Ground/Neutral bonding

[Jesse Bryant]

I have been seeing this quite a bit lately and want to know if there is any type of exception that I am not aware of.

There is a main panel box (service disconnect) at the power pole outside of the home. Ground wire from a driven ground rod runs into the panel and the grounds and neutrals are bonded.

4 wires (2 hots, ground and neutral) run in conduit underground from the panel at the pole, into the home and feed the distribution panel box in the garage. Here, the ground and neutrals are again bonded. This I know is incorrect. However, is it allowed if there is another main disconnect switch installed in the garage panel box or is the first disconnect switch at the pole the only one that counts.

I just can't understand why if it is incorrect, why I am seeing it so often; especially in the municipalities.

Thanks,
Jesse

[Jeff Remas]

If there is a main disconnect at the pole then everything downstream of that is a sub-feed and required a 4 wire with separated grounds and neutrals with no bonding of the neutral (grounded conductor).

No other main disconnect is required if there is a disconnect at the pole.

[Jerry Peck]

Additionally to what Jeff said, there also needs to be a grounding electrode connection at the second structure (the building), but the grounded conductor (neutral) is not allowed to be connected to it.

From the NEC definitions:
Structure. That which is built or constructed.

[Vern Heiler]

I just can't understand why if it is incorrect, why I am seeing it so often; especially in the municipalities.

Thanks,
Jesse

Logic has overcome there dogmatic following of the written code?

[Jesse Bryant]

thanks for the post Fritz. Good information and clearly explained.

[Jeff Remas]

Additionally to what Jeff said, there also needs to be a grounding electrode connection at the second structure (the building), but the grounded conductor (neutral) is not allowed to be connected to it.

From the NEC definitions:
Structure. That which is built or constructed.

That all depends on the code cycle in place during construction and what method was used to provide power from the main disconnect to the sub-feed. That is too general of a statement and needs to be clarified.

[Jerry Peck]

That all depends on the code cycle in place during construction and what method was used to provide power from the main disconnect to the sub-feed. That is too general of a statement and needs to be clarified.

Nope. Current code acknowledges that the correct way is to *not do* the neutral to ground bonding at the separate building after many years of discussions and debating the issue, thus recognizing that it is safer the way the current code says to do it.

Would you recommend a *less safe method* knowing there was a safer method?

Talking about home inspection here, not code inspection - with code inspection your hands are tied to what the code at the time said, unless new work was done, and then it opens up a new ball game. Home inspector are not tied to code, that is simply the starting point.

[Ted Menelly]

I grounded my neutral once with a little bonding. Does that make me knowledgeable enough :p

[Vern Heiler]

This has probably been posted before, but there's a good powerpoint presentation on this from Hike Holt's forum.
Bob Ludecke's Grounding Presentation (http://tirebiter.net/downloads/ludecke.html)

Fritz, did you save a copy? I lost my PPV program a few months ago when HD crashed. When I first tried to get the presentation was the first time I realized I didn't have PPV. After getting a copy of PPV, tirebiter web site goes down!:mad: I'd like to see it....thanks.

I understand what code says, bond at one point only. But looking at the described condition at the begining of the thread, bonding the ground and neutral together at both points is no different than running an extra strand of wire on the bare center tap conductor (neutral of the SEC) back to the transformer. There is a parallel path but nowhere to create a problem. No branches with outlets or user equipment.

[Jerry Peck]

I understand what code says, bond at one point only. But looking at the described condition at the begining of the thread, bonding the ground and neutral together at both points is no different than running an extra strand of wire on the bare center tap conductor (neutral of the SEC) back to the transformer. There is a parallel path but nowhere to create a problem. No branches with outlets or user equipment.

It is different.

Here is why.

With your reference to the underground service lateral back to the transformer, there is but one conductor, the neutral, carrying the neutral and ground current back to the transformer (with the neutral and ground current being one and the same at that point).

