Generator with 4 pole ATS?

[hraus]

I have a 1200 amp 480/277 volt service. The service hits a 1200 amp main breaker enclosure first and the neutral/ground from the padmount is bonded in this enclosure with the underground ground loop. The generator, which my company did not provide, has a 1200 amp breaker installed. The ATS is switching the neutral, which I assume is due to the 1200 amp size. The generator has a logical location for a ground/neutral termination point for lugs to be installed which has continuity to the generator frame/enclosure. This tells me that the neutral/ground is tied to the frame.

The engineer is calling for 4 wires plus a ground from the main breaker enclosure to the ATS and is also calling for 4 wires plus a ground from the generator to the ATS. These runs are 4 parallel runs of #350 with a #2 ground.

The ATS has a ground bar installed that stands alone fastened to the ATS enclosure.

Does this all sound correct? I am not sure where the #2 grounds would terminate at the generator? Should the ground bar in the ATS just be bonded to the exterior ground loop?

 

[ceb58]

I have a 1200 amp 480/277 volt service. The service hits a 1200 amp main breaker enclosure first and the neutral/ground from the padmount is bonded in this enclosure with the underground ground loop. The generator, which my company did not provide, has a 1200 amp breaker installed. The ATS is switching the neutral, which I assume is due to the 1200 amp size. The generator has a logical location for a ground/neutral termination point for lugs to be installed which has continuity to the generator frame/enclosure. This tells me that the neutral/ground is tied to the frame.

The engineer is calling for 4 wires plus a ground from the main breaker enclosure to the ATS and is also calling for 4 wires plus a ground from the generator to the ATS. These runs are 4 parallel runs of #350 with a #2 ground.

The ATS has a ground bar installed that stands alone fastened to the ATS enclosure.

Does this all sound correct? I am not sure where the #2 grounds would terminate at the generator? Should the ground bar in the ATS just be bonded to the exterior ground loop?

They are switching the neutral because on a service that size you would have GFI protection on the service. The generator is to be treated as a separately derived system 250.35 (A) . The N & G will be bonded at the generator , just like your main service. From there you have your phase conductors and EGC to the ATS. The EGC's from the service and generator will be bonded in the ATS with the neutrals now separated and isolated by the switch. Just remember now all OCD's down stream of the ATS are now considered a sub panel and the N - G must be separated and isolated from each other.