From a circuitry stand point, does it make a difference where the Grounding electrode conductor is attached to service entrance conductors in cases where the service entrance conductors are reduced in size.
For instance a 200a service feeds a two-flat, 3 (Otts?) feed the meter bank from the weatherhead, and then #3s feed each individual panel. If the GEC is connected to the neutral in one of the panels is this different from a circuitry standpoint than if the GEC was attached in the metersocket?

Since the GEC is sized according to the largest set of SE conductors, it would seem only right to make the connection at the largest set. The Handbook (Iknow it's not code) shows arrangements contrary to my statement. Please enlighten me.

Make sure your utility allows "foreign" connections in the meter socket. Our's doesn't.

NEC 250-24 (a)1 says the the connection has to be accessible. The meter seal is interpreted as not readily accessible around here.

From a circuitry standpoint, bringing the GEC to the neutral on one panel (#1) provides the fault path to ground for both panels (#1 & #2). The NEC minimum is that the GEC connect to the neutral bus in panel #1. I'd worry that the service neutral terminals between the disconnect in panel #2 and the meters might fail at some point resulting in the possible floating of the grounded conductor until the problem is corrected. There are probably going to be a few inter-connections between the groundING conductor webs of dwelling #1 and #2 that will then be carrying panel #2's neutral current and MAYBE some parallel paths off #2's groundING conductor web to ground will help, but I'd rather not accept that liability.

I like adding a GEC sized for the capacity of panel #2's service conductors (in this case the #3) connected between the neutral buses of panels #1 & #2.

Al

So do you run the ground rod connection directly into the panel instead of making the connection at the meter socket?

Yes.

A GEC serves only voltage gradient or for lightning/high V discharge. It would maybe clear a fault on the serving X-former's primary, ground impedance considered.
( 250-4A1)
Probably why a EGC cannot make to a GEC
( 250-24C first sentence)
The GEC can be connected at any point of the service conductors up to the MDP.
(250-24)
But the closer the Electrode really is the better
( 250-30A4)
This is due to lightning and high discharges following straighter lines.

Are you saying closer to the transformer is better? Also would it be beneficial for the discharge that it passes thru the largest conductor possible instead of having to go thru smaller SE conductors to get to the electrode? Is it simply an impedance to ground calculation?
Please remember I want to know from a pure circuitry stand point--disregard the code for the answer.

Also, I think I posted to this board before about what the GEC does exactly, I don't remember getting an understandable answer. Keeping the neutral at ground potential is understandable but I don't understand how it helps with a voltage surge. How does a surge on the phase conductor get to the GEC to get to ground?

Keep in mind that grounding is a complicated matter, and I think many people, including myself, don't FULLY understand all of the theoretical aspects of it.(I sometimes wonder if all the experts do). I think that grounding electrodes help to dissipate surges (or spikes) due to lightning strikes, which are looking for ground anyway, as opposed to surges that might be associated with load fluctuations.

[This message has been edited by Redsy (edited 10-27-2001).]

Steve T

Interesting question. . .

The GEC establishes a parallel return path for the unbalance load current. From a purely circuit based perspective, the way we install our branch circuits and feeders creates a mechanical assembly that doesn't have a net magnetic field up to the GEC connection. I could argue that the GEC be bonded to the neutral out on the secondary terminals of the transformer.

I am intrigued by several of the UK's service hookups that Pauluk has diagramed for us over in the International section.

Al

Steve T;
sorry about that, i'm a bit of a groundaholic off on a 2002 bender here.
(is there a support group out there?)

anyhow, as Redsy said, it's complex and the theory is not explained in the NEC, nor is it the documents job to do so ( diclaimers for placing hot coffee on top of the code book will be next)
Perhaps it's best if you ask yourself what the job classifications for GEC, EGC, & Bonding are ( it's burned up much cyberspace)
as applied in the field vs. code intent.

In your first post you have a 200A drop, residential 4/0 al. seu ( flat cable), then two feeders ( #3) from the meter to two 100A panels? Is this correct?

Does the meter have 2-100 amp breakers here? Or are both panels directly below the meter?
In either case, I would bond GEC to the meter's larger conductors and drain any large spikes there.


Al,
the 'parrallel' GEC vs. noodle thing is absolutly an all-time flamer! It's good to get some insight from other systems like Paul has done, he's to this forum what the Beatles were to pop!

