Objectionable Current on Ground Line - can it be re-routed to maintain code?

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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
I have a dear friend from college who is completely disabled by 'Electromagnetic Hyper Sensitivity'. Your writing strongly reminds me of him in a manic phase. That is to say: long winded, somewhat misdirected, with some important kernels of truth.

Your profile suggests that you are providing some sort of consulting service to help mitigate emfs, but it sure sounds like you are writing about your own home.

I accept the possibility that magnetic fields from unbalanced current flows may cause harm. I accept the reality that some people are deeply troubled by the presence of such magnetic fields. The reality of harm caused by electric _shock_ or fire is well known, and any changes to an electrical system to reduce unbalanced current flows must not increase the risk of shock or fire.

The suggestion for how to eliminate the current flow path has already been made. Eliminate the common metallic pipe system.

Code requires that interior metallic water piping be bonded to the system neutral. But an _isolated_ metallic water pipe system with a connection to a single point on the electrical system neutral will not have current flow and will not produce magnetic fields.

Code requires that _all_ available grounding electrodes be used to ground the system neutral. Included in the list of available grounding electrodes are underground water pipes. A very small amount of current will flow via these grounding electrodes through the soil. There is no practical way to eliminate this, unless you want to invest in transformer located in the home...and that transformer will produce significant magnetic fields.

The problem is _common_ underground metallic piping. These provide a continuous _metallic_ path between homes, and thus provide a continuous _metallic_ path parallel to the home neutral connections.

Lots of current can flow on this metallic parallel path, and this results in large magnetic fields surrounding the metallic pipes, the grounding electrode conductors to those pipes, and the service entrance conductors.

The best solution is to replace some portion of the underground pipe bringing water into the home. This eliminates the continuous metallic path joining one neutral to the others. You don't need to replace the entire underground run of pipe, you don't need to replace the water main. Simply a long enough section of the pipe between the home and the main to 'break' the continuous metallic path between houses.

The portion of pipe replaced need not be very large. Depending upon the location this may render the pipe 'no longer an acceptable grounding electrode', or it may permit the use of a portion of the pipe as a grounding electrode, but eliminate the continuous metallic path. Without the water pipe ground, additional grounding electrodes may need to be added.

Essentially: if you have that common underground metallic piping, code requires you to use it, but code does not require you to have the common underground metallic piping. So you eliminate the _metallic_ pipe and eliminate the code requirement to use it.

There would still be a 'parallel path' via the soil surrounding the grounding electrodes, but this is a high resistance path and thus there will be much lower current flow.

You are correct: that common underground water pipe provides protection from an 'open neutral' situation, because the water pipe can act as a backup neutral. However this backup neutral is _not_ something required by code. Code does not require the use of common underground water piping. It requires that a metal water pipe of certain length going into the home be used as a grounding electrode. _Grounding_ is not considered a suitable backup for the neutral.

Something that you mentioned is that your service conductors are underground. I think this changes the merit of your 'redirection' proposal. If you can route the grounding electrode conductor in close proximity to the service conductors, then any unbalanced current flowing on the GEC would balance and cancel out the unbalanced current on the service entrance conductors. This is something that would need to be evaluated by a careful site survey.

-Jon
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
I will read up on this thread but I do believe the concerns should be taken seriously as it is a code based question. Enough that many parts of the world will go through the trouble of TT or TN-S earthing.


The truth is about the only way to stop this is to add a dielectric union to the water main after being on contact with the earth for more than 10 feet. The pipe will still qualify as a grounding electrode but not pass the same degree of current.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Silencing the Fields
This book does a great job in explaining how electrical systems in the United States operate and how the NEC and the NESC ground practices impact current flow resulting in elevated magnetic fields. Ed's slant is on electromagnetic fields and my concern is the cause of these magnetic fields (current flowing where it?s not supposed to). You see if you have elevated electromagnetic fields, there is a problem, there is voltage on metal parts (shock hazard) and there is the possibly of a fire.


I can't think of a more dangerous practice than to take a current carrying conductor (neutral) and bond it to the metal parts of the electrical system, but this is a NEC requirement (I'm sure pushed by the electric utilities). This practice of bonding a current carrying conductor to metal parts is especially dangerous in building that has a swimming pool. I intend on making a proposal to prohibit the bonding of the neutral to metal parts at any location in a building, but unless people understand electrical systems, they won't understand the danger or the proposal.


