Ground Rod at Outside Generator
Mike, it was interesting reading about touch potential in response to the ground rod at the light pole. According to the USDA Rural Utilities Services (RUS) Bulletin 1751F-810, a standby generator shall be grounded to a driven ground rod regardless if the generator is separately derived or derived. The RUS Bulletin wants a ground rod in place to protect personnel against step potential voltages. Therefore, when doing a Grounding Audit using the RUS Grounding Checklist, we have to verify if the frame of the standby generator is grounded to a driven ground rod.
So, based on your explanation of the ground rod at a light pole, would the same explanation hold true for a ground rod at a standby generator?
Mike Holts Response: A ground rod at a generator that is not a separately derived system is not required to be grounded to the earth (but it can be 250.54). If a ground rod is installed it serves no purpose in reducing step or touch voltage to a safe value. Just like the light pole ground.
Looks like ground rods are showing up all over the place. About a year ago, I saw a job where ground rods were installed inside a building to some of the steel columns. I really hate to open up a can of worms, but here I go .. Driving ground rods inside a building and connecting them to the building steel columns that are not the perimeter columns is useless and serves no purpose. Now if I am wrong, please respond with a page number, section number of some national or international standard to support your position.
Mike Holts Comment: If you have any comments or feedback, please let me know, Mike@MikeHolt.com
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