mistermajestic4@msn.com
Member
Could someone please tell me what article and section allows neutrals and grounds of branch circuits being installed together in main panel, and seperated in sub-panels?
Main panel grounding
- Thread starter mistermajestic4@msn.com
- Start date
- Status
Volta
Senior Member
- Location
- Columbus, Ohio
It is not so much that the grounded (usually a neutral) and the grounding conductors are allowed together in a main panel, as that is the point that we derive the grounding from the grounded. They should not be reconnected on the load side of that disconnect.
Article 250 is the place to start for grounding questions. Check 250.24 in general, and sub-section (A)(5) and (C), to begin.
Article 250 is the place to start for grounding questions. Check 250.24 in general, and sub-section (A)(5) and (C), to begin.
Hmmm... I believe you have that backwards.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
mcclary's electrical
Senior Member
- Location
- VA
I believe he has it right
Rob, Smart is correct, the grounded conductor doesn't exist until the system grounding (earthing) is done, so "grounded" is derived from "grounding".
However, I think the topic is "bonding"
Roger
Volta
Senior Member
- Location
- Columbus, Ohio
Rob, Smart is correct, the grounded conductor doesn't exist until the system grounding (earthing) is done, so "grounded" is derived from "grounding".
However, I think the topic is "bonding"
Roger
Actually the grounded conductor is brought to the service disconnecting means from the utility. It is already grounded/earthed at the source (unless the copper was stolen for scrap :grin
.The premises system grounding conductors are bonded to the grounded. So we don't have to say derived, but grounded comes first.
Actually the grounded conductor is brought to the service disconnecting means from the utility. It is already grounded/earthed at the source (unless the copper was stolen for scrap :grin
The premises system grounding conductors are bonded to the grounded. So we don't have to say derived, but grounded comes first.
No, we may not even be talking about a POCO service, (even though the term Main Panel is used) we could be talking about an SDS or a corner grounded Delta. The grounded conductor doesn't exist to us until we as the installers earth it, what is upstream of the service point is unknown to us.
Roger
Volta
Senior Member
- Location
- Columbus, Ohio
It is true that the OP may have been referring to an SDS. But probably wasn't. You even proposed the possibility of a "corner grounded Delta". Still has a conductor grounded at the source. We won't attach the three phase legs blindly at the service point, but rather the building "white" will be connected to the source's grounded phase leg, which for a grounded service, must be brought to the service disconnect. 250.24(C).
It doesn't have a grounded conductor until we earth it.
No, we attach to the sources center tap, and even though we know that it is the grounded conductor from the POCO, our side (the NEC side) is where we have to look and establish it for our purposes.
Which can only happen after we have earthed a conductor to establish it as a grounded conductror.
Roger
Volta
Senior Member
- Location
- Columbus, Ohio
On occasion, I suppose, but usually the secondary is earthed at the pole (for O/H distribution).
Not the center tap for a corner ground, but a phase leg.
We better pick the right one
.We better pick the right one
Why would it matter electrically? Just pick one and earth it, then mark it as the grounded conductor
Roger
Last edited:
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
I'd tend to side with Volta, that the utility service includes a grounded conductor, rather than the idea that the utility service comes with a bunch of conductors, and that none of them are grounded until we make the bond.
If there is only a single bond between a system conductor and earth, then electrically it makes no difference which system conductor gets grounded. But on the utility side of the service disconnect (under NESC rules), multiple bonds are permitted and expected. It is expected that one conductor will be grounded at the supply transformer, and that each customer will further make bonds to earth. If one customer bonds one conductor, and another customer bonds a different conductor, then I would expect difficulties.
-Jon
If there is only a single bond between a system conductor and earth, then electrically it makes no difference which system conductor gets grounded. But on the utility side of the service disconnect (under NESC rules), multiple bonds are permitted and expected. It is expected that one conductor will be grounded at the supply transformer, and that each customer will further make bonds to earth. If one customer bonds one conductor, and another customer bonds a different conductor, then I would expect difficulties.
-Jon
Jon, the point being made is that we have to install a GES and bond a conductor to this GES, we do not have a grounded conductor as far as our side and the NEC is concerned until we do this, then we install the Main Bonding Jumper to the equipment for the EGC to be created.
Now going back to the corner grounded delta, it has always been my experience that we are supplied with an ungrounded delta (unless we are getting a center grounded system) and we establish the grounded conductor when we earth a particular phase conductor.
I am not aware of any multi grounded deltas supplied by any POCO, do you know of any?
Roger
Now going back to the corner grounded delta, it has always been my experience that we are supplied with an ungrounded delta (unless we are getting a center grounded system) and we establish the grounded conductor when we earth a particular phase conductor.
I am not aware of any multi grounded deltas supplied by any POCO, do you know of any?
Roger
Volta
Senior Member
- Location
- Columbus, Ohio
I can only think of a couple of corner grounded systems I've worked on, and truly don't know at this point what was done at the POCO source, but I think I'd be able to see. I'll try to look in the next few days.
While that may be true, if we are going to include the utility service, then we must also include how it affects the issue... we can't just say one of the conductors is grounded and therefore it came first... because it didn't in reality; it is grounded as a result of of earth grounding at the source end. The grounded conductor can be first only if we choose to blind ourselves to the reality.
AFAIK, transmission lines have no grounded conductor. So any grounded conductor on the customer side of transmission lines is a result of earth grounding.
Last edited:
Getting back to the original discussion, it is technically a violation (IMO :roll
to land EGC's on the Neutral bars of the main panel. However, you will not find this violation explicitly written in the Code. It is only through deductive reasoning I can surmise it to be a violation. In contemplating my assertion, consider this: As a result of the requirements for an MBJ/SBJ, all ground fault currents must pass through the MBJ/SBJ. When EGC's are landed on the Neutral bar of the main panel, ground fault currents on those EGC's do not pass through the MBJ/SBJ.Volta
Senior Member
- Location
- Columbus, Ohio
Agreed. By calling the grounded conductor first, I am solely speaking of the premises system. When the OP wrote "neutrals" and "grounds", I assumed, safely I think, that Grounded and Equipment Grounding Conductors were the subjects of discussion.
Of course you are right to say the the Grounding Electrode Conductor must be 'first' when compared to the 'neutral', whether at the distribution source or the service, but that comparison was not being made.
Maybe, but not neccessarily so with distribution.
Either side, of course.
Hmmm. In 250.28(A), can the grounded conductor terminal strip be considered "similar suitable conductor" to a bus? I that think between Art. 100 definition of MBJ (for the EGCs) and the installation direction of 250.24(C) (for the disconnect enclosure) some rewording is due. I'll have to think about that one.Getting back to the original discussion, it is technically a violation (IMO :roll
If you are right, we need a lot more EGC bars in this world!We need only to go to......
Hmmm. In 250.28(A), can the grounded conductor terminal strip be considered "similar suitable conductor" to a bus? I that think between Art. 100 definition of MBJ (for the EGCs) and the installation direction of 250.24(C) (for the disconnect enclosure) some rewording is due. I'll have to think about that one.
...or...
- Status