Test Question - Troubleshooting

[GoldDigger]

Current flowing on utility ground because Service Neutral is too small.

Very much too small if no current at all flows on the utility neutral, as in the original problem.

 

[Smart $]

The NEC is clear that the purpose of the GES (Grounding Electrode System) is to provide an effective low impedance path to operate the overcurrent protection when a fault occurs.

****That is to say, Fault Current is intended to flow in the GES. Period. It's just that simple.*****

The NEC is SILENT about isolating the path of the current in the conductors that comprise the GES. Think about that. A lowly #14 Equipment Grounding Conductor (EGC) out on the end of a branch circuit IS NOT PREVENTED from being connected to EARTH. The instant that happens, the EGC is another parallel path back to the source.

The NEC is also SILENT about deliberately introducing connections of the EGC to Earth. . . both of these silences mean that if there is a circuit completed from the Main Bonding Jumper to Earth and back to the Source as a parallel path along an EGC, or even a GEC, that it just IS.

If that isn't INTENDING to allow current in parallel paths, I don't know what is.

As Wayne (hurk27) said, I believe you are confusing GES with EGS... but not just that. I think you are further confusing contingent with intended. The whole grounding system is intended to mitigate hazards should they occur. It is not intended to mitigate avoidable hazards, and inadvertently reduce the likelihood of detection and remedial action.

And, BTW, the NEC is not completely silent on the matter. You have a section on mitigating objectionable current... but it's far from concise enough to say I'm right and you are wrong. I have no choice but to give your premise the benefit of doubt.

The aspect of an EGC becoming an earth path is also in the Code, but contradictory. We have one section which says you can connect a GE/GEC to any point of an EGC, then later we have a section which says we cannot used an EGC as a GEC. I think the CMP and technical correlating committee members as a whole are just as much on the fence as are many others that are left unsure. Your position just perpetuates the matter.

 

[ronaldrc]

Very much too small if no current at all flows on the utility neutral, as in the original problem.

I don't see in the example where it says there is no current being drawn by the load.

 

[GoldDigger]

I don't see in the example where it says there is no current being drawn by the load.

It does not tell us anything about the load current. It just says that there is current in the GEC and zero current in the neutral on the utility side of the ground/neutral bond.

 

[jxofaltrds]

But I would believe it is unavoidable in many cases and very acceptable by the NEC, all GEC's are in fact parallel with the utility neutral, they will always share the neutral current proportionally to the impedance of the path, many water pipe GE's are simply a parallel path through the neighbors house GE then back of their neutral to the transformer, these water pipes can be allot lower impedance then the MGN and or the involved service neutrals so having a current on the GEC can be quite normal, sometimes we might see a little of the primary current on this path because the water lines can also parallel the MGN between the houses down the street via the same GEC connections at each house, but I would expect that this current would be very small, a lost MGN connection could raise it a bit but over all it would be small because of the amount of current involved so unless this current is very large or there is a high voltage potential (10 volts or more ) to remote earth from the grounding this is allot of worrying over nothing.

For mike to suggest cutting the water pipe at the 10' mark from the house and put in an isolator to me would make the system much more dangerous because even though it is not an intended current path, it does provide some safety backup for a lost neutral condition, lightly dimming and brightening of lights is a lot better than having all the electronics burning up and or a fire breaking out because of a over voltage condition, a home owner should always be instructed to have an expert check out the service neutral anytime they see lights getting dimmer and brighter, even if it is not by much.

Mike just because you may have current on the GEC it does not mean you have a large difference of voltage potential between equipment or earth, if you think you have a problem then always measure the voltage between the service or grounding system and remote earth, if it is higher then 10 volts then you have a problem, but I have seen many times for it to be around 3 to 5 volts and be very normal because it is nothing but the normal voltage drop of the service neutral, only when we have a body of water where we have people normally in it such as pools and lakes/rivers with boat docks then even 3 volts can be a problem, but when we start seeing over 10 volts we know there is a problem with the neutral or transformer primary neutral or MGN, then we must act.

Sounds like I could do exactly what I said. It might give me permission to eliminate the copper water line as an electrode????? PS shall means must!
So I could isolate the interior water lines from the metal water line electrode and only have to bond the interior lines.


