Area controversy around sizing of GEC for ground rod

[roger]

If it is 3 point fall of potential test you would not connect to the grounding electrode conductor.

Dennis is correct, if it were the test results wouldn'mean much and the readings would be rediculously low if the POCO neutral is landed in the service equipment.

Roger

 

[roger]

Certainly. I would consider it a much more defensible position from the standpoint of my design. I would much rather see a #3/0 which was designed based on my intepretation of the code burnt in two and speculate what amazing act of nature caused that, vs. a pair of #6 burnt in two with a bunch of us standing around having a discussion equivalent to this thread trying to remind ourselves why we didn't go "humongous" (per the Table, of course). ;-)

So you go with a humongus conductor and the rods vaporize, same result. The point is, the rods are not going to out perform the #6, hence there is no reason to use more than a #6 for rods regardless of how many are driven.

Roger

 

[mivey]

Certainly. I would consider it a much more defensible position from the standpoint of my design. I would much rather see a #3/0 which was designed based on my intepretation of the code burnt in two and speculate what amazing act of nature caused that, vs. a pair of #6 burnt in two with a bunch of us standing around having a discussion equivalent to this thread trying to remind ourselves why we didn't go "humongous" (per the Table, of course). ;-)

Then allow me a moment of facetious fantasy :grin::

Ladies and gentlemen of the jury, Mr Bigwire made it clear that his years of experience and engineering expertise led him to determine that his client should use the humongous conductor instead of the #6 conductor allowed by the code.

The prosecution has brought before you a set of world-renowned witnesses with over 1,000 years of combined electrical engineering experience in the field of power system grounding. These experts have testified and proved that using the humongous wire instead of the #6 wire brings no appreciable benefit unless the rest of the ground path is designed with a lower resistance.

It should be clear that the defendants recognized the need to exceed the code requirements because they recognized the dangers posed to Mr Careless. Mr Bigwire has said it would not be fair to require his client to pay for a complete low-resistance path. He recognized the danger, but refused to spend the money needed to protect the deceased.

I helped stack the jury pool, and I know that many of you are living on fixed incomes and are having trouble making ends meet. I also know we all love a good conspiracy theory.

So I ask: Is it fair that Mr Careless was trapped in a job where his life was in danger and he was unaware of these dangers? The defendants were aware of the danger but did not think Mr Careless's life was worth the cost to prevent this tragedy. I ask you now, is it fair that Mr Careless has paid for Mr Bigwire's indifference with his life? This was clearly a danger recognized by the defendant but not worth the defendant's time or money to do anything about it.

As fellow citizens in a state of despair and suspicion please consider this: It it fair that Mr Careless's now-destitute wife & children should suffer & go hungry because the defendant wanted to save a few dollars? The defendants clearly weighed Mr Carless's life against the cost of litigation. While it won't bring Mr Careless back, we must consider the family he left behind and make the defendants to pay for their inhumanity to their fellow man.

 

[fredfriarpe]

Then allow me a moment of facetious fantasy :grin::

Ladies and gentlemen of the jury, Mr Bigwire made it clear that his years of experience and engineering expertise led him to determine that his client should use the humongous conductor instead of the #6 conductor allowed by the code.

The prosecution has brought before you a set of world-renowned witnesses with over 1,000 years of combined electrical engineering experience in the field of power system grounding. These experts have testified and proved that using the humongous wire instead of the #6 wire brings no appreciable benefit unless the rest of the ground path is designed with a lower resistance.

It should be clear that the defendants recognized the need to exceed the code requirements because they recognized the dangers posed to Mr Careless. Mr Bigwire has said it would not be fair to require his client to pay for a complete low-resistance path. He recognized the danger, but refused to spend the money needed to protect the deceased.

I helped stack the jury pool, and I know that many of you are living on fixed incomes and are having trouble making ends meet. I also know we all love a good conspiracy theory.

So I ask: Is it fair that Mr Careless was trapped in a job where his life was in danger and he was unaware of these dangers? The defendants were aware of the danger but did not think Mr Careless's life was worth the cost to prevent this tragedy. I ask you now, is it fair that Mr Careless has paid for Mr Bigwire's indifference with his life? This was clearly a danger recognized by the defendant but not worth the defendant's time or money to do anything about it.

As fellow citizens in a state of despair and suspicion please consider this: It it fair that Mr Careless's now-destitute wife & children should suffer & go hungry because the defendant wanted to save a few dollars? The defendants clearly weighed Mr Carless's life against the cost of litigation. While it won't bring Mr Careless back, we must consider the family he left behind and make the defendants to pay for their inhumanity to their fellow man.

Nice. Please tell me Jack Nicholson is in there somewhere!

$100 is $100 but...

I was flipping through my NEC Handbook noticing all the G.E.C. in the examples were sized per Table 250.66 - then it occured to me to read the FPN: under Article 250.66: "FPN: See 250.24(C) for size of ac system conductor brought to service equipment." I believe the table gives us values for creating a grounding electrode for ac systems (i.e. a transformer in an electrical room) or a UPS, but we have to look to 250.24 (C) for service applications.

Will that stand up in court? ;-)

 

[roger]

but we have to look to 250.24 (C) for service applications.

Will that stand up in court? ;-)

If you were trying to defend the size of the Neutral and it's fault clearing ability it might, but that has nothing to do with the GEC we're discussing.

Roger

 

[LarryFine]

I would not sign and seal a design of a 600A service with anything less than a #2/0(Cu) grounding electrode conductor, any more than I would a 4000A service with anything less than a #3/0 (Cu) grounding electrode conductor.

