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Old 01-28-2015, 06:54 AM   #21
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I did this experiment many years ago when I was teaching a grounding class for an neighboring local. When I set up the class I asked the training director to drive a ground rod for me in the grass outside the building. We had a couple of inches of rain in the day before the class....still only 4 amps when 120 volts was connected to the rod.
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Old 01-28-2015, 07:15 AM   #22
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that's about 30 ohms - you need another rod
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Old 01-28-2015, 07:30 AM   #23
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To the OP,
the old 250.32 allowed a 3 wire to detached buildings
N&G bonded, to a GEC

This had it's flaws , mainly due to everything becoming a potential noodle in between them, being summarily amended to N&G separation some code cycles ago.

You may still see them out there, but we can't install that way any more

Ironically, the poco can!

~CS~
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Old 01-28-2015, 07:58 AM   #24
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Quote:
Originally Posted by 3D Electric
Does anyone have any suggestions or comments on how they would like me to perform this experiment? I am going to record it so I can upload it here.

Yes, come to my job, pound the 2 rods in, do your test, and you can leave the rods there.
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Old 01-28-2015, 09:00 AM   #25
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Quote:
Originally Posted by hunterjo View Post
all these replies make sense. I know some building inspectors will allow a sub panel in a detached building to not have a grounded conductor just the 2 ground rods 2hot and one neutral with the grounded and grounding bar bonded. but in sub in attached building the neutral has to be floating. does this sound sight.
thanks again for all the feed back so far looking to read more good info
That Setup hasnt been legal since the 02 code
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Old 01-28-2015, 10:14 AM   #26
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can some explain why a attached building has a sub panel with the grounding bar and the grounded bar isolated but in a detached building both bars are bonded with ground rods.


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A sub panel has the grounds and the neutral separated. Being in a detached building has nothing to do with it being a sub panel. The grounds and neutrals are still required to be seperated.
Ok, obviously this thread is using the NEC.

Are the ground and neutral required to be isolated in a seperate building? Even in buildings housing livestock?

Borgi
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Old 01-28-2015, 10:22 AM   #27
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Ok, obviously this thread is using the NEC.

Are the ground and neutral required to be isolated in a seperate building? Even in buildings housing livestock?

Borgi
Yes....
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Old 01-28-2015, 10:53 AM   #28
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Very true, but driving a ground rod actually proves how little or how much resistance it has. Even if someone received half an ohm, as much as people would celebrate, that is still would not low enough to be truly safe with any standard breaker.


Nothing beats a copper wire back to the source, nothing.
Don't be so absolute. A grc conduit with no equipment ground has been proven in testing by US Steel to return fault current faster and better than the properly sized copper equipment ground matched to the test fault .
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Old 01-28-2015, 01:38 PM   #29
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Don't be so absolute. A grc conduit with no equipment ground has been proven in testing by US Steel to return fault current faster and better than the properly sized copper equipment ground matched to the test fault .


Any links, Im curious?

I did leave that out, my mistake. But when it comes to things like earth electrodes forget it.
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Old 01-28-2015, 01:48 PM   #30
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Originally Posted by chicken steve View Post
To the OP,
the old 250.32 allowed a 3 wire to detached buildings
N&G bonded, to a GEC

This had it's flaws , mainly due to everything becoming a potential noodle in between them, being summarily amended to N&G separation some code cycles ago.

You may still see them out there, but we can't install that way any more

Ironically, the poco can!

~CS~

The code would restrict it if anything like a phone line or pluming line was going out to the structure. The issue was that people would often add them latter in time creating an unknown issue. The CMP proposal also mentioned it would be safer eliminating the wire 3 feeds; which I would imagine refers to an open noodle.

POCOs are always an exception, being the only ones who do it in the industry.
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Old 01-28-2015, 02:12 PM   #31
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Any links, Im curious?
NEMA - Bulletin No 97

Steel Tube Institute - Equipment Grounding Using Steel Conduit

Top 2 results from a google search
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Old 01-28-2015, 02:14 PM   #32
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Thanks!
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Old 01-28-2015, 02:17 PM   #33
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Any links, Im curious?
Not that it has anything to do with "earthing" but, go to link below and check out the reports, while you're there download the GEMI software.

http://steeltubeinstitute.org/steel-...ysis-research/
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Old 01-28-2015, 03:53 PM   #34
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Originally Posted by 3D Electric View Post
Does anyone have any suggestions or comments on how they would like me to perform this experiment? I am going to record it so I can upload it here.

I really want to do this so, fill me in.
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Old 01-28-2015, 04:01 PM   #35
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This is the biggest offender I have seen in every place I have worked in the last 40 years.

from the above link -

"where the raceway is terminated at concentric or eccentric knockouts. The raceway must be bonded to the enclosure using the same"
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Old 01-28-2015, 04:31 PM   #36
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Originally Posted by xpertpc View Post
This is the biggest offender I have seen in every place I have worked in the last 40 years.

from the above link -

"where the raceway is terminated at concentric or eccentric knockouts. The raceway must be bonded to the enclosure using the same"
It depends on the voltage. There is no issue with 120 or 240V branch circuits or feeders with the concentric ko's. Services require bonding.

Also bonding is req. when you have more than 250v to ground depending on the situation.
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Old 01-28-2015, 04:59 PM   #37
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I really want to do this so, fill me in.

I want to see the results to

A test like that would add a lot to this site, as it debunks again the greatest misconception in the trade.
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Old 01-28-2015, 05:06 PM   #38
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I want to see the results to

A test like that would add a lot to this site, as it debunks again the greatest misconception in the trade.
Don has already mentioned that they did the experiment. McClary stated why you didn't need to do the experiment and I mentioned that a mike holt member performed the experiment. What more do you need. It will not blow the circuit unless you tie the rod to the service. 120v connected directly to the rod will only wake up the worms unless you live in one of those rare places on earth where you have less than 5 ohms.

V=amps x Resistance
or
R= V/I

R= 120V / 20 amps = 6 ohms
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Old 01-28-2015, 05:52 PM   #39
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Originally Posted by Dennis Alwon View Post
Don has already mentioned that they did the experiment. McClary stated why you didn't need to do the experiment and I mentioned that a mike holt member performed the experiment. What more do you need. It will not blow the circuit unless you tie the rod to the service. 120v connected directly to the rod will only wake up the worms unless you live in one of those rare places on earth where you have less than 5 ohms.

V=amps x Resistance
or
R= V/I

R= 120V / 20 amps = 6 ohms
We did a total of 9 cell towers in the last two years, and I can tell you that 5 ohms is very hard to get.
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Old 01-28-2015, 06:19 PM   #40
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We did a total of 9 cell towers in the last two years, and I can tell you that 5 ohms is very hard to get.
And virtually impossible with rods
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