Would one get shocked by from hot case by pure Grounding Electrode Only?

[tersh]

Supposed there was no neutral going into the house (just for sake of discussion), and you only have the 2 pole 240v powering your house.

If one of the hots shorts to the main panel metal enclosure. With a good ground rod, you'd expect between 2-3 A at 120V through ground back to the transformer grounded center tap.

Now the person who touches the hot shorted metal enclosure with the fingers touching the hot shorted enclosure and his bare feet touching the ground .

Is he as same potential as ground if his bare feet touch ground? Would he get a shock? Would the 2-3 A passes through him? Note since his bare feet is some distances away from the local ground rod. I wonder if there is potential differences between his bare feet and that of local ground rod.

What does NEC and other codes say about this, and theoretical considerations?


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[ActionDave]

Pretty much the same thing as this.

 

[ActionDave]

What does NEC and other codes say about this, and theoretical considerations?

250.4(A)(3),(4),(5),
250.4(B)(2),(3),(4)
250.6(A)
250.12
250.20
250.24
250.26
250.28
250.30
250.32
250.90
250.92
250.96
250.97
250.98
250.102
250.104
250.110
250.112
250.116
250.118
250.120
250.122
250.124
250.142

 

[tersh]

View attachment 21747 Pretty much the same thing as this.

Is the one he is touching a street light pole or is it the ground rod itself?

If it is street light pole, where is the ground rod located and the ac pole source? Which part of Mike Holt video contains this image (as he has many videos at youtube). Thanks.

 

[ActionDave]

Is the one he is touching a street light pole or is it the ground rod itself?

If it is street light pole, where is the ground rod located and the ac pole source? Which part of Mike Holt video contains this image (as he has many videos at youtube). Thanks.

If you look at the picture it is quite clear what he is touching, both the ground rod and the light pole are shown clearly in the illustration.

 

[tersh]

If you look at the picture it is quite clear what he is touching, both the ground rod and the light pole are shown clearly in the illustration.

Let me zoom in.

I can't find the ground rod. Where is it??

 

[ActionDave]

At the base of pole to the right of the 90V.

That's not what is important anyway. You asked what the NEC has to say about this and the code sections I listed make it clear that it has a lot to say.

 

[romex jockey]

Theoretically, he more proximal GES are to serving Xformers, and/or serving poco substations , the less R value is present in the step potential / earth fault loop impedance displayed.

But this is considering the predominant TN-S-C , the theory would differ in say, an IT

~RJ~

 

[electrofelon]

ITs all about voltage drop. The voltage drop is less along a better conductor compared to that along a worse conductor (for the same current). It is the poor resistance of dirt that results in a voltage gradient across a relatively short distance. If the person was touching the energized case and actually standing on the ground rod, she would only be exposed to the potential difference across the 5 feet of GEC which would be small.. But move away from the electrode, the voltage increases rapidly as the image shows. This is a common misunderstanding, thinking you can bond the ground to make it the same potential. IIRC even mike holt admits to believing that in the past.

 

[ptonsparky]

We recently had a very similar situation where there was no grounded conductor or equipment ground at the equipment. Ground rod only. Measured voltage from rod to screwdriver stuck into the earth 6’ away was about 90 volts. Bolted fault to one of the phases.

Yes, you get shocked.

 

[romex jockey]

We recently had a very similar situation where there was no grounded conductor or equipment ground at the equipment. Ground rod only. Measured voltage from rod to screwdriver stuck into the earth 6’ away was about 90 volts. Bolted fault to one of the phases.

Yes, you get shocked.

I'm guessing a delta ....~RJ~

 

[ptonsparky]

I'm guessing a delta ....~RJ~

No, it was 120/240 single phase. No EG was run with the 240 v lighting circuits to poles.

 

[tersh]

The voltage gradient in the soil above assumes the street light pole metal enclosure and ground rod is same location. But how about if the metal enclosure (like panel enclosure below) and ground rod distance differs. Where will you draw the gradient circles below.. in the center of the ground rod or the panel case? I'd like to understand what gradients (just qualitatively) the person feet are exposed to.

