Electric Power & Utilities/Generator Grounding

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Expert: Ron Robertson - 8/29/2009


Question
I'm installing an 8 KW standby gernerator complete with transfer switch. The generator has a grounding lug on the outside of it. Is an 8 foot copper coated grouding rod necessary? Or will a 4 foot rod be sufficient? The manual doesn't address this question.

Answer
Don....
Use of a ground rod is not required, nor is it a good idea. The generator transfer switch
does NOT switch the grounded(white) wire...therefore the code does not consider the generator a
"seperately derived system". It should be grounded as if it were any other appliance attached to your electrical system. If for some reason you decide to use a rod, it must be 8' in length, all 8' must be in the earth, and it must be electrically connected to the grounding electrode that your electric service is connected to to prevent ground "looping".

Ron

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Ron Robertson

Expertise

I can answer questions regarding: Code, services, feeders, branch circuits, transformers,overcurrent protection, basic motors and motor conrol, load and voltage drop calculations, troubleshooting. I will not answer questions on advanced motor control, logic controllers, and questions which are typically engineering functions: short circuit current calcs, power factor correction, etc.

Experience

Licensed electrician since 1968. Owner-Robertson Electric Company, residential/commercial contractor. Certified by International Association of Electrical Inspectors for residential and general code enforcement inspection, and plans review for compliance. Owner, FPN,Inc., providing electrical inspection for compliance for small municipalities; former Chiel Electrical Inspector, Village of Libertyville, IL; former licensed commercial electrical inspector, State of Wisconsin; Instructor for 3rd and 4th year apprentices, Associated Builders and Contractors, Northern Illinois Chapter.

Education/Credentials
4 years H.S., 2 years college, IAEI certified inspector; certified instructor, National Center for Construction Education and Research.

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