george t. everett
Senior Member
- Location
- New York
Is there any scenario that would require the grounding electrode conductor to a ground rod to be larger then a number 6?
Grounding Electrode Conductor
- Thread starter george t. everett
- Start date
- Status
- Location
- Massachusetts
Re: Grounding Electrode Conductor
Job specifications
Job specifications
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Grounding Electrode Conductor
Other than Bob's answer (which is very common in commercial), the only other thing I could think of is due to how you would route the grounding electrode conductor to form the grounding electrode system.
Example: 200A service. One #4 could be taken from the service to the Ufer, then the rod, then the water pipe.
Other than Bob's answer (which is very common in commercial), the only other thing I could think of is due to how you would route the grounding electrode conductor to form the grounding electrode system.
Example: 200A service. One #4 could be taken from the service to the Ufer, then the rod, then the water pipe.
Re: Grounding Electrode Conductor
George ,
We had a commercial job were it was required to have 4/0 -2/0 & 1/0 cad welded to the grounding rods 24" beneath grade,
there is a job we have now that uses mostly 2/0 .
Seems like #6 is mostly used on residential work and small commercial from what little I have seen , hope that this answer sheds some light on your question.
John
George ,
We had a commercial job were it was required to have 4/0 -2/0 & 1/0 cad welded to the grounding rods 24" beneath grade,
there is a job we have now that uses mostly 2/0 .
Seems like #6 is mostly used on residential work and small commercial from what little I have seen , hope that this answer sheds some light on your question.
John
- Location
- Massachusetts
Re: Grounding Electrode Conductor
I was thinking more on this and when we ground a pad mount transformer under the POCO rules it goes like this.
Four 3/4" x 8' foot rods one about 18" off of each corner of the pad, connected by a continuous ring of 4/0 bare.
From opposite sides of that ring we come into the transformer two times with 4/0 bare.
I think the use of 4/0 is as much about physical protection as it is about it's current carrying ability.
I was thinking more on this and when we ground a pad mount transformer under the POCO rules it goes like this.
Four 3/4" x 8' foot rods one about 18" off of each corner of the pad, connected by a continuous ring of 4/0 bare.
From opposite sides of that ring we come into the transformer two times with 4/0 bare.
I think the use of 4/0 is as much about physical protection as it is about it's current carrying ability.
Re: Grounding Electrode Conductor
Yes I believe that it is true,
All the sub-station columns , transformer frames, structural steel work , diesel tanks & work platforms were connected with 4/0 to the main grid.
The 2/0 and 1/0 were for fence connections along the fence line which connected to the 4/0 on the grounding grid that was throughout the sub-station area.
Grounding rods were 20ft x 3/4"within and 50ft x 3/4" on the corners of the grid layout.
John, Thanks
Yes I believe that it is true,
All the sub-station columns , transformer frames, structural steel work , diesel tanks & work platforms were connected with 4/0 to the main grid.
The 2/0 and 1/0 were for fence connections along the fence line which connected to the 4/0 on the grounding grid that was throughout the sub-station area.
Grounding rods were 20ft x 3/4"within and 50ft x 3/4" on the corners of the grid layout.
John, Thanks
G
Guest
Guest
Re: Grounding Electrode Conductor
If the #6 cannot follow the contour of the building you can jump to #4 in most cases.
If the #6 cannot follow the contour of the building you can jump to #4 in most cases.
Re: Grounding Electrode Conductor
As Iwire pointed out your job specification say otherwise. You can debate the GEC impedance all you want. But when it comes down to a spec, you are obligated.
In reality, the sites that require low resistance GES are requirements from a specification engineer. The sites probable facilitate sensitive equipment, customer is sensitive to protection, or warrantee requirements. It really does not matter as long as the customer is paying for it.
IMO the spec engineer is merely specifying a requirement to meet a design goal. The intent is so the contractor does not install two ground rods with mechanical clamps and calls it done. He/she is planning for a system that meets/exceeds any manufactures, NEC, local, or any other organization requirements.
I routinely specify ground rings constructed of 2/0 AWG with 10' rods, spaced every 20', with cad welds.
