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Ground Rods at Generators

jar546

jar546

CBO
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Oct 16, 2009
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Who among you still require a ground rod at a standby generator when it is a non-separately derived system?

I would estimate that 100% of generators for residential homes are NOT separately derived systems.
 
If there's no disconnect breaking the neutral then it could use the house ground. If a disconnect is used then it will need the grounding source.

I have had a few commercial generators installed here and all had a disconnect with grounding source under the generator.

Am I missing something?
 
No, I don't think you are missing anything. When the neutral is not switched a ground rod at the generator is not necessary but I see it specified by engineers and required by some code officials who may not know any better.
 
Not it.....My understanding is that the ground lug is part of the listing of the appliance, so that is why it is there, but not needed most of the time...
 
Older post, new question.
I have a 4-wire manual transfer switch for use with a portable generator. It appears that the neutral is switched, I think making this a separately derived system. Does that now require a separate grounding system for the generator? Would this be as simple as installing a GEC to the structures grounding electrode? Requiring the GEC to be reconnected each time the portable generator is reconnected?
 
Portable generators do not require a grounding electrode at all per 250.34(A).

Edit, disregard, if you are using a transfer switch to power a building, that section does not apply.
 
Sifu said:
Older post, new question.
I have a 4-wire manual transfer switch for use with a portable generator. It appears that the neutral is switched, I think making this a separately derived system. Does that now require a separate grounding system for the generator? Would this be as simple as installing a GEC to the structures grounding electrode? Requiring the GEC to be reconnected each time the portable generator is reconnected?
Click to expand...
Yes, I think it would be that simple, see 250.30 (A)(4).

Also see 250.30(C).
 
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