Grounding for a new production building

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joshtrevino

Member
Location
Beaumont, TX
I am designing a new production facility with several motors operating at 480V, low voltage power panels (120/208V), lighting, structural steel, etc. All electrical equipment cases will be bonded back to the source utilizing properly sized EGC's. The typical way that I have designed the grounding for such a building is a ground ring (2/0 or 4/0) with grounding rods driven and bonded to the ring every 20-30 feet. All building steel, equipment cases, panel cases, etc are then bonded to the ground ring.

I have a contractor asking why we need the grounding ring. His suggestion is to drive rods around the building perimeter with all equipment bonded back to the rods.

I understand that both a ground rod and a ground ring are permissible as grounding electrodes in NEC 250. What, if any, are the benefits of using a ground ring instead of just using driven rods? Does IEEE or othe suggest a best practice for this?
 
I am designing a new production facility with several motors operating at 480V, low voltage power panels (120/208V), lighting, structural steel, etc. All electrical equipment cases will be bonded back to the source utilizing properly sized EGC's. The typical way that I have designed the grounding for such a building is a ground ring (2/0 or 4/0) with grounding rods driven and bonded to the ring every 20-30 feet. All building steel, equipment cases, panel cases, etc are then bonded to the ground ring.

I have a contractor asking why we need the grounding ring. His suggestion is to drive rods around the building perimeter with all equipment bonded back to the rods.

I understand that both a ground rod and a ground ring are permissible as grounding electrodes in NEC 250. What, if any, are the benefits of using a ground ring instead of just using driven rods? Does IEEE or othe suggest a best practice for this?

I think you should ask yourself what exactly you are trying to accomplish with a more elaborate grounding electrode system. MY humble advice would be that unless you have some unusual situation or perhaps a history of frequent lightning and sensitive equipment, it is a waste of money. Also note that in the vast majority of cases, you will be tied into the utility's grounding system anyway which is bigger than your ground ring will ever be.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
If you have the ability to create a CEE (Ufer) electrode it will probably have a lower resistance than your set of electrodes and be more reliable through variable soil moisture, etc.
 
Ring, rods, or UFER your choise. Thats a design issue not a code issue. My opinion is if you have a ring or a ufer then the rods won't do you any good. Especially in TX.

As to bonding you equipment enclosures to the ring might I call your attention to Article 300:
300.3(B) Conductors of the Same Circuit.
All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cable-bus assembly, trench, cable or cord unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
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Licensed Electrician
I am designing a new production facility with several motors operating at 480V, low voltage power panels (120/208V), lighting, structural steel, etc. All electrical equipment cases will be bonded back to the source utilizing properly sized EGC's. The typical way that I have designed the grounding for such a building is a ground ring (2/0 or 4/0) with grounding rods driven and bonded to the ring every 20-30 feet. All building steel, equipment cases, panel cases, etc are then bonded to the ground ring.

I have a contractor asking why we need the grounding ring. His suggestion is to drive rods around the building perimeter with all equipment bonded back to the rods.

I understand that both a ground rod and a ground ring are permissible as grounding electrodes in NEC 250. What, if any, are the benefits of using a ground ring instead of just using driven rods? Does IEEE or othe suggest a best practice for this?
I only know what I know about extreme earthing from my work on cell sites. I have seen ground rings without ground rods, ground rings with ground rods, ground rods only, ground rods in patterns, ground rods placed randomly, chemical ground rods.... and so it goes.

The largest bonding wire I remember dealing with was 250MCM. 4/0 is somewhat popular, #2 tinned is the most common.

When I talk to the techs almost all of them agree that the sites that have a single point connection, rather than a star earthing/grounding system are the ones that they have the least trouble with.

From my own anecdotal observations I am convinced that how you connect to the earth is a matter of taste.

Uffer ground is probably the best, but it may not matter that much.

What matters most is that proper wiring (no down stream neutral to ground connections past the service) is maintained, and everything that is conductive is bonded together some how, some way, as long as all of it is brought back to one spot.
 
Although if this is new construction he will likely have to have a UFER right?

Each grounding electrode type listed in 250.52(A)1-8, if present, must be bonded to the grounding electrode system ( and a single rod cannot be the only grounding electrode ) but I see nothing in the NEC that requires or prefers a UFER over a ground ring or a series of rods.

In my neck of the left coast 'new construction' is just as likely to be a pole barn or even a post and beam structure.
 

joshtrevino

Member
Location
Beaumont, TX
If you have the ability to create a CEE (Ufer) electrode it will probably have a lower resistance than your set of electrodes and be more reliable through variable soil moisture, etc.