I just don't trust a RFQ that simply states a ground system that meets local code, If I do, I will get a two rod system with mechanical clamps.
By code no.
As Iwire pointed out your job specification say otherwise. You can debate the GEC impedance all you want. But when it comes down to a spec, you are obligated.
In reality, the sites that require low resistance GES are requirements from a specification engineer. The sites probable facilitate sensitive equipment, customer is sensitive to protection, or warrantee requirements. It really does not matter as long as the customer is paying for it.
IMO the spec engineer is merely specifying a requirement to meet a design goal. The intent is so the contractor does not install two ground rods with mechanical clamps and calls it done. He/she is planning for a system that meets/exceeds any manufactures, NEC, local, or any other organization requirements.
I routinely specify ground rings constructed of 2/0 AWG with 10' rods, spaced every 20', with cad welds.
I just don't trust a RFQ that simply states a ground system that meets local code, If I do, I will get a two rod system with mechanical clamps.
pierre
Senior Member
- Location
- Westchester County, New York
Re: Grounding Electrode Conductor
Dereck
In general, running a larger than 6 AWG copper conductor to the ground rod is a waste of money!!!
You and I both know that.
If for whatever the reason the specs call for a grounding system that exceeds the NEC, than would you not say that a ground resistance test should be performed to locate the area, or determine what type of system should be installed to perform the way necessary.
I am not against a good grounding system for all the right reasons, I just think that the misunderstanding of the nature of this subject wastes time and money, and leads the customer to thinking they are getting something they are not.
Years ago I learned about the 6 Ps
PROPER PREPERATION PREVENTS PISS POOR PERFORMANCE!
That is our industry in a nutshell
Pierre
Dereck
In general, running a larger than 6 AWG copper conductor to the ground rod is a waste of money!!!
You and I both know that.
If for whatever the reason the specs call for a grounding system that exceeds the NEC, than would you not say that a ground resistance test should be performed to locate the area, or determine what type of system should be installed to perform the way necessary.
I am not against a good grounding system for all the right reasons, I just think that the misunderstanding of the nature of this subject wastes time and money, and leads the customer to thinking they are getting something they are not.
Years ago I learned about the 6 Ps
PROPER PREPERATION PREVENTS PISS POOR PERFORMANCE!
That is our industry in a nutshell
Pierre
Re: Grounding Electrode Conductor
Pierre, thanks for the comments. Many of the sites I work with like radio, and fiber-optic regenerators only have a ring and rod system (no water pipe involved). Since all these sites have FAA and DOD communications there is no choice in selecting the ring conductor or jumper sizes. You either do it or loose a $12 Billion dollar a year contract.
For other sites I sometimes do have test performed by Lyncole, but as experience has taught me the added cost of the site inspection is often just as expensive as the ring/rod system I already knew I was going to install.
The business I am in does not allow me the options that are open to others in residential or commercial applications. What I/we do is not necessary for residential/commercial, and most industrial applications.
But I can say I do use a ring in all applications because it is integrated with lightning protection systems, so a soil test and site inspection is a mute point most of the time. The only real change I make from time-to-time is instead of using rods, I will use chemical rods in their place when I get into rocky or sandy soil conditions.
I do agree using anything larger than a # 6 AWG to bond rods is a waist of money for most applications, unless contractual or other circumstances apply.
Pierre, thanks for the comments. Many of the sites I work with like radio, and fiber-optic regenerators only have a ring and rod system (no water pipe involved). Since all these sites have FAA and DOD communications there is no choice in selecting the ring conductor or jumper sizes. You either do it or loose a $12 Billion dollar a year contract.
For other sites I sometimes do have test performed by Lyncole, but as experience has taught me the added cost of the site inspection is often just as expensive as the ring/rod system I already knew I was going to install.
The business I am in does not allow me the options that are open to others in residential or commercial applications. What I/we do is not necessary for residential/commercial, and most industrial applications.
But I can say I do use a ring in all applications because it is integrated with lightning protection systems, so a soil test and site inspection is a mute point most of the time. The only real change I make from time-to-time is instead of using rods, I will use chemical rods in their place when I get into rocky or sandy soil conditions.
