Aux Gnd am I using earth as effective ground path

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I have incoming electric service into 1600a main service disconnect. Load side of the main service I have 8 disconnect which fed to 8 different tenants.

The service system ground and main bonding jumper is at 1600a main service disconnect.

Each of the 8 disconnects also have GEC bonded to equipment ground bus and to the two system service ground electrodes but there is no main bonding jumper.

Is the 8 disconnects valid auxiliary ground electrodes that does not use ground as effective ground fault path per NEC 250?

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Little Bill said:
Grounding electrodes and conductors are not part of the fault clearing path. That is not their purpose.
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I dont follow you. The 8 disconnects that have gec going to system ground is not valid auxiliary electrodes because they use ground as effective ground path since the 8 disconnects are grounded and so is 1600 a main service disconnect and close to each other?

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an auxiliary electrode is a separate isolated electrode connected to the EGC of something. Sounds like what you have is not an auxiliary electrode. I dont see any violation with what you have, but it serves no purpose.
 
The ground-fault path is from the EGCs in the feeders to the neutral in the main disco through the bonding jumper there. It's important for fault current to find its way to the supply neutral, not the earth.
 
LarryFine said:
The ground-fault path is from the EGCs in the feeders to the neutral in the main disco through the bonding jumper there. It's important for fault current to find its way to the supply neutral, not the earth.
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I maybe wrong but In my case gec and egc in the 8 disco equipment bar may split fault current to main disco which has main bonding jumper. 8 disco and main disco are in same room close together with same electrodes. One path is from 8 disco egcs to main disco and other 8 disco gec thru ground to main disco. As a result 8 disco gec may create low impedance ground fault current path.

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I see now. If I'm not mistaken, only the main disco should have electrode conductors landed in it.
 
The GEC(s) from the GES terminate in the 1600 amp service disconnect. Beyond the main disconnect you need some sort of EGC to each of the 8 disconnects, can be metallic raceway or wire type EGC. If you want to also connect those 8 switches to the GEC or to a separate auxiliary grounding electrode {AGE 250.54} because it makes you feel all warm and fuzzy you can but it's not required.
 
Please confirm: You have a 1600A main disconnect, and then in separate enclosures you have 8 disconnects for tennants?

You have 'feeders' that go from your main disconnect to the tenant disconnects?

Do you have EGCs in the feeders from main to tennant disconnects? Or are those feeders in metallic conduit?

Do the 'GEC's that you describe go from the separate disconnect enclosures to the same grounding electrodes?

It sounds to me like you do have a _parallel_ fault current path which includes the GECs. This is not prohibited but not required. The requirement is that you have the EGCs and not depend upon the earth for fault clearance.''

-Jon
 
The OP also stated, I think, that there is no Main Bonding Jumper between neutral and ground at the 1200A main disconnect. That would be allowable only if it is not in fact considered to be the service disconnect.
 
GoldDigger said:
The OP also stated, I think, that there is no Main Bonding Jumper between neutral and ground at the 1200A main disconnect. That would be allowable only if it is not in fact considered to be the service disconnect.
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Please read again their is main bonding jumper at main service 1600 amp disco. Their is no main bonding jumper downstream 8 disco.

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codequestion said:
Please read again their is main bonding jumper at main service 1600 amp disco. Their is no main bonding jumper downstream 8 disco.
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Then why this?

Each of the 8 disconnects also have GEC bonded to equipment ground bus and to the two system service ground electrodes but there is no main bonding jumper.
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There is no reason for auxiliary electrodes if these disconnects are on the same building as the service equipment.

Roger
 
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