Now, bonding the second structure to neutral with the separate grounding conductor (now required) provides two conductors back to the service at the first structure (the pole). One of those conductors is sized to INTENTIONALLY carry the full current and the other is sized to carry any UNINTENTIONAL ground current. Now suppose that the neutral conductor is damaged underground (it happens quite often) or that there is a loose or otherwise bad or poor connection of the neutral conductor on either end.

Now, with one of the conditions mentioned above on the neutral, ALL, or MOST, of the neutral current is going to be trying to go back on that-now-undersized ground conductor. That is not good at all.

[Vern Heiler]

It is different.

Now, with one of the conditions mentioned above on the neutral, ALL, or MOST, of the neutral current is going to be trying to go back on that-now-undersized ground conductor. That is not good at all.

That would require the driven ground to be broken at the same time. Also, if that were to happen, there would now be close to 240v on many of the 120v outlets. :eek: Even worse!

[Jerry Peck]

That would require the driven ground to be broken at the same time.

Nope.

Think about it a minute.

You have a low impedance path back to the service pole through the neutral conductor.

You have a not-quite-as-low impedance path back to the service pole through the ground conductor.

You also have a much higher impedance path back to the service pole from ground rod to ground rod through the earth itself.

All three of the above are tied together at both ends, making three distinct and separate paths.

If you, for an example, have a complete break in the neural wire, where will MOST of the current try to go? Through the lowest resistance path - through the now-undersized ground conductor.


Also, if that were to happen, there would now be close to 240v on many of the 120v outlets. :eek: Even worse!

Nope, there would still be 120 volts on each outlet if you lost the neutral conductor only, the ground conductor (being tied to the neutral) would serve as a grounding point). If you lost the neutral conductor AND the ground conductor, then the ground rod/earth would try to serve as that grounding point, not well, mind you, but it would make an effort.

With just the neutral lost, and all three tied together, you still would have 120 volts on each leg, and with unbalanced current loading, you might see some difference in voltage between the two legs, but that fourth ground wire would make up most of the difference.

Now, if you lost the neutral conductor AND the ground conductor, with no current, you would still have 120 volts at each leg, HOWEVER, as soon as you started to draw more current on one leg than on the other leg, the voltages on each leg would change with the current flow - they would both still add up to 240 volts, but you could have 80 volts on one leg and 160 volts on the other leg.

[Jeff Remas]

through the now-undersized ground conductor.

What is a ground conductor?

Is it a cross between the grounded conductor and the grounding conductor or just a shortened version of neither?

[Vern Heiler]

Now, if you lost the neutral conductor AND the ground conductor, with no current, you would still have 120 volts at each leg, HOWEVER, as soon as you started to draw more current on one leg than on the other leg, the voltages on each leg would change with the current flow - they would both still add up to 240 volts, but you could have 80 volts on one leg and 160 volts on the other leg.

That is what I was saying. Only the spread can be much higher... Xistor radio on one side and say a 1500 w hair dryer on the other! More than a 80 160 split.

If you can draw me a picture that shows the discribed condition that doesn't look like a wire with one of the strands seperated away from the bundle, I'll give you a star:) .

[Jerry Peck]

What is a ground conductor?

Is it a cross between the grounded conductor and the grounding conductor or just a shortened version of neither?


Anyone with the common sense to read what was written would know the answer, but for you, the answer is groundING conductor.

[Jerry Peck]

Now, if you lost the neutral conductor AND the ground conductor, with no current, you would still have 120 volts at each leg, HOWEVER, as soon as you started to draw more current on one leg than on the other leg, the voltages on each leg would change with the current flow - they would both still add up to 240 volts, but you could have 80 volts on one leg and 160 volts on the other leg.

That is what I was saying.


No, I said "Now, with one of the conditions mentioned above on the neutral, ALL, or MOST, of the neutral current is going to be trying to go back on that-now-undersized ground conductor. That is not good at all.".

To which you replied "That would require the driven ground to be broken at the same time." .

The above states that if you lost the neutral AND the ground.

This is what you said in response to what I said.


It is different.

