SHOCKED BY CONCRETE??!!

[SG-1]

If you were to stand bare foot on my cement front porch with a thunderstorm near by you will think a lawnmower magneto hit you. Only your two bare dry feet need to be in contact with the cement. I believe the metal awning is collecting the charge. In my experience a ground fault is not necessary or contact with an energized object to be shocked while on concrete. Mother Nature can do this all by her self. :blink:

 

[glene77is]

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?

Two,
Good Thought ! :thumbsup:
That is what I was thinking,

Some unstated second contact point.
One on concrete,
Two via foot to ground.

 

[renosteinke]

I grew up in a (at the time) new house with a slab foundation and a vinyl tile floor. For a while, I got a shock whenever I touched the TV dial. My parents did not believe me - until they approached the TV wearing only socks, and got a shock themselves.

So, one does not have to persuade me that concrete - even dry concrete in cool weather - is a good enough conductor to let you get a pretty good tingle. Even when there's an additional 1/8" of vinyl tile and asphalt-based mastic atop it.

I do agree that the customer needs a source for the power- in my case, it was the TV. There's a potential between the concrete and something else.

I'll even go a bit further .... if the source is of a sufficiently high voltage, there might be enough of a voltage drop over even a few feet of distance for a person to feel a shock by simply reaching over a section of the concrete and touching it in a second spot. That's how much better a conductor the body is, as compared to concrete, of any type.

I once had a service call that was similar - folks getting a shock from the bathtub. I suggest the same troubleshooting procedure be followed by the OP.

I first measured that there was a potential (voltage) between the tub and the nearby sink. Then I killed the main.

The voltage went away- so I proceeded to turn on circuits until I found the one that was providing the power to the tub. With the circuit identified, I removed all appliances; this established that the source was an appliance, rather than the circuit itself. Ultimately, the problem was traced to an extension cord.

The OP needs to do the same, so he can know (first) if the problem is from the house wiring. If killing the main also removes the problem, then we have ruled out any esoteric 'stray voltage' issues. If not, a call to the PoCo is in order.

 

[mbeatty]

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:

Excellent analysis and question. Funny stuff!
Mark

 

[kwired]

I grew up in a (at the time) new house with a slab foundation and a vinyl tile floor. For a while, I got a shock whenever I touched the TV dial. My parents did not believe me - until they approached the TV wearing only socks, and got a shock themselves.

So, one does not have to persuade me that concrete - even dry concrete in cool weather - is a good enough conductor to let you get a pretty good tingle. Even when there's an additional 1/8" of vinyl tile and asphalt-based mastic atop it.

I do agree that the customer needs a source for the power- in my case, it was the TV. There's a potential between the concrete and something else.

I'll even go a bit further .... if the source is of a sufficiently high voltage, there might be enough of a voltage drop over even a few feet of distance for a person to feel a shock by simply reaching over a section of the concrete and touching it in a second spot. That's how much better a conductor the body is, as compared to concrete, of any type.

I once had a service call that was similar - folks getting a shock from the bathtub. I suggest the same troubleshooting procedure be followed by the OP.

I first measured that there was a potential (voltage) between the tub and the nearby sink. Then I killed the main.

The voltage went away- so I proceeded to turn on circuits until I found the one that was providing the power to the tub. With the circuit identified, I removed all appliances; this established that the source was an appliance, rather than the circuit itself. Ultimately, the problem was traced to an extension cord.

The OP needs to do the same, so he can know (first) if the problem is from the house wiring. If killing the main also removes the problem, then we have ruled out any esoteric 'stray voltage' issues. If not, a call to the PoCo is in order.

With the TV are you sure you were not getting a shock from static discharge?
Depending on what kind of socks you were wearing, I believe wool or silk on vinyl and shuffle your feet will build up static pretty easily. TV dial happeed to be good enough path to discharge you when you touched it.


As far as the OP - remember he said he was not on the call but heard what the customer problem was, and basically wanted suggestions as to what may be going on here. Most replies have been good information. The main thing is that one needs to know that you will not get shocked unless you are exposed to two different objects or areas of same object that have a voltage potential between them.

 

[mikeames]

I grew up in a (at the time) new house with a slab foundation and a vinyl tile floor. For a while, I got a shock whenever I touched the TV dial. My parents did not believe me - until they approached the TV wearing only socks, and got a shock themselves.

So, one does not have to persuade me that concrete - even dry concrete in cool weather - is a good enough conductor to let you get a pretty good tingle. Even when there's an additional 1/8" of vinyl tile and asphalt-based mastic atop it.

I do agree that the customer needs a source for the power- in my case, it was the TV. There's a potential between the concrete and something else.

