Grounding Electrode Conductor size for 11 sets of parallel 500KCMIL?

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ElectricNewEngland

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I have a Transformer feeding a Switchboard with a 4000A3P Main Breaker and 11 sets of parallel conductors at 4#500KCMIL CU conductors.
What is the grounding electrode conductor size that I should use?
Per Table 250.66 of 2011 NEC for 500 KCMIL, I think I need to use 1/0 grounding electrode conductor.
I have a coworker who tells me that it should be 3/0, because having the 11 sets of 500KCMIL puts me far over 1100KCMIL.
I cannot find in the code to prove he is right or wrong. Am I correct or is he correct?
 
Dennis Alwon said:
Is it to the building steel or water pipe? Or ground rod etc. Water pipe and steel will need 3/0
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It's all of the above. The switchboard is being installed in a new addition, which has it's steel grounded to the existing building steel and grounded at a point with a ground rod. We also have a grounding electrode inside a conduit connected to building steel, connected to a ground rod, connected to a cold water metallic pipe a the main water service entrance.
 
You can use 250.66 if you have a bonding jumper in each raceway based on the size of the 500 kcmil conductors in each raceway. Also your system bonding jumper needs to be sized according to 250.28(D)(1) or at 12.5% of the total parallel secondary conductor size.
 
ElectricNewEngland said:
It's all of the above. The switchboard is being installed in a new addition, which has it's steel grounded to the existing building steel and grounded at a point with a ground rod. We also have a grounding electrode inside a conduit connected to building steel, connected to a ground rod, connected to a cold water metallic pipe a the main water service entrance.
Click to expand...
The ground rod never needs to be more than a #6 unless it is engineered plans and they call for a larger GEC.
 
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