My building will have a rebar reinforced slab as well as rebar reinforced footings, all tied togther with tie wire. If I were to specify that the slab rebar be bonded to the steel column anchor bolts, it seems to me that that would provide an adequate grounding electrode(s) for the building and that no rods or ring would be needed.

Thoughts?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
My building will have a rebar reinforced slab as well as rebar reinforced footings, all tied togther with tie wire. If I were to specify that the slab rebar be bonded to the steel column anchor bolts, it seems to me that that would provide an adequate grounding electrode(s) for the building and that no rods or ring would be needed.

Thoughts?

ground rods or rings are never required.

i do not believe what you are suggesting is compliant.

if the rebar in the footers makes it qualify as a CEE, it has to be part of the grounding electrode system.

I do not believe that tie wire can be used to bond together different grounding electrodes.
 

joshtrevino

Member
Location
Beaumont, TX
ground rods or rings are never required.

i do not believe what you are suggesting is compliant.

if the rebar in the footers makes it qualify as a CEE, it has to be part of the grounding electrode system.

I do not believe that tie wire can be used to bond together different grounding electrodes.

My plan would be to bond motor cases, panel enclosures, and other normally noncurrent carrying conductive materials to the to the CEE (steel columns tied to the foundation) which will be bonded back to the source ground via the grounding electrode conductor. Would that not be compliant?

Also, by no means did I intend to use the tie wire as a bonding jumper. My intention was to bond the slab rebar
to the column anchor bolts to provide a local grounding electrode to bond motor cases and panel enclosures to in order to satisfy 250.4(A)(2).

I am by no means intending to be authoritative in this conversation. Young engineer trying to wade through the morass that is grounding and bonding.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
My plan would be to bond motor cases, panel enclosures, and other normally noncurrent carrying conductive materials to the to the CEE (steel columns tied to the foundation) which will be bonded back to the source ground via the grounding electrode conductor. Would that not be compliant?
My opinion is that the required bonding in this case would be via an EGC and not a GEC. I do not believe it will harm anything to tie it together like this if you also have an EGC, but you can't substitute this for the required EGC.

Also, by no means did I intend to use the tie wire as a bonding jumper. My intention was to bond the slab rebar
to the column anchor bolts to provide a local grounding electrode to bond motor cases and panel enclosures to in order to satisfy 250.4(A)(2).

I am by no means intending to be authoritative in this conversation. Young engineer trying to wade through the morass that is grounding and bonding.
The slab rebar is not a legal grounding electrode IMO.

normally 250.4A(2) is handled via the EGC.
 
My building will have a rebar reinforced slab as well as rebar reinforced footings, all tied togther with tie wire. If I were to specify that the slab rebar be bonded to the steel column anchor bolts, it seems to me that that would provide an adequate grounding electrode(s) for the building and that no rods or ring would be needed.

Thoughts?

If installed per 250.52(A)2 and 3 then, yes.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
My plan would be to bond motor cases, panel enclosures, and other normally noncurrent carrying conductive materials to the to the CEE (steel columns tied to the foundation) which will be bonded back to the source ground via the grounding electrode conductor.

Why?

What makes this production facility different from all the others that keep the grounding electrode at the main gear and run properly sized EGC's to all the equipment. Why bond everything, everywhere to the grounding electrode?
 
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I am designing a new production facility with several motors operating at 480V, low voltage power panels (120/208V), lighting, structural steel, etc. All electrical equipment cases will be bonded back to the source utilizing properly sized EGC's. The typical way that I have designed the grounding for such a building is a ground ring (2/0 or 4/0) with grounding rods driven and bonded to the ring every 20-30 feet. All building steel, equipment cases, panel cases, etc are then bonded to the ground ring.

My plan would be to bond motor cases, panel enclosures, and other normally noncurrent carrying conductive materials to the to the CEE (steel columns tied to the foundation) which will be bonded back to the source ground via the grounding electrode conductor.

Perhaps you can clarify what exactly you are doing. Maybe we are interpreting this wrong. With a "normal" code compliant installation, equipment cases connect to the branch circuit EGCs, then the feeder EGCs and back to the service where they land with the neutral (typically) thru the main bonding jumper and the Grounding electrode system connects there too. Are you proposing to run some sort of separate bonding jumper from equipment directly to the grounding electrode system? As was noted by another member, you do need an EGC run with the other circuit conductors but if you have that I see no code violation with running additional bonding jumpers directly to the GES but it would be unconventional and I cant think of what purpose or benefit it would provide.
 
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