250.66a against T250.66

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Klockopotomis

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Parker CO
So i have and several understandings about this-
if you do not know which GEC you will be using (rod, pipe or plate) then you use the T250.66.
However if you know that it is a rod or plate then you can use the minimum set forth in 250.66a.
Another explanation has something to do with older systems which used metal underground piping, however 250.66a doesn't just talk about "pipe" it refers to plate and rod. I do not understand the wording "that which is the sole connection". Does this mean that sometimes you have several GEC's connecting to the actual grounding electrode? Please help me with understanding only if you have an absolute fact about your understanding, I've been led down the wrong road and am frustrated.
 

ActionDave

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Your first connection to a grounding electrode is your grounding electrode conductor all other connections are jumpers. It is easiest to use the largest one required based off of table 250.66 and any of the qualifying electrodes in 250.52 that are present at the structure you are working on.

If your only grounding electrode is a ground rod or plate then the largest grounding electrode conductor you are required to use is 6AWG. Next step is to study 250.53.
 

GoldDigger

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But if you run a wire from the panel to a ground rod and from there to a CEE you cannot use that section to reduce the size of the wire from panel to rod below the size required for a CEE.
I like to think that the intention of the section was to apply to GECs that connect only to a rod ground, not that are the only connection to a rod.
 

kwired

Electron manager
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NE Nebraska
. I do not understand the wording "that which is the sole connection".

In any installation there may be multiple electrodes present, or even multiple electrodes that are added.

When they say "that which is the sole connection" they are talking about a section of conductor that only connects to a specific electrode. Example the typical ground rod only requires 6AWG copper as the largest conductor you need to run to the rod itself, but if there is building steel or water pipe electrode you will still need larger conductor run to those electrodes if 250.66 calls for larger conductor. You however could run the larger GEC to the building steel or water pipe and use a 6 AWG copper bonding jumper from the steel or water pipe, or from the GEC itself to go to the rod.
 

Smart $

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Ohio
...When they say "that which is the sole connection" they are talking about a section of conductor that only connects to a specific electrode. ...
The 2014 version of 250.66(A) expands the sole connection condition to include multiple rods, pipes, plates, or any combination thereof.
 

kwired

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Location
NE Nebraska
The 2014 version of 250.66(A) expands the sole connection condition to include multiple rods, pipes, plates, or any combination thereof.

Correct. Clarification of that would mean you could run 6 AWG to a rod and continue to additional rods with 6 AWG.

If 250.66 calls for a 2 AWG GEC you can run 6 AWG to a rod or rods, and even to pipes or plates that only require 6 AWG, but you can not run 6 AWG to a rod and continue on from that point to a water pipe or CEE if 250.66 says you need larger then 6 AWG. You could run to the water pipe with 2 AWG and from there run 4 AWG to the CEE and 6 AWG to the rod, plate or pipe.

It is more questionable though if you can run 2 AWG to the water pipe, from there 4 AWG to the CEE, and from there 6 AWG to the rod, plate, pipe, I think they want you to run separate 4 AWG to the CEE and separate 6 AWG to the rod in such an instance.

I may be oversimplifying but the question was a pretty basic question.
 

don_resqcapt19

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...
Another explanation has something to do with older systems which used metal underground piping, however 250.66a doesn't just talk about "pipe" it refers to plate and rod. ...
Pipe, as used in this section, is not a metal underground water pipe. It is a pipe that is driven into the ground just like you would drive a ground rod.

A metal underground water pipe needs a full sized grounding electrode conductor per Table 250.66.
 

Smart $

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Ohio
...

It is more questionable though if you can run 2 AWG to the water pipe, from there 4 AWG to the CEE, and from there 6 AWG to the rod, plate, pipe, I think they want you to run separate 4 AWG to the CEE and separate 6 AWG to the rod in such an instance.

...
I agree.

Or one could continue the full-size GEC (#2 in your example) to the CEE, and then run #6 from CEE to rod.
 

infinity

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It is more questionable though if you can run 2 AWG to the water pipe, from there 4 AWG to the CEE, and from there 6 AWG to the rod, plate, pipe, I think they want you to run separate 4 AWG to the CEE and separate 6 AWG to the rod in such an instance.

What sense does that make electrically?
 

infinity

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I took that to mean from the water pipe, not all the way from the panel.

