Parallel service grounding electrode conductor size

[NOV]

I’m looking at a project that has parallel 4500A MCB switchboards and I’m confused with the grounding requirements. It appears that the engineer had sized the grounding electrode conductor based on Table 250.122 and used a 600KCMIL conductor but my thought is that it should be done from Article and Table 250.66 and a #3/0 would be sufficient. Am I missing something? I have attached a snapshot of the service to clarify anything I may have miscommunicated. Thank you in advance.

 

[augie47]

IMO, 3/0 is the largest GEC ever needed.

 

[GoldDigger]

No CEE?

 

[NOV]

I'm sorry GoldDIgger, I'm not following...CEE?

 

[augie47]

Concrete encased electrode (UFER)
Might or might not be present at the site.
It's one of the 250.52 grounding electrodes and is connected via a conductor not required to be larger than #4.

 

[infinity]

Concrete Encased Electrode. Unless the footing is not in contact with the earth or the rebar is covered in a non-conductive coating for your project a CEE is required.

#3/0 is the largest GEC ever required.

 

[NOV]

Is the UFER ground required since there are ground rods or am I misreading 250.50, last paragraph?

 

[Dennis Alwon]

The ufer ground is required if it was available. All electrodes must be used unless their is an amendment in NY state

 

[tom baker]

Yes you are misreading. Uber is required, no ground rods with uber is far more effective than a ground rod.
And the largest gec for a ground rod is 6 AWG. See section 250.66
I will often see 3/0 to ground rods at a cell tower.
Sorry , ufer not uber

 

[Dennis Alwon]

Many engineers will spec conductors larger than what the NEC requires but their is no harm in that. It may be unnecessary but the engineer has to feel comfortable with it so they usually oversize it.

 

[NOV]

I find that a lot but oversizing can really drive the cost up, and owners seem to be always looking for VE options.

Thanks to all for the input and education!

 

[infinity]

I find that a lot but oversizing can really drive the cost up, and owners seem to be always looking for VE options.

Thanks to all for the input and education!

Yes wasting someone else's money is what we see all of the time in design. Many times we'll present a value engineered ideas to cut costs and the client approves it saving them money and making a few extra bucks for my boss.