to take the grounding wire from the sub to the main and connect your ground rod in the center of that wire would it still be considered a unbroken connection between the sub grounding and ground/neutral bus . I was trying to kill two birds with one stone but wasn't sure on the legitimacy of doing so for reasons such as the grounding wire from sub to main would have a grounding rod in the middle and if there was a preferred travel path weather it be to earth(through ground rod )or nuetral/ground bus – Cc365 Feb 18 at 21:25
  • I understand but I know that would not meet code in my jurisdiction as this can set up a differential voltage from the neutral to ground. yours may allow it. A grounding electrode conductor can be spliced with irreversible compression splices that are listed see exhibit 250.27 – Ed Beal Feb 18 at 23:45

No, the Equipment Grounding Conductor from the required 4 wire feeder to a 120/240v subpanel must be connected to the ground bus in the panel feeding it.

In all panels fed downstream from the service you will need remove any bonding jumper and separate Grounded Conductors (neutrals) and Equipment Grounding Conductors.

You need to re-connect all grounding electrodes (building steel, metal water piping, encased rebar, pipes, and rods) to the new service, connections need to "continuous" [per 250.64(C)].

The existing grounding electrode connections to the Grounded Conductor (neutral) must be disconnected in sub-panels, those connections could be could be completely removed, but I think you could leave them connected to the ground bus. I could be convinced otherwise, but to me I don't see any difference specified in the code between a panel mounted on building steel that is an electrode, or connections to any other type of electrode.

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  • Thanks that answered my question, I wasn't sure if the connection between the sub and main ground could be completed through the grounding electrode instead of sub to main then back to earth because the sub ground has to pass the grounding electrode on it's way to the main panel. Is there a reason for this or is it just because that would count as an unacceptable connection to the main grounding system even though they would be bonded together through the grounding electrode (just curious) – Cc365 Feb 18 at 20:37
  • @Cc365 -- I'm still not clear as to what you're planning to use/using for a wiring method between the main panel and the subpanel... – ThreePhaseEel Feb 19 at 0:00
  • 4/0 seu with #4 stranded bare on ground ran through 2" conduit to main outside of the house . I'm not sure what my question conveyed to you but there was no bonding of the neutrals to ground in the sub panel I was merely inquiring if the ground rod could be installed on the ground conductor from sub to main so I wouldn't have to run a separate #4 from the main to the ground rod . The sub ground would still be directly connected to the main neutral bus by continuous unbroken ground cable and the main could still reach earth through the same continuous cable – Cc365 Feb 19 at 2:31
  • @Cc365 -- wait...what type of conduit did you put in here? What you did seems wrong on several levels... – ThreePhaseEel Feb 20 at 3:48

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