[This message has been edited by sparky (edited 10-27-2001).]

Aw gee..... What can I say?

The lightning protection angle is something that intrigues me, and something I'd like to study in more depth.

The common texts here seldom mention it, and talk about grounding mostly in terms of ground-fault protection only.

Well Scott's posted some real zingers on parralleling, as well as some rather intensely in depth lightning posts.

Me being the simple tooltime ham & cheese sparky i can only speak simply on GEC's

They are a dead end, they do not complete a circuit. If there is a fault in the premisis system, the current rises a lot for a brief time until the OCPD does it's thing, there is much VD at that time. There may be a voltage on all the grounding conductors, boxes, panels, troughs, etc. for that amount of time ( trip curve here please) but the GEC is not part of this, nor does it play any real role in this as a deterent. I'm ranting i guess, chokin' on my ham & cheese.......
Mr. Moderator , a hiemlich please!!!

Look here, even Mike H. is stuggling to clarify the issue;

By Mike Holt for EC&M Magazine

For over 25 years I have attempted to explain the requirements of the National Electrical Code (NEC) and I have found that the most difficult sections to explain are those that required the understanding of basic electrical principles. It appears to me that many in the electrical industry do not have a good working knowledge on the basics of current flow and the wiring methods of both the electric utility and premises systems.

I have found that the most difficult subject for people to understand is grounding as contained in the NEC for personnel protection, particularly the requirements for services, separately derived systems and separate buildings. This short article is not about grounding, but hopefully it will provide you with an overview of the electrical system from the Substation (69kV) to the load.

Point No. 1. Electrons leaving the power supply are always trying to return to the power supply, not the earth. What many fail to recognize is that the magnetic field from alternating current on the primary winding induces a voltage in the secondary conductors. This causes electrons to leave the power supply (secondary winding), travel through the load to perform a useful function, and then return to the power supply via the circuit conductors. Figure A

Point No. 2. The grounding of electrical systems for utility system is different than the requirements for premises wiring system.
Utility System Grounding - The electric utility, in accordance with the National Electric Safety Code, utilizes a 'multipoint grounded system.' This system purposefully grounds the utility neutral 4 times a mile and at every transformer or lightning protection device.

Because the utility neutral is grounded at many locations, it is in parallel with the earth. This assists in providing a low impedance path necessary to clear for a high voltage ground fault. In addition, the earth is used to stabilize the system voltage in the event the neutral is opened by equipment failure, such as a tree falling during a wind or ice storm.

Premises Wiring (Not Over 600V) Grounding - Wiring in a building must be installed in accordance with the National Electrical Code, which utilizes a 'single point ground system.' In this system, neutral current is intended to only flow on the 'grounded (neutral) conductor,' fault current is intended to flow on the 'effective fault-current path,' and the earth serves no purpose in clearing ground faults.

Author's Comment: The 'effective fault-current path' is an intentionally constructed, permanent, low-impedance path designed and intended to carry fault current from the point of a line-to-case fault on a wiring system to the grounded (neutral) at the electrical supply source. It is created when all electrically conductive materials that are likely to be energized are bonded together and to the grounded (neutral) at the electrical supply.

Grounding Summary: The utility system utilizes the earth and the multipoint grounded neutral conductor for the fault-current path, where as the premises wiring system uses an 'equipment grounding conductor' for this purpose. The earth is used by the utility system to help clear high voltage ground faults, but the earth does not assist in clearing ground-fault for systems not over 600V. Figure B

Please let me know how I can make this short one page article better, I am limited to 500 words (currently it has 525) and one graphic. But you might have an idea or comment that I should consider.

I don't mind the references to the NEC, I just wanted to know about circuitry than code in this particular question and just wanted to be clear what my question was (very difficult to express in a bulletin board sometimes, thanks sparky!)

I tend to agree with you as the "best" location to make the GEC connection in this particular service arrangement. Also, I think it is better because if one panel is being worked on, the GEC isn't temporarily lost for even a short period of time for the rest of the working system. I know where the code requires the connection, but I may propose a local amendment for this particular arrangement of service that the GEC be made at the largest set of SE conductors.

Our utility (Com Ed, recently aquired by Exelon) does not oppose as of yet, ground connections in the meter socket. And there are manufacturer installed terminals to do just that. Com Ed does require the metersockets to be stamped CECHA approved.