Neutral bonding of trough after meter before disconnects

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FrankG1

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Harrington Park, NJ
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Electrical contractor
I have a 400A underground service for a car dealership that we built that will have a future 130kw generator. So after meter pan we put a trough for the ATS to be mounted on top of . We ran our 4- 500mcm wires straight thru trough to existing interior switchgear (we just converted overhead to underground) do i have to bond the trough with the neutral now or when we do ATS
Thank you
 
Well a EGC doesn't technically exist at this point and you must bond to the grounded conductor, but maybe set it up so it can more easily be converted when you add the ATS.
 
The wireway needs to be bonded. Metallic conduit could be used for that purpose, or a connection to the grounded conductor, or run a supply side bonding jumper from the location of the main bonding jumper back to the wireway.
 
don_resqcapt19 said:
The wireway needs to be bonded. Metallic conduit could be used for that purpose, or a connection to the grounded conductor, or run a supply side bonding jumper from the location of the main bonding jumper back to the wireway.
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Don
Regarding all options you mentioned, in a fault scenario we are at the mercy of the utility to clear…agree?

On your third option, if this is done, are we not setting up the main switch or panel for failure since the fault current will flow into the building first before returning via grounded conductor? Is this in fact allowed to wire upstream items downstream into building or main device (mbj location)?
 
MyCleveland said:
Don
Regarding all options you mentioned, in a fault scenario we are at the mercy of the utility to clear…agree?

On your third option, if this is done, are we not setting up the main switch or panel for failure since the fault current will flow into the building first before returning via grounded conductor? Is this in fact allowed to wire upstream items downstream into building or main device (mbj location)?
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Way rules are written, until you reach the mbj everything is bonded to the grounded conductor.

Typically service conductors have limited amount of entry into a building, yet at same time no specific length is mentioned. Just says "nearest the point of entry" or something of that nature.
 
kwired said:
Way rules are written, until you reach the mbj everything is bonded to the grounded conductor.

Typically service conductors have limited amount of entry into a building, yet at same time no specific length is mentioned. Just says "nearest the point of entry" or something of that nature.
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So are you saying bonding exterior metal to interior mbj is NOT allowed?

Don’t follow relevance of second statement.
 
MyCleveland said:
So are you saying bonding exterior metal to interior mbj is NOT allowed?

Don’t follow relevance of second statement.
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I am saying any bond to electrical system on supply side of the MBJ is made to the grounded conductor. This can and does put items not intended to carry current in parallel with grounded conductor current.

On load side of MBJ you don't bond to the grounded conductor you bond to EGC or possibly to a SSBJ or the GEC that ultimately goes to the supply side or the MBJ location but in itself isn't intended to be current carrying in normal use.
 
MyCleveland said:
Don
Regarding all options you mentioned, in a fault scenario we are at the mercy of the utility to clear…agree?

On your third option, if this is done, are we not setting up the main switch or panel for failure since the fault current will flow into the building first before returning via grounded conductor? Is this in fact allowed to wire upstream items downstream into building or main device (mbj location)?
Click to expand...
The use of a supply side bonding jumper is one of the three permitted ways to bond your wireway. What one you use is a design choice. There is no restrictions on using that method that I am aware of. The use of a metal raceway would be the same as the path would have to go into the service equipment, through the main bonding jumper, to the grounded conductor. The only method of the three permitted bonding methods for the line side wireway that does not bring the fault current into the building, would be a direct connection between the grounded conductor and the wireway at the wireway.

As far as clearing a line side fault, that often happens when the faulted conductor burns open.
 
Simply put, up to the service main, where the premises equipment grounding system begins, where the local electrodes land, and where the premises neutral zero-voltage reference is, the neutral and any metallic enclosures and raceways are considered to be one conductor.


I'm glad that was simply put. :giggle:
 
don_resqcapt19 said:
The use of a supply side bonding jumper is one of the three permitted ways to bond your wireway. What one you use is a design choice. There is no restrictions on using that method that I am aware of. The use of a metal raceway would be the same as the path would have to go into the service equipment, through the main bonding jumper, to the grounded conductor. The only method of the three permitted bonding methods for the line side wireway that does not bring the fault current into the building, would be a direct connection between the grounded conductor and the wireway at the wireway.

As far as clearing a line side fault, that often happens when the faulted conductor burns open.
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Thanks Don
I should really be rereading 250 before this…tired, been digging stumps all day and am old an exhausted.
Doesn’t 250 state everything ahead of the main shall be bonded using grounded conductor. For me implies at the point of item being bonded you utilize the grounded conductor available AT that point. Then immediate path to source without any potential damage to main/mbj.
With regard to your last statement, would you agree bonding to interior mbj is at a minimum a bad practice because of potential damage at main?
 
MyCleveland said:
Thanks Don
I should really be rereading 250 before this…tired, been digging stumps all day and am old an exhausted.
Doesn’t 250 state everything ahead of the main shall be bonded using grounded conductor. For me implies at the point of item being bonded you utilize the grounded conductor available AT that point. Then immediate path to source without any potential damage to main/mbj.
With regard to your last statement, would you agree bonding to interior mbj is at a minimum a bad practice because of potential damage at main?
Click to expand...
It does not say that. It only permits the grounded conductor to be used for that purpose.
I see no real world issue with running a supply side bonding jumper back from the location of the MBJ.

If you see an issue, you have plenty of time to write a PI and substantiation for a 2026 code change. They must be submitted before some date in September of 2023.
 
don_resqcapt19 said:
It does not say that. It only permits the grounded conductor to be used for that purpose.
I see no real world issue with running a supply side bonding jumper back from the location of the MBJ.

If you see an issue, you have plenty of time to write a PI and substantiation for a 2026 code change. They must be submitted before some date in September of 2023.
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Just wanted your thoughts on the topic…no intention on taking it up with NFPA.

Thanks again.
 
don_resqcapt19 said:
It does not say that. It only permits the grounded conductor to be used for that purpose.
I see no real world issue with running a supply side bonding jumper back from the location of the MBJ.

If you see an issue, you have plenty of time to write a PI and substantiation for a 2026 code change. They must be submitted before some date in September of 2023.
Click to expand...
You can make bonding jumpers that attach to the grounded conductor, you don't necessarily have to directly land the grounded conductor to the item in question to bond it.
 
kwired said:
You can make bonding jumpers that attach to the grounded conductor, you don't necessarily have to directly land the grounded conductor to the item in question to bond it.
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Would those jumpers not be supply side bonding jumpers?
 
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