300-5 when related to Grounding Electrode Conductor

Hello,

Back story on issue. I am working on a project where the 4/0 tinned bare copper GEC for a centrally located electrical room has been installed after all underslab conduit was installed but before the slab is to be poured. It has been laid on top of the vapor barrier and run approx 75' feet to the foundation wall where it was sleeved with PVC through the wall to the exterior ground ring of the facility. I had flagged this installation based on the 300-5 colunm 1 as requiring an installation of any cable or conductor to be installed in conduit as it is a conductor under a slab of a building. As it is installed right now there is only the thickness of the concrete slab over it. My understanding from school and mentors has always been that not only is installing the GEC in conduit when below a building slab, this is good practice because if anyone ever needed to cut or drill the slab for whatever and cut the unprotected GEC there could be a risk of accidental energzation of the structure or equipment in the event of a fault somewhere. As the old addage goes. Current will source every path to ground not just the easiest. I have found that my interprtation of 250-64 is that it deals with the standard for an exterior installation but can't I find this instance of under a building slab specifically addressed. No the CM is telling me I'm way off base in my observation. I need help here guys. I don't mind being incorrect, but where is it written.... Thanks!
 

roger

Moderator
Staff member
The installation is fine as is. At our voltages (unless your central room has MV or HV) the GEC is for " (1) Electrical System Grounding Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation." It would not be carrying any current that could "energize" the building.

Not that it has any bearing on this but, by being under the concrete it is outside the building (see 230.6) and protected by the concrete.

Roger
 
The installation is fine as is. At our voltages (unless your central room has MV or HV) the GEC is for " (1) Electrical System Grounding Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation." It would not be carrying any current that could "energize" the building.

Not that it has any bearing on this but, by being under the concrete it is outside the building (see 230.6) and protected by the concrete.

Roger
So Roger, Not to belabor the issue but here is the rub.... It does meet all of your note (1) requirments which are achieved on the exterior of the facility. And like most others you address all the same issues of 250 responders. All which would still be attained if this installation were installed in conduit. So having met the requirement for it's ability to perform under the 250.64 and 230.6 sections..... now we have to address how it's installed which 250-nowhere does not address under the slab of a facility. so we must look to installations and burial depths which is covered under 300-5.... The column (1) specifically states cables and conductors which are direct buried. it gives depths and a note that states under a building slab to be installed in conduit.... it is clear not to state a type of cable or conductor. it just says conductor. my question better defined is not whether it meets 250.64, but rather why is it not a violation of 300-5? Thank you Sir!!
 
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roger

Moderator
Staff member
my question better defined is not whether it meets 250.64, but rather why is it not a violation of 300-5? Thank you Sir!!
So just so I'm clear on your position, you would say the GEC and jumpers below would be a violation of 300.5.

I would actually agree but, I don't see how 300.5 applies to a GEC's



BTW, welcome to the forums

Roger
 

tom baker

First Chief Moderator
Staff member
Burial depth for GEC is not required to comply with 300.5. The CMP has discussed this before, and determined that its obvious what the conductor is for. They didn't want the ground rod conductor buried 24" then coming up to a ground rod and then back down to 24".
 

jwelectric

Senior Member
The note under 250.4(A)(1) also mentions that there should be as few bends in the conductor as possible.
 

don_resqcapt19

Moderator
Staff member
From proposal 3-39 for the 2014 code.
Substantiation: Although grounding electrode conductors and bonding jumpers are not required to meet the minimum cover requirements of this table some inspectors have been requiring them to be installed as such. Their (incorrect) interpretation of this table is that an individual grounding electrode conductor or bonding jumper would fall under Column 1 which is for Direct buried Cables or Conductors. The addition of this not the T300.5 will clarify that the conductors listed in Column 1 are not grounding electrode conductors or bonding jumpers.
Panel Meeting Action: Reject
Panel Statement: The scope of Article 300 covers wiring methods for all wiring installations, unless modified by the other articles in Chapter 3. Article 300 and Table 300.5 would not apply to grounding electrode conductors and bonding conductors installed from the grounding electrodes to the grounding electrode, unless a wiring method provides physical protection as required by 250.64(E).
It appears to me that CMP 3 is saying that if the cable is directly buried, then Article 300 does not apply, but if it is in a protective raceway, it does apply:?
The following is part of CMP5's comment on the above proposal.
Submitter: Code-Making Panel 5, Comment on Proposal No: 3-39
Recommendation: Code-Making Panel 5 recommends continuing to reject the change to Table 300.5. However, Code-Making Panel 5 agrees with the submitter that the requirements are unclear, but that 250.64(B) should be amended by adding the following text:
Grounding electrode conductors and grounding electrode bonding jumpers shall not be required to comply with 300.5.
Substantiation: There is continuing confusion as to whether or not Table 300.5 applies to grounding electrode conductors and grounding electrode bonding jumpers. Code-Making Panel 5 agrees with the submitter that Table 300.5 should not be used because it introduces requirements that may not be appropriate. For example, installing the grounding electrode conductor where it is routed down the exterior wall of a building, offset to the burial depth, and then back up to connect to an electrode that is close to the foundation wall would introduce sharp bends that would decrease its effectiveness. However, Code-Making Panel 5 prefers to include this clarification in 250.64(B) where the other requirements for the installation of Grounding Electrode Conductors are located.
 
So just so I'm clear on your position, you would say the GEC and jumpers below would be a violation of 300.5.

I would actually agree but, I don't see how 300.5 applies to a GEC's



BTW, welcome to the forums

Roger
Thank you all for the clarification on this issue!!!! I have a much better grasp of the issue and answer... Chuck E.
 
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infinity

Moderator
Staff member
From proposal 3-39 for the 2014 code.

It appears to me that CMP 3 is saying that if the cable is directly buried, then Article 300 does not apply, but if it is in a protective raceway, it does apply:?
The following is part of CMP5's comment on the above proposal.
I'm glad that the CMP cleared that one up.:)

That proposal looks familiar. :roll:
 
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