Some NEC Definitions - A repost

[Phil Graham]

In light of the persistently short-sided policies regarding linking exhibited on PSW that resulted in others' posts being removed, I voluntarily removed a post today and transitioned it here. Hopefully it is helpful for those looking to learn some of the vocabulary from the NEC:

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The code cycle I reference is the 2011 NEC, while being mindful of the upcoming 2014 cycle based on the 2013 code draft. In many cases I'm paraphrasing the code definitions and statements, please see the NEC for the full definition. If I quote the code directly, I'll indicate that by placing "quotes" around the text. Code quotes with brackets [ROP x-x] after them refer to quotes from the code in sections where I am quoting proposed changes for the 2014 code cycle. The proposed changes have improved definition clarity, and are worth mentioning.

This first post is definitions. All definitions for the NEC are in article 100 (NEC 100). These are selected set of definitions relevant to the code terminology that discusses generators and their grounding. These definitions are listed in numerical order such that they build on each other. Once it is clear that people grasp the definitions, we can move on to generators and grounding using the vocabulary of the code. Mike might end up splitting this out into a separate thread:

Terminology Definitions (NEC 100)

Bonding - "Connected to establish electrical continuity and conductivity." Connection of two electrically conducting elements together achieves two main purposes:

• A) It holds the points at the same voltage potential
• B) Serves as a path for current in the event that a voltage potential difference (e.g. from an external voltage source) creates a current flow.

Grounding - Physically connecting an electrical system to the contents of planet earth.

Grounding Electrode - the physical conductor that ties to planet earth to facilitate grounding

Grounded - An electrical conductor physically connected to the earth by nature of it being bonded to a grounding electrode or grounding electrode system

Grounding Electrode Conductor (GEC) - A conducting element used to connect a grounded conductor to a grounding electrode

Bonding Jumper - "A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected."

Ground Fault - "An unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit and the normally non–current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth. [ROP 5–11]"

Equipment Grounding Conductors (EGC) - The conductive path(s) that provides a ground-fault current path and connects normally non–current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both. [ROP 5–14a]

• Informational Note No. 1: It is recognized that the equipment grounding conductor also performs bonding.
• Informational Note No. 2: See 250.118 for a list of acceptable equipment grounding conductors."

Service - "The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served."

Separately Derived System - "A premises wiring system or portion of a premises wiring system other than a service. Power for such systems is derived from a source of electric energy or equipment with no direct connection from circuit conductors of one system to circuit conductors of another system, other than connections through the earth, grounding electrode(s), grounding electrode conductors, bonding jumpers used to connect grounding electrodes, equipment grounding conductors, metal enclosures, or metallic raceways. [ROP 5–20]"

Overcurrent Protective Device (OCPD) - A device that opens a circuit if the current rises above a certain amount. Think a circuit breaker or fuse.

Effective Ground-Fault Current Path - "An intentionally constructed, low-impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground-fault detectors. [ROP 5–6]"

Note that NEC, especially in older editions, plays overly loose with grounding or grounded where often the author meant to refer to bonding. The new, upcoming code cycle for 2014 is more consistent in its wording, but grounding terminology can still be found in circumstances that actually discussing bonding.

The code, and your local authority having jurisdiction (AHJ) are the ultimate authorities on electrical matters.

 

[John Roberts]

Re: Some NEC Definitions - A repost

It's been a while since the last time I was gonged..... It felt good...

The technical term for that forum action is chicken-sh__

Human safety is important.. in fact I said that in my post that was deleted.

JR

.

 

[Jay Barracato]

Re: Some NEC Definitions - A repost

It's been a while since the last time I was gonged..... It felt good...

The technical term for that forum action is chicken-sh__

Human safety is important.. in fact I said that in my post that was deleted.

JR

.

Sometimes I feel the reason for this alternative forum was to put all the Smart Asses in the same places, other times I feel it was to put all the Smart in one place.


edit- and I do like that someone is finally seeing the problems with using the same term for grounding and bonding

 

[Phil Graham]

Re: Some NEC Definitions - A repost

Sometimes I feel the reason for this alternative forum was to put all the Smart Asses in the same places, other times I feel it was to put all the Smart in one place.

