250.66

[augie47]

To me the Code is clear, 250.66(A) addresses the "size of alternating-current grounding electrode conductors (Section title) to (A) rod, pipe or plate electrodes is not required to be larger than #6.
That section does not even discuss routing simply provides the size.
The only caveat is "sole connection to the electrode" which covers the somewhat unique situation where one might run to the rod and the from the rod to another electrode such as the water system in which case the #6 would be a "weak link in the chain", but as long at the electrode conductor in question attaches only to the ground rod it needs only to be a #6.

 

[charlie b]

Gus, I know I can go from the N-G bond directly to a ground rod, and only need to use #6. But if there is a ground bar in the middle of that run, the not-so-clear point is whether all the conductors, starting at the N-G bond and ending at the rod, all of them (in my case both of them, the two on either side of the ground bar on the wall) get to be called GECs. Consider a high rise building with an electrical room on each floor, and with a step-down transformer in each electrical room. I put a ground bar on the wall of each room, and run a wire from the 15th floor room's bar to the 14th floor room's bar, and so forth all the way down to the main electrical room on the first floor, and from there to a pair of ground rods. Are all of those wires GECs? Right now, I am thinking that the only wires that get to be called GECs are the ones that go from each floor's N-G bond point to the ground bar in that room, and the one that goes from the main service panel's N-G bond point to the ground bar in that room. All the rest are bonding jumpers, and that includes the wires going to the ground rods.

 

[augie47]

To me 250.64(F) allows that bar and does not change the size of the electrode conductor to the rod (from the bar) (the caveat I mentioned above would require the jumper to the bar to be larger than the #6).
The analogy to the transformers seems misplaced (no offense intended) as it is discussed in 250.30 and is unique to multiple SDS.

 

[david]

250.64 (F)
Grounding electrode conductors &
Bonding jumpers interconnecting grounding electrodes
250.64 (F) (1) bonding jumpers per 250.53 (C )
250.53(C) Bonding Jumper. …………………………………..be sized in accordance with 250.66, and shall be connected in the manner specified in 250.70.
250.66 Size of Alternating-Current Grounding Electrode Conductor……………………except as permitted in 250.66(A) through (C).


As I see it is a bonding jumper that is sized in compliance with 250.66 including (A) through (C)

This forum has debated sizing of grounding electrode systems before, its the same debate except a bar has been added as a legal portion to tie the bonding jumpers to. It is just an additional link in the system.

 

[charlie b]

OK, thanks David.

 

[david]

I am sure you see these all the time. You drill a bunch of holes in a flat bar and mount it on the wall. It becomes a common connection point for anything that needs to find its way to planet Earth. There will be wires running from similar bars in electrical rooms and telecomm rooms throughout the building, all of them tied to the bar in the main electrical room. It is not a substitute for the ground bar in the main panel. Indeed it is not for connection of equipment grounding conductors.

That's the part I think is unclear, 250.64(F) allows the bar and I said it is treated as a link in the grounding electrodes. it is not being defined as a grounding electrode, I think its very gray if this bar can be used to interconnect different systems. I think the code is silent on that, it only indicates it is allowed for a specific purpose. on the other hand I don't think it is an issue how would interconnecting other systems at this bar hurt anything

 

[charlie b]

250.64(F) allows the bar and I said it is treated as a link in the grounding electrodes. it is not being defined as a grounding electrode

It could not be. You don't get to call something a grounding electrode unless it touches dirt.

on the other hand I don't think it is an issue how would interconnecting other systems at this bar hurt anything

I agree with you here. I also see no difference (electrically) between putting this bar in the middle or going directly from N-G bond to dirt. But the words, as written, do appear to treat the two installations differently.

 

[electrofelon]

I am sure you see these all the time....

Yes I see lots of things all the time and it doesnt meet its code compliant But in this case, I stand corrected. As David noted, 250.64(F) allows this. My recollection was that the "busbar method" was only for services with multiple service enclosures (250.64(D)(3)). Was this a semi recent change/addition? I swear I remember a thread about this a while back and how the busbar method was only for multiple enclosures...?

