250.53(F), 2017 NEC

[Dale001289]

The above article states:
"The ground ring shall be installed not less than 750mm (30 in.) below the surface".

If the ground ring is supplemented with ground rods, does it still have to be buried 30"? Both qualify as grounding electrodes.

In my industry, i.e. refineries and chemical plants, we frequently use a #4/0 bare copper grounding conductor as the so-called 'main ground ring' with taps to equipment usually @ #2 AWG or #2/0 AWG.
To obtain the required resistance of (usually) less than 5 ohms, the #4/0 is typically supplemented with ground rods to form the overall equipotential grid. Is the #4/0 therefore, really a bonding jumper between rods? And if that's the case, is it no longer the 'ground ring' and can it be buried at a much lesser depth, of say 18"?

 

[jumper]

You stated it was a ground ring therefore it has to be 30" down.

Ground rings do not require supplemental electrodes, that is your spec.

 

[GoldDigger]

If the GECs/bonding jumpers connecting the rod electrodes happen to be bare copper and circle the building, then they do not have to follow the 30" specification for a ground ring. You just cannot take credit for having a ground ring if the contract calls for one.

 

[Dale001289]

If the GECs/bonding jumpers connecting the rod electrodes happen to be bare copper and circle the building, then they do not have to follow the 30" specification for a ground ring. You just cannot take credit for having a ground ring if the contract calls for one.

If grounds rods are all over the place, (as is usually the case with large chemical plants) whether or not we call it a 'ground ring' sounds like semantics.
I happen to agree with you (BTW), the problem I have is convincing the Client that 250.53(F) is not applicable.
Any suggestions?

 

[jumper]

If grounds rods are all over the place, (as is usually the case with large chemical plants) whether or not we call it a 'ground ring' sounds like semantics.
I happen to agree with you (BTW), the problem I have is convincing the Client that 250.53(F) is not applicable.
Any suggestions?

Does your contract/specs say to install a "ground ring" or not?

As I stated earlier, you called it a ground ring.

 

[jumper]

Similar thread:

http://forums.mikeholt.com/showthread.php?t=88841

 

[Dale001289]

Similar thread:

http://forums.mikeholt.com/showthread.php?t=88841

I read it - good stuff, thanks.
I also checked the contract/specification; they both call for a "#4/0 bare copper ground 'loop' along with driven ground rods"...

Is a ground 'loop' and a ground 'ring' the same thing? Does it even matter what we call it if accompanied by ground rods?
I believe the 30" depth is not required in this case.

 

[Smart $]

I read it - good stuff, thanks.
I also checked the contract/specification; they both call for a "#4/0 bare copper ground 'loop' along with driven ground rods"...

Is a ground 'loop' and a ground 'ring' the same thing? Does it even matter what we call it if accompanied by ground rods?
I believe the 30" depth is not required in this case.

Ground 'loop' is not NEC terminology. You'll have to RFI whoever wrote the spec' as to whether they meant Ground Ring or otherwise.

Technically, it cannot be a ground ring unless it is buried not less than 30" AND it completely encircles the building or structure. Anything short of that disqualifies it as a Ground Ring... but it can still be a ground 'loop'.

 

[jumper]

I read it - good stuff, thanks.
I also checked the contract/specification; they both call for a "#4/0 bare copper ground 'loop' along with driven ground rods"...

Is a ground 'loop' and a ground 'ring' the same thing? Does it even matter what we call it if accompanied by ground rods?
I believe the 30" depth is not required in this case.

IMO, if it says ground loop-then it is a vague description that is not in the NEC.

If it says ground ring, then I would say it has to be installed per code since that is defined.

 

[Dale001289]

Ground 'loop' is not NEC terminology. You'll have to RFI whoever wrote the spec' as to whether they meant Ground Ring or otherwise.

Technically, it cannot be a ground ring unless it is buried not less than 30" AND it completely encircles the building or structure. Anything short of that disqualifies it as a Ground Ring... but it can still be a ground 'loop'.

Good point Smart. We see this constantly in the Petro-Chem industry. Contract says 'loop' but really means 'ring' - or does it?
One of our tasks is to protect the Client from himself. Many simply don't know the NEC that well.
I can see benefit to burying the ring at 30" - usually, soil is wetter. But once we throw rods into the mix, I believe it no longer matters what we call it since the rods become the primary electrode.
We need to reach and maintain 5 ohms max on the equipotential plane. This is the bottom line.