Generator Grounding Detail

[mshields]

Am reviewing someone else’s generator grounding detail. They show a neutral to ground connection at the emergency switchboard instead of where I would show it; at the generator. They run a neutral and a ground wire back from the emergency switchboard to the generator. And I guess so long as they don’t bond the two together again at the generator, it’s ok. Do you agree?

 

[kwired]

Am reviewing someone else’s generator grounding detail. They show a neutral to ground connection at the emergency switchboard instead of where I would show it; at the generator. They run a neutral and a ground wire back from the emergency switchboard to the generator. And I guess so long as they don’t bond the two together again at the generator, it’s ok. Do you agree?

Separate N and G are necessary either way. Where to bond depends if it is set up as separately derived system or not.

 

[LarryFine]

The idea is that the neutral is never bonded to the EGC/GE system more than once (in the active system). Simple explanation:

If the neutral is switched, then each source's neutral is bonded before the transfer switch, and the load neutral is isolated ~ SDS.

If the neutral is un-switched, then each source's neutral is isolated before the transfer switch, and the load neutral is bonded ~ non-SDS.

 

[ron]

Separate N and G are necessary either way. Where to bond depends if it is set up as separately derived system or not.

Not necessarily. If the loads are 3 wire only, then no need to bring the neutral out of the generator if you do the N-G bond in the generator.

 

[kwired]

Not necessarily. If the loads are 3 wire only, then no need to bring the neutral out of the generator if you do the N-G bond in the generator.

Yes, only a current carrying conductor applies to such rules. EGC's and GEC's always need to be run and with no switching components. Metal raceways and enclosures can be the EGC path.