If the intent of the code is such that for a grounding electrode conductor, all we need is one #6 for each ground rod - no matter if the current-carrying conductors entering the equipment are for a 100A service or a 4000A service or higher, why bother having Table 250.66 at all? Why wouldn't the code clearly state something like "For each grounding electrode provide a #6 conductor"? How could we justify that two ground rods with two #6 would provide an equal grounding electrode system to a #3/0 connected to two rods?

You do understand that there are other electrodes than made electrodes and driven rods, and that those electrodes still require the table-sized conductor, right?

 

[LarryFine]

I would much rather see a #3/0 which was designed based on my intepretation of the code burnt in two and speculate what amazing act of nature caused that, vs. a pair of #6 burnt in two with a bunch of us standing around having a discussion equivalent to this thread trying to remind ourselves why we didn't go "humongous" (per the Table, of course). ;-)

Never happen. A single #6 wire to a pair of driven rods will never see enough current to get warm, even with a line conductor tied directly to it. It wouldn't even trip a 20a breaker.

 

[fredfriarpe]

If you were trying to defend the size of the Neutral and it's fault clearing ability it might, but that has nothing to do with the GEC we're discussing.

Roger

It would apply to the service described in the original post; the remainder of the discussion has made me dizzy.

It's what sucks about getting older - we forget why we do stuff, although we believe it to be correct "just because." When I was a newly minted design engineer back in the day I probably stormed into my boss's office and pointed at the (A) that we've been discussing and asked why we're going crazy putting #3/0 conductors in when #6 would be fine. I'm quite sure he would have turned back a page and pointed at the fine print note and had me read the appropriate section, and I would have walked back to my desk with my tail between my legs after reading the (1) (2) and (3) in that section. But it made me exercise some brain cells at least, which is never a bad thing.

As he would say, "It's your liquor store you can rob it any time you want" - but I'm going to continue on my career as Mr. BigWire and deal with the consequences as they come.

 

[fredfriarpe]

You do understand that there are other electrodes than made electrodes and driven rods, and that those electrodes still require the table-sized conductor, right?

Yes I do; it's the trouble with these threads when they get this long. I posted that I found my answer in the FPN: at the beginning of Article 250.66 and realize why I'm stubbornly sticking to what I have been doing for a long time.

 

[LarryFine]

Yes I do; it's the trouble with these threads when they get this long. I posted that I found my answer in the FPN: at the beginning of Article 250.66 and realize why I'm stubbornly sticking to what I have been doing for a long time.

That has to do with the system grounded conductor, not a grounding electrode conductor.

 

[roger]

That has to do with the system grounded conductor, not a grounding electrode conductor.

Fred, do you understand what Larry is saying?

Roger

 

[fredfriarpe]

That has to do with the system grounded conductor, not a grounding electrode conductor.

I got that and stand corrected. Be that as it may, when I jumped in I believe the discussion was of 250.66 (A) and what constitutes a "sole connection" to an electrode (presumably singular electrode) therefore allowing the #6 conductor. Perhaps I've always worked in areas where single electrodes for service were not allowed and never exercised the option. I'm certainly not the only one sizing using Table 250.66 - I like electricians and always learn something from them - I certainly would give them a heads-up if I thought I was adding extra expense to their project by using the table, but in my experience this controversy has never occurred.

 

[fredfriarpe]

I spent quite a bit of time googling this topic today; Holy Smokes the debate has been around forever - and all the names are familiar, back to 2005 and before.

The clearest explanation of the single ground rod topic, which was alluded to earlier, was that for each single ground rod (pipe, or plate), there is no benefit of running a conductor larger than #6. In my projects, I would have spec'd #6 for a 100A service based on the Table, which would also have fit the exception - no matter one or two rods. Any larger services would have by default indicated a connection to rods, water pipe, and building steel (and sometimes a counterpoise loop) - so by default I'm using the table since I'm above and beyond rods, pipes, or plates.) If indeed in the past I have connected a 200A service pedestal along I-4 somewhere in Central Florida (hypothetically speaking, or course), I've bilked the taxpayers out of some tax dollars to pay for some extra copper and formally apologize.

The original post is a pedestal - probably somewhere out in a field where the only electrode system will be driven rods and the #6 would fly.

Thanks for stimulating my brain cells, off to find an adult beverage and kill some of them back off!

 

[fredfriarpe]

In my projects, I would have spec'd #6 for a 100A service based on the Table

#8 Copper. I'm tired.

 

[Dennis Alwon]

Thanks for stimulating my brain cells, off to find an adult beverage and kill some of them back off!

Hey, you deserve it. Have one on Larry.

 

[mivey]

Nice. Please tell me Jack Nicholson is in there somewhere!

Oddly enough, I could not get his agent to return my call.

 

[mivey]

Hey, you deserve it. Have one on Larry.

Hey everybody! Larry's buying!

 

[fredfriarpe]

Oddly enough, I could not get his agent to return my call.

Deep down, in those union meetings they don't like to talk about, they want us on that wall. OK, OK, they wish we'd fall off, but it's all good - I'm just happy to be part of the team.

 

[mivey]

Deep down, in those union meetings they don't like to talk about, they want us on that wall. OK, OK, they wish we'd fall off, but it's all good - I'm just happy to be part of the team.

Jack's been in so much stuff you could probably make a movie out of his clips alone.

 

[LarryFine]

Hey everybody! Larry's buying!

Yay! Larry's buying!





Hey, wait! I'M Larry!