generator ground rod

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kjw444

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Hi, I have a 16kw residential generator. The problem I have is trying to figure out why I need a ground rod at the generator? Is it only incase the generator gets struck by lightning? I have no clue? The setup is as follows from generator into ats into 200a main panel. Everything is fine I am just wondering why they have a copper lug on the outside frame near the bottom. I have no problem installing a ground rod I just want to know why and what article. I have searched through art. 250 to no avail. Thanks.
 
IF the generator manufacture requires a ground rod then so be it,(110.3 (B)) otherwise you would only need one if the transfer switch switches the grounded conductor...which would make your generator a SDS.... 250.30 (A)
 
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Generators (optional standby systems) 702

Grounding - 250.30 - grounding of separately derived systems
 
Check with your AHJ.
We have several municipalities where they end up getting disconnected at final per the inspector.
In reality, do you really think that ground rod is going to protect the generator from a lightning strike?
 
dezwitinc said:
Check with your AHJ.
We have several municipalities where they end up getting disconnected at final per the inspector.
In reality, do you really think that ground rod is going to protect the generator from a lightning strike?
Click to expand...


Why would he need to check with his AHJ? If there is a state amendment fine, but otherwise why would he need to check?

The only reason I ask is the inspectors around here do not know what a SDS is, and always fail a generator without a ground rod...
 
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dezwitinc said:
Check with your AHJ.
We have several municipalities where they end up getting disconnected at final per the inspector.
In reality, do you really think that ground rod is going to protect the generator from a lightning strike?
Click to expand...

I don't think a ground rod will protect from lightning, I was just wondering what the point of using one was.
 
kjw444 said:
I don't think a ground rod will protect from lightning, I was just wondering what the point of using one was.
Click to expand...


There is none unless it is a SDS, then it would be just like a regular POCO service, so again it would pretty much be useless...:grin:
 
according to IEEE std 446 7.9.4, When the grounded conductor (neutral) is solidly connected, e.g. not switched in the transfer equipment, the standby system supplied by an onsite generator should not be considered a separately derived system. The grounded conductor is only connected to ground at the service. Driving a ground rod at the generator is to connect the frame to ground, only.
 
What do you suppose this means?


702.10(B) Nonseparately Derived System. Where a portable optional standby source is used as a nonseparately derived system, the equipment grounding conductor shall be bonded to the system grounding electrode.
Click to expand...
Directly? Eventually?
 
georgestolz said:
What do you suppose this means?


702.10(B) Nonseparately Derived System. Where a portable optional standby source is used as a nonseparately derived system, the equipment grounding conductor shall be bonded to the system grounding electrode.


Directly? Eventually?
Click to expand...

I'd say it means a separate ground rod is not required.
 
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