This part I agree with as much as I don't want to admit it. In newer NEC editions all ground and neutral conductors after the service disconnect must be separate and the neutral can not function as an EGC there after. Ditto visa versa. The same concept however does not apply to Utilities. Utilities will treat ground and neutral as the same thing with the neutral conductor earthed everywhere and tied into the customer's LV neutral which per code is then also earthed again. This creates a slew of problems and risks.


http://www.google.com/url?sa=t&rct=...=Xq97NzuAfWdkHp-QuQuh4A&bvm=bv.95277229,d.eXY


Just recently:

http://www.twincities.com/localnews/ci_26795352/farm-family-awarded-record-6-3m-stray-voltage


You are correct, utilities do influence the NEC's grounding and bonding of services. For example outside of North America where this utility practice is not used ground rods are only required for TT earthing. Even a TN-C-S service (used here) would not require any grounding electrodes, only bonding if metal parts like water pipes that could inadvertently become energized.


Which leads me to this: California and most of the world does not even have to worry about this conversation. Most utility transformers are connected phase to phase, and the LV supply has either an EGC going all the way back to the utility transformer or the neutral is left unbonded to the building's grounding system with ground rods and RCD used to clear a fault. Both TN-S and TT do not pass any ground current naturally being ultra low EMF systems. EMFs aside there is no stray voltage or energized grounding system if the utility neutral broke.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
I accept the possibility that magnetic fields from unbalanced current flows may cause harm. I accept the reality that some people are deeply troubled by the presence of such magnetic fields. The reality of harm caused by electric _shock_ or fire is well known, and any changes to an electrical system to reduce unbalanced current flows must not increase the risk of shock or fire.

-Jon

Id say those people are crazy or might have an advantage... who knows, its irrelevant. The truth is those who are at risk can not feel EMFs. The vast majority of us can not feel them either way. However, that does not mean that EMFs could not be a latent health hazard. Many known toxins can not be detected by the 5 senses. But that doesn't mean they are benign.



I think the reason why people associate EMFs with insane people comes from propaganda. Sometimes its necessary to have bogus internet videos with schizophrenics rambling about EMFs then genuinely addressing a potential health concern with a scientific basis. If it is ever proven EMFs pose a hazard to human health, even a small one, POCOs will be sued out of existence within 24 hours. Simple lawsuits over stray voltage caused by the very issue of using earth as a conductor has grown into a multi million dollar industry alone. EMFs? I don't want to think about it.

POCOs don't want to change, they will do anything to save money at all costs. Even after 9/11 and the August 2003 black out Washington has tried to address a separate yet even bigger issue of them keeping the US power system in a state of limbo. To this day POCOs still refuse to do much about it pushing off long needed reliability and infrastructure replacement projects all to please their investors. :happyno:
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
One unavoidable consequence of keeping ground and neutral separate is that you have an ungrounded system and must deal with that properly, otherwise a second fault could energize exposed metal without necessarily having an adequate return path to clear the combined faults!
Or else we go to the European system of requiring better than 1 ohm earth electrode resistances, tested regularly.


TT earthing does not require a stable 1 ohm, actually around 150 ohms. But there is a better solution: TN_S earthing. Have the ground and neutral isolated all the way back to the transformer, best of both worlds. Problem solved. Getting that to change is that hard part, however :rant:
 

romex jockey

Senior Member
Location
Vermont
Occupation
electrician
Just a quick thought, could one ask the serving poco to install isolators @ the xformer AND STILL be NEC complaint to said h20 pipe?

It's done on farms all the time....


~RJ~
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
Code requires that _all_ available grounding electrodes be used to ground the system neutral. Included in the list of available grounding electrodes are underground water pipes. A very small amount of current will flow via these grounding electrodes through the soil. There is no practical way to eliminate this, unless you want to invest in transformer located in the home...and that transformer will produce significant magnetic fields.


-Jon

250.6 Objectionable Current

(A) Arrangement to Prevent Objectionable Current. The grounding of electrical systems, circuit conductors, surge arresters, surge-protective devices, and conductive normally non? current-carrying metal parts of equipment shall be installed and arranged in a manner that will prevent objectionable current.

(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 causing the objectionable current.
(4) Take other suitable remedial and approved action.
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
250.6(A) says that you 'shall' prevent objectionable current.

IMHO that trumps 250.50. I also believe that you have an obligation to mitigate a hazard until it can be 'fixed'.

If you truly enforce this, then you have required every service you've ever inspected to have no grounding electrode conductor connections. Or, the laws of physics do not apply in Columbus OH.

Any grounding electrode connected to the neutral of a service will present a parallel path for neutral current. Period.

