# Grounding Electrode Conductor?



## abond82

I was talking to a code worker today about the GEC size on a 400 amp service to our ground rod. I thought we needed a 1/O ground to the ground rod but he said it only had to be a #4. He showed me in the 2008 NEC the paragraph that states the GEC to the ground rod will not be required to be larger than #4.... Are we reading this correctly? I thought it had to be sized with the service...


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## wildleg

used to only have to be a #6 to the ground rod, did they change that in 2008 ?


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## RIVETER

*Gec*

The code is the code...but the code is the minimum you HAVE to do. It would also be the maximum.


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## abond82

ya i think it may have been #6 copper..... so on a 400 a service we only have to run a #6????? where do you get a 1/O grounding electrode conductor?


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## wildleg

article 250. the #6 only applies to ground rods, the gec has to comply with the code article


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## abond82

it also says that for ground plates, conduits, etc. what about building steel, ufer or cold water????


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## Murphy

yes it only has to be number six because groundrods have x amount of resistance so number six is the largest wire neccessary for the path.


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## abond82

but everything else is sized by service size.... correct???


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## Murphy

Correct


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## Old Spark

In my area, Northern California the plans always call for the grounding wire to the uffer to be based on table 250.66. We never challenged it. I wish we had, because 250.66 B clearly states a #4 AWG copper wire. I've wasted a lot of money in 25 years. 
P.S. the inspectors usually checked to see if we followed the plans on the uffer wire size and not one every said, "I wonder why the plans call for this #3/0"


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## CTshockhazard

abond82 said:


> but everything else is sized by service size.... correct???





Murphy said:


> Correct


Sort of.

It's sized according to the largest ungrounded service entrance conductor or with a paralleled installation, the sum of the size of the ungrounded conductors.


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## Dennis Alwon

abond82 said:


> ya i think it may have been #6 copper..... so on a 400 a service we only have to run a #6????? where do you get a 1/O grounding electrode conductor?


You only need a number 6 to the ground rod. You still need a 1/0 or a #2 depending on the service setup. to the water pipes for a 400 amp service.


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## Amish Electrician

You have stumbled on one of the most profound parts of the NEC. To understand it, you must first ask yourself: what is the GEC there for?

If it's there to clear faults, then clearly it must be large enough to handle the amount of current it will carry. We would also assume that it have essentially no resistance.

But wait a moment ... aren't we allowed up to 25 ohms of resistance at the ground rod? Doing simple math, there's no way that the GEC will ever carry more than a few amps - not enough to trip the smallest (15-amp) breaker. 

I guess it's not there to carry fault current at all. So, what is it for?

Well, let's re-examine our theory. Where does electricity want to go? Do a little experiment with a battery and a flashlight bulb. Hook one wire between the bulb and the battery. Attach the other to the other 'pole' on the bulb. and leave it free. Does the bulb light? Stick the wire in the ground; does it light? I guess electricity doesn't want to 'go to ground' after all. Touch it to the ground rod of your house - any light? Not until that wire touches the other end of the battery do you get light.

The lesson? Electricity wants to 'go home' to where it was made. For the electricity in your house, 'home' is the PoCo transformer. That's where the current must flow to clear a fault. Think of your ground wires (EGC's) as if they were 'drip pans,' place there to catch any electricity that 'leaks' out.

So, what other electricity is around us? Static electricity. Whether from brushing the cat, or building up in the clouds above, "static" is the only electricity that can be said to consider the 'ground' as 'home.' This is what current the GEC might be expected to carry.

So, how big need this wire be? Well, I suppose there are all manner of ways to make a guess as to just how much current it might one day carry .... but the one factor that's completely irrelevant is the size of the service to the building. Remember that 25 ohm calculation again .... there's no way that wire will ever see more than a few amps from the household electric.

What connection there is in the NEC between service size and the GEC has it's roots in the days when 'grounding' was not as well understood as it is today. Even now, there are some different theories at work - which is part of the reason Article 250 is so hard to read.

