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Grounding Rods & Standby Generators

Question: I am thoroughly confused about how many ground rods I need to install on my standby generator? Some people have told me one and others have said two. So I am asking you; how many ground rods do I need for my standby generator?

Answer: The problem is that you are not asking the right question. The question should be; what is the maximum resistance to ground that I can have with one grounding rod or electrode?

The answer to that question is 25 ohms. If you have 25 ohms or less resistance to ground with one grounding rod or electrode you have satisfied the electrical code. As the test meter to verify ground resistance is quite expensive most electricians will take the opposite route. That is if the resistance is greater than 25 ohms from the electrode to ground you must add a second electrode at least 6 feet away from the first electrode.

That is why some people are telling you two electrodes and others are saying one.

As a note it is highly unlikely that you will have 25 ohms or less with one electrode, so even if you had the test meter you would probably have to install the second electrode anyways.

Note: Always check your local building codes to verify all electrical requirements in your jurisdiction.