1000A feeder off a generator

[mshields]

not sure what size the generator is in this scenario that has been partially described to me, so I'm going to use hypothetical to explain my confusion.


Let's say you've got a 1000A ATS associated with a 1000A feeder to a 3 phase, 3 wire DP with only 3 phase motors on it.


The 1000A part tells me that I'm going to have to have ground fault protection. Where there is ground fault, I would normally provide a 4 pole transfer switch and bond the neutral to ground at the generator. i.e. as a SDS.


So in this scenario where there is no need for a neutral, there is therefore no need for 4 pole transfer switches and at the generator there will be no neutral to bond to ground. So, is the generator in this case a SDS? Is there anything wrong with the system I describe above?

Thanks,

Mike

 

[iceworm]

not sure what size the generator is in this scenario that has been partially described to me, so I'm going to use hypothetical to explain my confusion.


Let's say you've got a 1000A ATS associated with a 1000A feeder to a 3 phase, 3 wire DP with only 3 phase motors on it.


The 1000A part tells me that I'm going to have to have ground fault protection. Where there is ground fault, I would normally provide a 4 pole transfer switch and bond the neutral to ground at the generator. i.e. as a SDS.


So in this scenario where there is no need for a neutral, there is therefore no need for 4 pole transfer switches and at the generator there will be no neutral to bond to ground. So, is the generator in this case a SDS? Is there anything wrong with the system I describe above?

Thanks,

Mike

I'm missing something.
What tells you that ground fault protection is required?

 

[dmsv10]

This should help answer some questions. https://www.csemag.com/articles/choosing-between-3-pole-and-4-pole-transfer-switches/

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[augie47]

If the gen output is 3phase,3 wire no GF Needed,

 

[ron]

Every alternator output that I've seen in commercial installations have been 4 wire output and either the N-G bond occurs at the gen or someplace downstream. If the neutral is not needed downstream, then there is no good reason to bring it downstream of the N-G bond.

Since you will have a 3 wire feeder, you will have no need for a 4 pole ATS since you have no neutral to switch. It is worth it to be sure the N-G bond is done someplace upstream, but there is nothing for you to do with the neutral in your feeder since it is 3 wire.

 

[dmsv10]

Every alternator output that I've seen in commercial installations have been 4 wire output and either the N-G bond occurs at the gen or someplace downstream. If the neutral is not needed downstream, then there is no good reason to bring it downstream of the N-G bond.

Since you will have a 3 wire feeder, you will have no need for a 4 pole ATS since you have no neutral to switch. It is worth it to be sure the N-G bond is done someplace upstream, but there is nothing for you to do with the neutral in your feeder since it is 3 wire.

Correct, per NEC 230.95 as quoted,
The NEC requires ground fault protection for 480/277V, 3-phase, 4-wire, wye-connected services rated 1,000A or more, but it’s optional in other configurations that don’t.

So, as mentioned, three phase, three wire, no neutral, no GF requirement. Other than at the primary utility or norm power supply to ATS.

There was a similar post on this site referencing the same question.

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