GEC

[jbtass]

I have reason to believe the engineers I work with are sizing the Grounding Electrode Conductors (GEC) wrong. Please inform me if I am not doing this correct. This is not everything on the print will be here forever but heres partial as seen below:

800A 3Phase 480V MDP (2) parallel 500kcmil, Feeds 400A, 3Phase, 480v HP1, Feeds 75kVA xfmr, Which Feeds 200A, 3Phase, 120/208V LP1.

GEC Common 2/0 Main GEC from MDP to ground box 1 (GB1) with groundbar per NEC. tapped with 1/0 GEC from HP1 back to GB1, tapped with #6 GEC from xfmr back to GB1, tapped with #4 GEC from LP1 back to GB1, tapped with #6 GEC from Anode to GB1, tapped with 2/0 GEC from building steel to GB1. (23) groundboxes throught the facility basically done the same way.


My questions are: when multi tapping to the equipment the GEC has to be the sized per the largest conductor in the equipment.

Sorry for any troubles understanding easier to show one-line. Please let me know

 

[Dennis Alwon]

The grounding electrode conductor only needs to go to the MDP. 2/0 to the steel or electrodes available and that's it. Once you leave the 800 amp panels you are no longer in service equipment or am I missing something

 

[Pharon]

800A 3Phase 480V MDP (2) parallel 500kcmil

Unless I'm reading this wrong, isn't that a violation of 240.4(C)?

Edit: nevermind -- looks like it's fine UP TO 800A.

 

[jbtass]

should be more specific

should be more specific

I should have been more specific this is a grounding loop system that will run underground to about 30 ground boxes throughout the yard each ground box will then branch off into a seperate building creating a grounding system for each individual building as well as the entire yard. The grounding system is set up to be able to be tested at the main groundbar inside the Main Distribution Building. Which is why I need in this case a 2/0 GEC to each individual box. My main question is and either im not getting or the engineers are not getting from each ground box to equipment inside of the buildings should the GEC's Be sized per 250.66 or It is kind of a unique situation because it is not covered under the code book completely. You can take parts and try to combine these articles to cover what you would like done. My References 250.32 (E), 250.64 (D)(1),(2), 250.66.

 

[kwired]

I should have been more specific this is a grounding loop system that will run underground to about 30 ground boxes throughout the yard each ground box will then branch off into a seperate building creating a grounding system for each individual building as well as the entire yard. The grounding system is set up to be able to be tested at the main groundbar inside the Main Distribution Building. Which is why I need in this case a 2/0 GEC to each individual box. My main question is and either im not getting or the engineers are not getting from each ground box to equipment inside of the buildings should the GEC's Be sized per 250.66 or It is kind of a unique situation because it is not covered under the code book completely. You can take parts and try to combine these articles to cover what you would like done. My References 250.32 (E), 250.64 (D)(1),(2), 250.66.

I don't think the NEC applies to your ground loop system, all that it required is properly sized GEC at each building to all available electrodes at each building. I suppose your loop system could be considered a made electrode of some type but only requirements would probably be sizing of GEC to connect to it. (This all coming off the top of my head, no code references to go on as of yet from me)

 

[jbtass]

I don't think the NEC applies to your ground loop system, all that it required is properly sized GEC at each building to all available electrodes at each building. I suppose your loop system could be considered a made electrode of some type but only requirements would probably be sizing of GEC to connect to it. (This all coming off the top of my head, no code references to go on as of yet from me)

I agree with that. I think honestly if this is the way that they would like to design these grounding systems I am going to with worst case scenerios and go with my grounding system. Thank You for your response

 

[jbtass]

GEC is wrong

GEC is wrong

I have just found out that the standard for the company is 2/0 common GEC and #2 THHN every where else. It pisses me off when these engineers think because they have a degree they know what they are talking about. I know I might be just an electrician and I didn't go to a 6 year college. But these people are idiots and have know clue about electrical, the code, and what is going to work in the field. Engineers need to stick with their math equations and leave the electrical to people who know what the hell they are doing. Please reply

