Existing GEC in primary sub panel and understanding 250.64(C)(2)

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darunedefig

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HV, New York
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Electrician
I am trying to better understand:
NEC 2017 250.64(C)(2): Sections of busbars shall be permitted to be connected
together to form a grounding electrode conductor.
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I have a residential job with an existing 200A main service panel that has a 200A main breaker. Currently there are no load breakers in this panel, but I am wanting to use 2 spaces of the 8 spaced MSP. There is a neutral wire, L1, and L2 going from the utility meter to the adjacent exterior MSP. L1, L2, neutral and a "ground" going from exterior MSP to a primary subpanel located electrically 15' away in basement. The neutral to "ground" connection happens in the MSP.
This is all normal except that the GEC from the ground rod (next to utility meter and exterior MSP) goes into basement along joists to the ground bar in the primary subpanel. The primary subpanel has grounds and neutrals separated. The copper GEC, coming from ground rod, connects at the bottom of the ground bar. At the top of the ground bar there is an Aluminum ground that goes back to the MSP. So the GEC is not continuous from the GE to the MSP where the N-G connection happens. (unless 250.64(C) applies?)
I don't know why the GEC doesn't just go from ground rod directly to MSP. I would think this would be a violation?
I see an inspection sticker on the primary subpanel, but not the MSP. Maybe inspector only looked in the basement.
 
You are correct that the GES should terminate in the service equipment not the subpanel
 
Thanks for the confirmation on my situation. Outside of that I was wondering also what 250.64(C)(2) might look like. I am trying to understand an example of where that might occur? I searched the forum, but didn't find (C)(2) really mentioned.
 
darunedefig said:
So the GEC is not continuous from the GE to the MSP where the N-G connection happens. (unless 250.64(C) applies?)
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I believe you nailed this with 250.64(C).

Without length or bending restrictions for GEC's, except where SDS must hit hose bibs, the only violation was broke GEC conductor without exothermic welds.
darunedefig said:
Thanks for the confirmation on my situation. Outside of that I was wondering also what 250.64(C)(2) might look like. I am trying to understand an example of where that might occur? I searched the forum, but didn't find (C)(2) really mentioned.
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Busbar sections in (2) are bolted together in a similar fashion to structural steal building framing in (3), not the same thing as torqued wire to lugs.
 
250.70 allows GEC bond per "listed lugs, listed pressure connectors, listed clamps, or other listed means", but 250.64(C) requires that GEC "shall be installed in one continuous length with‐out a splice or joint."
 
Are the ground rods the only grounding electrodes present?

If there is another grounding electrode, and it has an unspliced GEC going to the service disconnect (or to the grounded service conductor anywhere on the utility side of the service disconnect), then other grounding electrodes only require bonding jumpers. So if the ground rod bonding jumper goes to the subpanel ground bar, the EGC from there to the service disconnect would just need to be large enough to also qualify as a bonding jumper.

Cheers, Wayne
 
wwhitney said:
So if the ground rod bonding jumper goes to the subpanel ground bar, the EGC from there to the service disconnect would just need to be large enough to also qualify as a bonding jumper.
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250.24(D) requires GEC bond to "grounded service conductor to the grounding electrode(s)", and 250.64(C) requires that GEC "shall be installed in one continuous length with‐out a splice or joint."
 
ramsy said:
250.24(D) requires GEC bond to "grounded service conductor to the grounding electrode(s)", and 250.64(C) requires that GEC "shall be installed in one continuous length with‐out a splice or joint."
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None of the above is in conflict with my comment. You can have one GE and GEC that satisfies the above requirements, and then the other GEs can be connected via bonding jumpers that are allowed to be spliced.

Cheers, Wayne
 
wwhitney said:
Are the ground rods the only grounding electrodes present?

If there is another grounding electrode, and it has an unspliced GEC going to the service disconnect (or to the grounded service conductor anywhere on the utility side of the service disconnect), then other grounding electrodes only require bonding jumpers. So if the ground rod bonding jumper goes to the subpanel ground bar, the EGC from there to the service disconnect would just need to be large enough to also qualify as a bonding jumper.

Cheers, Wayne
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The wires in the exterior main service panel were only what I previously described. There was not a GEC going to service disconnect, but instead went to primary subpanel. From the discussions in this thread, the "EGC" wire going from primary sub to main can not count as a GEC.
 
darunedefig said:
The wires in the exterior main service panel were only what I previously described. There was not a GEC going to service disconnect, but instead went to primary subpanel. From the discussions in this thread, the "EGC" wire going from primary sub to main can not count as a GEC.
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Agreed on the last point, unless it were irreversibly spliced to that wire from the ground rods.

If you know there are other electrodes (water pipe, CEE, etc), it would be worth checking where those are connected. It is allowed (by the NEC at least) for the GEC to land in the meter can or at another location on the utility side of the main disconnect. So if one of them has a compliant GEC, I believe there's no need to move the bonding jumper from the ground rods to the service disconnect.

Cheers, Wayne
 
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