Where did grounding myths come from?

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mbrooke

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I still hear people saying electrons go to ground and ground rods clear a fault. But that myth has to come from somewhere. Did the NEC allow ground rods to clear a fault in the past? Was it TT earthing in Europe what gave the CMP a false impression of ground rods? Or was it oversimplification?


Starting at 1:06:45, I found it thought provoking that even CMP members was in the dark:


https://www.youtube.com/watch?v=mpgAVE4UwFw


I will admit I believed the same for years only up until this video.
 
I was pondering the exact same thought last week.....and not just how they came about but why they persist with such prevalence. Maybe it follows from watching cloud to ground lightning "go to ground"? That all I got.
 

mbrooke

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I was pondering the exact same thought last week.....and not just how they came about but why they persist with such prevalence. Maybe it follows from watching cloud to ground lightning "go to ground"? That all I got.


Best I could ponder were text books over simplifying a complex subject. :?
 
Best I could ponder were text books over simplifying a complex subject. :?

Books really help further these myths and always seem to get it wrong. The PV installation and design manual put out by solar energy international shows (and states in words ) a sketch of someone not getting shocked because the metal array they are holding onto is dirted and the current is "choosing" that path to dirt. I recently saw one of those "how to wire" books and it had a great one. Under the grounding section it said something like, "the earth has a unique ability to absorb a large number of electrons which greatly decreases shock risk from energized equipment."
 

mbrooke

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Books really help further these myths and always seem to get it wrong. The PV installation and design manual put out by solar energy international shows (and states in words ) a sketch of someone not getting shocked because the metal array they are holding onto is dirted and the current is "choosing" that path to dirt. I recently saw one of those "how to wire" books and it had a great one. Under the grounding section it said something like, "the earth has a unique ability to absorb a large number of electrons which greatly decreases shock risk from energized equipment."


That is exactly what I am talking about. I seriously think its intentional.
 

don_resqcapt19

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In my opinion a lot of this confusion for 600 volt and under systems comes from the code using the term Equipment Grounding Conductor for the fault clearing conductor. The use of the word "grounding" in this term implies that the connection to the earth is the important function of the fault clearing conductor. That and the fact that many electricians do not really understand the electrical theory of fault clearing...the part that says the current has to get back to its source.
 

mbrooke

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But it is not a myth with higher voltages.

A ground rod could cause the OCPD to open on a 13.8kv line.

Its not a myth with TT earthing either which is used all over the world. In fact if you have an RCD/GFP breaker or set your zero sequence pick values low enough on protective relays just about any ground rod will pop a circuit.


But at the 600 volt and under level where most breakers are none GFP its a dangerous myth. In addition to TT earthing being forbidden in the NEC.
 

mbrooke

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In my opinion a lot of this confusion for 600 volt and under systems comes from the code using the term Equipment Grounding Conductor for the fault clearing conductor. The use of the word "grounding" in this term implies that the connection to the earth is the important function of the fault clearing conductor. That and the fact that many electricians do not really understand the electrical theory of fault clearing...the part that says the current has to get back to its source.

Ground wires should be called "bond wires"
 

kwired

Electron manager
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Use of terms "ground" or variations of that base word or "earth" do not help. Then we use conductors that are "grounded" or "earthed" at some point as a "return path" for fault current, which is an accurate statement - but easily misunderstood. What is misunderstood is that the conductor whose function is fault clearing only isn't there so much to connect to earth, as it is there to return fault current to the source - it just happens to be a conductor that is normally at "ground potential".


Lightning is not necessarily trying to get back to earth though many believe this is what is happening in almost all lightning events. It is simply opposite charges in two different places and once the voltage is high enough for electrons to jump the gap or the two areas finally move close enough for jumping the gap we have discharge. Lightning does sometimes jump from ground to cloud instead of from cloud to ground. Lightning also jumps from cloud to cloud instead of to ground.
 

electricalist

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dallas tx
For me the term grounding electrode to a water pipe within the first 5' that it enters the building some how implies that the pipe being in the ground has something to do with why it needs to be connected. At least that's my mis understanding.
 

jap

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For me the term grounding electrode to a water pipe within the first 5' that it enters the building some how implies that the pipe being in the ground has something to do with why it needs to be connected. At least that's my mis understanding.

So your saying the water pipe being in the ground has nothing to do with it? or that you need to get on it before it encounters any fittings or unions?
 

electricalist

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dallas tx
Exactly ,if we bond the water line to the grounded conductor for safety then if there is any non conductive connections after that point then what does it protect? The water? Or is it a semi ground rod that needs to be supplemented . the water heater ought to have an e.g. bonding it.
 

mbrooke

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Even when people know that current goes to the transformer, I still see old school thinking driving the debate. Ground rods and water bonds are always obsessed about for pages but the soil contact part is worthless.

We bond to water pipes in case they were to become energized and maintain equal potential. POCOs get free noodle if its municipal metal piping. That's all there is to it.



