Ground ring installation

[mshSnow]

The engineer who designed the electrical system for a new facility we'really building had new grounding ring connected to near by building ground grid. Is there any code requirement for this? Can we just have that connected to a different grounding source such as a column? I do not see anything wrong since all columns are bonded to the grid anyway, unless there is a code or standard requiremwnt. Let me know what you guys think.

 

[Marmite]

Ask the designer. Grounding is a system, which is safety critical. The designer is best placed to be able to determine the sensitivity of the ground grid design to your proposed on site changes.

Regards
Marmite

 

[7anoter4]

In my opinion, it is very difficult to calculate and to test the foundation grounding [Ufer Grounding].
So any means to reduce the grounding resistance has to be exploited.
The foundation grounding create a safety cage in order to mitigate the touch voltage and to protect sensible electronics against transient voltages.
The IEEE 142 standard ch.4.2 Ground electrodes 4.2.3 Concrete encased electrodes recommends this foundation grounding type.
NEC art.250.52 Grounding Electrodes.(A) Electrodes Permitted for Grounding. (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.”
If the foundation grounding was not correct executed-or there is any doubt about this-a grounding grid is a required solution.

 

[7anoter4]

Sorry. “Grounding ring” I mean instead of “grounding grid”.

 

[waross]

Do I understand that the ground grid for a new building is to be connected to the ground grid of an existing building?
Does the same party own both buildings?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mshSnow]

Waross...this is correct. Both buildings are owned by one party, and all power sources are in existing buildings. It just would save time/cost to not have to trench and locate existing ground ring. From answers here, it seems like there is no reason why we can't use other means of grounding such as columns...etc.

 

[jghrist]

There will need to a grounding electrode for the new building that meets the requirements of NEC 250 III. The connection to the existing building grounding electrode system will be through the grounding conductor of the circuit serving the new building.

 

[cuky2000]

The NEC 250.52(A)(2) allow the use the Metal Frame of Building or Structure as a grounding electrode conditioned that the metal frame of a building should be at least 10 ft. in contact with the earth, or the hold-down bolts of a steel column are connected to a concrete-encased electrode (rebar). The connection from the hold-down bolts to the concrete-encased electrode can be by welding, exothermic welding or using steel tie down wires. To avoid misinterpretation or controversy in this issue, check with your local NEC Authority Having Jurisdiction (AHJ).

From the technical point of view a reinforced concrete column is comparable with a ground rod. See the figure below.