After further study

[joeyww12000]

Ok code gurus, help me out. I was getting confused on GEC size requirements but maybe I got it now. If Im getting this now, let me know. From my service I bond neutral and ground and take a GEC per table 250.66 based on size of service conductors to ground rod. All other GEC's are supplemental grounds with a NEC requirement of #6 cu, #4 al for 250.66 (a) and #4 for 250.66 (b). Inside the switchgear the neutral bus is already connected to groundbar which in turn is connected to switchgear casing, GEC ran to groundrod per 250.66. If this were not the case the bonding jumper between Neutral and case ground would have to be based on table 250.66 also? If you havent figured it out guys I use this site for study purposes. I study every morning before work. Thats why I ask so many questions and Im sorry if you get tired of answering. I really appreciate it though.

 

[iwire]

Joey, Article 250 can be tough, I strongly suggest you get yourself a 2008 Soares Book on Grounding and Bonding

Of course your free to ask as many questions here as you want as well.

 

[Dennis Alwon]

From my service I bond neutral and ground and take a GEC per table 250.66 based on size of service conductors to ground rod.

Not to the ground rod. The ground rod is a supplementary electrode and does not need larger than a #6. Art. 250.66(A)

All other GEC's are supplemental grounds with a NEC requirement of #6 cu, #4 al for 250.66 (a) and #4 for 250.66 (b).

Nope building steel, water pipes need to be sized by 250.66.

I suggest reading 250.53 , 250.54, 250.56 and 250.66 . Of course the whole art. is important but this may get you started.

 

[George Stolz]

From my service I bond neutral and ground and take a GEC per table 250.66 based on size of service conductors to ground rod. All other GEC's are supplemental grounds with a NEC requirement of #6 cu, #4 al for 250.66 (a) and #4 for 250.66 (b).

First, imagine that all electrodes are created equal. There are no primary/supplemental grounds. If a grounding electrode exists, it gets a full sized GEC.

Now, amend that thought with 250.66(A), (B), and (C). These electrodes can be connected with undersized GECs.

Now, factor in that the water pipe electrode (if present) may get broken and fixed with plastic in the future. If the electrical service is relying on solely that electrode to earth it, then that water pipe needs to be supplemented with another electrode. If a ground rod is driven for this purpose, then it is called a "supplemental electrode". (250.53(D), (E)).

 

[iwire]

First, imagine that all electrodes are created equal. There are no primary/supplemental grounds. If a grounding electrode exists, it gets a full sized GEC.

I agree and will note that many times you will not need any ground rods at all.

 

[joeyww12000]

Im just using our latest job as example. We have a 1200a service. At the switchgear we have a GEC to groundrod, GEC to rebar, GEC to water pipe, GEC to building steel. Except for the groundrod which is in print specs to be installed, all other means of ground exhist already. 250.50 says these must be bonded together, correct? We have a GEC to each of these coming from the bonded neutral/groundbar inside of our switchgear. What table or section of code do you use to size each of these GEC's. Rod, Pipe, or plate electrodes 250.66 (a)......groundrod, waterpipe? #6 copper or #4 al? 250.66 (B)......#4 copper to GEC in rebar, concrete incased electrode? Which GEC is sized in accordance to Table 250.66? You guys must really be tired of me...lol:grin: :-?

 

[George Stolz]

I'm not sure where you're losing us, or if you are. They all get full sized GECs aside from the ones mentioned in 250.66(A) (B) and (C), as mentioned above.

You can run separate GECs to each, or daisy chain the electrodes together from one GEC, 250.64(F). If you daisy-chain, the GEC must be big enough to cover the largest GEC required, regardless of the type of electrode you hit first.

Bear in mind if the engineer specs a 3/0 CU GEC to a ground rod, some jurisdictions will expect to see that instead of the code required #6 CU.