earthing. the ECMag article

[K8MHZ]

Then why does the code still use the term "equipment grounding conductor" when it is very clear that the term should be "equipment bonding conductor"?

According to the definitions, the EGC connects equipment to ground at some point. (".....metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor or both.") So, if there is no ground, there could be no EGC. An EGC does perform bonding (see FPN) but to a grounded device or conductor.

So, if you have a non grounded system (like in a motorhome) you would not be able to have an EGC, as defined.

 

[Strathead]

Then why does the code still use the term "equipment grounding conductor" when it is very clear that the term should be "equipment bonding conductor"?


The NEC has eliminated much confusion starting in the 08.

Ground - The earth.

Bonded - Connected to establish electrical continuity and conductivity.

That's from the 08 NEC. I see no confusion. The new definitions are pretty straight forward.

To me, your suggestion is a bit confusing.

And grounded conductor. In English ground, grounded, and grounding are variations of the same word. They should not have two distinct meanings. To K8HHZ My suggestion was a quick wing it to represent the problem not a "serious" proposal.

 

[Strathead]

Then why does the code still use the term "equipment grounding conductor" when it is very clear that the term should be "equipment bonding conductor"?

According to the definitions, the EGC connects equipment to ground at some point. (".....metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor or both.") So, if there is no ground, there could be no EGC. An EGC does perform bonding (see FPN) but to a grounded device or conductor.

So, if you have a non grounded system (like in a motorhome) you would not be able to have an EGC, as defined.

So are you trying to say that you don't need to bond things together in a motor home, because there is not earth ground? If not, then I think you are helping to make our poiint that the code is confusing in this area.

 

[K8MHZ]

So are you trying to say that you don't need to bond things together in a motor home, because there is not earth ground? If not, then I think you are helping to make our poiint that the code is confusing in this area.

I am not saying that at all. Yes, BONDING is essential and and the act of doing so is correctly called bonding, not grounding.

Where is the confusion?

 

[Strathead]

I am not saying that at all. Yes, BONDING is essential and and the act of doing so is correctly called bonding, not grounding.

Where is the confusion?

Absolutely no offense is meant, but color me stupid, because I am thoroughly confused about all of the terms and their use. Don't get me wrong I believe I understand the fundamentals of article 250, but I am only about 205 sure of much that has been posted in this thread.

 

[K8MHZ]

Absolutely no offense is meant, but color me stupid, because I am thoroughly confused about all of the terms and their use. Don't get me wrong I believe I understand the fundamentals of article 250, but I am only about 205 sure of much that has been posted in this thread.

I'm sure it doesn't help matters that the NEC changes 250 so much practically every code cycle.

Add to that, the NEC has its share of legalese and a tendency to make the reader jump from article to article does tend to convolute things a bit.

I think the recent changes have cleared things up a bit. If non-grounded applications of an EGC got changed to being called an 'equipment bonding conductor' I would have no problem with that, and it indeed is at least in Article 551. But, where in the NEC does it address an EGC being used where there is no grounding (earthing) present? Even floating buildings are required to be grounded.

Take note of 551.56. It addresses the connections of non-current carrying to the chassis as bonding, not grounding. The rule is that the exposed equipment be bonded to the grounding terminal or enclosure of the distribution panelboard. That does not mean the equipment shall, at all times, be connected to the earth (which would be tough while under way). It just means that it needs to be bonded together and connected to a terminal that will be connected to the earth when powered by a grounded source.

Now back up to 551.55(B). Notice the distinction between equipment grounding and bonding conductors?

I think they are starting to get it right.

 

[don_resqcapt19]

According to the definitions, the EGC connects equipment to ground at some point. (".....metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor or both.") ...

That is also part of the problem as it strongly implies the grounding system is part of the fault clearing path. The conductor that the code calls the EGC does not need to be connected to earth to do its job. It is indirectly connected to earth on grounded systems, but the connection to earth has nothing to do with the function of the conductor.

... So, if you have a non grounded system (like in a motorhome) you would not be able to have an EGC, as defined.

Equipment Bonding Conductor would work for the name of that conductor.

 

[K8MHZ]

That is also part of the problem as it strongly implies the grounding system is part of the fault clearing path. The conductor that the code calls the EGC does not need to be connected to earth to do its job. It is indirectly connected to earth on grounded systems, but the connection to earth has nothing to do with the function of the conductor.
Equipment Bonding Conductor would work for the name of that conductor.

Well, I don't see the same implication. All I see is a distinction. It is a wide spread myth, very common among ham radio operators, too, that electricity seeks the path of least resistance to ground. Of course, we both know that is not true.

Equipment grounding conductor and equipment bonding conductor are both already used.