The code - often supplimented by local ammendment in this area - goes to great lengths to make sure we have a 'good ground,' without explaining WHY a good ground is so important. (Remember, I'm NOT talking about bonding here!) I mean, everything will work just fine without there being any ground electrode at all - as evidenced by the places that do not require one. I can see the day when we do away with this completely - or go to the opposite extreme, and try to make the entire world an equipotential plane.


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## abond82

Very interesting points....

I guess as all of us know it will always come down to what each inspector wants, not how "we" interpret the NEC.


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## brian john

abond82 said:


> Very interesting points....
> 
> I guess as all of us know it will always come down to what each inspector wants, not how "we" interpret the NEC.


NO it comes down to the code, if you go by what the inspector wants you may have an improper installation. It is your duty to know what is right and if the inspector is wrong you should correct him or work within the system to correct him. Other wise he will go around screwing up other jobs and contractors


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## RIVETER

*Gec*



Amish Electrician said:


> You have stumbled on one of the most profound parts of the NEC. To understand it, you must first ask yourself: what is the GEC there for?
> 
> If it's there to clear faults, then clearly it must be large enough to handle the amount of current it will carry. We would also assume that it have essentially no resistance.
> 
> But wait a moment ... aren't we allowed up to 25 ohms of resistance at the ground rod? Doing simple math, there's no way that the GEC will ever carry more than a few amps - not enough to trip the smallest (15-amp) breaker.
> 
> I guess it's not there to carry fault current at all. So, what is it for?
> 
> Well, let's re-examine our theory. Where does electricity want to go? Do a little experiment with a battery and a flashlight bulb. Hook one wire between the bulb and the battery. Attach the other to the other 'pole' on the bulb. and leave it free. Does the bulb light? Stick the wire in the ground; does it light? I guess electricity doesn't want to 'go to ground' after all. Touch it to the ground rod of your house - any light? Not until that wire touches the other end of the battery do you get light.
> 
> The lesson? Electricity wants to 'go home' to where it was made. For the electricity in your house, 'home' is the PoCo transformer. That's where the current must flow to clear a fault. Think of your ground wires (EGC's) as if they were 'drip pans,' place there to catch any electricity that 'leaks' out.
> 
> So, what other electricity is around us? Static electricity. Whether from brushing the cat, or building up in the clouds above, "static" is the only electricity that can be said to consider the 'ground' as 'home.' This is what current the GEC might be expected to carry.
> 
> So, how big need this wire be? Well, I suppose there are all manner of ways to make a guess as to just how much current it might one day carry .... but the one factor that's completely irrelevant is the size of the service to the building. Remember that 25 ohm calculation again .... there's no way that wire will ever see more than a few amps from the household electric.
> 
> What connection there is in the NEC between service size and the GEC has it's roots in the days when 'grounding' was not as well understood as it is today. Even now, there are some different theories at work - which is part of the reason Article 250 is so hard to read.
> 
> The code - often supplimented by local ammendment in this area - goes to great lengths to make sure we have a 'good ground,' without explaining WHY a good ground is so important. (Remember, I'm NOT talking about bonding here!) I mean, everything will work just fine without there being any ground electrode at all - as evidenced by the places that do not require one. I can see the day when we do away with this completely - or go to the opposite extreme, and try to make the entire world an equipotential plane.


Hello, Amish Electrician. What you have said is not Incorrect. I will just say that when you say the GEC will never conduct more than a few amps is not wholey true. In a lightning strike situation, and most of us will never know if we have had a part of one or not, I would think that it takes more than a few amps to heat the sap in a tree to the point of explosion. As opposed to the mechanical ground which could, but may never see current.


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## Amish Electrician

I was careful to say the GEC will never see more than a few amps *from the household electric*.

