Test Question - Troubleshooting

[iwire]

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

Sorry, it did not come across to me that way.

Could be my mistake.

 

[J.P.]

I'm really lost. I don't see a diagram or a question, just a choice of answers to a invisible question......

 

[George Stolz]

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.

Perhaps in the future you could simply state your position and cite the references, instead of quoting entire sections. I really didn't understand what you were driving at.

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

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.

Your reference would be valid if they decided to use the copper water line in lieu of a wire-type conductor marked white. I seriously doubt this was the case. Actually, the definition of Neutral Conductor defeats your argument; a copper water line is never intended to carry neutral current under normal conditions. It carries neutral current as a byproduct of a code-compliant installation. The white conductor at the service is the neutral conductor because it was intentionally installed for the express purpose of handling neutral current.

I don't think you need to even think about 250.6 at all if you elect to destroy a metal water pipe electrode. Simply cut it outside where it exits the structure and the electrode ceases to exist. There is no requirement to make exterior water piping continuous to make an electrode. It is required to be supplemented precisely because this may occur whether we like it or not.

If the Authority Having Jurisdiction deems normal byproducts of grounding and bonding to create "objectionable current", then they have the option of amending the NEC to prohibit it. The NEC does not.

 

[George Stolz]

I'm really lost. I don't see a diagram or a question, just a choice of answers to a invisible question......

The diagram is in the original post. It may appear small, you may have to click on it to see it.

http://forums.mikeholt.com/showthread.php?t=164045&p=1591206#post1591206

 

[hurk27]

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



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.

Mike I think what we are all trying to tell you is ahead of the main service disconnect or at multiple SDS's in a single building the code does not treat parallel neutral current as objectionable, because if it did you would not be able to have the rules that require things like when two or more meters are fed from a single service drop or when more then one service is located on a single building will all have a common GEC that is in parallel to the neutral and will share the neutral current.

Please look at these exhibits in the 2011 hand book:


Electrode taps:
Code 250.64 Page 244 Exhibit 250.27
" " 250.66 " " 247 " " 250.30
" " 250.92 " " 252 " " 250.36

Intersystem Bonding:
Code 250.94 Page 255 Exhibit 250.44

The bad thing about the intersystem bonding is the CATV it is bonded at the house to the neutral and also at the pole to the MGN, unlike the water pipe it it is a small conductor and can catch fire if you have a lost neutral condition that puts enough current on it, but it is still a requirement in both the NEC as well as the NTSC.

There are other places in the NEC where we will see requirements to parallel the neutral, the above are just a few examples I can think of, this should show that the NEC does not conceder parallel neutral current on grounding as objectionable because it is required.

Think of this, almost all meters come with the neutral terminal in the can bonded to the meter can, if you use a metal raceway between the meter and service disconnect or main panel you have just paralleled the neutral with the raceway.

Any building with two or more services that have a common water pipe or building steel that is used as an electrode, or even if you have a common ground rod (which the NEC requires I might add) you will have a paralleled neutral.

So you need to stop worrying about parallel neutral currents ahead of the main service disconnects because the NEC has requirements that is going to cause them, and there's no way around them in a code compliant installation.

Removed to SDS multiple reference as it is not a parallel neutral condition

 

[jxofaltrds]

....

So you need to stop worrying about parallel neutral currents ahead of the main service disconnects because the NEC has requirements that is going to cause them, and there's no way around them in a code compliant installation.

Rem....

First these are not ahead of the main disconnect. They are made at the disconnect.

I do worry about current taking paths back to the source that can harm individuals.

I still hold my Plumbing License even thought I no longer do contracting. With my plumbing hat on now - I use to carry car jumper cables when I had to repair (cut) copper water lines. One because I didn't like the sparks and two when I understood that neutral current could be on the lines because of a lost POCO neutral. I didn't want to get hurt. What about the water co employees?

What if Joe Homeowner repairs his own pipes and doesn't have our knowledge? What if he uses a quick repair coupler and isolates a connection to the water line (not with in 5' like the old days) and he has no POCO neutral?

My point is once we know that there is a potential problem I believe that we must correct it.

Help me here. Wasn't the water line one of the first electrodes? Is it time to revisit its use?

Just because we use to do it doesn't make it right. We use to test with our fingers. We use to stick fingers up the rectum for electrocution victims.

 

[ronaldrc]

First these are not ahead of the main disconnect. They are made at the disconnect.

I do worry about current taking paths back to the source that can harm individuals.

I still hold my Plumbing License even thought I no longer do contracting. With my plumbing hat on now - I use to carry car jumper cables when I had to repair (cut) copper water lines. One because I didn't like the sparks and two when I understood that neutral current could be on the lines because of a lost POCO neutral. I didn't want to get hurt. What about the water co employees?

What if Joe Homeowner repairs his own pipes and doesn't have our knowledge? What if he uses a quick repair coupler and isolates a connection to the water line (not with in 5' like the old days) and he has no POCO neutral?

My point is once we know that there is a potential problem I believe that we must correct it.

