Auxiliary Ground Electrode, Grounding Electrode System, where is the line

[W@ttson]

Do you consider its supply to be a branch circuit or a feeder?

If it's a branch circuit, no electrodes are required, but are permissible.

If it's a feeder, an electrode system is required.

In neither case is the supply's bare wire a GEC; it's only an EGC.

Yeah I guess that's what it comes down to. If you consider it as X or Y.

Its interesting, if you consider it as a feeder and a GES is required at the remote structure, its falls in to this part of my post #1

"Suppose you are wiring a detached garage. You install a 30A "subpanel" in the garage. You send a feeder of #10/3. You land your EGC in the panel from the feeder, you run a Ground electrode bonding jumper from 2 ground rods that you drove near the detached garage to the ground bar in the panel. Can it be thought of that the ground electrodes at the garage are auxiliary ground electrodes in the eyes of the main service ground electrode system (complying with 250.54 in reference to the main service GES) and the actual ground electrodes of the ground electrode system of the garage (complying with 250.50 in reference to the garage)?"

Kind of like the remote structure is a system of auxiliary electrodes in the eyes of the main GES, but to the remote structure, the electrodes are strict GES electrodes.

 

[W@ttson]

Thank you all for taking the time to offer your responses. I appreciate the discussions.

 

[jaggedben]

A GES belongs to a structure or building, not to any particular power source. A GES at a separate structure has no particular relationship to a service or GES at another structure. The NEC does not ever require multiple GES at separate structures to be connected by any kind of bonding jumper other than an EGC. (The exception in 250.32 allows them to be connected only by a grounded conductor when grandfathered.)

 

[wwhitney]

(The exception in 250.32 allows them to be connected only by a grounded conductor when grandfathered.)

Or, for completeness, even in new installations under 250.30(A)(1) Exception 2 and associated allowances.

Cheers, Wayne

 

[don_resqcapt19]

Yeah I guess that's what it comes down to. If you consider it as X or Y.

Its interesting, if you consider it as a feeder and a GES is required at the remote structure, its falls in to this part of my post #1

"Suppose you are wiring a detached garage. You install a 30A "subpanel" in the garage. You send a feeder of #10/3. You land your EGC in the panel from the feeder, you run a Ground electrode bonding jumper from 2 ground rods that you drove near the detached garage to the ground bar in the panel. Can it be thought of that the ground electrodes at the garage are auxiliary ground electrodes in the eyes of the main service ground electrode system (complying with 250.54 in reference to the main service GES) and the actual ground electrodes of the ground electrode system of the garage (complying with 250.50 in reference to the garage)?"

Kind of like the remote structure is a system of auxiliary electrodes in the eyes of the main GES, but to the remote structure, the electrodes are strict GES electrodes.

No, the garage requires its own grounding electrode system and those rods are the required grounding electrode system, along with any other electrodes that may exist at the garage. The connection between the rods and the panel is a grounding electrode conductor. You may want to think of the feeder EGC as a grounding electrode bonding jumper that connects the grounding electrode at the house to the grounding electrode system at the garage, but its main function is as an equipment grounding conductor for fault clearing purposes.

 

[jaggedben]

... You may want to think of the feeder EGC as a grounding electrode bonding jumper that connects the grounding electrode at the house to the grounding electrode system at the garage, but its main function is as an equipment grounding conductor for fault clearing purposes.

To be clear, under NEC rules that is its *only* function.

 

[W@ttson]

No, the garage requires its own grounding electrode system and those rods are the required grounding electrode system, along with any other electrodes that may exist at the garage. The connection between the rods and the panel is a grounding electrode conductor. You may want to think of the feeder EGC as a grounding electrode bonding jumper that connects the grounding electrode at the house to the grounding electrode system at the garage, but its main function is as an equipment grounding conductor for fault clearing purposes.

In my day to day I get bullied into adding a ton of ground electrodes in tons of places, I like utilizing an EGC to interconnect and serve as my ground electrode bonding jumper. (Partially bullied, partially trying to abide by some standards outside of the NEC).

In other words I auxiliary electrodes and their ability to be connected by EGC to the system.

I remote GES and their ability to be connected back to the main service via EGC.

Yes, I understand the detach garage GES and the main building GES and their individual requirements. I just like that the interconnection does not need to be sized per 250.66, but rather it’s sized as a regular EGC.

This allowance gets me out of some sticky situations where utilizing existing cables installed in places that cannot be replaced and then having other exterior entities require me to start slapping electrodes in remote areas.

 

[jaggedben]

In my day to day I get bullied into adding a ton of ground electrodes in tons of places, I like utilizing an EGC to interconnect and serve as my ground electrode bonding jumper. (Partially bullied, partially trying to abide by some standards outside of the NEC).

That makes me feel bad for you. I certainly hope that by 'bullied' that you do not mean that you are not getting paid for the work and materials. Also in my understanding it is possible that in some instances those extra electrodes do more harm than good. Personally I would not let myself be bullied into installing electrodes that were not required by code, engineered plans, or manufacturers instructions.

In other words I auxiliary electrodes and their ability to be connected by EGC to the system.

I remote GES and their ability to be connected back to the main service via EGC.

Yes, I understand the detach garage GES and the main building GES and their individual requirements. I just like that the interconnection does not need to be sized per 250.66, but rather it’s sized as a regular EGC.

This allowance gets me out of some sticky situations where utilizing existing cables installed in places that cannot be replaced and then having other exterior entities require me to start slapping electrodes in remote areas.

So was there ever a real problem or a question here? I guess not. Carry on. Hope we helped.

 

[W@ttson]

That makes me feel bad for you. I certainly hope that by 'bullied' that you do not mean that you are not getting paid for the work and materials. Also in my understanding it is possible that in some instances those extra electrodes do more harm than good. Personally I would not let myself be bullied into installing electrodes that were not required by code, engineered plans, or manufacturers instructions.



So was there ever a real problem or a question here? I guess not. Carry on. Hope we helped.

Everyone gets paid, I get paid, copper industry gets paid, contractor gets paid. The electrodes are not required by NEC but are required by other standards I need to adhere to and the client expects certain ohmic values. I few years ago I had my head blown away with the actual purpose of ground electrodes and since then I have not looked at them as the holy grail of solving all problems and cringe when I see typical details of pull boxes with ground rods called out. But traditions are tough to break and the public’s perception is also hard to sway.


There wasn’t anything specific. Sometimes I think about the NEC, how it relates with what I do, and try to look at the codes application. Or alternate interpretations of sections. I also like to discuss sections that I find contradicting other sections under specific circumstances.

I did find the discussions here helpful on this topic. I hope others did as well and I hope someone in the future looking into auxiliary ground electrodes, GES systems, and the requirements of 250.50 finds it helpful.

 

[LarryFine]

A concern with extra remote electrodes is that nearby lightning can cause voltage gradients that in turn raise the voltage on equipment that causes currents between equipment that are normally equi-potential.