Personally I believe a UFER is just as important as a water bond in the even of an open service neutral, but I rarely see that connected. All the fixation is on soil which does absolutely nothing about anything. Lightning yes, but outside of something that may never happen forget about it.


The code is to much obsessed with earthing and not concerned about bonding.
 

mbrooke

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Use of terms "ground" or variations of that base word or "earth" do not help. Then we use conductors that are "grounded" or "earthed" at some point as a "return path" for fault current, which is an accurate statement - but easily misunderstood.

I think it boils down that at one point in time the CMP literally thought soil did everything for an electrical system. Truth is outside of indirect lightening it does nothing. And a direct lightning hit will make no difference.

Earth does not soaking up electrons, does not provide equal potential, does not stabilize or anything else. Statements like "earthing" via water pipe or water pipe electrode are misleading. We do not bond water lines so much because part of the pipe is in contact with soil, we bond for reasons far more important: clearing a fault and maintaining equal potential.



In fact the entire goal is to create a faraday cage within the structure, not gain access to everything that just so happens to touch soil like myths lead us to believe. Soil electrodes vs faraday cage are two very different concepts and the a latter is what protects life and property. People should view every building as sitting on a giant rubber mat and then consider earthing electrodes in the picture after everything is bonded within the structure.



What is misunderstood is that the conductor whose function is fault clearing only isn't there so much to connect to earth, as it is there to return fault current to the source - it just happens to be a conductor that is normally at "ground potential".


Exactly :thumbsup:

And I would further argue that the EGC isn't so much at ground potential but rather at the same potential as the faraday cage in the building. Further, during a fault the voltage drop across the EGC will produce a voltage potential between the faulting chassis other bonded objects like water pipes which will usually be half the normal line to neutral voltage.


The only time the statement holds some truth is in a TT earthing system. TT earthing is used exclusively in some parts of the world like France. And yes the earth is used for fault clearing, and earth wire may be a correct term for an EGC, however the soil is not absorbing electrons. Rather it is just conducting them back to the transformer. TT earthing is just using the soil an EGC, nothing more than that. And because soil is so poor at conducting electricity in order for TT earthing to work you need a low level deferential RCD breaker.




Lightning is not necessarily trying to get back to earth though many believe this is what is happening in almost all lightning events. It is simply opposite charges in two different places and once the voltage is high enough for electrons to jump the gap or the two areas finally move close enough for jumping the gap we have discharge. Lightning does sometimes jump from ground to cloud instead of from cloud to ground. Lightning also jumps from cloud to cloud instead of to ground.


Very true. Its not the earth itself, but difference of potential between cloud to ground. Many people will say "drive a ground rod for lighting protection" Well, truth is if you want lightning protection don't look at the NEC. Look at the NFPA 780. You would be surprised what lightening protection really involves.
 

mbrooke

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Exactly ,if we bond the water line to the grounded conductor for safety then if there is any non conductive connections after that point then what does it protect? The water? Or is it a semi ground rod that needs to be supplemented . the water heater ought to have an e.g. bonding it.


Nothing, and code should mandate all jumpers be bonded. The fact the water line is in contact with the soil means squat. The fact you have unboned pipes is the real danger. Same for no UFER grounding. Its no that the UFER is in contact with earth, its if your neutral breaks the slab of your home will be at opposite potential of everything else.
 

kwired

Electron manager
Location
NE Nebraska
Exactly ,if we bond the water line to the grounded conductor for safety then if there is any non conductive connections after that point then what does it protect? The water? Or is it a semi ground rod that needs to be supplemented . the water heater ought to have an e.g. bonding it.

We have two things that need bonded with the water pipe situation.

1. if there is 10 feet or more of metallic pipe in contact with the earth NEC requires us to use it as part of the grounding electrode system part III of art 250.

2. metal water piping system inside the structure must be bonded to the electrical system per part V of art 250.

It is possible to kill both birds with one stone with a carefully placed connection to the electrical system and if there is no electrical isolation between interior piping system and the portion of piping considered to be part of the grounding electrode system.

It has been close to 20 years or so now since they started requiring us to connect the GEC within 5 feet of entry for a metal underground water pipe. I think it was either 1993 or 1996 when this change came about, but am leaning toward 1993. Before then all metallic piping systems were much more common then they are now, and they allowed you to connect the GEC to any convenient place on the piping system instead of making you run it to within 5 feet of entry to the building. You were going to have a reliable path to the underground portion of piping until non metallic piping started to appear. Only thing they did make you do is add a bonding jumper around things that were expected to open continuity to the grounding elecrode at certain times, like a water meter.
 

electricalist

Senior Member
Location
dallas tx
So I googled why do we drive ground rods and I come across an electrical company in Maryland that claims its so that unwanted current travels to the ground to protect us from getting shocked in the event current is on a metal object ..equipment pipes etc.
This helps to confuse the whole purpose.
If bonding is the effective ground fault path for safety. Then the ground must be to bond the earth. Just kidding.
 
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