Ground Ring requirement for electrical room espansion

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philly

Senior Member
We are currently looking at expanding the structure of an existing electrical room and I had a question regarding the ground grid/ground ring for the new expansion portion of the building.

It appears that the existing building has a ground ring which encompasses the building with ground rods and test wells installed at the buildings corners. When expanding the building we planned on tying into the existing buildings ground ring and running a 4/0 bare copper wire along the perimeter of the new building with ground rods at each of the corners. The bare copper wire will be run within the building slab and stub up above the slab at the proposed equipment locations for switchgear, mcc's, panels etc..

The 4/0 ground ring with ground rods a the corners is what I have typically seen done for such installations. Am I on the right track with this type of ground installation for a new building expansion? Is there NEC reference provides these requirements or is this just a typical industry practice? I know 250.66 has requirements for grounding conductor so I'm wondering if this installation is discussed here?

Also when installing ground rods I have seen them installed as a single rod as well as in a triad configuration. Are there requirements with dictate the use of either configuration?

Thanks
 

tom baker

First Chief Moderator
Staff member
The NEC covers ground rings in 250.52 (A)(3), min 20 ft bare 2AWG 30 inches deep encircling the building.
You don't state the voltage, but 4/0 with ground rods seems excessive for 277/480, unless you have been talking to the copper development association.
I think these types of ground systems are a hold over from some old boilerplate that never gets changed
Adding on, I don't see how you can comply with a ground ring.
And best of all, the NEC would required a concrete encased electrode, which is the best electrode by far, costs little and is simple to spec.
And its not promoted by the Rebar Manufactures Association
 

roger

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I agree with Tom, connect a #4 to the new CEE and be done with it. I have always wondered if design engineers are automatically give stock in a copper mine when they get their degree.:D

Roger
 

philly

Senior Member
Yes system voltage is 480V. Would things be different if a higher voltage (4.16kV, 13.8kV, etc...) was involved?

I agree that the ground ring I typically see is some boiler spec/detail or just what is blindly applied in a lot of cases. That is what provoked my question in order to understand the requirements rather than to just blindly apply it again.

So it sounds like rather than a ground ring, a simple concrete encased electrode will be sufficient. I'm thinking that this CEE would then have a #4 bare copper which tied into the existing ground system in the existing building as well as connect to any equipment in the new expansion. In the new expansion would you simply run the #4 from the CEE to the equipment locations. In the room there will be Panels, and VFD's on the wall. Would you simply run the #4 to these locations for connection to any equipment? Is it necessary to bond this to the rebar in the new slab?

I've also noticed several rooms that have a ground bar mounted on the wall which is connected to the ground wire coming up from the slab and then is used to connect panel grounds and grounds from separately derived system such as transformers etc... Any particular reason to use this ground bar as opposed to just connecting to #4 ground wire directly? Perhaps just for ease of multiple connections? Any NEC references for this?

Thanks
 

Smart $

Esteemed Member
Location
Ohio
The thing that concerns me is you are stating this is a building expansion. To me that means the existing ground ring has to be interrupted and extended around the addition. If you don't, either by leaving it in place or interrupting and not extending, you are effectively eliminating a grounding electrode from the system, which could be deemed a violation in and of itself.
 

kwired

Electron manager
Location
NE Nebraska
The thing that concerns me is you are stating this is a building expansion. To me that means the existing ground ring has to be interrupted and extended around the addition. If you don't, either by leaving it in place or interrupting and not extending, you are effectively eliminating a grounding electrode from the system, which could be deemed a violation in and of itself.
True, but if there is already an existing CEE or building steel - no additional GES components are really necessary other then connection to any additional service equipment that is being added.
 

Smart $

Esteemed Member
Location
Ohio
True, but if there is already an existing CEE or building steel - no additional GES components are really necessary other then connection to any additional service equipment that is being added.
I agree, no additional electrodes are necessary. But all existing electrodes are required to be part of the GES. I think the AHJ will say the ground ring must be maintained.
 

roger

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True, but if there is already an existing CEE or building steel - no additional GES components are really necessary other then connection to any additional service equipment that is being added.
I agree that an additional electrode is not necessary however, if the new CEE is not connected to the existing GES and it meets the requirement of being a CEE then it is an additional electrode and must be connected to the existing GES per 250.50

Roger
 

roger

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if you break the existing ground ring it is no longer a qualifying GE so nothing is required to be attached to it.
Even if the ring is broke and can no longer qualify as a ring the rods still qualify so they must be attached to the GES as well as an existing water pipe electrode, building steel, CEE's etc...