Help me here. Wasn't the water line one of the first electrodes? Is it time to revisit its use?

Just because we use to do it doesn't make it right. We use to test with our fingers. We use to stick fingers up the rectum for electrocution victims.

This is not a uncommon thing on services with a high voltage drop on their feeder.

I understand your concern for safety. Like you said it could be a loose or open neutral.
I am assuming you had a amp clamp around the main bonding jumper?

If it had been me I would have turned the main power off and took the bonding jumper off
then turn the power back on and took a voltage reading from my neutral to the ground if it is less than a few volts which it usually is.Then you can make the assumption that it is just the NEC acceptable voltage drop
from a long feeder or the reduced neutral size for the single phase 120/240.If you don't trust your
meter take a 12 volt bulb and test it.

I have removed grounds on some services during trouble shooting and have seen sparks like a arcing welder.
Measure the voltage and sometimes would be less than a few volts. But the amperage would be very high.

It was no more than voltage drop and the utility ground trying to conduct that voltage drop.


Ronald

 

[Pharon]

There is no definition in the NEC for 'objectionable current', but for what it's worth, this is the Handbook elaboration on 250.6(B):

Many electronic controls and computer equipment are sensitive
to stray currents. Circulating currents on EGCs, metal raceways,
and building steel develop potential differences between ground
and the neutral of electronic equipment. Installation designers
must look for ways to isolate electronic equipment from the
effects of such stray circulating currents.

Isolating the electronic equipment from all other power equipment
by disconnecting it from the power equipment ground is not
the right solution, nor is removing the equipment grounding means
or adding nonmetallic spacers in the metallic raceway system. These
solutions are contrary to fundamental safety grounding principles
covered in the requirements of Article 250. Furthermore, if the electronic
equipment is grounded to an earth ground that is isolated
from the common power system ground, a potential difference is
created, which is a shock hazard. The error is compounded because
such isolation does not establish a low-impedance ground-fault
return path to the power source, which is necessary to actuate the
overcurrent protection device. Section 250.6(B) is not intended to
allow disconnection of all power grounding connections to the electronic
equipment. See the commentary following 250.6(D).

 

[al hildenbrand]

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

Sorry, it did not come across to me that way.

Could be my mistake.

I don't think it is your mistake, Bob.

The turn in this thread has me realizing, recalling some of my other similar exchanges with you, Smart, that I would benefit from unpacking your meaning of "intended".

 

[Smart $]

I don't think it is your mistake, Bob.

The turn in this thread has me realizing, recalling some of my other similar exchanges with you, Smart, that I would benefit from unpacking your meaning of "intended".

Actually it is...

You both remember previous discussion regarding objectionable current and "reading between the lines" of my post. If you recount earlier discussions in their entirety, you'd realize those were regarding neutral current on service conduits between enclosures. I've never combined that and neutral current on the GES into one concept... and the discussion here is regarding neutral current on the GES.

 

[jxofaltrds]

This is not a uncommon thing on services with a high voltage drop on their feeder.

I understand your concern for safety. Like you said it could be a loose or open neutral.
I am assuming you had a amp clamp around the main bonding jumper?

If it had been me I would have turned the main power off and took the bonding jumper off
then turn the power back on and took a voltage reading from my neutral to the ground if it is less than a few volts which it usually is.Then you can make the assumption that it is just the NEC acceptable voltage drop
from a long feeder or the reduced neutral size for the single phase 120/240.If you don't trust your
meter take a 12 volt bulb and test it.

I have removed grounds on some services during trouble shooting and have seen sparks like a arcing welder.
Measure the voltage and sometimes would be less than a few volts. But the amperage would be very high.

It was no more than voltage drop and the utility ground trying to conduct that voltage drop.


Ronald

Don't do any of that!!!! I was told that I was an idiot for doing some of what you suggest.

Ronald I agree with you.

 

[jxofaltrds]

Actually it is...

You both remember previous discussion regarding objectionable current and "reading between the lines" of my post. If you recount earlier discussions in their entirety, you'd realize those were regarding neutral current on service conduits between enclosures. I've never combined that and neutral current on the GES into one concept... and the discussion here is regarding neutral current on the GES.

TY. :thumbsup:

 

[al hildenbrand]

If you recount earlier discussions in their entirety, you'd realize those were regarding neutral current on service conduits between enclosures. I've never combined that and neutral current on the GES into one concept... and the discussion here is regarding neutral current on the GES.

To call the part of the total unbalance current that is traveling in any one of the multiple parallel paths as "neutral current" is, in my opinion, not possible.

In my mind, "neutral current" exists only inside the insulated path on the load side of the Main Bonding Jumper in either the modern not-re-grounded feeder neutral and/or the branch circuit neutral. In my mind, the theoretical junction point of the main bonding jumper splits the "neutral current" into "grounded service conductor current" and to other currents that are not really given names by the NEC. These other currents exist by the requirements of the NEC in all but the rarest of occupancies. In the Real World, the theoretical main bonding jumper point in the circuit has to include all the other conductive paths that happen when conductive materials, by mechanical assembly, form a complete path that current can travel along back to the Source (the PoCo transformer).

