Sufficient Ground Rod ???

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adavey

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Is there any way measure and determine if a ground rod is adequalty installed for a 400 Amp single phase service (240V) ??????????????
 
Re: Sufficient Ground Rod ???

I'm assuming so w/out actually visually seeing the install. I'm not at work, but i believe I spec'd out 5/8" ground rod at 10' depth.

Is a voltage measuremnt from line to ground rod ok to do ???? Assuming it's a good ground I should get 120V. More specifically, can I measure ground rod resistance when installed ??????
 
Re: Sufficient Ground Rod ???

adavey, the rods resistance at our voltages is of no consequence, but if you must check it accurately you will need a ground megger and will need to use a fall of potential type of test.

I wouldn't worry about it.

Roger
 
Re: Sufficient Ground Rod ???

Originally posted by adavey:

Is a voltage measuremnt from line to ground rod ok to do ???? Assuming it's a good ground I should get 120V.
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No.
More specifically, can I measure ground rod resistance when installed ??????
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Yes, but that won't tell you anything.

The best thing I can tel you, honestly, is to not lose any sleep over it. It isn't doing much anyway. :)

[ February 14, 2006, 08:36 PM: Message edited by: ryan_618 ]
 
Re: Sufficient Ground Rod ???

Is the ground rod a secondary grounding element to the ground system (water main being primary) ??????? Being an engineer I can't help to know how, but also why.
 
Re: Sufficient Ground Rod ???

Originally posted by adavey:
Is the ground rod a secondary grounding element to the ground system (water main being primary) ?
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Read 250.50. All electrodes are created equal in the eyes of the NEC. They all must be used. :)
 
Re: Sufficient Ground Rod ???

In ten years, new electricans will want to know what a ground rod is.
Thank you Mr. Ufer.
 
Re: Sufficient Ground Rod ???

If you have only a CCE, you're done. It's not going anywhere.
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We recently installed a ground grid for a new 34.5kV substation which was on a piece of ground that once was an old mine in New Jersey (filled in with sand). We drove sectional ground rods down 50' at multiple locations and still barely got below 5 ohms. My design called for 1 or less. Installed a CCE, problem solved.
 
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