I do agree using anything larger than a # 6 AWG to bond rods is a waist of money for most applications, unless contractual or other circumstances apply.
G
Guest
Guest
Re: Grounding Electrode Conductor
Also #6 & #4 fall under different guidlines for "protection". It may be cheaper to run #4 than be required to protect #6. Of course even #4 is subject to protection requirements-- but at a different standard.
[ October 17, 2003, 04:16 PM: Message edited by: awwt ]
#4 is one way to eliminate the "follow the contour" requirement. If you don't want to follow the contour with #6 you have to protect it. It may be cheaper or easier to go #4. That was my point.
Also #6 & #4 fall under different guidlines for "protection". It may be cheaper to run #4 than be required to protect #6. Of course even #4 is subject to protection requirements-- but at a different standard.
[ October 17, 2003, 04:16 PM: Message edited by: awwt ]
Re: Grounding Electrode Conductor
awwt, where is it stated that a #4 doesn't have to be secured to the surface that carries it?
And being that it does have to be secured to the surface, (250.64(B)) how can that be acheived without following the contour or providing supports from the surface that carries it?
The first sentence of 250.64.(B) blankets the rest of the section.
A grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. This covers any size. The diferences you mention doesn't change the requirements of securing.
Roger
[ October 17, 2003, 04:27 PM: Message edited by: roger ]
awwt, where is it stated that a #4 doesn't have to be secured to the surface that carries it?
And being that it does have to be secured to the surface, (250.64(B)) how can that be acheived without following the contour or providing supports from the surface that carries it?
The first sentence of 250.64.(B) blankets the rest of the section.
A grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. This covers any size. The diferences you mention doesn't change the requirements of securing.
Roger
[ October 17, 2003, 04:27 PM: Message edited by: roger ]
G
Guest
Guest
Re: Grounding Electrode Conductor
I have no issue with the securing part you mentioned.
My interpretation is that #6, if otherwise unprotected, must more closely follow the contour (surface) of the construction. Both #6 & #4 must be securely fastened to the surface.
My interpretation comes from the 3rd sentence in 250.64(B):
My purpose in offering this information is in response to the original question only. My trade practices may exceed these requirements.
I have no issue with the securing part you mentioned.
My interpretation is that #6, if otherwise unprotected, must more closely follow the contour (surface) of the construction. Both #6 & #4 must be securely fastened to the surface.
My interpretation comes from the 3rd sentence in 250.64(B):
It only mentions #6 so there must be a difference between how we can run #6 vs. #4. The citation implies that where it is not securely fastened, it must be protected. So to run #6 unprotected we need to follow the surface (follow the contour).
My purpose in offering this information is in response to the original question only. My trade practices may exceed these requirements.
Re: Grounding Electrode Conductor
wayne ,
I have read 250.64 (b) several times and agree with Roger also, I believe that there is a point of severe physical damage and physical damage that this article refers to that might be giving you some confusion and mis- representation of this article.
John
wayne ,
I have read 250.64 (b) several times and agree with Roger also, I believe that there is a point of severe physical damage and physical damage that this article refers to that might be giving you some confusion and mis- representation of this article.
John
G
Guest
Guest
Re: Grounding Electrode Conductor
My answers above are fairly specific. Can you be more specific in your critique? What I mean is break it down by what the code states vs. what I stated. Thanks!
I don't think what Roger stated is mutually exclusive, but rather deals with a separate issue that I was not making (securing vs. following the contour).
[ October 17, 2003, 08:20 PM: Message edited by: awwt ]
My answers above are fairly specific. Can you be more specific in your critique? What I mean is break it down by what the code states vs. what I stated. Thanks!
I don't think what Roger stated is mutually exclusive, but rather deals with a separate issue that I was not making (securing vs. following the contour).
[ October 17, 2003, 08:20 PM: Message edited by: awwt ]
Re: Grounding Electrode Conductor
Wayne ,
Your answers are specific in" how you interpet" this article, that does not make them accurate and correct though,
I believe that the article is putting emphasis on" severe physical damage and severe damage" and how both size wires should be protected
John, Perhaps I am missing your pointy on this one Wayne .
