Switchboard Grounding

[horses]

I need some input on the following. I'm doing g a hotel that has (3) switchboards that are fed from the utility transformer, (2) 1200A 120/208V 3P 4W MB and (1) 800A 120/208V 3P 4W MB. The riser only shows (1) 3/0 from each going to an Individual ground rod i understand the sizing of the 3/0 based on table 250.66 and using the equivalent size of the largest service conductor, but it seems like there should be (1) grounding electrode conductor to the ground rod and each of the (3) switchboards should be bonded to the grounding electrode conductor.

The (2) 1200A switchboards are fed with (4) parallel runs of (4) 500 aluminum and the (1) 800A switchboard has (3) parallel runs of (4) 400 aluminum.

The Engineer didn't address the offer ground or building steel ground?

Your feedback is greatly appreciated!

 

[roger]

You need to submit a COR. All the electrodes present must be used and unless the single rod measures 25 ohms you will need two. The rods do not need 3/0 either, they only need to be connected with #6 CU.

Roger

 

[tom baker]

You are quoting table 250.66. You need to look at section 250.66 A), B), and C).
if this is a new hotel you wiil need a concrete encased electrode, and any other electrodes that are present, such as a water line. Ground rods are not required if you use a cee.