Testing 25 ohms to ground

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Jpflex

Jpflex

Electrician big leagues
Location
Victorville
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Electrician commercial and residential
Hi on a grounding electrode rod commonly adjacent ti residential breaker panels, what is the name of the tool which can test resistance between Earth and ground rod And how is it done?

NEC Allows exemption of one electrode conductor is resistance is “25 ohms or less?”

Thanks

Also to the best of my memory I calculated grounding conductor to be 6 AWG based (Or 8???) on Largest conductor (feeder?) being less than 1/0

Is this right. Thanks
 
earth ground resistance tester/meter

Earth Ground Testers | Digital Earth Resistance Testers | Fluke

Built to withstand an entire spectrum of ground testing methods, Fluke's family of earth ground testers have been designed to be accurate, safe and easy to use. Browse our top selling 1623-2 GEO earth ground resistance meter, 1625-2 GEO earth ground tester and the 1630 ground resistance meter today.
www.fluke.com www.fluke.com

The normal method requires two earth probes spaced out:

Fall-of-Potential Measurement | Fluke

The Fall-of-Potential test method is used to measure the ability of an earth ground system or an individual electrode to dissipate energy from a site.
www.fluke.com www.fluke.com
 
Jpflex said:
Hi on a grounding electrode rod commonly adjacent ti residential breaker panels, what is the name of the tool which can test resistance between Earth and ground rod And how is it done?

NEC Allows exemption of one electrode conductor is resistance is “25 ohms or less?”

Thanks
Click to expand...
99.87% of people will just install 2 rods and skip the testing.
 
Gene B said:
earth ground resistance tester/meter

Earth Ground Testers | Digital Earth Resistance Testers | Fluke

Built to withstand an entire spectrum of ground testing methods, Fluke's family of earth ground testers have been designed to be accurate, safe and easy to use. Browse our top selling 1623-2 GEO earth ground resistance meter, 1625-2 GEO earth ground tester and the 1630 ground resistance meter today.
www.fluke.com www.fluke.com

The normal method requires two earth probes spaced out:

Fall-of-Potential Measurement | Fluke

The Fall-of-Potential test method is used to measure the ability of an earth ground system or an individual electrode to dissipate energy from a site.
www.fluke.com www.fluke.com
Click to expand...
Thanks I read the fluke article good stuff
 
Jpflex said:
Is placing Testing stakes as difficult as pounding in ground electrode rods?
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Testing stakes are roughly 18 - 24", so pounding them in isn't too bad.
However it can be problematic finding undisturbed soil with no large underground metallic objects between the test points. I think our standard test leads were 1000' and 5000'.
 
Actually I have made this or similar joke before:

How to install grounds rods
1) go to supply house and buy 2 ground rod (boss will see 2 were purchased).
2) take one rod home and use for side jobs or throw in bushes at job site where inspector and boss wont see
3) cut remaining rod in half
4) install the two ground rod halfs 6 feet apart
5) go to bar
 
Are there any studies or papers on what ground resistance for typical one or two ground rod systems might be?
 
tom baker said:
In the Puget sound, area (Seattle) due to gravel from glacier that carved it, one rod can be 3,000 ohms
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Yet somehow, 2 ground rods is still somehow all you need, even if 1 rod tested that high.

I would think if you drive 1 rod, and find out it is 60 ohms, that a second identical rod would bring it down to 30 ohms (best case scenario), unless there is something serious that I'm missing about how conductance to ground works. I know this isn't what the rule requires, but I would expect you'd need to divide the 1-rod resistance by 25 Ohms and round up to the next whole number, in order to have the same electrode performance as you'd get form the standard of 25 Ohms or less.
 
I have a tester and won’t use it.
Easier to drive two rods and forget it.

IF you pass the test with one, at some point in time someone will bring up the fact there is only one rod, and you need two
(You don’t, but everyone assumes you do)
 
Carultch said:
Yet somehow, 2 ground rods is still somehow all you need, even if 1 rod tested that high.
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Primarily because the resistance to ground is all but meaningless for 60hz systems. It is just important the system be referenced to dirt, and 100 years of experience have shown 25ohms or 2 rods does this.
 
jim dungar said:
It is just important the system be referenced to dirt, and 100 years of experience have shown 25ohms or 2 rods does this.
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What if both rods minimum 6 ft apart were driven into sand as opposed to good quality dirt. I've had to relocate a ground rod or two because I could literally pull the entire rod out by hand.
 
Carultch said:
Yet somehow, 2 ground rods is still somehow all you need, even if 1 rod tested that high.

I would think if you drive 1 rod, and find out it is 60 ohms, that a second identical rod would bring it down to 30 ohms (best case scenario), unless there is something serious that I'm missing about how conductance to ground works. I know this isn't what the rule requires, but I would expect you'd need to divide the 1-rod resistance by 25 Ohms and round up to the next whole number, in order to have the same electrode performance as you'd get form the standard of 25 Ohms or less.
Click to expand...
It's because if you can't get it with 2 rods your wasting your time and the dirt isn't going to make as much of a difference as all the bonding metal and gfi requirements will.

They work so poorly that in my state it's a ufer or ground ring for new construction no other options. Existing buildings are allowed to just do ground rods but the point is made even in the state amendments.
 
letgomywago said:
It's because if you can't get it with 2 rods your wasting your time and the dirt isn't going to make as much of a difference as all the bonding metal and gfi requirements will.

They work so poorly that in my state it's a ufer or ground ring for new construction no other options. Existing buildings are allowed to just do ground rods but the point is made even in the state amendments.
Click to expand...
Many people do not understand this, including pretty much everyone on the CMP, but a low ground resistance doesnt matter for system grounding and equipment earthing. So yeah rods may be a poor way to get a low ground resistance, but it doesnt matter what that number is in the first place.
 
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