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.

250.4(A)(5) or (B)(4)

(5) Effective Ground-Fault Current Path. Electrical equipment
and wiring and other electrically conductive material
likely to become energized shall be installed in a manner that
creates a low-impedance circuit facilitating the operation of
the overcurrent device or ground detector for high-impedance
grounded systems. It shall be capable of safely carrying the
maximum ground-fault current likely to be imposed on it from
any point on the wiring system where a ground fault may
occur to the electrical supply source. The earth shall not be
considered as an effective ground-fault current path.

(4) Path for Fault Current. Electrical equipment, wiring,
and other electrically conductive material likely to become
energized shall be installed in a manner that creates a low impedance
circuit from any point on the wiring system to
the electrical supply source to facilitate the operation of
overcurrent devices should a second ground fault from a
different phase occur on the wiring system. The earth shall
not be considered as an effective fault-current path.

 

[ronaldrc]

I still don't see where everyone is assuming there is zero current on the load side of the neutral.

I know Don said there was not . Don was that just because he did not mark the drawing with the
load amperage or what?

Or did the OP say there was no load on the neutral and I missed it some where?

The way I look at this is the main is in the up position and unless every thing on the load side of the neutral
is cut off in some way there should be a load on the neutral.

With a very long service drop and with a city wide metal water line as the grounding system this would be common place to have a large voltage drop that the ground would pick up the difference in the drop if there was a fault.

Its not a fault unless something on the load side of the main has a neutral to equipment ground touching some where down stream of the main.

I 'm sorry if I just repeated what some one else has already said, if so I agree.

There might not be any thing wrong here at all other than just the allowable voltage drop.

Just because there is a voltage between the neutral and ground doesn't mean there is a fault
with the service.

 

[jxofaltrds]

I still don't see where everyone is assuming there is zero current on the load side of the neutral.

I know Don said there was not . Don was that just because he did not mark the drawing with the
load amperage or what?

Or did the OP say there was no load on the neutral and I missed it some where?

The way I look at this is the main is in the up position and unless every thing on the load side of the neutral
is cut off in some way there should be a load on the neutral.

With a very long service drop and with a city wide metal water line as the grounding system this would be common place to have a large voltage drop that the ground would pick up the difference in the drop if there was a fault.

Its not a fault unless something on the load side of the main has a neutral to equipment ground touching some where down stream of the main.

I 'm sorry if I just repeated what some one else has already said, if so I agree.

There might not be any thing wrong here at all other than just the allowable voltage drop.

Just because there is a voltage between the neutral and ground doesn't mean there is a fault
with the service.

Ron(?)

My example was meant to be vague. If the 'return current' is not going back on the utility neutral and is going back via the public metal water lines (to the source) how would you answer the poll? Forget voltages. Don't put too much thought into it.

 

[ronaldrc]

Ron(?)

My example was meant to be vague. If the 'return current' is not going back on the utility neutral and is going back via the public metal water lines (to the source) how would you answer the poll? Forget voltages. Don't put too much thought into it.

If its not going back on the utility neutral and on the ground that leaves nothing but a open neutral.

Please direct me to the post where you stated that and not some one else's assumetion,

"If the 'return current' is not going back on the utility neutral and is going back via the public metal water lines"

Thanks for the reply

 

[jxofaltrds]

If its not going back on the utility neutral and on the ground that leaves nothing but a open neutral.

Please direct me to the post where you stated that and not some one else's assumetion,

"If the 'return current' is not going back on the utility neutral and is going back via the public metal water lines"

Thanks for the reply

You gave away the answer too soon, I thought that was obvious with some assumption from the information provided.

This is a thought question. Not a 2+2 (code) question.

Please look at the limited graphic that I started with.

It (neutral current) is leaving structure #1 and entering structure #2 via the water lines. Then back to the source.

 

[GoldDigger]

This is a thought question. Not a 2+2 (code) question.

Please look at the limited graphic that I started with.

It (neutral current) is leaving structure #1 and entering structure #2 via the water lines. Then back to the source.

