GES conductor sizing

[TimNY]

Ok, not my forte` (heck I'm just getting the lingo down), but I am seeing installations approved that don't appear correct.

I'm going to lay out how I interpret the code, and I'd appreciate if you guys could steer me in the right direction.

IRC states that the GEC and the bonding jumpers must be sized in accordance with E3503.1.

In examining E3503.1 for a 2/0 200a service (2/0 being the governing factor in the table, not the amperage), I see that the minimum conductor size is 4ga copper.

What I am used to seeing is (2) grounding rods installed 6' apart. Each rod has a #6 conductor to the panelboard. I see that E3503.1 fn d says, in part, "Where the sole grounding electrode system is a ground rod or pipe as covered in Section E3508.2, the grounding electrode conductor shall not be required to be larger than 6 AWG copper or 4 AWG aluminum."

So I get where the #6 is coming from. Rather than do the resistance test, they pound a second rod per E3508.4.

What I don't get is why #6 is allowed when a metal underground water pipe is bonded (maybe it shouldn't be). The same is true of a system that may have an CEE and a ground rod. In these scenarios shouldn't the GEC and bonding jumper be a #4?

I have never seen an install without the ground rods. Am I missing something, or could you simply bond an underground water pipe with a #4 and forgo the ground rods altogether? The same question with a CEE?

Sorry if these seem like trivial questions; what I think I know and what I see are two completely different things. I'm not too ashamed to ask for help!

Thanks!

 

[chris kennedy]

"Where the sole grounding electrode system is a ground rod or pipe as covered in Section E3508.2, the grounding electrode conductor shall not be required to be larger than 6 AWG copper or 4 AWG aluminum."

Your over looking the important wording.

250.66(A) Connections to Rod, Pipe, or Plate Electrodes. Where the grounding electrode conductor is connected to rod, pipe, or plate electrodes as permitted in 250.52(A)(5) or (A)(7), that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.

 

[TimNY]

By strict wording of the IRC.. if a ground rod is not the sole grounding electrode, the conductor must be #4. At least, that is what I am reading.

I can definitely see where the conductor to the ground rod is allowed to be #6 in all scenarios per the NEC section you quote. E3301.2.1 would allow you to follow the NEC and comply with the #6.

What about just running a #4 to the CEE or the metal water pipe (when only one exists for a building) and calling it a day?

Thanks for your help.

 

[Francis Vineyard]

Tim, you’re not alone in discovering how easy it is to understand and navigate NFPA.

It’s the sole conductor or the conductor that only serves the ground rod(s) or pipe.

If there is only a water pipe then the current code requires it be supplemented which is usually done with a rod. Typically in this set up a #4 to the water pipe then a #6 from the water pipe or main panel to the rod.

I think the NFPA 70 could do a better explanation of sizing "common" grounding electrode conductors and bonding jumpers with Table 3503.1 to distinguish the sole connection.

 

[TimNY]

Thanks Francis. Footnote d is misleading to me. I guess you need to interpolate that since the 'd' is next to the conductor size; 'sole grounding electrode system' is in relation to that conductor and not a broad statement.

Since you can comply with either the E-chapters or the NEC, I don't see where the E-chapter requires a metal water pipe or a CEE to be supplemented. I have to reread if I can find time at the office. Reading online is tedious.

 

[north star]

* * * *

TimNY,

That's why some jurisdictions are not adopting the IRC

chapters of electrical, but rather adopting the NEC in

it's entirety, ...hopefully to reduce the confusion somewhat!

I agree with others on this forum that the NEC is a very

hard standard to read & interpret.



* * * *

 

[TommyJay]

"What I am used to seeing is (2) grounding rods installed 6' apart. Each rod has a #6 conductor to the panelboard."

I came across a situation where a panel had ONE #6 conductor connected to BOTH grounding rods. I looked in the Codecheck electrical field manual and found nothing that specifically states that each rod had to be connected separately to the panel. The manual covers commonly made electrical code errors, so my question is: what is addressed in full regarding ground rods?

 

[TimNY]

Chris or Francis can correct me, but afaik a single #6 is fine in that situation.

The violation comes when they use a single ground rod clamp to secure the GEC and the bonding jumper to the next rod. A single conductor run through the acorn nut to the next rod is fine.

I still don't see where in the E-chapters of the IRC it states you have to supplement a water pipe or a CEE with ground rods.

 

[Francis Vineyard]

Tim & Welcome aboard TommyJay

E3805.1.1-2003 or E3805.1.1.1-2006 Typically acorn clamps are listed for a single conductor; so the conductor is usually unspliced through the first rod clamp. However it is permitted to terminate the wire at the first rod; then have the another clamp with the bonding jumper continue to the next rod, pipe or plate electrode per E3508.2-03 or E3508.3-06

TommyJay may want to consider getting the Illustrated Guide To The National Electric Code by Charles R. Miller, can use this book for residential instead of buying the residential version.

Learn to use the cross-reference in Appendix in the IRC; CAUTION some devices and applications are different between the two code books and should be enforced accordingly to the AHJ.

I thought there's a thread discussion of electrical study books but no success.

 

[peach]

grounding is NOT bonding.. two different critters. You don't run a ground to the cold water - you bond it.

 

[north star]

& & & &

Another word for bonding is "connected".

# # # #

 

[raider1]

grounding is NOT bonding.. two different critters. You don't run a ground to the cold water - you bond it.

If the cold water pipe has 10 feet in contact with the earth and qualifies as a grounding electrode then you do run a grounding electrode conductor to it. (Or possibly a bonding jumper from another electrode.)

Grounding is defined as connecting an object to the earth.

Bonding is connecting non-current carrying metal parts of electrical systems together and to the source to provide a fault current path.

Chris

 

[peach]

then copper water service pipe always qualifies and no CEE or ground rod is required?

 

[Bryan Holland]

then copper water service pipe always qualifies and no CEE or ground rod is required?

No. ANY of the recognized electrodes that are present must be bonded together to form the grounding electrode system. Its not a choice. If the electrode exists, it must be used.

The ONLY electrode that is required to be supplemented is the metal water piping. ANY of the other recgonized electrodes can serve as the supplement.

 

[TimNY]

Thanks, Bryan. Seems like a simple enough concept but I for one was confused. I know there are electricians that are in the same boat.