likely to be energized?

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karl riley

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A homeowner decides to stop the neutral current traveling in the water pipe due to the fact that it is carrying several amps and causing a high magnetic field in his child's room. There is a valid health concern. A plumber inserts a plastic spacer or dielectric union within a foot of where the water service enters in the basement. An electrician adds another ground rod outside. The water pipe is still bonded within 5' of the water pipe entrance.

This leaves a foot or less of pipe sticking out of the wall which is not bonded. I am wondering if this could be considered under the category of unlikely to be energised? Insulating tape can be wrapped around that foot of pipe, or some other hard insulating covering, so that it becomes almost impossible to energize.

Would an AHJ be justified in deciding to allow this?

Karl
 
I don't see a problem. The (exterior) water line is (now) completely isolated from the electrical system (?). It's no more likely to be energized than any other metallic object on the outside of the house. If the problem (current flowing on water line) is coming from a neighbor's system down the street, the POCO (or someone qualified) needs to locate the cause and source of the voltage. If the (water line) current is coming from the electrical system in the home owner's house, the changes made will not have any effect.
Somebody probably has a bad (as in loose, broken or corroded) service ground (neutral). Cutting the underground water line loose from the Grounding electrode system will tell you if it's at the homeowner's service or from somewhere else.
steve
 
Karl,
I can't see how the metal pipe could become energized as it must still be used as a grounding electrode.
Don
 
Karl, notice the difference in language between 250.104(A) and 250.104(B). (B) applies to other systems that are likely to become energized, whereas (A) applies to water piping systems, regardless of the liklihood of energization. Notice also, however, that (A) applies to metal piping systems. I would not call a 12" length of isolated piping a system, therefore I would not require bonding.
 
Ryan, that's a good point. I will re-read those sections. I only have the '93 Code where I am at present, so I am assuming there has been no change.
Karl
 
Ryan,
I would not call a 12" length of isolated piping a system, therefore I would not require bonding.
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I am assuming that this pipe is not an isolated section of metal pipe, but is a continuation of the metal underground water pipe system and must be used as grounding electrode.
Don
 
don_resqcapt19 said:
Ryan,

I am assuming that this pipe is not an isolated section of metal pipe, but is a continuation of the metal underground water pipe system and must be used as grounding electrode.
Don
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and the interior metal piping must be bonded per 250.104, as previously mentioned

Charlie
 
I see a lot of installations where the building is fed with plastic and the plumber will install 10-15 feet of copper and manifold off with plastic (pex) the stuff is everywhere.

I do not consider that short section of cooper as a system but every one seems to ground it.

Charlie
 
Charlie,
and the interior metal piping must be bonded per 250.104, as previously mentioned
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It appears to me that Carl wants to leave out the grounding electrode connection to the exposed 1' of pipe. My point is that as long as this is part of a metal underground water pipe system it will be connected to the grounding system. In this case there would also be a bonding connection to the interior water pipe system. The dielectric between the interior and the exterior piping systems should eliminate current flow that is causing the magnetic field even with both parts of the piping system connected to the electrical system.
Don
 
don_resqcapt19 said:
Charlie,

It appears to me that Carl wants to leave out the grounding electrode connection to the exposed 1' of pipe. My point is that as long as this is part of a metal underground water pipe system it will be connected to the grounding system. In this case there would also be a bonding connection to the interior water pipe system. The dielectric between the interior and the exterior piping systems should eliminate current flow that is causing the magnetic field even with both parts of the piping system connected to the electrical system.
Don
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Don I ment to ensure that I agreed with your statements

Charlie
 
I am not sure I am following the thinking. Yes this pipe was part of the grounding electrode system, but was removed as an electrode according to the objectionable current paragaph. It then needs to be replaced by a ground rod or other. That is done.

So it seems to come down to whether bonding the water piping "system" must include every inch of it. As I see the sense of this bonding, several parts of a metal water piping system might be energized. Any appliance with water and electrical connections is such. So those are all covered by the bonding connection that does exist.

So given that one is allowed to eliminate one grounding electrode and replace it with another, and we have done so, is that one foot of pipe necessary to bond, thus cancelling our action? In the case I am thinking of it is more like 5", and covered with insulating tape.

All opinions welcome.

Karl
 
Karl, good to hear from you.
I have a research study from the American Water Works Association (AWWA) on grounding to water services. They recommend an insulating spacer on metallic water lines, but leave ten ft of metal in contact with the soil (at the house end) and the spacer should be 1 to 2 ft long.
By the way, the AWWA states that one water meter reader a day gets shocked from currents on metal water service lines.
 