Or if structure one is the only one on the transformer, it could still be leaving structure one and returning to the transformer secondary via the utility secondary ground.
That will result in additional symptoms consistent with a high resistance neutral (depending in part of the resistance of the utility multiply grounded neutral network and in part on the resistance of the water pipe to remote earth), but will also satisfy the diagram.

 

[George Stolz]

For any who attempt to apply 250.6 to the normal function of a neutral connected to a municipal water system, I wonder if they use no steel to interconnect service enclosures? Install no steel raceways or enclosures in their installations beyond a service disconnect? Never install electrical equipment on a steel sided building? Never install steel equipment in metal-framed structures? Never install metal equipment on stucco?

My point being, alternate paths for neutral current are absolutely unavoidable if you stop and really examine potential alternate paths for neutral current, and then stop to appreciate how many paths could spring up that you simply have been blind to. People seem to believe they have stumbled onto something really astounding when evaluating the municipal water system "problem", while almost entirely turning a blind eye to the fact that the only reason this particular path stands out is because it's resistance is lower than most others. It's only a problem when the real failure occurs: an open neutral.

Our bed was made for us long before we were born; we live on an MGN continent, and therefore we must continue on in the same way because the lot has been cast.

People seem to spend more time chasing their tails worrying about bad grounding boogeymen and the like, and they end up failing to observe basic workmanship in their terminations, which ironically winds up ferrying current onto their grounding conductors!

:slaphead:

 

[Smart $]

... My point being, alternate paths for neutral current are absolutely unavoidable...

I agree... but as witnessed here, there are those that believe neutral current through the GES and supply-side bonding is intended. It is a consequence of grounded systems and bonding, but it is not intended under nominal conditions. Taking measures to reduce neutral current under nominal conditions could actually impose a greater hazard under abnormal conditions. The underlying principle of system grounding is to minimize hazards under abnormal conditions. If anyone considers taking measures under 250.6, they should analyze how it would affect the system under abnormal conditions before proceeding.

 

[ActionDave]

.....Our bed was made for us long before we were born; we live on an MGN continent, and therefore we must continue on in the same way because the lot has been cast.

People seem to spend more time chasing their tails worrying about bad grounding boogeymen and the like, and they end up failing to observe basic workmanship in their terminations, which ironically winds up ferrying current onto their grounding conductors!

:slaphead:

I can't find an emoticon for applause. If I could I would use it here.

 

[iwire]

I agree... but as witnessed here, there are those that believe neutral current through the GES and supply-side bonding is intended. It is a consequence of grounded systems and bonding, but it is not intended under nominal conditions. Taking measures to reduce neutral current under nominal conditions could actually impose a greater hazard under abnormal conditions. The underlying principle of system grounding is to minimize hazards under abnormal conditions. If anyone considers taking measures under 250.6, they should analyze how it would affect the system under abnormal conditions before proceeding.

Smart, you make a lot of sense sometimes and are very sharp but in this case IMO you are splitting hairs over nothing.

Intended or not it is a result of NEC requirements and in reality causes little if any problems in premises wiring systems.

Personally I think 250.6 should be removed unless they define objectionable current and spell out the allowable remedies if it exists.

 

[jumper]

I can't find an emoticon for applause. If I could I would use it here.

Here ya go.

​

 

[jxofaltrds]

I agree... but as witnessed here, there are those that believe neutral current through the GES and supply-side bonding is intended. It is a consequence of grounded systems and bonding, but it is not intended under nominal conditions. Taking measures to reduce neutral current under nominal conditions could actually impose a greater hazard under abnormal conditions. The underlying principle of system grounding is to minimize hazards under abnormal conditions. If anyone considers taking measures under 250.6, they should analyze how it would affect the system under abnormal conditions before proceeding.

No I do not believe that thinking about abnormal conditions is required in the code. Unless 90.1(B) applies :lol:

(B) Adequacy. This Code contains provisions that are considered
necessary for safety. Compliance therewith and
proper maintenance results in an installation that is essentially
free from hazard but not necessarily efficient, convenient,
or adequate for good service or future expansion of
electrical use.

Smart, you make a lot of sense sometimes and are very sharp but in this case IMO you are splitting hairs over nothing.

Intended or not it is a result of NEC requirements and in reality causes little if any problems in premises wiring systems.