Current on GECs is not objectionable, and there is absolutely no merit to the statement that the broad and inspecific 250.6 trumps the very specific Part III of Article 250.
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
If you truly enforce this, then you have required every service you've ever inspected to have no grounding electrode conductor connections. Or, the laws of physics do not apply in Columbus OH.

Any grounding electrode connected to the neutral of a service will present a parallel path for neutral current. Period.

Current on GECs is not objectionable, and there is absolutely no merit to the statement that the broad and inspecific 250.6 trumps the very specific Part III of Article 250.

First we are addressing a problem and seeing how/if the NEC allows us to 'fix it'.

So if current is entering my structure via the metal water lines I can not eliminate it? 250.6 allows me to do so.

250.4 General Requirements for Grounding and Bonding
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.

(A) Grounded Systems.

(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

If you don't like the word trump how about allows as in an exception?
 

romex jockey

Senior Member
Location
Vermont
Occupation
electrician
If you truly enforce this, then you have required every service you've ever inspected to have no grounding electrode conductor connections. Or, the laws of physics do not apply in Columbus OH.

Any grounding electrode connected to the neutral of a service will present a parallel path for neutral current. Period.

Current on GECs is not objectionable, and there is absolutely no merit to the statement that the broad and inspecific 250.6 trumps the very specific Part III of Article 250.

Have you run this by many water dept folks George?

If so, you may find find they've a slightly different view of what is/is not 'objectionable'

~RJ~
 

iwire

Moderator
Staff member
Location
Massachusetts
We can BS forever about this but here is the bottom line in my opinion.

The American public will not tolerate the rate increases that would be required to pay for changing our countries electrical distribution system to one with a separate EGC. Because of that the NEC can only try to live with what we have.
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
We can BS forever about this but here is the bottom line in my opinion.

The American public will not tolerate the rate increases that would be required to pay for changing our countries electrical distribution system to one with a separate EGC. Because of that the NEC can only try to live with what we have.

We are not trying to change anything.

OP has a problem. I showed how the NEC allows us to solve this.

So what is the big deal?

I never said get rid of all metal waterline electrodes. If it is a safety hazard it MUST be addressed.

Wish I could find Mike's video on the house that burnt down and neutral current is still on the interior metal lath with the homes power disconnected.
 

iwire

Moderator
Staff member
Location
Massachusetts
We are not trying to change anything.

There are many topics being discuses in this thread.

OP has a problem.

In your opinion

I showed how the NEC allows us to solve this.

Again in your opinion.

So what is the big deal?

No big deal just voicing my own opinion.

If it is a safety hazard it MUST be addressed.

I do not see a safety problem.

Wish I could find Mike's video on the house that burnt down and neutral current is still on the interior metal lath with the homes power disconnected.

That sounds like failed or open neutral issue not a simple pararallel path issue.
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
OP "I have objectionable net current on a grounding wire to a water meter,"

OP defined a problem.

Not my opinion. My interpretation is that 250.6 applies here.

I am not talking about parallel paths per se. I am saying remove that path when there is an issue.

"250.6 of the NEC specifies that objectionable current is not to flow on grounding and bonding paths but few understand what objectionable current is, why it?s dangerous and how to remove it."
From: http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/ObjectionableCurrent~20020610.htm
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Interesting interpretation regarding 250.6.

IMHO the interpretation does not apply, but because of a jurisdiction issue, not a physics/technical issue.

Consider: If the transformer and several homes taken together were all customer owned on a _single_ property, then it would be clear that the current on the water pipes was 'objectionable' per the NEC. (I understand that the NEC does not fully define 'objectionable current', but if you consider the NEC requirements that would come into play in this hypothetical situation, you would see that this current would be eliminated.)

In this hypothetical situation, the water pipe bond at each home would be _prohibited_, the neutral would not be grounded in each home, and a separate EGC would be required as part of the 'service drop' (which, in this hypothetical, is a feeder to a detached structure).

Another approach, which would meet the goals of the original poster and be fully compliant with the NEC, would be to have installed some sort of freestanding meter pedestal/service disconnect. This would be a box right at the edge of the customer's property which contains the utility connection, the meter, the main breaker, and the grounding connections to the neutral. The connection between this stand alone structure and the home would be an NEC compliant feeder with separate EGC. All bonding in the home itself would be to the EGC, not to the neutral.

Any local unbalanced currents, caused by parallel neutral current paths, would be between the utility and this freestanding meter structure.

-Jon
 
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