And, again, I repeat. I would benefit from your unpacking what "intended" means to you.

 

[Smart $]

To call the part of the total unbalance current that is traveling in any one of the multiple parallel paths as "neutral current" is, in my opinion, not possible.

In my mind, "neutral current" exists only inside the insulated path on the load side of the Main Bonding Jumper in either the modern not-re-grounded feeder neutral and/or the branch circuit neutral. In my mind, the theoretical junction point of the main bonding jumper splits the "neutral current" into "grounded service conductor current" and to other currents that are not really given names by the NEC. These other currents exist by the requirements of the NEC in all but the rarest of occupancies. In the Real World, the theoretical main bonding jumper point in the circuit has to include all the other conductive paths that happen when conductive materials, by mechanical assembly, form a complete path that current can travel along back to the Source (the PoCo transformer).

And, again, I repeat. I would benefit from your unpacking what "intended" means to you.

You can look at it that way... but IMO, and quite likely many others (but I'll let them speak for themselves), you are wrong.

First lets describe the normal system current... originates at an NEC power source having a neutral point of connection to the distribution system, travels through one or more ungrounded conductors, to and through one or more loads, and the unbalanced system current "returns" to the power source on the neutral conductor. All unbalanced ungounded conductor current is neutral current. It is intended that all the neutral current return on the neutral conductor.

There are no explicit exceptions to the above... only consequential exceptions, as a result of grounding requirements, and none of these can be considered as "intended".

Here's a thought for you to ponder... Where a power source with a neutral point is permitted to be an ungrounded system (atypical of most, I know), what would you call any current from the power source returning to it on the grounding system?

 

[GoldDigger]

Here's a thought for you to ponder... Where a power source with a neutral point is permitted to be an ungrounded system (atypical of most, I know), what would you call any current from the power source returning to it on the grounding system?

I would call it magical if the source is truly ungrounded.
Or else I would call it fault current if it happened because of two or more concurrent ground faults within the system.

 

[al hildenbrand]

All unbalanced ungounded conductor current is neutral current.

The only place that this current you have just named exists is on a theoretical circuit diagram with resistance-less line conductors and a "point" of zero dimension as the Main Bonding Jumper (MJB), the node towards which all the branch and feeder neutral currents aggregate, and from which other currents leave. It is sloppy thinking to call the summed neutral currents in the theoretical point of the MJB as the same as the current in the Grounded Service Conductor in this context of "Test Question - Troubleshooting" and it's diagram.

It is intended that all the neutral current return on the neutral conductor.

And it is even sloppier thinking to say that the power of "intention" can overrule the Laws of Physics in the Real World and that the summed branch and feeder neutral current will, therefore, go only into the Grounded Service Conductor regardless of other current paths that return to the same source.

You really need to explain what "intended" means to you. From my reading it seems almost mystical.

IF, between the MBJ and the source, there are two or more current paths, the current in the Grounded Service Conductor will NEVER equal "all unbalanced ungrounded conductor current", EXCEPT for when the unbalance current is Zero, and, therefore, the Grounded Service Conductor current is a different current than "all unbalanced ungrounded conductor current."

 

[Smart $]

I would call it magical if the source is truly ungrounded.

:thumbsdown:


You know darn well the NEC does not consider reactive or magnetic coupling as a means of grounding.

 

[GoldDigger]

:thumbsdown:


You know darn well the NEC does not consider reactive or magnetic coupling as a means of grounding.

Quite true.
In which case I would call any current returning to the source over the ground system "small".

 

[Smart $]

The only place that this current you have just named exists is on a theoretical circuit diagram with resistance-less line conductors and a "point" of zero dimension as the Main Bonding Jumper (MJB), the node towards which all the branch and feeder neutral currents aggregate, and from which other currents leave. It is sloppy thinking to call the summed neutral currents in the theoretical point of the MJB as the same as the current in the Grounded Service Conductor in this context of "Test Question - Troubleshooting" and it's diagram. And it is even sloppier thinking to say that the power of "intention" can overrule the Laws of Physics in the Real World and that the summed branch and feeder neutral current will, therefore, go only into the Grounded Service Conductor regardless of other current paths that return to the same source.

You really need to explain what "intended" means to you. From my reading it seems almost mystical.

IF, between the MBJ and the source, there are two or more current paths, the current in the Grounded Service Conductor will NEVER equal "all unbalanced ungrounded conductor current", EXCEPT for when the unbalance current is Zero, and, therefore, the Grounded Service Conductor current is a different current than "all unbalanced ungrounded conductor current."

I believe your reply exemplifies the root of our disagreement. There is no MBJ, grounded, or grounding conductor involved in a discussion about neutral current.

Until we agree on other more basic definitions, explaining intended vs. consequential is pointless.

 

[Smart $]

Quite true.
In which case I would call any current returning to the source over the ground system "small".

:thumbsup:

...and certainly not neutral current.