Personally I think 250.6 should be removed unless they define objectionable current and spell out the allowable remedies if it exists.

In my example it is considered objectionable because the GEC and copper metal water lines are 'acting' as a neutral. Violation.

It is no different than this:

 

[Smart $]

Smart, you make a lot of sense sometimes and are very sharp but in this case IMO you are splitting hairs over nothing.

Intended or not it is a result of NEC requirements and in reality causes little if any problems in premises wiring systems.

Personally I think 250.6 should be removed unless they define objectionable current and spell out the allowable remedies if it exists.

Geeesh, Bob. I essentially said the same thing you did... just a bit more wordy. :roll:

 

[Smart $]

No I do not believe that thinking about abnormal conditions is required in the code.

I believe it is required. 250.6(B) general statement, in effect, states alterations cannot defeat the requirements of 250.4(A)(5) and (B)(4).

In my example it is considered objectionable because the GEC and copper metal water lines are 'acting' as a neutral. Violation.

It is no different than this:

View attachment 10821

That picture is a demonstration of neutral current on an EGC... not a GEC. It is a non-compliant installation, so it has no bearing on the issue being discussed.

In the original OP condition, some of the current on the GEC was fault current... which is not objectionable current by my understanding. The only problem I see is fault detection.

After the utility neutral fault was corrected, the remaining current through the GEC cannot be attributed definitively to objectionable current as long as Code lacks a definition for such.

 

[jxofaltrds]

I believe it is required. 250.6(B) general statement, in effect, states alterations cannot defeat the requirements of 250.4(A)(5) and (B)(4).

My alteration ("Alterations to Stop Objectionable Current.") does not - why I put those two sections in my post.

That picture is a demonstration of neutral current on an EGC... not a GEC. It is a non-compliant installation, so it has no bearing on the issue being discussed.

In the original OP condition, some of the current on the GEC was fault current... which is not objectionable current by my understanding (correct). The only problem I see is fault detection.

After the utility neutral fault was corrected, the remaining current through the GEC cannot be attributed definitively to objectionable current as long as Code lacks a definition for such.

The picture shows a 'like" condition. It does have bearing or I would not have used it.

I'm the OP and the current was NOT fault current it was neutral current returning to the source. No "fault" was corrected.

IMHO neutral current is only permitted on the grounded conductor in a 'normal' condition.

Neutral Conductor. The conductor connected to the neutral
point of a system that is intended to carry current under
normal conditions.

 

[Smart $]

My alteration ("Alterations to Stop Objectionable Current.") does not - why I put those two sections in my post.

First, with no Code definition for objectionable current, how can you really classify it as such? It comes down to a matter of opinion... and I'll give you that.

Anyway, I'm referring to this:

Follow up question. Now that the utility made a repair there is still objectionable current on the copper metal water lines I say that this should be removed by isolating the water lines (10'+; 250.52(A)(1)) outside. One of my concerns is that since the GEC is bare copper and runs in a chase with the interior copper water lines and metal HVAC runs that it 'may' be coming in contact with these interior parts. I say replace it with an insulated GEC (connected within 5'; 250.68(C)(1)) to remove any touch potential on these parts.

I realize isolating the water line beyond 10' outside would not be a Code violation, but in the case of an open service neutral (which is a fault condition), you'd be relegating the fault current path to earth and creating a potential hazard to life and property should such a fault occur.

As to the second alteration, I don't believe you gain anything.

The picture shows a 'like" condition. It does have bearing or I would not have used it.

It's only 'like' in the sense there's neutral current on a grounding conductor. But using a non-compliant scenario to make a point is not a good way to go about it IMO.

I'm the OP and the current was NOT fault current it was neutral current returning to the source. No "fault" was corrected.

Correct me if I'm wrong, but the OP was a fault condition: open service neutral. You later said that was corrected. What we're talking about now is a normal, compliant condition.

IMHO neutral current is only permitted on the grounded conductor in a 'normal' condition.

I agree with that in regards to neutral current on the equipment grounding system... but it is not explicit enough to prohibit neutral current on the grounding electrode system. Even if there is no low-impedance pathway you will still have some current transferred through earth.