Now, with one of the conditions mentioned above on the neutral, ALL, or MOST, of the neutral current is going to be trying to go back on that-now-undersized ground conductor. That is not good at all.


That would require the driven ground to be broken at the same time. Also, if that were to happen, there would now be close to 240v on many of the 120v outlets. :eek: Even worse!

Crimeny ... I know you will not follow that ... I'm even having a hard time following it. :eek:

Dang it's hard referring to he said he said he said he said ... :(

[Vern Heiler]

No, post# 11. You said, "Now, with one of the conditions mentioned above on the neutral, ALL, or MOST, of the neutral current is going to be trying to go back on that-now-undersized ground conductor. That is not good at all."

Which I contested due to the driven ground being still present providing a second path. Not a great path but a path.

But I have not received the diagram that shows how the condition is dangerous!

I understand there have to be rules, and rules can not be written to cover all circumstances.

[Jeff Remas]

Anyone with the common sense to read what was written would know the answer, but for you, the answer is groundING conductor.


Thank you for correcting your mistake and clarifying your post.

[Roland Miller]

Someone must have called him because we determined Jerry has no common sense. :p

[Jerry Peck]

Someone must have called him because we determined Jerry has no common sense. :p


Obviously not, because if I did I would stop replying to your posts. :p

But I cannot let incorrect information remain uncorrected. :rolleyes:

[Fred Warner]

But I cannot let incorrect information remain uncorrected. :rolleyes:

That being the case, you might want to explain to the posters that there's no such thing as the water pipe being the "primary" grounding electrode.

[John Arnold]

That being the case, you might want to explain to the posters that there's no such thing as the water pipe being the "primary" grounding electrode.

2006 IRC E3508.1.1 "Metal underground water pipe" says that under certain (pretty common) conditions, the water pipe can be considered as a grounding electrode. It then goes on to describe "supplemental" electrodes that are needed in addition.
So, if the water pipe is a grounding electrode, and the additional electrode(s) is/are "supplemental", wouldn't that make the water pipe "primary"?

[Jeff Remas]

2006 IRC E3508.1.1 "Metal underground water pipe" says that under certain (pretty common) conditions, the water pipe can be considered as a grounding electrode. It then goes on to describe "supplemental" electrodes that are needed in addition.
So, if the water pipe is a grounding electrode, and the additional electrode(s) is/are "supplemental", wouldn't that make the water pipe "primary"?

In this case, the word primary was used by me to make a point that the water pipe was being connected to first as the initial grounding electrode. There is no such thing as a primary or secondary grounding electrode, only a grounding electrode system. We are apparently back to splitting hairs unnecessarily not realizing that this is not a court of law and not direct text for a code book, but simple language for the purpose of allowing people to understand a situation.

[John Arnold]

...We are apparently back to splitting hairs unnecessarily not realizing that this is not a court of law and not direct text for a code book, but simple language for the purpose of allowing people to understand a situation.

And understanding the language is exactly what I was trying to do. Not split hairs. If you have two grounding electrodes, and one of them is referred to as "supplemental", it seems reasonable to me to regard the other one as "primary".
And, if you look at my post, you'll see I was responding to Fred, not you.

[John Arnold]

In this case, the word primary was used by me to make a point...

Actually, I can't even find where you used the word primary in this thread. Are you talking about another thread?

I think you're referring to "2nd ground rod debate".

[Fred Warner]

Not trying to "split hairs", just trying to be precise in an effort to be helpful.
Look at E3508.1 and notice the wording "where available" on the premises...it then goes on to say "metal underground water pipe", "concrete-encased electrode", "ground rings", "rod and pipe electrodes" and "plate" electrodes.
Speaking from my own experience, only, rarely are "ground rings", "rod and pipe electrodes" or "plate" electrodes "available" at the premises. What is "available" is the underground metal water pipe and the CEE. So where available, a metal underground water pipe must be used as part of the grounding electrode system. This is where the code requires that it be supplemented by an electrode listed in E3508.1.2 through E3508.1.5.
Typically, where I'm from, that supplemental electrode is an 8' ground rod driven the full depth and connected with a direct-burial listed acorn clamp and a grounding electrode conductor sized in accordance with poco rules which generally require a GEC of #4cu.
If a metal underground water pipe and/or a CEE were not "available" then plates, rings and rods or pipes would have to be used as per E3508.1.