In the case of lightning, all bets are off. In the event of a direct hit, million-volt lightning strike, that wire would see 40,000 amps trying to push their way through. Not even the 3/4" ground rod can carry that kind of current for long. I expect that all those electrons - like motorists caught in a rush-hour snarl - would look for ways to jump off the GEC "freeway" and try to take 'alternate routes.'


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## Old Spark

Thanks Mr. Reviter. I've been doing electrical for over 25 years and did not know what you just explained. I've always been led to believe that the ufer ground was the important ground for clearing a fault, allowing the breaker to open. I can now see why we always must check to see that the grounding buss is bonded to the neutral buss with a large enough conductor. What I don't understand is why so many engineers and inspectors, who should know this stuff, have been spending all their efforts getting us to have a large enough ufer and don't even look to see if we have bonded the grounding buss to the neutral buss on the MSB. Now that I'm retired I find out. Oh well, at least the oversized ufer does not hurt anything.


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## Bob Badger

Amish Electrician said:


> In the case of lightning, all bets are off. In the event of a direct hit, million-volt lightning strike, that wire would see 40,000 amps trying to push their way through. Not even the 3/4" ground rod can carry that kind of current for long. I expect that all those electrons - like motorists caught in a rush-hour snarl - would look for ways to jump off the GEC "freeway" and try to take 'alternate routes.'


I agree with this and your previous post 100%.


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## brian john

David Channell said:


> . What I don't understand is why so many engineers and inspectors, who should know this stuff, have been spending all their efforts getting us to have a large enough ufer and don't even look to see if we have bonded the grounding buss to the neutral buss on the MSB. Now that I'm retired I find out. Oh well, at least the oversized ufer does not hurt anything.


 
Because and this is the GOD's honest truth, they believe in the magic that they think is electricity or as I have often stated the HOO-DOO VOO-DOO art of grounding.

I will add it is not uncommon to higher amperage then noted on the GEC exceeding 30 amps (based on experience) when the houses/town houses share a common transformer and common metallic utility piping system (water or gas)


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## supertrician29

*foreman*

aCtually your all wrong your nuetral creates your equipment ground for. Overcurrent protection and gec is to keep lighting from hitting the system that's why your only bonded at first means of dissconet they have totally seperate purposes


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## RIVETER

*Gec*



supertrician29 said:


> aCtually your all wrong your nuetral creates your equipment ground for. Overcurrent protection and gec is to keep lighting from hitting the system that's why your only bonded at first means of dissconet they have totally seperate purposes


You are going to have to tell us that you mis-spoke when you said that the neutral creates the equipment ground...or you are just plain wrong. And as far as the GEC keeping the lightning from hitting the system...just say you mis-poke again.


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## Old Spark

I thought lightning rods were the item to use if you are in an area where lightning strikes are common. The book I studied about lightning protection, it is totally separate from the electrical system. We were taught to install a lightning rod or rods atop the highest point of a building with the wires running down to driven ground rods. There was no connection with the electrical system at all.


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## RePhase277

supertrician29 said:


> aCtually your all wrong your nuetral creates your equipment ground for. Overcurrent protection and gec is to keep lighting from hitting the system that's why your only bonded at first means of dissconet they have totally seperate purposes



No sir, it is you who is wrong. Overcurrent protection has nothing to do with lightning. But yes the EGC originates at the bonded neutral of the service equipment. The GEC has nothing to do with the operation of overcurrent devices.


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## Old Spark

How does the gec stop lightning from hitting anything? Lightning hits what ever it wants to hit.


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## RePhase277

David Channell said:


> How does the gec stop lightning from hitting anything? Lightning hits what ever it wants to hit.


It doesn't stop it, it just gives it a preferred path to ground. Remember that we are dealing with two different electric circuits in a building: one circuit is from the transformer to the equipment, and the other is from the sky to the ground. We have to tie them together just in case the lightning finds its way onto the regular circuit.