That makes more sense, but is it required to do so? Wouldn't a #2 to the WP with a #4 jumper to the CEE and a #6 from the CEE to the ground rod be complaint?
 

Smart $

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That makes more sense, but is it required to do so? Wouldn't a #2 to the WP with a #4 jumper to the CEE and a #6 from the CEE to the ground rod be complaint?
IMO, no.

The GEC from water pipe to CEE is not a sole connection to a CEE [250.66(B)].

Given the logic behind the 2014 changes, it should be compliant... not that I agree with the 2014 changes, though.
 

Smart $

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Ohio
But then it is not a grounding electrode conductor it's just a bonding jumper.
I don't get where people such as yourself come up with these notions that a bonding jumper has some magical properties and handles charge flow differently. IMO they come up with this notion to avoid irreversible connections. Yes, I know it is permitted in some places [250.68(C)], but it is still in the grounding electrode system. It's not an equipment bonding jumper. It's an electrode bonding jumper. And note 250.68(C) also covers extending with a GEC... not just a bonding jumper. So how does one differentiate between a GEC extension that is reversible from an electrode bonding jumper at those locations?

The whole notion why 2014 changed 250.66(A) and (B) to include multiples of each (not multiples not any combination of either... yet!!!) was born out of this concept. What happened to the concept if it will carry more current it has to be capable of carrying more current and/or have less impedance? If one rod, pipe, plate, or CEE, and a sole conductor to each can dissipate X amount of current is the smallest capable... it defies logic and physics to say that same small conductor can dissipate 2, 3, 4, 5... etc. times the current or charge. I suppose if you make the connection to earth small enough or with enough impedance... its never going to carry more current anyway. :happyyes:
 

ActionDave

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I don't get where people such as yourself come up with these notions that a bonding jumper has some magical properties and handles charge flow differently. IMO they come up with this notion to avoid irreversible connections. Yes, I know it is permitted in some places [250.68(C)], but it is still in the grounding electrode system. It's not an equipment bonding jumper. It's an electrode bonding jumper. And note 250.68(C) also covers extending with a GEC... not just a bonding jumper. So how does one differentiate between a GEC extension that is reversible from an electrode bonding jumper at those locations?
There is one grounding electrode conductor to the first electrode, everything else makes up the grounding electrode system.

The whole notion why 2014 changed 250.66(A) and (B) to include multiples of each (not multiples not any combination of either... yet!!!) was born out of this concept. What happened to the concept if it will carry more current it has to be capable of carrying more current and/or have less impedance? If one rod, pipe, plate, or CEE, and a sole conductor to each can dissipate X amount of current is the smallest capable... it defies logic and physics to say that same small conductor can dissipate 2, 3, 4, 5... etc. times the current or charge. I suppose if you make the connection to earth small enough or with enough impedance... its never going to carry more current anyway. :happyyes:
500 MCM or #6, either will do just as well helping the earth suck in as much current as it can through the straw that is a ground rod, at least that is what the science degreed people tell me so I don't see why anything larger than #6 would be needed for any connection to any ground rod.
 

kwired

Electron manager
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NE Nebraska
That makes more sense, but is it required to do so? Wouldn't a #2 to the WP with a #4 jumper to the CEE and a #6 from the CEE to the ground rod be complaint?
Exactly what I brought up, mostly to see what others have to say. I don't know if it meets intent of the rule or not, seems if you want to be strict with the interpretation of the rules- see reply to Dave below, I kind of said same thing there that I want to say here even though this is displayed first, I'm backwards today.:)

But then it is not a grounding electrode conductor it's just a bonding jumper.

did not read the last couple posts thoroughly, but IMO you still need a minimum #4 bonding jumper for the sole connection to the CEE. Should the jumper used end up bonding something other then a CEE - I really don't know if that is acceptable or not, but in general wouldn't install it that way myself. In fact if there is already a CEE I myself would never have a rod in the first place, the CEE is a better electrode and the NEC doesn't require a CEE to be supplemented. But is a situation that I guess could exist.
 

Smart $

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Ohio
There is one grounding electrode conductor to the first electrode, everything else makes up the grounding electrode system.
Let's say the middle electrode is building steel electrode supplemented by a CEE [250.52(A)(2)]. Is the conductor from water pipe electrode to building steel an electrode bonding jumper or a GEC?