 

[iwire]

I have just found out that the standard for the company is 2/0 common GEC and #2 THHN every where else. It pisses me off when these engineers think because they have a degree they know what they are talking about. I know I might be just an electrician and I didn't go to a 6 year college. But these people are idiots and have know clue about electrical, the code, and what is going to work in the field. Engineers need to stick with their math equations and leave the electrical to people who know what the hell they are doing. Please reply

I am also an electrician, I make mistakes, you make mistakes and engineers make mistakes.

Here at Holts forum we expect a bit more restraint used and more respect given to each other.

 

[Pharon]

Maybe I'm missing something, but if your ungrounded conductors are 1000kcmil (2 sets of x 500), wouldn't that require your ground ring to be a minimum of #2/0 per Table 250.66? I'm looking at Exhibit 250.30 in the NEC Handbook, and it sort of implies that, anyway.

 

[__dan]

It's not clear exactly regarding your application, but I would look at the origin of each separately derived system for the application of the GEC. If you have a single SDS, 250.30 A 3 would apply with a GEC per 250.66 to the first electrodes and supplemental electrodes allowed to be interconnected or bonded to the first electrode with a smaller wire, maybe #6 to #4 depending.

If you are truly running a common GEC to connect multiple SDS's, 250.30 A 4 (a) would apply and the common GEC would be 3/0, suitable for tapping and tapped using irreversible listed connectors.

That is what I would pay attention to. I believe you may be in the first scenario with individual SDS's connected by GEC to the first grounding electrode per 250.66 and the 2/0 is a bonding jumper to supplemental electrodes. The point to examine is the individual SDS where the system bonding jumper is attached, the wire size to the first grounding electrode, and that the GEC is not also the feeder EGC (which may or may not comply).

 

[iwire]

FWIW. The taps made on a common GEC for multiple SDS do not have to be ireversible.

Any listed connector is fine.

 

[infinity]

I am also an electrician, I make mistakes, you make mistakes and engineers make mistakes.

Here at Holts forum we expect a bit more restraint used and more respect given to each other.

I agree, we've all worked with less than qualified engineers and I have personally worked with many veteran electricians who couldn't wire a 3-way switch.

 

[jbtass]

It's not clear exactly regarding your application, but I would look at the origin of each separately derived system for the application of the GEC. If you have a single SDS, 250.30 A 3 would apply with a GEC per 250.66 to the first electrodes and supplemental electrodes allowed to be interconnected or bonded to the first electrode with a smaller wire, maybe #6 to #4 depending.

If you are truly running a common GEC to connect multiple SDS's, 250.30 A 4 (a) would apply and the common GEC would be 3/0, suitable for tapping and tapped using irreversible listed connectors.

That is what I would pay attention to. I believe you may be in the first scenario with individual SDS's connected by GEC to the first grounding electrode per 250.66 and the 2/0 is a bonding jumper to supplemental electrodes. The point to examine is the individual SDS where the system bonding jumper is attached, the wire size to the first grounding electrode, and that the GEC is not also the feeder EGC (which may or may not comply).

Dan, I think you are completely correct I was looking at some old drawings and that is exactly what they did as well. I also agree and reiterate to all the designers and engineers here to not got the EGC and GEC mixed up such as where i believe it's 250.34 states to reference 250.118 which is EGC. It gets confusing which always goes back to don't read the code book understand the code book. thank you for everyones input and I apologize for my temper tantrum the other day.

 

[GoldDigger]

Suppose that there is a network of comparable ground electrodes, properly bonded to each other. And a number of SDS, maybe in different areas.
Now can the GEC from each SDS go to a different "first" electrode, or do you have to identify one that they all connect to or upsize the bonding jumper between selected electrodes to match the required GEC size?
What if one electrode is "better", like a CEE, while others are just rods?

Tapatalk!