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Discussion Starter · #1 ·
Hey guys. Quick question. At the utility transformer, the neutral is bonded to a GEC of some sort right? Im here studying article 250 and trying to compare separately derived systems to main services. Thanks in advance
 

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animal lover /rat bastard
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neither article 250, nor the rest of the NEC apply to utility owned/operated transformers. forget about them. ( 90.2)
 

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Wildleg is correct, NEC ends at the Mast/Service entrance, pardon this pic having the canadian code section # on it but it may help clear things up a little for you on how a single phase service works. H1-H2 gives you 220V/240V.
 

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Discussion Starter · #4 ·
Ok guys here's where the fog comes in. In a service, we only are allowed to bond the neutral, ECG, and GEC once in our service. But in separately derived transformers, we must bond neutral to case in transformer, then again at supply side disconnect. So when I think about a service, it brings me to believe that at the utility, there has to be a bond as well. Not that it matters. It's just my imagination.
 

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animal lover /rat bastard
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Ok guys here's where the fog comes in. In a service, we only are allowed to bond the neutral, ECG, and GEC once in our service. But in separately derived transformers, we must bond neutral to case in transformer, then again at supply side disconnect. So when I think about a service, it brings me to believe that at the utility, there has to be a bond as well. Not that it matters. It's just my imagination.
NOOOOOO ! you bond (neutral/ground) either at case or 1st disco, not both ! 250.30(?)

250.30 (2011)
....
1) System Bonding Jumper. An unspliced system bonding
jumper shall comply with 250.28(A) through (D). This
connection shall be made at any single point on the separately
derived system from the source to the first system
disconnecting means or overcurrent device, or it shall be
made at the source of a separately derived system that has
no disconnecting means or overcurrent devices, in accordance
with 250.30(A)(1)(a) or (b). The system bonding
jumper shall remain within the enclosure where it origi-
nates. If the source is located outside the building or structure
supplied, a system bonding jumper shall be installed at
the grounding electrode connection in compliance with
250.30(C).
Exception No. 1:.....
 
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Discussion Starter · #6 ·
wildleg said:
NOOOOOO ! you bond (neutral/ground) either at case or 1st disco, not both ! 250.30(?)
Thanks for your help. Supply side bonding jumper threw me off. But I think I understand. I'll reply to this again if I have another question. Thanks again
 

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animal lover /rat bastard
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Shouldn't this be called the MBJ, and not SSBJ? What's the difference?
bonds exposed metal parts to ground.


main bonding jumper is the only one that bonds ungrounded conductor to grounding system.
 

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Discussion Starter · #9 ·
wildleg said:
bonds exposed metal parts to ground. main bonding jumper is the only one that bonds ungrounded conductor to grounding system.
Thanks for all the help but still very blurry on the difference between the 2. Before the 2011 edition, SSBJ was referred to as MBJ, correct?
 

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Donuts > Fried Eggs
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When you bond you're creating a connection between your system neutral and equipment ground. You bond any service at one single point. The utility doesn't have equipment grounds so where or how they are bonded is of no concern to you.

I don't believe "supply side bonding jumper" is a thing. There's "main bonding jumper" and "system bonding jumper" and I believe the only difference is one refers to a new service, and the other refers to a separately derived system.

EDIT: Alright, I take that back. Not sure how I managed to go three years without seeing that "Supply Side Bonding Jumper" was a thing. What the hell is the difference between that and the MBJ?
 

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Wildleg is correct, NEC ends at the Mast/Service entrance, pardon this pic having the canadian code section # on it but it may help clear things up a little for you on how a single phase service works. H1-H2 gives you 220V/240V.


This doesn't happen here Daks

Here the poco xformer is fed Hot & Neutral

The Primary side Neutral is bonded right through to the Secondary Neutral, pole GEC (usually #6 solid) , pole guys , etc

Something we, as NEC or CEC disciples would not normally do

~CS~
 

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Ok guys here's where the fog comes in. In a service, we only are allowed to bond the neutral, ECG, and GEC once in our service. But in separately derived transformers, we must bond neutral to case in transformer, then again at supply side disconnect. So when I think about a service, it brings me to believe that at the utility, there has to be a bond as well. Not that it matters. It's just my imagination.

It might help if you think in terms of 'Earthing a Neutral' here Sunny

Every time we earth a noodle, we install an MBJ & GEC's

The fundamental theory being we created a protective point for mother nature & surges, as well as assuring localized sine wave stability, or the zero line in this>


All fine and well, until we have more than one Earthed Noodle in proximity to each other

The best ex is the usual pad mounted Xformer, GEC's made onto XO circled around it, secondaries to a meter with a GEC

Some are even arms length close to each other.....:eek:

ThiMk about it.......:whistling2:


~CS~
 

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Discussion Starter · #13 ·
If the system bonding jumper is at the first disconnect means than the wire from sds is called supply side bonding jumper and shall be sized according to 250.66.

If the system bonding jumper is at the sds than the wire from sds to first disconnect means is called an equipment grounding conductor and is sized according to 150.122.

Is this a correct analysis?

Thanks for replies.
 

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Discussion Starter · #15 ·
Sunny 1 said:
If the system bonding jumper is at the first disconnect means than the wire from sds is called supply side bonding jumper and shall be sized according to 250.66. If the system bonding jumper is at the sds than the wire from sds to first disconnect means is called an equipment grounding conductor and is sized according to 150.122. Is this a correct analysis? Thanks for replies.
This is someone's post off of Holt. Pretty cut and dry. Do you guys agree with this?
 

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This doesn't happen here Daks

Here the poco xformer is fed Hot & Neutral

The Primary side Neutral is bonded right through to the Secondary Neutral, pole GEC (usually #6 solid) , pole guys , etc

Something we, as NEC or CEC disciples would not normally do

~CS~
K I should have included this pic too to help explain further. The pole part we generally don't worry about unless we are installing a pad mounted transformer for a large service. Lol
 

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