Jay,

I think there's a fair amount of overlap in that Venn diagram ~~:smile: I wrote Doug a reply I hope is balanced, fair, and will be considered. [edit: that discoursive section of the thread was trimmed to the ether, le sigh...]

edit- and I do like that someone is finally seeing the problems with using the same term for grounding and bonding

Totally agreed. The 2013 draft is shaping up much better than previous editions in regards to use/misuse of these terms.

 

[Phil Graham]

Re: Some NEC Definitions - A repost

It's been a while since the last time I was gonged..... It felt good...

The technical term for that forum action is chicken-sh__

Human safety is important.. in fact I said that in my post that was deleted.

JR,

I know that you and I have not always gotten along, especially in regards to our individual capacities for discussing governmental policies/politics (mine is very low), but I'm on the same page with you when it comes to safety, and I'm glad to see you stick by your principles on this one.

 

[Silas Pradetto]

Re: Some NEC Definitions - A repost

Jay,

I think there's a fair amount of overlap in that Venn diagram ~~:smile: I wrote Doug a reply I hope is balanced, fair, and will be considered. [edit: that discoursive section of the thread was trimmed to the ether, le sigh...]



Totally agreed. The 2013 draft is shaping up much better than previous editions in regards to use/misuse of these terms.

While the NEC may be almost in the 2013 edition, many local regulating authorities do not use the newest version. Connecticut is still working with NEC 2005. Just an FYI.

 

[John Roberts]

Re: Some NEC Definitions - A repost

JR,

I know that you and I have not always gotten along, especially in regards to our individual capacities for discussing governmental policies/politics (mine is very low), but I'm on the same page with you when it comes to safety, and I'm glad to see you stick by your principles on this one.

There should be a lot of agreement between us about physical laws and "things". If we disagree is is probably about subjective things and we have different life experiences so should view things differently. Apparently the majority of the country does not agree with me about recent political choices. We'll see how that turns out. It is pointless for me to be feel bad about spilled milk.
===
After trading a few barbs about the the "rules" over at PSW, The sheriff himself re-posted the link to your article, perhaps after realizing it was the right thing to do.

[edit] now not only my post with the link, but my exchange with Doug about policy is all disappeared with only Doug's re-post of the link left remaining... as if he spontaneously posted it... interesting. Oh well, at least the information is out there. [/edit]

JR

PS: Theres an old saying about politics. If you are not a liberal when young there is something wrong with your heart. If you are not conservative after experiencing life there is something wrong with your brain. Note: I offer this for entertainment value not as some universal truth. Opinions vary

 

[Jay Barracato]

There should be a lot of agreement between us about physical laws and "things". If we disagree is is probably about subjective things and we have different life experiences so should view things differently. Apparently the majority of the country does not agree with me about recent political choices. We'll see how that turns out. It is pointless for me to be feel bad about spilled milk.
===
After trading a few barbs about the the "rules" over at PSW, The sheriff himself re-posted the link to your article, perhaps after realizing it was the right thing to do.

JR

PS: Theres an old saying about politics. If you are not a liberal when young there is something wrong with your heart. If you are not conservative after experiencing life there is something wrong with your brain. Note: I offer this for entertainment value not as some universal truth. Opinions vary

If you use those labels in the traditional sense, I can see that but over the last decade both groups have changed into something I don't recognize.

I did say for a long time I was liberal on the local scale but conservative on the national scale.

Now I think anyone who insists on either label as a true description must have been dropped too many times as a baby.

 

[John Roberts]

Re: Some NEC Definitions - A repost

Sometimes I feel the reason for this alternative forum was to put all the Smart Asses in the same places, other times I feel it was to put all the Smart in one place.


edit- and I do like that someone is finally seeing the problems with using the same term for grounding and bonding

IIRC this forum was born out of frustration with how PSW was being operated. I can only speak for myself... and I still post over there, despite multiple run-ins with one of the mods. If anything I find it a little irritating when people post the same questions to both forums, but me being irritated is a normal state.

JR

PS: in the context of circuit design (inside the chassis) I wouldn't mind if ground was dropped completely from the vocabulary or stopped at the chassis, since it engenders far more misconceptions than reality about what ground is or even means wrt circuit behavior. I don't doubt there is confusion outside the chassis too.

 

[John Roberts]

Re: Some NEC Definitions - A repost

If you use those labels in the traditional sense, I can see that but over the last decade both groups have changed into something I don't recognize.

