Delete Section 250.66

[bphgravity]

1. 250.66 and the Table

2. Delete all the text, add new text in 250.66, delete 250.66(B).

3. Delete Table 250.66 and reword 250.66 to state, "The size of the grounding electrode conductor of a grounded or ungrounded ac system shall not be less than 4 AWG copper wire or 2 AWG aluminum wire, except as permitted in 250.66(A).

4. Instead of me providing substantiation for the change, how about the CMP provide me substantiation for requiring a GEC larger than #4 copper for any application?

I have two structures both served with 600 kcmil service entrances. One has a underground metal water pipe, the other has no present electrodes. The first structure requires a 2/0 GEC the second only requires a ground rod or two and #6 AWG GEC. Both are compliant to the MINIMUM requirement of the NEC and will both ne as effective for whatever purpose the grounding electrode system supposedly accomplishes.

If a concrete encased electrode is considered to be the most effective and low-impedance electrode of choice, than why is it only required to be connected with #4 while other possibly less effective electrodes require such large conductors?

The code is suppose to be a minimum standard and exceeding what is proven to be an acceptable minimum installation is a design consideration and should not be in the NEC.

 

[jwelectric]

Re: Delete Section 250.66

I agree with you in part based on a question I was asked. This question can be found here .

If the concrete encased electrode that is tied to the building steel why would two different conductors be required and why would one need to be larger than the other?

 

[George Stolz]

Re: Delete Section 250.66

I believe it will hit the floor with a thud, but it could be a resounding thud.

I'd be at the edge of my seat to see their response.

 

[ryan_618]

Re: Delete Section 250.66

Originally posted by georgestolz:

I'd be at the edge of my seat to see their response.

Response:

Submitter has not provided a technical substantiation. Action: Reject.

 

[George Stolz]

Re: Delete Section 250.66

 thud

 

[bphgravity]

Re: Delete Section 250.66

My technical substaniation is that the code is a minimum standard. If a structure is considered compliant to the code and completely safe with only a #6 to a couple of grounds, then there is no reason to require a water pipe to be connected with anything larger.

It's not logical nor should be a code require to require anything above the minimum. Simply changing the electrode type shouldn't change the minimum safety requirement.

If the table is accurate, then I guess we should suppose all electrical systems that are only connected by ground rods are unsafe.

 

[sandsnow]

Re: Delete Section 250.66

I agree
If I can connect a 2000amp swbd to one grd rod(with 25 ohms or less) and only need a #6, why do I have to use anything larger for any other type of electrode.

Bryan, bravo

 

[ryan_618]

Re: Delete Section 250.66

Works for me. Give it a shot.

 

[peter d]

Re: Delete Section 250.66

The only problem I see is that Table 250.66 would still need to remain or be relocated because we still need it to size main bonding jumpers per 250.28(D), don't we?

Or does it not matter? (Something tells me it may not be an issue because the MBJ is an part of the GEC system.)


At any rate, I like the proposal. I can only speak from the residential front, but many new homes have a platic water main and plastic interior plumbing. In this case we would only need to drive 2 ground rods and bond to the rebar. Let's assume a 400 amp service. Well, we know how this will turn out. If we have a metal water pipe, I need a 1/0. But in the absence of that, I'm fine with a #6. Yeah, I'm really liking this one Bryan.