Conductor that bonds non-current carrying metal and is connected to earth, equipment grounding conductor.

Conductor that bonds non-current carrying metal and is not connected to earth, equipment bonding conductor.

Is that not the way it is done in the 08 and newer NEC books?

We could also have just a plain bonding conductor, one that connects current carrying conductors together, but I haven't seen that in the NEC.

 

[K8MHZ]

Equipment Bonding Conductor would work for the name of that conductor.

I agree, and that's what it would be as defined by the current NEC editions.

 

[don_resqcapt19]

Well, I don't see the same implication. All I see is a distinction. It is a wide spread myth, very common among ham radio operators, too, that electricity seeks the path of least resistance to ground. Of course, we both know that is not true.

Yes, but the use of the term EGC leads many to believe all you have to do to make something safe is to connect it to earth.

Equipment grounding conductor and equipment bonding conductor are both already used.

The fuction of what we call the EGC is bonding not grounding. Yes it does (or should) result in an indirect connection to earth but that is not its purpose. Its purpose is to provide a fault clearing path and that purpose is the same for either a grounded or ungrounded system.

Conductor that bonds non-current carrying metal and is connected to earth, equipment grounding conductor.

Conductor that bonds non-current carrying metal and is not connected to earth, equipment bonding conductor.

They both are bonding conductors and the issue is the use of the word grounding.

Is that not the way it is done in the 08 and newer NEC books?

The are both used for conductors that are directly or indirectly connected to earth.

We could also have just a plain bonding conductor, one that connects current carrying conductors together, but I haven't seen that in the NEC.

Not sure I understand that one.

If you talk to our friends to the north, you will find that they will tell you that a lot of the confusion about grounding went away when they replaced the term Equipment Grounding Conductor with the term Equipment Bonding Conductor.

 

[jumper]

I am in total favor of getting rid of any reference to "ground" that has nothing to do with dirt.

Bonding is so much simpler to understand IMHO.

I gotta admit that at times: I do not even really understand why we connect our electrical systems to a piece of metal in the dirt.

Before anyone explains: Yeah, I know, common reference, lightning, and such...250.4, but the truth is that I just do it 'cause the NEC says to. The more I think about it -the whole grounding/earthing concept seems like a combination of wishful thinking and voodoo reasoning.

 

[K8MHZ]

The more I think about it -the whole grounding/earthing concept seems like a combination of wishful thinking and voodoo reasoning.

I like that.

I'll use it to explain why we only need two spikes in a sand pit to comply with the NEC's grounding requirements.

Understanding the science is easy. It's the reasoning that throws most of us for a loop.

My inspector pal and I talk about this stuff all the time. The ONLY thing that earthing has accomplished to any reasonable level at all is providing a voltage reference.

That's it. The NEC's earthing requirements do little if anything to clear faults, prevent shocks or protect us from lightning.

It's the NEC's bonding requirements that lead us (for the most part) to safety.

What I don't understand is why we would want to increase harmful voltages intentionally.

Think about this. We (theoretically) install a service in a structure with a basement but make no connection to ground at the service. The only connection to the ground is at the pig, some 300 feet away, and it's just a single ground rod.

What would the available fault potential be? Think about working in a finished wood structure. Do you get a shock when you grab a bare hot wire and are not touching any other metal? No? That is because of the resistance between your feet and the neutral is very high because of the vinyl, wood, etc.

Down in the basement there will be some resistance between the floor and the neutral, too. Usually it's much less and it's easy to get poked. Without ground rods at our theoretical service, we get to include 300 feet of earth in series with an old single ground rod for our total resistance.

Now we decide to comply with the NEC and poke two rods in the ground right next to the basement wall. Are we not decreasing the resistance between the concrete floor and the neutral by doing so? And, by doing so providing MORE available fault current if a person completes a path from the floor to the hot wire?

I think that question is the best argument for a prudent explanation of earthing requirements.

If we did away with all earth connections, the worst thing that would happen would be that we would lose our voltage reference. Other things would happen, too, but losing that reference would be a bad, bad thing. In most cases, people wouldn't even notice that their system was not connected to the earth.

 

[don_resqcapt19]

If the system is grounded at any point, I belive that the path through the earth and anything connected to the earth will have a low enough resistance to carry enough current that you could receive a fatal shock. Even the capacitance coupling on an ungrounded system can supply enough current to kill.
Yes, a grounding electrode system closer to you will provide a better path for current, but I bet there would be very little difference in the acutal current through your body, unless you are within a few feet of the grounding electrode.

 

[jumper]

I like that.

Understanding the science is easy. It's the reasoning that throws most of us for a loop.