I did say for a long time I was liberal on the local scale but conservative on the national scale.

Now I think anyone who insists on either label as a true description must have been dropped too many times as a baby.

As i said I offered that for "entertainment" value. It is an old saying, while it paints an empathetic idealistic bias vs a more practical real world bias.

I am not big on political labels, I only know that I am not sympathetic to the thinking and behavior of the current administration. I did vote against them twice, but I was in the minority both times.

JR

PS: I did hit the floor hard with head a couple times playing basketball... maybe that explains it.

 

[Phil Graham]

Re: Some NEC Definitions - A repost

While the NEC may be almost in the 2013 edition, many local regulating authorities do not use the newest version. Connecticut is still working with NEC 2005. Just an FYI.

The code cycle that your AHJ uses is a totally separate issue than quoting the new code draft for clarity of definitions. Bonding, Grounding, etc. aren't physically any different today than they were for the 2005 code cycle, the just happen to be clearer in the new code cycle ~~:smile:

Now, having conversation with the AHJ out of the 2005 code cycle would be harder because the older wording is not as cogent as in the new cycle.

 

[Phil Graham]

Re: Some NEC Definitions - A repost

There should be a lot of agreement between us about physical laws and "things". If we disagree is is probably about subjective things and we have different life experiences so should view things differently.

JR,

The thing is I don't think we would disagree that much politically. I'm registered independent, fairly libertarian minded, and a fiscal conservative. That doesn't seem particularly orthogonal to your views.

When I say my capacity for discussing about politics is low, I mean literally that ~~:smile:

To me, discussing politics is like discussing the properties of speaker cones made out of unobtanium. We don't have unobtanium, so I'll reserve my brain cells for things that I can effectuate in daily life. Major political parties, near as I can tell, are primarily interested with maintaining power stasis and/or sniping at each other. Once and a while, when real crises hit, they align to do something that hopefully isn't purely reactionary, but often tends that way.

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As a practical example, I have strong feelings about nuclear power, and by extension, nuclear power policy. I even studied some radiochemistry as part of my minor in graduate school. I personally think that nuclear power is an inevitability for much industrial undertaking. I also think that the way we do nuclear power currently is rather frightening, and I would prefer to see a paradigm shift in the way we approach the problem from an engineering standpoint. However I have no way to personally effectuate a paradigm shift in nuclear power generation, and frankly neither do the "evangelists" who are trying currently. So I expend very little effort on this topic.

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There are some things that I can "move the needle" on, and so these things are where I focus:

• I work to love my wife well and respond to her in kindness
• I can clean up my community spaces and be involved in my neighborhood
• I can give money to my church and help insure that most of it goes back out into the community
• I can watch my waistline and eat healthy, nutritious food
• I live connected to the people life brings across my path

Last week my old neighbor was evicted. It was partly his own stupid fault, and partly the dysfunctional landlords. He didn't have enough room to take everything (across the country) with him in his U-Haul, and was distraught at the landlords getting some of his stuff. Within a couple hours I was able to rally several people to help get a meaningful amount of his remaining stuff off site and into a friend's shed. We'll figure out how to sell the remaining stuff and give him back the money. He might not strictly "deserve" the help, but it was the gracious, kind thing to do. Plus, we've all had bad times in life where a hand makes all the difference.

Doing the things above are time consuming. Helping my old neighbor on a whim totally re-shaped last weekend, for instance. By spending the time on local, achievable things I find a schedule devoid of room to tilt at political windmills and/or bemoan policies I wish were different, but aren't.

 

[John Roberts]

Re: Some NEC Definitions - A repost

I understand and miss the good old days when I too could ignore national politics between elections. While it is trite to say it is different this time, and politics has always been an ugly sport, the consequences of bad choices at the highest levels seems more consequential now. That said I grew up during the cold war and international relations certainly had consequences back then too. This is probably yet another side-effect of getting older (cognitive decline ).

I'm with you on nuclear power (I think?) and the unfortunate choices made that contributed to the Japanese disaster (before, during, and after) seems to have shifted popular opinion even more strongly against it. One of my conspiracy nut friends at the gym was telling me that CA is now glowing in the dark and the government is hiding it. I expected nuclear energy to be eclipsed (by something better) within a century, now it looks like it will fall out favor much sooner. (I know your criticisms are more than just that, and agree (?) that it is an opportunity missed).