 

[ptonsparky]

The voltage gradient in the soil above assumes the street light pole metal enclosure and ground rod is same location. But how about if the metal enclosure (like panel enclosure below) and ground rod distance differs. Where will you draw the gradient circles below.. in the center of the ground rod or the panel case? I'd like to understand what gradients (just qualitatively) the person feet are exposed to.

Using the gradients in the upper picture, how far away from the ground rod is your stick figure?

The gradient will will be different at your house than mine. It most likely will be different than the guy with two rods versus your one. Dry sand vs wet clay?

Is is he standing on concrete in direct contact with the soil or does it have two inches of insulation under it as mine does?

 

[tersh]

Using the gradients in the upper picture, how far away from the ground rod is your stick figure?

The gradient will will be different at your house than mine. It most likely will be different than the guy with two rods versus your one. Dry sand vs wet clay?

Is is he standing on concrete in direct contact with the soil or does it have two inches of insulation under it as mine does?

The person is say 10 meters away (32 feet) from local electrode ground rod (the panel is also 10 meters away from ground rod). Let's assume the person stands on bare feet and dry sand. So I guess the gradient concentric circle starts at the local electrode ground rod (you can make it two rods.. I just want to know where to start the gradients circle and if the person would be shocked)?

 

[ptonsparky]

The person is say 10 meters away (32 feet) from local electrode ground rod (the panel is also 10 meters away from ground rod). Let's assume the person stands on bare feet and dry sand. So I guess the gradient concentric circle starts at the local electrode ground rod (you can make it two rods.. I just want to know where to start the gradients circle and if the person would be shocked)?

I’ve never done the testing so keep that in mind. IMO. The gradients shown in the illustrations are not static. They will change from day to day and possibly hour to hour. Totally dry sand may not allow enough current to flow, while working your feet down three inches could be an eye opener. Being shocked is also subjective.

We can’t tell you that at exactly 32 feet you will feel a shock or how strong you judge it to be. Do you run Marathons in your bare feet or haven’t had your shoes off outside in 30 years. How old are you? Male, Female? IDK what transgender will do to that.

 

[gadfly56]

The person is say 10 meters away (32 feet) from local electrode ground rod (the panel is also 10 meters away from ground rod). Let's assume the person stands on bare feet and dry sand. So I guess the gradient concentric circle starts at the local electrode ground rod (you can make it two rods.. I just want to know where to start the gradients circle and if the person would be shocked)?

1. At the ground rod.
2. Since you mentioned "bare feet", probably, keeping in mind all the caveats ptonsparky mentioned.

 

[don_resqcapt19]

The gradients stay pretty much the same. They are based on percentages of the total soil resistance, and assume that 100% of the voltage is dropped within x' of the grounding electrode. I think most such tables assume 100% drop at 25-50 feet from the rod. All a lower soil resistivity does is increase the current from into the earth. The voltage drop at x' remains relatively constant for various soil sensitivities.

 

[kwired]

The voltage gradient in the soil above assumes the street light pole metal enclosure and ground rod is same location. But how about if the metal enclosure (like panel enclosure below) and ground rod distance differs. Where will you draw the gradient circles below.. in the center of the ground rod or the panel case? I'd like to understand what gradients (just qualitatively) the person feet are exposed to.

Panel and rod are at same potential because there is a bond conductor between them, disregarding any voltage drop on that bond conductor which will be negligible anyway if it is short length, so that leaves you with how far are you from the rod where you are contacting earth will determine what voltage you are subjected to. If the panel were mounted on a conductive/semi conductive surface, there may be additional voltage gradient zones present relative to that surface.

 

[JPinVA]

What does NEC and other codes say about this, and theoretical considerations?

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In a nutshell, the NEC requires a low impedance path back to source to trip the OCPD.