And interesting amendment from the '02 code to the '05 code was the change in language from "where available" and "if available" to "where present". This meant that under the '02 NEC if the CEE was not available, don't bother with it. Of course when an underground metal water pipe is brought to a 1FD, it's always "available".
So the change in '05 is the wording "where present". This was a substantial change and when one considers the precision of language, it is worth mentioning.
So if a building or structure did not have an underground metal water pipe "present", the GES would consist of whatever was present and qualified as electrodes. It's in this sense that I make the statement that the water pipe is not the "primary" grounding electrode. :)

As far as the remark about it not being court, it's always best to use proper terminology so that in the likely event one ends up in court defending a certain circumstance, one uses proper terminology for those professionals present.

[Fred Warner]

My apologies for posting about grounding electrodes in the wrong thread. Oops. Please disregard. :o

[Fred Warner]

I have been seeing this quite a bit lately and want to know if there is any type of exception that I am not aware of.

There is a main panel box (service disconnect) at the power pole outside of the home. Ground wire from a driven ground rod runs into the panel and the grounds and neutrals are bonded.
This is the service and from what you describe it is in compliance. The service here is located at a structure.


......4 wires (2 hots, ground and neutral) run in conduit underground from the panel at the pole, into the home and feed the distribution panel box in the garage. Here, the ground and neutrals are again bonded. This I know is incorrect. However, is it allowed if there is another main disconnect switch installed in the garage panel box or is the first disconnect switch at the pole the only one that counts.
Take a look at 250.32 in the 05 code. When the grounded conductor is permitted to be regrounded it is when parallel paths are not present for neutral return current to flow on. If there was a water pipe, for example that went from the garage out to the power pole, this would be a parallel path for neutral current to flow on. With the 4th conductor, namely, the equipment grounding conductor being routed with the feeder assembly, it will be necessary to remove the connection that bonds the grounded and equipment grounding conductors together in the panelboard in the garage and separate the conductors in such a manner as to connect the EGC's to the EG bus and "float" the neutral conductors on the neutral bus. This assures that neutral return current is not intentionally imposed on the equipment grounding conductor. Also, this remote panelboard is required to have a grounding electrode system present if it has more than 1 branch circuit connected to it. :)
The '08 code is much more strict in an obvious attempt to minimize problems arising out of mis-use of 250.32 in earlier editions.


I just can't understand why if it is incorrect, why I am seeing it so often; especially in the municipalities.

Thanks,
Jesse

250.32 is an often-times misunderstood area in the code. Many installers are not aware that the grounded conductor is a current-carrying conductor.

[Jerry Peck]

And interesting amendment from the '02 code to the '05 code was the change in language from "where available" and "if available" to "where present". This meant that under the '02 NEC if the CEE was not available, don't bother with it. Of course when an underground metal water pipe is brought to a 1FD, it's always "available".
So the change in '05 is the wording "where present". This was a substantial change and when one considers the precision of language, it is worth mentioning.
So if a building or structure did not have an underground metal water pipe "present", the GES would consist of whatever was present and qualified as electrodes. It's in this sense that I make the statement that the water pipe is not the "primary" grounding electrode. :)


Fred,

In addition to what you said above, the 2002 NEC "allowed" a concrete encased electrode to "not be available" by nature of pouring the concrete *before* the electrician is on site, regardless of the fact that it "was present".

The 2005 wording change to "if present" from "if available" meant that the concrete encased electrode is now required to be used, no getting around it, "if present". As very few structures do not have steel rebar in their footings, that means that all (but those very few) structures are now required to have the steel used as a concrete encased electrode.

