Separately Derived Generator?

[davidaengelhart]

What NEC® section(s) requires that an emergency generator to be separately derived?
When is a emergency generator required to be separately derived per the NEC®?
When shall an emergency generator be separately derived per the NFPA 70®?
3 questions, same inquiry. Just making sure the question is understood.
Thanks in advance.

 

[charlie b]

None.
Never.
Whenever the designer so chooses.

Three answers, same inquiry. Just wanted to make sure the answer is understood.

(p.s. This is a design choice. There is no code requirement to do it either way.)

 

[qcroanoke]

What NEC® section(s) requires that an emergency generator to be separately derived?
When is a emergency generator required to be separately derived per the NEC®?
When shall an emergency generator be separately derived per the NFPA 70®?
3 questions, same inquiry. Just making sure the question is understood.
Thanks in advance.

COPS Article 708.20 (C)
Only article I can find that even talks about separately derived systems.
But that says all sources of power

 

[tom baker]

If there is a requirement for ground fault protection of the service or feeder, then a separately derived generator is almost always required so the ground fault sensing coil will operate properly.
95% of generators are not SDS. Its simpler to have a non SDS generator
There is good information at the Cummins Generator Website.