Test Ground Rod or Conductor?

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Depends on how you do it, where you do it, if the system is properly installed and if you read and understand the instructions that came with the tester.

Just like electrical material anyone can buy material, (or test equipment) but proper installation (use) is critical to achieving proper results.
 
Unless there is a specific reason to test the ground like a spec or otherwise being paid to do so, it is much easier to drive two rods and call it done for the day.

The AEMC meter in which you refer is what I call a BALL PARK meter. In other words it will always read higher than the actual impedance @ the test frequency of 160 Hz it uses. So if your spec say 5-ohms, and the meter reads 5-ohm's, assuming you know how to use it, the actual impedence is something less than 5-ohms.
 
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For a fall-of-potential test the ground rod must be isolated form the electrical system for the test. As others have said, it depends on the type of equipment that you use and the reason for doing the test.
 
Thank you for the quick feed back. The reason for my line of questioning is that I am trying to get a beter understanding of what the industry standards are for testing a ground rod before I approach the DSA inspector to get his interpentation of the specs. My DSA inspector and the project specifications requires a witness test of the ground rods installed to bond new portable classroom buildings. One of the conductors is connected to the steel frame and the other to the panel board. I also have a ground conductor connected to the panel with the feeder set comming back from the service. My specs have two sections, 1. Grounding and Bonding - "Use suitable test instrument to measure resistance to ground. Perform testing in accordance with test instrument manufacturer's recommendations using the fall-of petential method". 2. Secondary Grounding - "Measure ground resistance from system neutral connections at service entrance to convenient ground reference point using suitable ground testing equipment. Resistance shall not exceed 10 ohms".
My AEMCO clamp-on test equipment instruction manual shows all applications scenarios, testing the conductor between the structure bond and the ground rod connection point. It also clarifies that empirical testing has validated that both the fall -of - potential method and the clamp-on method will provide accurate and repeatable readings for ground electrode resistance.

My final questions are;
1. Is the ground electrode in this application the secondary or primary ground for the structure?
2. Do I need to isolate the electrode to test the rod or can I test the connected system.

Jeff
 
But the spec says to use the fall of potential method. You may want to have someone come in and do the test for you, should only cost a couple of hundred bucks. www.netaworld.org will give you a list of testing companies that specilize in this in CA.
 
The fall-of-potential method requires the installation of two test rods. The test places high voltage on the ground rod, so it must be isolated from the electrical system for the test.
 
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