Don, I just re-read your posts. If I then ran a GEC to the 1' of pipe going out it would re-establish the current and magnetic field we are trying to get rid of.

And answering Hillbilly's post also, what is happening is that neutral current from this house is given a parallel path back to the transformer by going to a neighbors house and then to their neutral bonding/grounding point and back to the Tfrmr through their SE cable. And vice versa. The homeowner opened his main switch and there was still current, obviously coming from a neighbor's neutral and going to the same Tfrme. The POCO is not involved since they don't do the GEC to water pipes.

This circulation of neutral in metallic water systems has been extensively studied by EPRI (Utility research org) in relation to objectionable magnetic fields.

Karl
 
but was removed as an electrode according to the objectionable current paragaph. It then needs to be replaced by a ground rod or other. That is done.
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CMP 5 says you can't do that. I submitted a proposal to permit this exact thing for the 2005 code and they rejected it and said that 250.6 does not permit you to disconnect a grounding electrode.
If I then ran a GEC to the 1' of pipe going out it would re-establish the current and magnetic field we are trying to get rid of.
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But only on the 1' of pipe that is in the house, that should eliminate the problem within the bedroom. There would be no current flowing on the pipe on the house side of the dielectric.
Don
 
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Safety wise, in either scenario, what will happen if someone grabs ahold of the metal stub with one hand and the house piping with the other....effective shunting the plastic section?
 
Does the objectionable current section allow you to remove an electrode? All ground electrodes will have some current going through them, but perhaps you could call the proximity of the ground electrode to humans what is objectionable. I don't even know why this was originally even done, as don't the people who fear the pipe current also fear the current on all the wires in the walls and ceiling of their house?

If you could manage to ground the pipe from the outside, then I think all your issues will be solved. Whether that short pipe section that is currently unbonded is a problem or not looks to be an issue of interpretation, but that goes away if you also bond that section.
 
Don, the current travels on the GEC to the bonding point 5' or less from the entry of the pipe. If I now do this to the 1' of pipe, it changes nothing, as the GEC is carrying the current to the pipe just as it was 4' back.

I have always recommended putting the spacer in 10' or more outside, as Tom mentions the AWWA recommends. But the problem is that it can be expensive, particularly in cold climates where the pipe may be 5' down.

Don, I am surprised that the permission to remove one or more grounding electrodes that I read in the Code is not what I am reading. Unless it was changed, since I am away from home and reading a '93 Code. I was not aware that there had been a change.

I get the feeling that some of the reluctance to give up a water pipe electrode is due to the old misconceptions that connection to earth is what trips breakers. We are just talking about lightning protection, basically. And since plastic is being used extensively now, obviously they are getting along without a water pipe electrode.

So it seems to me that to let the plumber put his dielectric union a few inches from the entry point, and then wrap the unbonded stub with tape or something harder would be a boon to homeowners dealing with a health issue.

Any opinions welcome.

Karl
 
5-119 Log #1882 NEC-P05 ​
​
(250-50 Exception (New) ) ​


​


Final Action: Reject​

Submitter: Donald A. Ganiere Ottawa, IL
Recommendation:​


Add a new Exception as follows:

Exception: Where an approved insulating section of water pipe is installed within 300 mm (1 ft) of the water pipe?s entrance to the building, the metal under ground water pipe shall not be required to be used as a grounding electrode.
Substantiation:
The use of the metal under ground water pipe creates a parallel path for grounded conductor current. This path causes excessive EMF and also presents an electrical shock hazard to water workers. This proposal allows the designers of the electrical system to eliminate these possible hazards if they so choose. Current code requires that these hazards be created.​
Panel Meeting Action: Reject
Panel Statement:
The panel maintains its position that all electrodes on the premises "if available" are required to be bonded together to form the grounding electrode system. The submitter does not include substantiation that clearly indicates that the proposed change increases electrical safety. If grounding electrodes on the premises are not bonded together, the possibility of differences of potential can exist between those that form the grounding electrode system and those that are isolated from the system. Also when events such as line surges and lightning strikes at the building or premises or in the vicinity of the building or structure, the potential on all conducting elements (grounding electrodes) in the earth should rise at the same potential thus reducing fire and shock hazards in or on the building. ​
Number Eligible to Vote: 16
Ballot Results: Affirmative: 16




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Karl,
Don, the current travels on the GEC to the bonding point 5' or less from the entry of the pipe. If I now do this to the 1' of pipe, it changes nothing, as the GEC is carrying the current to the pipe just as it was 4' back.
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I guess I was thinking that you had a new route for the GEC to the metal underground water pipe. It appears that is the only code compliant solution, based on CMP 5's response to my proposal.
Don
 
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