 

[wwhitney]

• Is the wire from the ground bar on the wall to the ground rod a "grounding electrode conductor," thus allowing it to be sized at #6, or
• Is that wire a "bonding jumper," thus requiring it to be sized at 3/0?

Why should a bonding jumper be required to be 3/0 in this scenario?

In the 2011 NEC, 250.53(C) says that bonding jumpers "shall be sized in accordance with 250.66". It refers to all of article 250.66, not just Table 250.66. So the permission in 250.66(A) for #6 copper to connect to a ground rod applies to the bonding jumper as well.

Edit: I mean, the words "bonding jumper" don't appear in 250.66. So the only way to read 250.53(C) as a guide to sizing bonding jumpers is for its language to mean "read 250.66 and substitute 'bonding jumper' wherever you see 'grounding electrode conductor'".

Cheers, Wayne

 

[charlie b]

That's an interesting take on the situation, Wayne. But I'm afraid I can't agree with it. I know of no other circumstance in which the code lets us substitute one word or phrase for another when applying a code requirement to an installation. I can size a bonding jumper per 250.66 without trying to call it a GEC first. The bit about using a #6 with a ground rod is clear in its applicability to GECs.

 

[wwhitney]

I can size a bonding jumper per 250.66 without trying to call it a GEC first.

How? The words "bonding jumper" don't appear in 250.66.

A similar situation occurs in 338.10(4)(a): "In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334." The word "SE" never appears in Article 334; what 338.10(4)(a) is telling us is to treat the Type SE cable as Type NM cable and apply the provisions of Part II of Article 334 as if the SE cable were NM cable.

Likewise, 250.53(C) is telling us to treat the bonding jumper as a grounding electrode conductor and apply the provisions of 250.66 as if the bonding jumper were a grounding electrode conductor.

Cheers, Wayne

 

[david]

I can size a bonding jumper per 250.66 without trying to call it a GEC first.

I agree there is no reason to try and define it or call the bonding jumpers GEC. The NEC often sends us to different sections for specific application in this case sized per 250.66 and connected in accordance with 250.70

{250.70 Methods of Grounding and Bonding Conductor Connection to Electrodes.
The grounding or bonding conductor shall be connected to the grounding electrode by exothermic welding, listed lugs, listed pressure connectors, listed clamps, or other listed means).

In a bonded grounding electrode system the grounding electrode conductors terminates at the grounding electrode or a bonding bar, from that point in a bonded system bonding jumper bonds the electrode that the grounding electrode conductor landed on to the rest of the electrodes making up the grounding electrode system.

There is no need to try and call the bonding jumpers grounding electrode conductors

 

[wwhitney]

I'm not saying a "bonding jumper" is a "grounding electrode conductor". I'm saying that 250.53(C) instructs us to size it the same as a grounding electrode conductor under 250.66. When 250.53(C) sends us to 250.66 to size the bonding jumper, it references all of 250.66, not just table 250.66. Therefore 250.66(A) applies to the bonding jumper.

Now you might say "wait, 250.66(A) is talking about grounding electrode conductors, not bonding jumpers." By that logic, none of 250.66 could apply to bonding jumpers, as the words bonding jumper don't appear in it.

People seem to be reading 250.53(C) as if it said "sized in accordance with Table 250.66." It doesn't, it says "sized in accordance with 250.66." 250.66 specifically exempts installations covered under 250.66(A) from Table 250.66.

Cheers, Wayne

 

[Smart $]

That's an interesting take on the situation, Wayne. But I'm afraid I can't agree with it. I know of no other circumstance in which the code lets us substitute one word or phrase for another when applying a code requirement to an installation. I can size a bonding jumper per 250.66 without trying to call it a GEC first. The bit about using a #6 with a ground rod is clear in its applicability to GECs.

FWIW, I agrrreee with Wayne. Have all along, but I figured I'd let you guys hack it out.

Post #7

... I think intent has us sizing these "jumpers" no different than GEC's [250.53(C)].

 

[wwhitney]

FWIW, I agrrreee with Wayne.

OK, it's settled then.

Cheers, Wayne