depth of grounding ring

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kfenn22

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what is the min. depth that you can buried a grounding ring?
The ring will not have any grounding rods, we are just using 2/0 bare copper.

I have always used 30" min, but I was told by a grounding company that 18" is the min depth. 18" allowed by NEC?

We have ran into bedrock at 2'-0" below grade.

Please help.
 
250.53(F) says 30" minimum. There are no exceptions listed. You can either back fill to get the 30" or use another type of electrode.
 
A CEE has no minimum burial depth. Now the question: can you _add_ a CEE to a building without major work on the building foundation. Can a CEE be spaced away from the building?

-Jon
 
Concrete Encased Electrode, or 'Ufer'.

Normally this is the rebar in the foundation, but it can be 4ga or larger bare copper wire in the concrete. The requirements are that the electrode be surrounded by a minimum of 2" of concrete, near the base of the concrete, that the concrete be a 'foundation or footing', and that the concrete be in contact with soil. No burial depth requirement.

-Jon
 
kfenn22 said:
what is the min. depth that you can buried a grounding ring?
The ring will not have any grounding rods, we are just using 2/0 bare copper.

I have always used 30" min, but I was told by a grounding company that 18" is the min depth. 18" allowed by NEC?

Please help.
Click to expand...

The 18" depth for a ground ring is the requirement under NFPA 780 Lightning Protection Systems Maybe that's whare you came up with 18"?
 
infinity said:
250.53(F) says 30" minimum. There are no exceptions listed. You can either back fill to get the 30" or use another type of electrode.
Click to expand...

I was on a construction site once where the ground ring and grid were laid directly on top of the ground, the poured over with concrete.
 
masterelect1 said:
That does not fit the definition of "encased"
Click to expand...

Yea really. :) They actually had to drills holes in the slab forms to poke the ground conductor through. They had forgotten to install the ground system and didn't want to go back and do it since they had already prepped the site for the slab. The only person with the authority to make them do it was spineless, so it was installed that way.

Ironically, it was a Rail Gun test facility on a naval base...they had 2 MJ of capacitor inside to power the electromagnetic launcher, and grounding was particularly important to them.
 
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