# CT Cabinet, parallel bonding



## wildleg (Apr 12, 2009)

GEORGE D said:


> Can't seem to find my answer anywhere at the moment, but do I have to bond both service grounded conductors to ct cabinet. or will one suffice? Also, can I land GEC on seperate lug in ct, or do they have to tie together (I know the MBJ cannot be seperate, either wire, screw, buss, etc..)


when doing commercial services the first thing you should do is read the utility companies green (blue/orange/whatever) book and see what they want. Where I live one poco wants bonding outside the cabt, others allow inside, etc. MBJ here is generally in the first disco, yours may vary (?)


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## GEORGE D (Apr 2, 2009)

Yeah, I'm sure the CT's around here get bonded to grounded conductor, just not sure if both are necessary. Actually, the engineer must have designed for MBJ to be in CT, considering he's showing a (5) wire service entrance, but I thought that the MB had to be established within the disconnect enclosure? Any help is appreciated


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## Pete m. (Nov 19, 2011)

Wildleg gave good advice about checking with the POCO's requirements.

As it stands I would say the installation would be a violation of 310.10(H) because that "5th" wire will end up in parallel with the grounded conductor if the grounded conductor is used for bonding in the C/T can (as it typically is in this area).

Although it is posiible that if you "float" the grounded conductor in the C/T can you could use the "5th" wire as a SSBJ sized in accordance with 250.102(C)(1).

Pete


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## ponyboy (Nov 18, 2012)

If the poco wants a bond in the ct can you do it and act like it doesn't exist. Then you bond again at the first ocpd after the metering just like normal. The poco here sizes the ct binding jumper with some voodoo formula I've yet to learn but it's typically about 4/0 for a 1200 amp service and 500mcn for a 3000 amp service. 


Sent from my iPhone using Tapatalk


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## GEORGE D (Apr 2, 2009)

I think the engineer most likely screwed up, adding the 5th wire. I'm just going to exclude it. As for ct bond, I plan on just landing one of the neutrals and see what happens.


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## RIVETER (Sep 26, 2009)

GEORGE D said:


> Can't seem to find my answer anywhere at the moment, but do I have to bond both service grounded conductors to ct cabinet. or will one suffice? Also, can I land GEC on seperate lug in ct, or do they have to tie together (I know the MBJ cannot be seperate, either wire, screw, buss, etc..)


I believe that the bonding you are talking about is to give a clear path for fault current in the event of something like a "primary to secondary" short at supplying transformer. In that case I'd do both. IMO.


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## cabletie (Feb 12, 2011)

Around here it is done like pony boy described it, the neutral comes in and is landed on a stud that is welded to the bottom of the CT cabinet. It leaves and is bonded again at the first disconnect/Ocp. 
It is no diferent than a typical single phase meter socket. 
No main bonding jumper or any grounding electrode conductors are ever terminated or ran through metering equipment 
You may have bonding bushings depending on the setup. That could terminate on the same stud.


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## RIVETER (Sep 26, 2009)

cabletie said:


> Around here it is done like pony boy described it, the neutral comes in and is landed on a stud that is welded to the bottom of the CT cabinet. It leaves and is bonded again at the first disconnect/Ocp.
> It is no diferent than a typical single phase meter socket.
> No main bonding jumper or any grounding electrode conductors are ever terminated or ran through metering equipment
> You may have bonding bushings depending on the setup. That could terminate on the same stud.


Do you disagree with post # 7?


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## cabletie (Feb 12, 2011)

I think that is also the same thing, so I agree. The neutral is bonded to the cabinet, and if bonding bushings are used they are also bonded to the cabinet. 

What I did not completely understand from the OP was when he said "both". I was thinking he was talking about both neutrals if it was a parallel. If it was, then both neutrals would terminate on the stud with a 2 barrel lug, and both neutrals would leave on a 2 barrel lug.


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## RIVETER (Sep 26, 2009)

cabletie said:


> I think that is also the same thing, so I agree. The neutral is bonded to the cabinet, and if bonding bushings are used they are also bonded to the cabinet.
> 
> What I did not completely understand from the OP was when he said "both". I was thinking he was talking about both neutrals if it was a parallel. If it was, then both neutrals would terminate on the stud with a 2 barrel lug, and both neutrals would leave on a 2 barrel lug.


All of the attachments, including the neutrals is a sore point because they mostly are mechanical and really need to be rechecked from time to time. The expense of doing so is the hindrance. The utility wants that extra level of insurance.


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