I'll even go a bit further .... if the source is of a sufficiently high voltage, there might be enough of a voltage drop over even a few feet of distance for a person to feel a shock by simply reaching over a section of the concrete and touching it in a second spot. That's how much better a conductor the body is, as compared to concrete, of any type.

I once had a service call that was similar - folks getting a shock from the bathtub. I suggest the same troubleshooting procedure be followed by the OP.

I first measured that there was a potential (voltage) between the tub and the nearby sink. Then I killed the main.

The voltage went away- so I proceeded to turn on circuits until I found the one that was providing the power to the tub. With the circuit identified, I removed all appliances; this established that the source was an appliance, rather than the circuit itself. Ultimately, the problem was traced to an extension cord.

The OP needs to do the same, so he can know (first) if the problem is from the house wiring. If killing the main also removes the problem, then we have ruled out any esoteric 'stray voltage' issues. If not, a call to the PoCo is in order.

Based on what zog posted assume the concrete had 1 meg of resistance. (forget about the vinyl for now) 120 volts/ 1000000 = .00012 amps or .12 milli amps or 120 micro amps . That would be hard for some to even notice. Unless you were touching the fly-back xfmr that's something else altogether then you would be picking yourself up off the floor.

 

[glene77is]

Mike,
"Unless you were touching the fly-back xfmr that's something else altogether then you would be picking yourself up off the floor. "
The fly-back Voltage might peak at 12,000 V, and certainly bites.

But, the 120 micro-Amps is ten times the leakage current JHAC sets as the standard in hospitals, because some equipment is connected intra-veneously to the heart. I was required to test at the 10 micro-Amp level.

Anyway, your discussion is interesting. Thanks for the post.

Not all the relevant info could be provided by the OP,
but this has been a very interesting thread. :thumbsup:

 

[mr wizard]

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:

The OP stated the husband got shocked when he tried it, too. Oh yeah, kinky for sure! Really though, if they are sitting on metal patio furniture, with rubber feet on the furniture, coupled with the dry weather a lot of the country is having, they could have got hit with a nasty dose of static electricity when they touched the patio concrete with their bare hands. Beyond that I would have to think the furniture is somehow connected to a metal patio cover which may have a light attached to it with a short. So many scenarios to this it could be contemplated forever :blink:

 

[hillbilly1]

The OP stated the husband got shocked when he tried it, too. Oh yeah, kinky for sure! Really though, if they are sitting on metal patio furniture, with rubber feet on the furniture, coupled with the dry weather a lot of the country is having, they could have got hit with a nasty dose of static electricity when they touched the patio concrete with their bare hands. Beyond that I would have to think the furniture is somehow connected to a metal patio cover which may have a light attached to it with a short. So many scenarios to this it could be contemplated forever :blink:

Yeah, too bad the OP didn't take the job so we could find out what actually happend!

 

[mikeames]

Mike,
"Unless you were touching the fly-back xfmr that's something else altogether then you would be picking yourself up off the floor. "
The fly-back Voltage might peak at 12,000 V, and certainly bites.

But, the 120 micro-Amps is ten times the leakage current JHAC sets as the standard in hospitals, because some equipment is connected intra-veneously to the heart. I was required to test at the 10 micro-Amp level.

Anyway, your discussion is interesting. Thanks for the post.

Not all the relevant info could be provided by the OP,
but this has been a very interesting thread. :thumbsup:

That's kind of my point. Its 10 times whats deemed safe for intra-veneous hospital equipment. Throw in the flooring and the mastic as described and it's probably around the 10 micro amps.

 

[malachi constant]

I first measured that there was a potential (voltage) between the tub and the nearby sink. Then I killed the main.

I read that three times before I figured out you said "main", not "man". Capping the customer is one way to take care of a service call, but not a good one!

Seriously though, troubleshooting as you described is exactly the way to go.

 

[kwired]

I read that three times before I figured out you said "main", not "man". Capping the customer is one way to take care of a service call, but not a good one!

Seriously though, troubleshooting as you described is exactly the way to go.

I hope he gets payment before 'killing the man'

 

[kingpb]

Step and touch potentials seem to come to mind IEEE 80. Could a service ground be tied to steel/rebar in the concrete?

 

[glene77is]

Step and touch potentials seem to come to mind IEEE 80.

Could a service ground be tied to steel/rebar in the concrete?

King,
You may have stepped onto something good now ! :thumbsup:

 

[doslover]

Live concrete

Live concrete

Had the same thing happen. I was getting shocks. My dog was getting shocks. The concrete was damp. I was getting about a 35 volt reading from the concrete to a ground wire.

I turned breakers off & on until I isolated circuit causing the voltage. Turns out when customer was installing plywood as wallboard, a 2-1/2" nail had gone through the romex, through the hot wire and was rubbing up against the ground wire. The ground rods were just outside the wall where the concrete was "live". Replaced the spiked wire and the voltage went away.