Wayne ,
Your answers are specific in" how you interpet" this article, that does not make them accurate and correct though,
I believe that the article is putting emphasis on" severe physical damage and severe damage" and how both size wires should be protected
John, Perhaps I am missing your pointy on this one Wayne .
G
Guest
Guest
Re: Grounding Electrode Conductor
I'm asking for help in picking apart my interpretation regarding #6 has to closely follow the contour of the building, but #4 does not have to closely follow the contour of the building. The #4 is less susceptible to damage so its standard of required protection is lower. The #6 relies on the building structure for attachment & protection. The #4 relies on the building structure for attachment only. Pick away, and please provide documentation for the position. I already agree that both #6 & #4 have to be secured to the building.
../Wayne C.
[ October 17, 2003, 10:34 PM: Message edited by: awwt ]
I'm asking for help in picking apart my interpretation regarding #6 has to closely follow the contour of the building, but #4 does not have to closely follow the contour of the building. The #4 is less susceptible to damage so its standard of required protection is lower. The #6 relies on the building structure for attachment & protection. The #4 relies on the building structure for attachment only. Pick away, and please provide documentation for the position. I already agree that both #6 & #4 have to be secured to the building.
../Wayne C.
[ October 17, 2003, 10:34 PM: Message edited by: awwt ]
Re: Grounding Electrode Conductor
awwt, easy question, (well for most) how does this,
If there is still confusion, go back to the word surface and apply whatever physical mass you may invision, if it is flat, there is no concern in contour, if it curves OH BOY. :roll:
Unless they are grasping for straws, it is pretty plain.
Roger
awwt, easy question, (well for most) how does this,
get misinterpreted by literate people?
If there is still confusion, go back to the word surface and apply whatever physical mass you may invision, if it is flat, there is no concern in contour, if it curves OH BOY. :roll:
Unless they are grasping for straws, it is pretty plain.
Roger
G
Guest
Guest
Re: Grounding Electrode Conductor
Dear Roger,
I hope you did not intend for me (or anybody) to take that personally or literate-ly
I am not familiar with concept of a blanket sentence. My MO is to read the whole paragraph.
I believe the third sentence modifies (or clarifies) the first sentence. Otherwise why would it be there? If the 1st sentence makes the 3rd sentence moot, why is it there? Why is #6 called out?
Any constructive answers from anybody are helpful & appreciated.
[Edit add: The way I read the citation is that #6 needs to tightly follow the contour of the building. If you jump to #4 you can be more liberal in following the contours. You still need to support both. I believe my AHJ would expect to see the #6 following every nook & cranny possible, where with #4 a few gaps could just be bridged if using #4. The NEC does not require that #4 be used, but I believe it opens up your routing options. We are talking about bare, not AC or in pipe. There is no NEC requirement for a grounding electrode conductor to be in excess of #6-- unless routed per Ryan as mentioned above].
../Wayne C.
[ October 17, 2003, 11:26 PM: Message edited by: awwt ]
Dear Roger,
I hope you did not intend for me (or anybody) to take that personally or literate-ly
I am not familiar with concept of a blanket sentence. My MO is to read the whole paragraph.
I believe the third sentence modifies (or clarifies) the first sentence. Otherwise why would it be there? If the 1st sentence makes the 3rd sentence moot, why is it there? Why is #6 called out?
Any constructive answers from anybody are helpful & appreciated.
[Edit add: The way I read the citation is that #6 needs to tightly follow the contour of the building. If you jump to #4 you can be more liberal in following the contours. You still need to support both. I believe my AHJ would expect to see the #6 following every nook & cranny possible, where with #4 a few gaps could just be bridged if using #4. The NEC does not require that #4 be used, but I believe it opens up your routing options. We are talking about bare, not AC or in pipe. There is no NEC requirement for a grounding electrode conductor to be in excess of #6-- unless routed per Ryan as mentioned above].
../Wayne C.
[ October 17, 2003, 11:26 PM: Message edited by: awwt ]
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