IMO, bonding jumpers should only be used to bond non-current-carrying metal parts that are not electrodes. Anything that bonds earthing electrodes to the intentionally conductive parts of the electrical system should be a GEC.

500 MCM or #6, either will do just as well helping the earth suck in as much current as it can through the straw that is a ground rod, at least that is what the science degreed people tell me so I don't see why anything larger than #6 would be needed for any connection to any ground rod.
Okay, let's say current-carrying properties of a rod electrode are directly associated to copper mass of the electrode rather than surface area or total combined conductivity.

You connect two or more to the system. What is the total impedance compared to one? I understand if one had sufficient impedance to earth, we wouldn't be using a second... but that's on the assumption 25 ohms is sufficient. The 25 ohm value seems to be an arbitrary value someone pulled out of thin air.

What about when the 25 ohm is not sufficient? How is the impedance of a water pipe any different. It doesn't even have to be copper coated, there is no guarantee that it is connected to a community supply consisting of metal piping, and tap water isn't more conductive than the steel core of a ground rod.

Also, why can we not just run #8 or #10 to a single rod if a #6 will support multiple rods?

Seems to me that grounding conductor sizing is based more on assumptions, superstitions, and perhaps politics than solid physics and logical analyses.
 

ActionDave

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Let's say the middle electrode is building steel electrode supplemented by a CEE [250.52(A)(2)]. Is the conductor from water pipe electrode to building steel an electrode bonding jumper or a GEC?
Bonding jumper.

IMO, bonding jumpers should only be used to bond non-current-carrying metal parts that are not electrodes. Anything that bonds earthing electrodes to the intentionally conductive parts of the electrical system should be a GEC.
IMO there is only one bond and it is at the service or SDS everything else is earthing/GES or equipment grounding. The CMP's keep approving new verbiage and adding new terms like "equipment bonding jumper" and "system bonding jumper" that make a simple idea harder to learn and look up references for in the codebook. That is another discussion though.

Okay, let's say current-carrying properties of a rod electrode are directly associated to copper mass of the electrode rather than surface area or total combined conductivity.

You connect two or more to the system. What is the total impedance compared to one? I understand if one had sufficient impedance to earth, we wouldn't be using a second... but that's on the assumption 25 ohms is sufficient. The 25 ohm value seems to be an arbitrary value someone pulled out of thin air.

What about when the 25 ohm is not sufficient? How is the impedance of a water pipe any different. It doesn't even have to be copper coated, there is no guarantee that it is connected to a community supply consisting of metal piping, and tap water isn't more conductive than the steel core of a ground rod.
The most extensive work I have ever done with grounding/earthing is on cell sites and to be honest I have never studied it that hard but I do read a little and talk to engineers and techs when I get the chance.

The engineers are all over the map but most agree that single point grounding is the best. The techs that maintain the sites say the ones with single point grounding give them the least trouble.

From this I conclude the absolute best grounding electrode system is single point with every piece of metal bonded. The best size size for a the conductors? IDK. Have to go back and ask the engineers and they are going to give answers all over the map. Good old horse sense and all the work done by Mr. Uffer lead me to believe that #4 CU is up to the task. However, these are buildings on mountaintops with huge metal structures pushing up thirty to more than a hundred feet in the air and hundreds of thousands of dollars worth of electronic equipment in them. Good old horse sense also tells me that an NEC minimum GES is going to serve a house or an average office building just fine.

I started as an electrician in the 90's and from that perspective it seems we came out of the '80's and into the early 2000's with a lot of myths about grounding/earthing when what turned out to be the problem was a lot of bad wiring.

Also, why can we not just run #8 or #10 to a single rod if a #6 will support multiple rods?
If allowed I think you could and it would be just fine.

Seems to me that grounding conductor sizing is based more on assumptions, superstitions, and perhaps politics than solid physics and logical analyses.
I agree with this one hundred percent. I've seen some crazy stuff speced and the reasons for it were based in something other than reason.
 
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Smart $

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Ohio
Bonding jumper.


...
So where does Code say you can use a bonding jumper for system grounding (i.e. between electrodes)? I don't mean bonding equipment, enclosure, raceway, or any other non-current carrying part. I'm talking about conductor(s) between the main bonding jumper and any required grounding electrode.
 
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