My own stupid electrical question / filling hole in concrete floor

Page 2 of 2  

todd wrote:

Todd, I think we're probably using different terminology. But yes, I'd be willing to agree the copper pipe is energized, in the sense that the assumed ground fault current is flowing through it.
In the eye of the NEC, there is a connection at the service entrance between the green grounding wire and the white neutral and ground. An appliance ground fault current SHOULD flow through the green grounding conductor to the service entrance, and from there, take the path of least resistance through that neutral wire back to the transformer on the pole. Of course the higher resistance path through the ground is in parallel with the neutral wire, so you get some current through the ground as well. It is normally not a good thing for there to be a lot of current through the ground, and its presence could indicate a problem with the neutral connection, etc.

Yes, the latter is what I assumed also.
My assertion was that if there was enough

Agreed. Except that there is no voltage to speak of on the ground wire while it is connected to the copper pipe (i.e., to ground). There is a current through the wire. When the connection to the pipe is broken, at that time a voltage is present between the pipe and the wire. Placing yourself across that voltage is what could be hazardous.
If that was the case, I wouldn't handle anything

Well, touching the plumbing fixtures should be safe because they are essentially at ground potential, again due to the copper pipe connection. That is a benefit of the grounding system. But if currents are detected in the grounding wire, something is amiss and maybe should be corrected.

Fascinating. I'd be lost in that area.

The reason for that jumper is more likely that the meter itself does not represent a good, low-resistance path. You see those jumpers around plastic-bodied filters also. In the past, service entrance grounds were often connected to metal plumbing systems. In many cases these systems were "upgraded" to plastic, and the residence was left without any ground connection at all!
FWIW, with so much PVC in use in new construction, the NEC now requires a dedicated ground rod or two at the service entrance.

Chuck
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
As long as the ground is still attached, zero risk. If you disconnect the ground and there is something bleeding current to ground, it will be live.
I had a "hot" computer case once. If I touched it, while touching something grounded I got a heck of a zap. Turned out the extension cord I was using had the ground broken inside of the male end of the cord. AC inducts current into nearby conductors real well, so it was loading the ground wire, no longer connected to a ground, with lots of juice. Since the case of the computer is directly connected to the ground lead... Replacing the cord solved the problem.
--
Bill Berglin

"Life should not be a journey to the grave with the intention of
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Um, no. You'd need miles of wire to induct any appreciable amount of charge into a parallel unconnected wire at the frequencies power lines work at.

Something else was also connected to the ground lead - quite likely the power line neutral (the "white wire" - I'm guessing this since you've stated the extension cord was defective). As you observed, when the far end of the ground lead wasn't grounded, this provided enough charge on the case to give you a tingle.
John
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.