Roger
 

petersonra

Senior Member
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Key word highlighted.

That can be likened to disconnecting a ground rod... which is also a violation.

JMNSHO.

It is more like removing a ground rod that is not required in the first place.

You are only required to connect to qualifying GE. If it is no longer there, there is no need to attach to it.

As long as you are attached to the minimum number of required GE afterward, it does not matter if you remove an existing GE.
 

Smart $

Esteemed Member
Location
Ohio
JMNSHO.

It is more like removing a ground rod that is not required in the first place.

You are only required to connect to qualifying GE. If it is no longer there, there is no need to attach to it.

As long as you are attached to the minimum number of required GE afterward, it does not matter if you remove an existing GE.
I understand. Code says all electrodes that are present. So not required if not present.

The point is that the ground ring is present but will be broken. That is not the same as removing the ground ring. Is broken the same as not present??? Final say is AHJ's.
 

roger

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JMNSHO.


You are only required to connect to qualifying GE. If it is no longer there, there is no need to attach to it.
Which means the OP would have to remove all the ring components including the rods that he mentions. You may no longer have a ring electrode but you have rod electrodes still in place.


Roger
 

don_resqcapt19

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I understand. Code says all electrodes that are present. So not required if not present.

The point is that the ground ring is present but will be broken. That is not the same as removing the ground ring. Is broken the same as not present??? Final say is AHJ's.
If it is broken, it is no longer a ring.
If it is not a ring, it is not a required grounding electrode.
 

Smart $

Esteemed Member
Location
Ohio
If it is broken, it is no longer a ring.
No, it is still a ring, only a broken ring. Whether broken intentionally or not does not matter IMO. I agree with Roger's assessment.... for it to not be a ring, all the components of the ring must be removed.
 

petersonra

Senior Member
Location
Northern illinois
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(4) Ground Ring. A ground ring encircling the building or
structure, in direct contact with the earth, consisting of at
least 6.0 m (20 ft) of bare copper conductor not smaller
than 2 AWG.

A broken ground ring no longer "encircles" anything. Therefore it is not a qualifying electrode.

I understand. Code says all electrodes that are present. So not required if not present.

The point is that the ground ring is present but will be broken. That is not the same as removing the ground ring. Is broken the same as not present??? Final say is AHJ's.
The AHJ does not get to make this stuff up. If it does not encircle the building the ring itself is no longer a qualifying GE.

Which means the OP would have to remove all the ring components including the rods that he mentions. You may no longer have a ring electrode but you have rod electrodes still in place.


Roger

Just because the ring is broken does not mean the leftover rods are still not using the 4/0 buried cable as a bonding means to the other GE.

If it is broken, it is no longer a ring.
If it is not a ring, it is not a required grounding electrode.

No, it is still a ring, only a broken ring. Whether broken intentionally or not does not matter IMO. I agree with Roger's assessment.... for it to not be a ring, all the components of the ring must be removed.

The rods are not part of the ring. They are extra GE that have to be connected unless removed.
 

roger

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Just because the ring is broken does not mean the leftover rods are still not using the 4/0 buried cable as a bonding means to the other GE
And what do you think I've been saying? In post #3 I said to connect a #4 to the new CEE and be done with it, this would simply mean connecting the new CEE to the existing GES which would include the remnants of the ring.

In post # 9 you said nothing needed to be connected to it

Roger
 

don_resqcapt19

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No, it is still a ring, only a broken ring. Whether broken intentionally or not does not matter IMO. I agree with Roger's assessment.... for it to not be a ring, all the components of the ring must be removed.
When I proposed a "grounding lateral" to be used as permitted grounding electrode, the panel comments made it very clear that the only buried conductor that can be used as a grounding electrode is one that completely encircles a building. A broken ring does not completely encircle the building.
 

GoldDigger

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When I proposed a "grounding lateral" to be used as permitted grounding electrode, the panel comments made it very clear that the only buried conductor that can be used as a grounding electrode is one that completely encircles a building. A broken ring does not completely encircle the building.
That makes a lot of sense. But if there are two or more rod electrodes connected along the way, then the wire which would have been part of the ring becomes simply the GEC or bonding jumper(s) and still both can and must be connected as part of the GES. It just is not a ground ring and not subject to any of the special provisions applicable to ground rings.
 
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