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.
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.
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).]
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.
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).]