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## jwjrw

InPhase277 said:


> It doesn't stop it, it just gives it a preferred path to ground. Remember that we are dealing with two different electric circuits in a building: one circuit is from the transformer to the equipment, and the other is from the sky to the ground. We have to tie them together just in case the lightning finds its way onto the regular circuit.


 
Your ground rod system is to dissipate the current to the Earth. Your GEC establishes a reference to ground for exposed noncurrent carring metal equipment


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## RIVETER

*Gec*



jwjrw said:


> Your ground rod system is to dissipate the current to the Earth. Your GEC establishes a reference to ground for exposed noncurrent carring metal equipment


You are getting closer. The purpose of the GEC is to direct a possible lightning strike, or other abberant voltages to earth for dissipation. You BOND the Neutral at the service disconnect to the Ground (GEC) . The EGC has nothing to do with the exposed non-current carrying metal parts of the system except that it is at the same potential. You may be confusing the GEC with the EGC. the fact that the exposed non-current carrying metal is BONDED to the neutral at the service is the reason the circuit breaker will trip if a hot to GROUND fault exists.


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## jwjrw

RIVETER said:


> You are getting closer. The purpose of the GEC is to direct a possible lightning strike, or other abberant voltages to earth for dissipation. You BOND the Neutral at the service disconnect to the Ground (GEC) . The EGC has nothing to do with the exposed non-current carrying metal parts of the system except that it is at the same potential. You may be confusing the GEC with the EGC. the fact that the exposed non-current carrying metal is BONDED to the neutral at the service is the reason the circuit breaker will trip if a hot to GROUND fault exists.


 
Didnt you read what I said? I said your ground rod system dissipates lightning. I was refering to the ECG system there.
Then what I said about the GEC was straight out of the NEC handbook.
I posted it so as to make it clear what a gec is. Im sure it does help with excess voltage but the GEC is the bond to ground. 
So really im not close IM RIGHT:whistling2:


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## Bob Badger

RIVETER said:


> You are getting closer. The purpose of the GEC is to direct a possible lightning strike, *or other abberant voltages to earth for dissipation.*


You are spreading a myth.

The only voltage / current that 'dissipates to earth' is from lightning.

Any other current flow on an electrode does not 'dissipate to the earth' the earth is not an electron sponge. All other current is just using the earth as a conductor to bring that current back to it's source which in most cases will be a utility transformer.

It may not seem like much but to me understanding the earth is not just 'absorbing' power is one of the first steps in understanding grounding and bonding in general.


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## jwjrw

Bob Badger said:


> You are spreading a myth.
> 
> The only voltage / current that 'dissipates to earth' is from lightning.
> 
> Any other current flow on an electrode does not 'dissipate to the earth' the earth is not an electron sponge. All other current is just using the earth as a conductor to bring that current back to it's source which in most cases will be a utility transformer.
> 
> It may not seem like much but to me understanding the earth is not just 'absorbing' power is one of the first steps in understanding grounding and bonding in general.


I tried to tell him:whistling2:!


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## RePhase277

jwjrw said:


> Your ground rod system is to dissipate the current to the Earth. *Your GEC establishes a reference to ground for exposed noncurrent carring metal equipment*


Again, that is not the function of the GEC. The bonded neutral is what establishes a potential reference for non-current carrying metal.


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## jwjrw

InPhase277 said:


> Again, that is not the function of the GEC. The bonded neutral is what establishes a potential reference for non-current carrying metal.


The GEC is a conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the GES. 

I posted the definition of a GEC on an ungrounded system by mistake. I knew what I meant but didnt word it properly.


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## RIVETER

*Gec*

Isn't this fun? The GEC is the grounding electrode conductor...which means it is the wire that is attached to the GROUNDING ELECTRODE. It serves no normal function in the operation of the electrical system.


