likely to be energized?

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Mark, I am now trying to keep up with the posts! The current on the GEC and water pipes creates an unusually high field because there are no other conductors running with it to cancel the field, such as you have in all correct circuits.

Also, the current can be high, depending on how much neutral is being produced, and how low the impedance of the pipes is compared to the SE neutral. It can be easily 30% of the neutral flowing in the pipe to the neighbors. So their neutral may be carrying more than intended. It's an interesting topic. An unintended parallel path for electric current that flows throughout a neighborhood or development, unsuspected even by most electricians, but better known to water workers!

Karl
 
Don, good for you for submitting this sensible proposal. And you were also talking about 1'.

But I was not referring to the requirement of using all available grounding electrodes. That had already been done in this house. I was referring to the article or section that allows the removal of one or more electrodes due to objectionable current. (Sorry, I am at a coffee house using wireless and don't have my Code book with me).

And yes, re-routing the GEC along the wall by the floor of the basement would in this case have cut the field in the bedroom way down to acceptable. But the owner intends to use the basement for activities in the future.

Karl
 
Karl,
But I was not referring to the requirement of using all available grounding electrodes.
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I understand, but I think that CMP5's position is that 250.6 does not permit you to delete a required grounding electrode. 250.6 only permits you to delete a grounding connection that is causing objection current and only if there are multiple grounding connections. It does not address disconnecting grounding electrodes.
250.6(B) Alterations to Stop Objectionable Current If the use of multiple grounding connections results in objectionable current, one or more of the following alterations shall be permitted to be made, provided that the requirements of 250.4(A)(5) or (B)(4) are met:
(1) Discontinue one or more but not all of such grounding connections.
(2) Change the locations of the grounding connections.
(3) Interrupt the continuity of the conductor or conductive path interconnecting the grounding connections.
(4) Take other suitable remedial and approved action.
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Don
 
This seems to me to be a strange thread, and here's why:

Any current on a water pipe would only be between the grounding connection and the outside. Add the water-pipe GEC itself, and still none of it should be traveling anywhere else on the piping system.

Unless the bedroom has the water-pipe GEC running around it, what am I missing?
 
LarryFine said:
This seems to me to be a strange thread, and here's why:

Any current on a water pipe would only be between the grounding connection and the outside. Add the water-pipe GEC itself, and still none of it should be traveling anywhere else on the piping system.

Unless the bedroom has the water-pipe GEC running around it, what am I missing?
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If I've followed the thread correctly the GEC itself was the radiator of the magnetic field due to the GEC and the common underground piping electrode serving as a parallel path for neutral current. The point of connection wasn't the issue so much as the fact that the underground metal water piping in a utility supplied water system is common to all of the homes served. The OP was trying to use a nonmetallic coupling as a means to eliminate the connection to this common electrode but since the union was installed indoors rather than outside the foundation wall there was still sufficient underground metal water piping available to inside the basement to make it available on the premise served by the service in question.
 
Tom, that's a good summary. Sometimes when threads get long some of the info in them gets forgotten.

Don, why is it assumed that the grounding connection to the water pipe is not included in the permission to interrupt a grounding connection carrying objectionable current? What do they assume that "grounding connection " means? I am not arguing, just trying to understand the meaning of the words in the Code and how they are interpreted.

I do feel that in the background there is that pervasive misunderstanding about the function of grounding electrodes that we and Mike Holt have been dealing with for years or decades. It leads to a fear of changing anything.

Consider this: since it is allowed by Code to put the insulating coupling in the underground water pipe 10' or more outside the house, that 10' is no better contact than a ground rod. So if we put the insulator where it enters the house and add a second ground rod, what's the difference for the lightning-diffusing function?

And Larry, yes it is the GEC that is giving off the main magnetic field, as has been described in this thread.

Karl
 
Karl,
You have a lot of good questions that CMP5 doesn't want to talk about. The section (250.6) is not clear, but based on the response to my proposal and other panel statements, it seems that you must use all grounding electrodes that are present. It appears that the only thing that CMP5 says that 250.6 does is to eliminate multiple connections to any item, but at least one must remain.
Don
 
Don, if that is what it means, I understand their ruling. I thought it meant multiple connections to multiple electrodes. But I will have to go back and re-read.

When discussing Code there are two aspects: 1) What the Code says, 1)(a) how we interpret what it says, and 2) whether a particular instance makes electrical sense.

In this case I think you have cleared up 1 and 1a. It does not appear to me to make electrical sense to deny the insulating spacer just inside the house, with suitable insulation wrapped around it, except for what you mentioned that the committee said about potential diferences between the two sides of the insulating union. I recognize that this needs to be considered. What potential differences do you think could exist, and what would happen if they exceeded the insulating impedance of the dielectric union? I am thhinking of lightning strikes in the neighborhood.

As it stands now, I might leave it to the local AHJ to decide if the inside insulator is allowed. Otherwise I would have to return to my usual recommendation of the insulator 10' or more outside the building, with a compromise (partial) solution of running the GEC as low as possible in the basement or crawl space.

But I am interested in the potential difference question.

Karl
 
I tend to think that on this particular matter, it would benefit the CMP to read this section with Charlie's Rule in their lap, and start over.

Reading 250.6, it seems evident to me that it would permit removing a grounding connection to an electrode, under either (1) or (4). They've got their head in the sand, IMO.

Realistically, I wonder who or what would be damaged by flashover from a bonded interior system to an unconnected water pipe electrode. If the PVC between metal were melted or otherwise damaged in a lightning event, what would happen? Water would spray everywhere! :D
 
George, we are thinking along the same path. I have re-read the section on objectionable current and I think it is worth a thread of its own to try to clarify the meaning, so I am now going to start a new thread.

A dielectric union is metallic but has plastic or nylon threads. So a high voltage surge from lightning could jump the threads but the metal casing should stay intact. Maybe it would leak some.

Karl
 
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