grounding

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AKwiring

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Do you guys test the earth ground resistance of your ground rods to ensure the resistance is less than 25 ohms or do you just drive in two rods and call it good?

Do you recommend a good earth ground tester that isn't too expensive? We don't do a lot of electronic installation, mostly residential 100 or 200 amp.
 
AKwiring said:
Do you guys test the earth ground resistance of your ground rods to ensure the resistance is less than 25 ohms or do you just drive in two rods and call it good?

Do you recommend a good earth ground tester that isn't too expensive? We don't do a lot of electronic installation, mostly residential 100 or 200 amp.
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Most of us don't test the resistance of a ground rod. If you did get 25 ohms you would have to meet the inspector out there to prove it. In most cases you will not meet the 25 ohms with either 1 or 2 rods but the code only requires 2 so we just do two and get on to the next thing.
 
I agree with what the others have already said, Just drive the second rod and be done with it.

For what it is worth you could drive an awful lot of ground rod for the price of a earth ground resistance meter.

Chris
 
We drive two rods and leave. Unless of course we've used a CEE. Then we don't drive any rods.
 
isn't too expensive

isn't too expensive

Doorbell xformer secondary connected to both rods. Measure voltage across rods and current out of xformer. Divide. Less than 25 passes, 5 may be the best you can do.

May not meet the definition of "due diligence". If not, "beat feet."
 
langjahr@comcast.net said:
Doorbell xformer secondary connected to both rods. Measure voltage across rods and current out of xformer. Divide. Less than 25 passes
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Over 25 passes. Your measuring between rods. You have satisified 250.56.
 
langjahr@comcast.net said:
Doorbell xformer secondary connected to both rods. Measure voltage across rods and current out of xformer. Divide. Less than 25 passes, 5 may be the best you can do.

May not meet the definition of "due diligence". If not, "beat feet."
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If you already have the second rod whats the point in measuring the resistance?

Chris
 
Over 25 passes

Over 25 passes

My bad. What are spec limits for the configuration we're discussing?
 
I have tried to argue the point with an inspector that we had well under 25 ohms with a single rod. His reply was " we need third party testing to verify ".
Oh brother ! And I have a good earth ground tester, not to mention the other simple and cheap methods of testing the rod. Second rod is cheap and no arguing.
 
acrwc10 said:
I have tried to argue the point with an inspector that we had well under 25 ohms with a single rod. His reply was " we need third party testing to verify ".
Oh brother ! And I have a good earth ground tester, not to mention the other simple and cheap methods of testing the rod. Second rod is cheap and no arguing.
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Have you ever preformed the ground resistance test with the inspector present?

Chris
 
Do you guys test the earth ground resistance of your ground rods to ensure the resistance is less than 25 ohms or do you just drive in two rods and call it good?
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I just drive in the rods and swear it is good!

In our area ground rods are nearly useless. We live near Lake Michigan and most of the ground is white sand. The inspector here did some testing and found that a *60 foot* rod had a measured impedance of 1300 ohms.

All we drive the rods in for is to satisfy the code and pass inspection. Measurement would be futile.
 
two grond rods

two grond rods

Y would buy a ground rod tester when 99% or more 0f ground rods driven will not meet the 25 ohm rule.How many of you have driven a ground rod with 25 ohm or less when tested .
 
Doorbell xformer secondary connected to both rods. Measure voltage across rods and current out of xformer. Divide. Less than 25 passes, 5 may be the best you can do.
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Hardly a calibrated test.

Y would buy a ground rod tester when 99%
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Depends on where you live or actually work.

Is it really worth it vs just driving two rods?
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Drive two and walk, unless testing it is specified. For the cost of the test set and the time to perform a CORRECT PROPER TEST you could drive 3 rods on every job for years.

Have you ever preformed the ground resistance test with the inspector present?
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Yes numerous times and in almost every case the inspector may as well as have been on another job for all he understood. If I was the type of person to paper a job, I could have bamboozled him and he would have been none the wiser. None of them asked for an explanation of the test or how I knew what I was doing was proper
 
Even if you own a test set the hours of labor to perform the test and meet the inspector will cost more than buying and driving the second rod.

We only drag out a test set if there is a performance criteria spelled out in a job spec.

Roger
 
brian john said:
Yes numerous times and in almost every case the inspector may as well as have been on another job for all he understood. If I was the type of person to paper a job, I could have bamboozled him and he would have been none the wiser. None of them asked for an explanation of the test or how I knew what I was doing was proper
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I had one ask me what he heck I thought I was testing way over there when I was driving my current (Z) rod 500 ft away. I just looked at him and said planet earth, he mumbled something and walked away, came back 10 minutes later and asked what this plot was for on my test report.

Makes me wonder what types of grounding tests he witnessed before and how many "Homemade" tests like mentioned earlier in this thread have been accepted by him and other inspectors. What is the point of having the test witnessed?
 
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