Are you saying I am not crazy when I ponder this?

The ONLY thing that earthing has accomplished to any reasonable level at all is providing a voltage reference.

That I understand.

That's it. The NEC's earthing requirements do little if anything to clear faults, prevent shocks or protect us from lightning.

True

It's the NEC's bonding requirements that lead us (for the most part) to safety

This is what I understand.

If we did away with all earth connections, the worst thing that would happen would be that we would lose our voltage reference. Other things would happen, too, but losing that reference would be a bad, bad thing. In most cases, people wouldn't even notice that their system was not connected to the earth

So, beyond the importance of reference, why am I connecting my service to dirt?:?

 

[K8MHZ]

If the system is grounded at any point, I belive that the path through the earth and anything connected to the earth will have a low enough resistance to carry enough current that you could receive a fatal shock. Even the capacitance coupling on an ungrounded system can supply enough current to kill.
Yes, a grounding electrode system closer to you will provide a better path for current, but I bet there would be very little difference in the acutal current through your body, unless you are within a few feet of the grounding electrode.

Remember, all earth is not the same. In sandy soil, like ours, proximity is more important than people with normal dirt. Our sand is like little beads of glass insulation. I don't know how deep it is, but it's goes as least as deep as any basement I have seen here.

When I get chance, I'll take some measurements from one side of my house to the other. If I can see a difference that would indicate to some extent the 'earth resistance' between the side of the house with the electrodes and the other. (My electrodes are water pipe. Probably 40 feet of contact on the well and at least 20 feet from the house to the garage spigot).

 

[K8MHZ]

So, beyond the importance of reference, why am I connecting my service to dirt?:?

To get that green sticker!!!

I did a house a while back built on sand. I pushed both ground rods in by hand. No hammer needed.

I did get my sticker, though! :lol:

Seriously, the NEC requirements for at least a minimal electrode system at every service and the NESC requirements for electrodes at various places work together to comprise a huge grounding electrode system that is very good for a voltage reference. I am to understand that the existence of such a stable reference aids in the maintenance of voltage stability. Since this is of great importance to the POCOs, and really of no value to us, all we usually care about is compliance.

When we start questioning the reasoning behind earthing, it is from the perspective of the utilization end of the system at a single premises. From that perspective, earthing as required is a big fail. It does nothing for safety, as many have pointed out.

It may very well be that the NEC requirements for earthing are meant to coincide with the NESC requirements.

 

[don_resqcapt19]

Remember, all earth is not the same. In sandy soil, like ours, proximity is more important than people with normal dirt. Our sand is like little beads of glass insulation. I don't know how deep it is, but it's goes as least as deep as any basement I have seen here.

When I get chance, I'll take some measurements from one side of my house to the other. If I can see a difference that would indicate to some extent the 'earth resistance' between the side of the house with the electrodes and the other. (My electrodes are water pipe. Probably 40 feet of contact on the well and at least 20 feet from the house to the garage spigot).

I am sure there will be differences, but I would bet that none would be so high as to limit the current from contact with a 120 volt source to less than 30 mA. If the circuit can flow enough current to kill, it really doesn't make any difference how much more current could flow on the circuit as the result of a lower impedance path.

 

[K8MHZ]

I am sure there will be differences, but I would bet that none would be so high as to limit the current from contact with a 120 volt source to less than 30 mA. If the circuit can flow enough current to kill, it really doesn't make any difference how much more current could flow on the circuit as the result of a lower impedance path.

I disagree.

We are talking about available current, not fixed current.

The resistance of a person and their clothing must be factored in. If only 30mA were available, less than that would pass through a person. If 100mA were available, it is more likely that 30mA would pass through a person than if there were only 30mA available.

 

[don_resqcapt19]

I disagree.

We are talking about available current, not fixed current.

The resistance of a person and their clothing must be factored in. If only 30mA were available, less than that would pass through a person. If 100mA were available, it is more likely that 30mA would pass through a person than if there were only 30mA available.

No we are not talking about available or fixed current. We are really taking about the current limiting of the earth do to its impedance. I really doubt that the impedance of the path via earth would be high enough to limit the current from contact with a 120 volt source to a "safe" value.
The amount of current available doesn't make any difference. The only things that matter are the votlage and the impedance of the path.

 

[K8MHZ]

No we are not talking about available or fixed current. We are really taking about the current limiting of the earth do to its impedance. I really doubt that the impedance of the path via earth would be high enough to limit the current from contact with a 120 volt source to a "safe" value.
The amount of current available doesn't make any difference. The only things that matter are the votlage and the impedance of the path.

So, are you trying to say that two ground rods do, or don't make a difference?