Grounding Code

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triniboy

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Hi out there can anybody help me I am on a construction site for a new LNG plant and I want to know does a a bare copper 4/0 ground wire that is run in a trench have to have a concrete covering on it like other trenches to meet the NEC code
 

infinity

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What is the purpose of this #4/0 conductor? Is a part of a grounding ring?

Welcome to the forum. :)
 

A/A Fuel GTX

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WI & AZ
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Electrician
Assuming it is a Concrete Encased Electrode, yes. See 250.52(A)(3). However, it only has to be a #4 CU to meet code. Anything larger is a design issue.
 

triniboy

Member
infinity said:
What is the purpose of this #4/0 conductor? Is a part of a grounding ring?

Welcome to the forum. :)
Yes it is part of the grounding grid for the plant other sections of the grid are contained in the trenches with the electrical and instrumentation cables which have a concrete layer of 2" minimum but at some places they have constructed trenches just for the grounding cable so I was wondering if these grounding trenches need the concrete cover as well.
 

infinity

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If this conductor is part of a grounding ring then it only needs to be covered by 30" or more of dirt. Look at 250.52(A)(4) and 250.53(F).
 

cowboyjwc

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While I don't disagree with Rob. I think that your soil conditions might dictate whether you encase it with concrete or not. I believe that the reason it is a "concrete encased electrode" is because if you just lay it on the ground there is a good chance that it will just rot away.
 

winnie

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Springfield, MA, USA
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Electric motor research
A _copper_ ground ring needs to be thick enough, but need only be buried in soil. You are not permitted to use rebar to make a 'ground ring'.

A 'CEE' can be made with rebar and tie wire, but it must be encased in concrete.

Rebar buried directly in soil would vanish quite quickly. Copper would last quite a bit longer.

Note that if you have lots of copper buried in the soil forming a ground ring, and you also have concrete encased electrodes, the CEE can become a sacrificial anode relative to the copper. See http://ecmweb.com/design_engineering/electric_cathodic_protection_systems/

-Jon
 
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