New generator grounding

[David Rogers]

I am on a project where there is a 120/208v, 3 ph feed from a building subpanel, 60 amps. At this time, it is the only feed to a 100a, 120/208v, 3ph, load center (BR breakers). Our project is to add a new 120/208v, 3 ph, generator, 3 pole transfer switch, and feed just this load center. The load center feeds a freezer/frig at a school. There is a bond conductor from the main service to the subpanel that feeds the load center, and to the load center that has a #8. Since the generator feed shares the neutral of the serving utility, I thought this was not a separately derived system, so a bonding conductor between the generator and the load center was all that was needed. The design on the plans calls to add two ground rods and a #8 grounded bonding conductor from the ground bus of the load center to the new ground rods. Is this correct?

 

[augie47]

(a) You are correct with 3 phase generator and 3 pole T/S , the generator is not a SDS
(b) You will need the 3 phases, a grounded conductor and an equipment grounding conductor to your generator.
(c) The separtate building should have had a grounding electrod system on the original feed with the GEC conencted to tha panel grounding bar.

 

[David Rogers]

Thanks..........got it!

 

[LarryFine]

And don't forget, the genny neutral should be floating, not bonded.