SHOCKED BY CONCRETE??!!

[SPierce]

I did not take it, but we received a call from a gal who said when she was sitting on her concrete front porch and she touched the concrete with her bare hand, she received a shock. Apparently her husband was shocked also by doing this. Any ideas on what might be causing this? Thank you.

 

[iwire]

I did not take it, but we received a call from a gal who said when she was sitting on her concrete front porch and she touched the concrete with her bare hand, she received a shock. Apparently her husband was shocked also by doing this. Any ideas on what might be causing this? Thank you.

What else where they touching?

Can't get a shock from just one thing.

 

[S'mise]

They must have been touching something else (or another slab of concrete)

Concrete is a good conductor. Probably a nicked underground feeder.
Start shutting off breakers.

 

[mikeames]

We have debated this before so Ill just say, define good conductor. I don't think concrete is a good conductor. Soaking wet damp concrete does conduct no question but if concrete were a good conductor we would not need x amount of feet of rebar or copper wire. We could just bolt a lug to it and be done.

 

[Jraef]

Hmmm... sitting ON the concrete porch, then touching the SAME concrete with her bare hand? So the only difference is the presumably capacitive properties of her pants and (presumably) panties? Was she wearing mylar panties and gold lame' hot pants right after scuttling across a nylon carpet with lexan shoes?

Kinky:thumbsup:

 

[iwire]

We have debated this before so Ill just say, define good conductor. I don't think concrete is a good conductor.

In terms of delivering a lethal shock to a human, cement is an excellent conductor.

In terms of using concrete as a conductor to power a motor it is a very poor conductor.

 

[hillbilly1]

Lots of varibles here too, is it a mobile home? The concrete patio on those usually are not physically tied to a grounding electrode system, and many have aluminum siding, touching the siding while bending down to touch the concrete can make a path as iwire was pointing out.

 

[mikeames]

In terms of delivering a lethal shock to a human, cement is an excellent conductor.

In terms of using concrete as a conductor to power a motor it is a very poor conductor.

I agree but I still classify it as a poor conductor.

 

[hillbilly1]

Concrete draws moisture, which in effect makes the concrete encased grounding electrode a better conductor.

 

[Hv&Lv]

I did not take it, but we received a call from a gal who said when she was sitting on her concrete front porch and she touched the concrete with her bare hand, she received a shock. Apparently her husband was shocked also by doing this. Any ideas on what might be causing this? Thank you.

Lost neutral either in service or primary, or loose connection. Any problems other than shock?

 

[MichaelGP3]

I'm going to guess that with the hot weather, the woman may be sweating more than usual, and now is the path of least resistance. Whereas when it was 65 degrees F outdoors, something else was.

 

[SG-1]

I am thinking it could be step potential. Their bare feet may be touching the concrete a few feet away. Or the distance between their hands. There has to be a ground fault that includes the slab.

 

[sii]

In terms of using concrete as a conductor to power a motor it is a very poor conductor.

I'm guessing someone tried though?

 

[kwired]

I'm going to guess that with the hot weather, the woman may be sweating more than usual, and now is the path of least resistance. Whereas when it was 65 degrees F outdoors, something else was.

Maybe so but you still need to contact two points of different potential or there will be no current flow. Birds can safely sit on high voltage power lines because they are only in contact with the one line they are sitting on.

 

[zog]

For what it is worth, here are the values used by OSHA and IEEE and some comparitive materials.


Materials Resistance (Ohms)
Rubber gloves or soles More than 20 M
Dry concrete above grade 1-5 M
Dry concrete on grade 0.2-1 M
Leather sole, dry 100-500 k
Leather sole, damp 5-20k
Wet concrete on grade 1-5 k

 

[Jraef]

Maybe so but you still need to contact two points of different potential or there will be no current flow. Birds can safely sit on high voltage power lines because they are only in contact with the one line they are sitting on.

Yep.
Hence iwire's comment #2 and my comment #5. All the other stuff is irrelevant if there is no difference in potential between TWO points of contact. So unless her butt and hand somehow made contact with two things with different potentials (or my comment about capacitive undies in which SHE becomes the power source), there is no shock.

 

[kwired]

Yep.
Hence iwire's comment #2 and my comment #5. All the other stuff is irrelevant if there is no difference in potential between TWO points of contact. So unless her butt and hand somehow made contact with two things with different potentials (or my comment about capacitive undies in which SHE becomes the power source), there is no shock.

I think most of the replies are by people that realize that there needs to be another point of different potential. Apparently the OP does not, or he would not have asked. We are here to help him understand that.

One of the first things that should have been done when checking out the situation is to identify what the second point of differing potential contact is.

 

[K8MHZ]

Yep.
Hence iwire's comment #2 and my comment #5. All the other stuff is irrelevant if there is no difference in potential between TWO points of contact. So unless her butt and hand somehow made contact with two things with different potentials (or my comment about capacitive undies in which SHE becomes the power source), there is no shock.

Different slabs, maybe? Even if just a result of cracks, a fault in one may make for a difference in potential with respect to the other.

 

[Twoskinsoneman]

Yep.
Hence iwire's comment #2 and my comment #5. All the other stuff is irrelevant if there is no difference in potential between TWO points of contact. So unless her butt and hand somehow made contact with two things with different potentials (or my comment about capacitive undies in which SHE becomes the power source), there is no shock.

I would tend to agree. Just for argument sake if there was a connection between and ungrounded conductor and the concrete, could a voltage gradient be setup in the concrete where you could be leaning back touching the concrete with you hand and a few feet away your bare for is touching the concrete with a few volts difference due to the gradient?

 

[kwired]

I would tend to agree. Just for argument sake if there was a connection between and ungrounded conductor and the concrete, could a voltage gradient be setup in the concrete where you could be leaning back touching the concrete with you hand and a few feet away your bare for is touching the concrete with a few volts difference due to the gradient?

Concrete that is wet possibly, concrete that is dry I just can't see having that good of conductivity to do that at only 120 volts.