[Roland Miller]

[quote=Jerry Peck;72459]Fred,

In addition to what you said above, the 2002 NEC "allowed" a concrete encased electrode to "not be available" by nature of pouring the concrete *before* the electrician is on site, regardless of the fact that it "was present".

This is only someone's opinion of what they would have liked it to mean. The people that actually understood the NEC never had this opinion.

[Jerry Peck]

This is only someone's opinion of what they would have liked it to mean. The people that actually understood the NEC never had this opinion.


Roland,

Not only my opinion, but the opinion of NFPA instructors who discussed this at IAEI seminars. I would say that if anyone "actually understood the NEC" it would be those people.

This is from the 2005 NEC Commentary:

"Because the installation of the footings and foundation is one of the first elements of a construction project and in most cases has long been completed by the time the electric service is installed, this revised text necessitates an awareness and coordinated effort on the part of designers and the construction trades in making sure that the concrete-encased electrode is incorporated into the grounding electrode system."

Guess they did not "actually understood the NEC" either? :rolleyes:

Roland, you really do need to stop and think before you respond: Is it your personal opinion or do you have documentation to back it up? If only your personal opinion, you really do not want to present it as 'the way people who understand it' think, because, apparently (based on your comments) you do not understand it, you are just spouting "your opinion".

[Roland Miller]

Show us some facts--otherwise it is just your opinion...:confused:

[Jerry Peck]

Show us some facts--otherwise it is just your opinion...:confused:

Let me get this straight here ... I am conversing with someone who thinks the NEC Handbook does not know what is going on and why?

Wow! Now I know why you are always so far off base!

Crimeny, and I thought this guy actually thought he knew something, and all this time I've been responding to someone who does not ... what a waste of my time. :rolleyes:

[Jeff Remas]

The NEC handbook is no different than the ICC commentaries in that unless they are adopted as code in a jurisdiction, they are not approved for reference in code compliance situations.

[Jerry Peck]

The NEC handbook is no different than the ICC commentaries in that unless they are adopted as code in a jurisdiction, they are not approved for reference in code compliance situations.

You are correct in that the handbooks and commentaries *are not* adopted as code. And, in fact, you will find that *I* never said they were.

HOWEVER ... you will also find that AHJ very much DO GO READ the handbooks and commentaries to see what the intent of the code was, and typically make their calls in accordance with those written intents. :)

Thus, are the handbooks and commentaries adopted? Nope, but they might was well be. :cool:

[Jeff Remas]

You can read them to help you understand intent for making a decision but cannot reference it as part of your decision.

Hence the AHJ must make calls on his/her own as needed since much of the code is subject to interpretation.

[Jerry Peck]

You can read them to help you understand intent for making a decision but cannot reference it as part of your decision.

Hence the AHJ must make calls on his/her own as needed since much of the code is subject to interpretation.

I understand that, that is what I was referencing in my post above ... AND ... once the AHJ has read and understood what the intent is, that it almost always (there will always be those few cowboys who do what they want when they want) make their interpretation defensible, which means in accordance with the intent as spelled out in the handbooks and the commentaries, and, if questions remain, they will call the authoring agency (such as the ICC, UL, etc.) for clarification.

One thing that Building Officials know is that they must be able to defend their interpretations and that their interpretations must have a legitimate basis. Otherwise, if they are challenge or questioned about it, they very will could be held PERSONALLY LIABLE for stepping outside their official duties as the Building Official. Which also means that the political entity for whom they work may well withdraw, and refuse to provide, legal representation. That means their legal representation comes out of their own pocket. Usually, but not always, that is enough to keep most Building Officials from making wild interpretations which go against the handbooks and the commentaries.

Which gets us back to what I said in my other post:

Thus, are the handbooks and commentaries adopted? Nope, but they might was well be. :cool:

[Jeff Remas]

Some municipalities have adopted the commentaries from the ICC just for that reason.

This is why I belong to the NFPA and the ICC. I can call and get a written opinion and or interpretation that I can file.