While you probably didn't mean too, you made an argument for local and states rights vs. expanding federal power. Local problems and local questions are better answered and handled locally by the people directly affected. The federal should be busy enough dealing with the outside world, while opinions vary about how well they are handling that.

I'll stop now, but one more comment in passing. I regret that people like you who are smart enough and educated enough to understand the larger picture withdraw from the debate. That said I also understand why. 99.9% of political discussion is sound bites engineered to prevent any real exchange of information and ideas. Instead it appeals to emotional responses. Unpleasant business and not very linear while rational only in appealing to the lowest common denominator of individual's perceived self-interest.

When in doubt do what's right.

JR

 

[John Roberts]

Re: Some NEC Definitions - A repost

Bonding Jumper - "A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected."

Ground Fault - "An unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit and the normally non–current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth. [ROP 5–11]"

Equipment Grounding Conductors (EGC) - The conductive path(s) that provides a ground-fault current path and connects normally non–current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both. [ROP 5–14a]

• Informational Note No. 1: It is recognized that the equipment grounding conductor also performs bonding.
• Informational Note No. 2: See 250.118 for a list of acceptable equipment grounding conductors."

[B


Effective Ground-Fault Current Path - "An intentionally constructed, low-impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground-fault detectors. [ROP 5–6]"

Does the ground bonding deal with robustness by specifying a wire gauge for expected fault current? I guess that's implicit.

UL product safety testing has an internal ground bonding specification that defines an acceptable voltage rise due to conductor resistance for a given current, to mitigate concerns about incidental exposure to voltage. So the ground bonding must both conduct long enough to trip the mains breaker, while not allowing too much voltage rise in the process of doing that.

IIRC this bonding spec was only for external panel connections labelled as "ground". Some manufacturers dealt with this by labeling external ground connections as 0V or anything other than "ground". It's not just a style decision, it's weaseling on a safety spec. I once had to redesign a product's PCB because a PCB ground trace could not pass the UL bonding test.

JR

[edit- there are cases like floating transformer outputs for constant voltage systems, where 0V is not connected to ground and shouldn't be. So 0v is the correct nomenclature). [/edit]

 

[Phil Graham]

Re: Some NEC Definitions - A repost

Does the ground bonding deal with robustness by specifying a wire gauge for expected fault current? I guess that's implicit.

There are whole sections that address the sizing of EGC and GEC. I don't have the section numbers in my head at the moment.

[edit- there are cases like floating transformer outputs for constant voltage systems, where 0V is not connected to ground and shouldn't be. So 0v is the correct nomenclature). [/edit]

JR,

Was their any particular reason why one leg of the CV system wasn't bonded to ground in the similar manner of 3ph grounded delta services?

 

[John Roberts]

Re: Some NEC Definitions - A repost

JR,

Was their any particular reason why one leg of the CV system wasn't bonded to ground in the similar manner of 3ph grounded delta services?

This was due to customer preferences. When Peavey entered that market we first engineered auto-formers to generate the 70v/100V audio outputs. For power transfer auto-formers are more efficient than isolated winding transformers, so can be smaller, lighter, and cheaper, a big deal for cost in these low technology products.

The push-back from the market was strong. In the install business, labor and service calls are significant for contractors/installers. The floating CV output is more tolerant of inadvertent short circuits between any one leg to ground. These shorts could occur during initial installation or later from some inadvertent insulation failure when some other worker is messing around near the CV wiring. With a grounded CV output winding there is a 50-50 chance that such grounding shuts down the system and the other 50% causes a ground loop. With the floating output, the system is still fully functional. So smoother installation, and eliminating a significant number of wiring related service calls, was compelling for that market, not to mention that they are resistant to change.

I was surprised because the install market was also very price sensitive, and we offered a cheaper equivalent solution. In fact auto-formers delivered slightly better LF response (higher LF saturation levels) than full isolated transformers, but the customer is always right, so we redesigned every output transformer for full floating output windings.

Since install products often had I/O screw terminals with sundry terminals labelled "ground", every one of these grounds needed to support carrying tens of amps to the line cord ground with only modest voltage rise, in case a mains fault occurs in a different product connected to the properly grounded one.

The customer is always right. It's far easier to give them what they want, than convince them to want something else, even if auto-formers would reduce global warming.

JR