Ground Resistance Testing

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Could someone help me with procedures for testing the ground resistance with a clamp on meter. I have a 3/0 copper conductor from the service neutral to (2) 10' rods and to the building steel. Where would be the best place to clamp for an accurate reading?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Is this a clamp-on ground-resistance tester, or merely a clamp-on ammeter?

If the former, read the instructions; if the latter, you really can't.
 

brian john

Senior Member
Location
Leesburg, VA
Mike:

Where are you trying to read the resistance with this clamp. (I assume it is designed for this purpose.

We use the AEMC tester the best thing I could recommend is reading this site.

You have to be careful utilizing this meter, many companies I have done work for use these clamp on testers and the way they utilize them is improper for the application.



http://www.aemc.com/techinfo/appnotes/Ground_Resistance_Testers/APP_3711_3731_Useage.pdf
 
Larry have you read the instructions for this type of meter, I have and are not very clear. I am familiar with series and parallel risistance formulas. But I have not used this meter before. When I clamp on G.E.C I get a reading of
.037 ohms. If I disconnect from the neutral I get 999 ohms
 

brian john

Senior Member
Location
Leesburg, VA
dereckbc said:
You were reading a loop, common mistake.


The number of test reports I have seen with this result. The reason see the reports as our follow or retest after several years does not match the original test.
 
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