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175kw Generator grounding #203227
09/15/11 12:58 PM
09/15/11 12:58 PM
M
Micmann  Offline OP
Member
Joined: Apr 2005
Posts: 20
I have a set of drawings from an engineer for a 175kw 120/240 single phase generator. In the drawing he has two ground rods at the generator and bonds the rods and the generator with 4/0 copper. He then shows the 4/0 copper running to the structure and bonding at the structure main/ATS (the main and ATS will be in one unit) with the grounding system. From the breaker in the generator he has two paralleled 1/0 running with the generator feeders as equipment grounds. My question is does the 4/0 from the rods and generator casing need to run to the structure grounding system? Isnít the generator breaker the first disconnecting means and if the neutral and ground are bonded together in the generator doesnít the paralleled 1/0ís satisfy the grounding of the structure not needing the 4/0 to be run all the way to the ATS? Iím not asking to doubt the engineer. Itís mostly for my own knowledge for future installations to make sure Iím not missing something I donít understand.

Thanks
Mic

2017 / 2014 NEC & Related Books and Study Guides
Re: 175kw Generator grounding [Re: Micmann] #203231
09/15/11 01:56 PM
09/15/11 01:56 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,227
Estero,Fl,usa
The grounding conductors are all going to be bonded together. The only question is how you deal with the grounded (neutral) conductor. That will depend on whether it is switched in the transfer equipment.
The ultimate goal is that you only have one main bonding jumper in the system in either condition (utility or generator)


Greg Fretwell

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