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## Amish Electrician

FWIW, the NEC requires ALL grounding electrodes to be bonded to a common ground grid. So, if you install a system of lightning rods, there needs to be a connection somewhere to the household electrical system. 

I agree that lightning protection needs the installation of the appropriate lightning rods, etc.

I won't pretend to understand the theory behind lightning strikes. Perhaps, while doing nothing to actually intercept a lightning strike, the usual grounding electrode in some way helps prevent the house from accumulating the charge that attracts lightning in the first place. I just don't know.

I will say that if the world was completely without either lightning, or static electricity, I would be at a loss to understand the function of any ground rod.

I've heard the 'common reference plane' stuff before, and I am completely mystified as to what that means. If you're saying you want everything around the electrical system to be at the same potential, to prevent voltage gradients .... well, a single ground rod is not going to do that. You would need to deliberately make an 'equipotential grid.'


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## jwjrw

RIVETER said:


> Isn't this fun? The GEC is the grounding electrode conductor...which means it is the wire that is attached to the GROUNDING ELECTRODE. It serves no normal function in the operation of the electrical system.


 
The GEC ties the GES to the grounded conductor. Seems like that is a normal and necessary function. Where are sparky and codeone when you need em?


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## eddy current

InPhase277 said:


> and the other is from the sky to the ground.


Sky to ground or ground to sky? :laughing:


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## Old Spark

In my sixty plus years in the Sacramento California area, I've never heard of a lightning strike here, not to a tree, a building, or the ground. Forty miles North in a flat farming community where we built a gas station, we were told that lightning strikes were likely, so we had to install ground rods to ground the canopy. These did not tie into the electrical system, just the canopy per the electrical inspector. That was 20 years ago, never heard of a lightning strike on that canopy, but I suspect sometime in the past it has happened somewhere in that area. We do have static electricity like anywhere else. We have to ground the fuel trucks as they drop fuel for static and airports also require grounding of the airplanes during fueling. I've seen what happens when someone fills a gas can in the back of a pickup with a plastic bed liner. When they remove the nozzel from the can it catches on fire from a static spark. I'm sure we have to have the ground rods or ufer ground for services just in case. But it sounds like it doen't get used for anything except to drain static electricity then. How often do you guys see or hear of lightning strikes in your areas?


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## RIVETER

*Gec*

We see it a lot here in Kentucky, or at least lightning gets the blame a lot. When it does strike it is usually devastating to the house. It makes you wonder if a rod only works well for strikes that are close but not directly on you.


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## Old Spark

I would expect a lightning strike to be devastating. That much power, so many amps. How could a number 4 wire began to handle that load. Now static, I would think that a #12 could drain off, but we've been informed that it takes at least a #4 because there is so little power. Will we ever know all we need to know about electricity?


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## brian john

eddy current said:


> Sky to ground or ground to sky? :laughing:


Actually both, there is an up streamer and a down streamer that touch somewhere in between ground and cloud. There is also cloud to cloud and cloud to space lightning.


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## brian john

David Channell said:


> I would expect a lightning strike to be devastating. That much power, so many amps. How could a number 4 wire began to handle that load. Now static, I would think that a #12 could drain off, but we've been informed that it takes at least a #4 because there is so little power.


One issue is the resistance of a driven electrode and how much current a single rod (or two) can handle based on averages, another issue is the fast nature of the event, which as a engineering that specialized in lightning told me is why we get away with a smaller size GEC.

Additionally a flat braided GEC would be better than a circular conductor due to skin effect of lighting this along with longer electrodes spread out from the service in multiple directions supposedly works best?

He felt that a large grid and GEC should be installed at all services but his explanation for why we do not was based on the small number of hits and related fires, the excessive cost trying to achieve a low resistance along with extra material is hard to justify based on the fact that Mother NAture can always throw something even this upgraded electrode could not handle.



> Will we ever know all we need to know about electricity?


We won't, but there are specialists in every aspect of the trade that should know or paint a good picture of knowing.


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