Steel building grounding

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dahualin

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I have seen different kind of grounding system for steel buildings. In addition to the ground electrodes of ground rods to main ground busbar, Main water pipe, and concrete encased rebar in slab.
I have seen steel structure been used as one of the electrodes. My question regarding this is how many steel columns need to be grounded using ground rod. Let's say 100 columns in total for the building, how many of them need to be grounded with ground rod? Can I just ground one column?
I have see copper ground loop around the building installed as one of the electrodes. My question is why we need spend the money to install the ground loop. Is this necessary even we have other ground electrodes already?
I understand if the building has lightning protection system, an electrical ground loop around the building is necessary.
What do you think?

Thanks.
 

infinity

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You need to use the ones that are present. If using a water pipe as an electrode it needs to be supplemented by one other electrode. That could be on that is present or one that is made like a ground rod or ground ring. If the building has a structural steel frame only one point of attachment with a bonding jumper or GEC is likely required.

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dahualin

Senior Member
You need to use the ones that are present. If using a water pipe as an electrode it needs to be supplemented by one other electrode. That could be on that is present or one that is made like a ground rod or ground ring. If the building has a structural steel frame only one point of attachment with a bonding jumper or GEC is likely required.

1113918256_2.jpg

If we can use ground rod, why we put a ground ring that is much more expensive. The second question I have is not about how many bonding jump we need between steel column and main ground busbar. The question is about how many steel columns need grounded with ground rod. Thanks.
 

dahualin

Senior Member
Are these all columns connected with structural steel?

I don't quite understand your question. Steel columns are part of the building steel structure. I believe all steel columns are connected with each other through beams, trusses, braces etc.
 

infinity

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I don't quite understand your question. Steel columns are part of the building steel structure. I believe all steel columns are connected with each other through beams, trusses, braces etc.


If you look back to my first post you will see that I said that the structural steel frame will only require one GEC or bonding jumper. If you have a water pipe and structural steel electrode you will not need another made electrode, i.e.-ground rod, plate or ground ring. If the structure has 1/2" or larger rebar in the footing you must use the CEE too.
 

brian john

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Location
Leesburg, VA
I don't quite understand your question. Steel columns are part of the building steel structure. I believe all steel columns are connected with each other through beams, trusses, braces etc.


Not all strucual steel is connected together with other framing components, depends on the building type.
 

tkb

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Not all structural steel is connected together with other framing components, depends on the building type.

I have seen buildings built with expansion joints and the separate framing for each side of the joint without a steel connection between them.
That is why some buildings have double columns about a third down the length.

I have looked for this in new construction and have install a jumper in this location.
 

dahualin

Senior Member
If you look back to my first post you will see that I said that the structural steel frame will only require one GEC or bonding jumper. If you have a water pipe and structural steel electrode you will not need another made electrode, i.e.-ground rod, plate or ground ring. If the structure has 1/2" or larger rebar in the footing you must use the CEE too.

Maybe my question is not stated very clearly. My question is if we need another made electrode, why we use ground ring around the building? Obviously it is the most expensive option.
 

dahualin

Senior Member
Not all strucual steel is connected together with other framing components, depends on the building type.

OK, Let's assume that the steel structure has every steels connected with each other and the building has 100 steel columns. How many steel columns need to be grounded with ground rod? I am not asking the bonding jumper between steel column to electrical grounding system. I have seen almost half of the steel columns that is 50 columns grounded with ground rod.
 
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infinity

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Maybe my question is not stated very clearly. My question is if we need another made electrode, why we use ground ring around the building? Obviously it is the most expensive option.



I would start by asking who said that a ground ring was needed? An engineer? If you have a CEE and/or the building steel present then the ground ring is not needed or required by the NEC. By code you do not need any made electrodes from the installation that you've described.
 

infinity

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OK, Let's assume that the steel structure has every steels connected with each other and the building has 100 steel column. How many steel column need to be grounded with ground rod? I am not asking the bonding jumper between steel column to electrical grounding system. I have seen almost half of the steel columns that is 50 columns grounded with ground rod.


The answer is none.
 

dahualin

Senior Member
The answer is none.

We have to ground the metal frame of the structure if we want to use it as grounding electrode as per requirement of NEC Article 250.52.(2). Most of time, we connect the structure to the earth by using ground rods connected to steel columns. But I am not sure how many columns need this kind of grounding.

I have read Masterspec in 1995 format section 16060 item 3.5 H:
Grounding for Steel Building Structure: Install a driven ground rod at base of each corner column and at intermediate exterior columns at distances not more than 60 feet (18 m) apart.
I am not sure which code requires that or it is a kind of commen practice.
 

brian john

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Location
Leesburg, VA
1. A ground ring is not NEC mandated grounding electrode it is a specification usually of the design engineer or owner.
2. If the building steel is all connected you need to bond the building steel to the grounding electrode for the building.
3. Additionally bonding might be required as part of lighting protection systems.
 
OK, Let's assume that the steel structure has every steels connected with each other and the building has 100 steel columns. How many steel columns need to be grounded with ground rod? I am not asking the bonding jumper between steel column to electrical grounding system. I have seen almost half of the steel columns that is 50 columns grounded with ground rod.

Typically an inspector would only request additional means of grounding if the GEC read more than 25 ohms to earth ground. In my experience it is the electrical engineer of record who dictates the methods of grounding that are acceptable to his/her job. So if he draws a grounding ring or a bond to each column then he has a rhyme and a reason for it. The E drawings of the plans should show his/her acceptable methods of grounding.
 

infinity

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Typically an inspector would only request additional means of grounding if the GEC read more than 25 ohms to earth ground. In my experience it is the electrical engineer of record who dictates the methods of grounding that are acceptable to his/her job. So if he draws a grounding ring or a bond to each column then he has a rhyme and a reason for it. The E drawings of the plans should show his/her acceptable methods of grounding.


Sparky, I would just note that the 25 ohm requirement is only enforceable for ground rods, plate, and pipe electrodes. Other electrodes can exceed 25 ohms to ground and still not require anything additional.
 

brian john

Senior Member
Location
Leesburg, VA
he has a rhyme and a reason for it

Or he has always done it that way and the guy that taught him did it that way and that guy taht taught him once attended a seminar where they suggested it be done that way. Actually I guess that is a rhyme or more a reason?
 

dahualin

Senior Member
Typically an inspector would only request additional means of grounding if the GEC read more than 25 ohms to earth ground. In my experience it is the electrical engineer of record who dictates the methods of grounding that are acceptable to his/her job. So if he draws a grounding ring or a bond to each column then he has a rhyme and a reason for it. The E drawings of the plans should show his/her acceptable methods of grounding.

I am trying to figure out why other engineers design ground ring or ground a lot of steel columns with ground rod. Is there any code or common practice can justify those design? Since value engineering is very popular right now, Those ground ring and ground rods for steel columns are the targets to be cut if they are not necessary.
 

infinity

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This is a design issue not a code issue. Just bond the CEE, structural steel and water pipe to the service neutral and as far as the NEC is concerned you're done. Made electrodes are not required. Lightning protection may be another story.
 
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