Last week I got a call that the water tank was shocking the horse's. My initial thought was the neutral and ground were bonded together at the water tank. They were not. In addition to the egc there was a bare wire ran under the slab, to what I don't know. The panel is a sub panel fed with 3 wire from another building. I figured the wire was either going to a ground rod or tied into the other water tank that is fed from the other building. Either way I don't need/want it so I determ it. Before I do I shoved some #12 bare in the mud and took a volt reading from the egc to ground. I read 14.7v after I determ it I read 30v not what I expected to see.
I string the #12 wire that has one end stuck in the mud inside for further measurements.
There is a metal water pipe coming into the building that I assume connects between the other buildings onsite since I don't want any other paths back to the other buildings I determ the wire from the water pipe. I plug in my shop vac to a recep and measure from the #12 in mud to the egc in the circuit, 57v. My thinking is there are parallel paths back to the source. The only other path I could think of is the #6 leaving the panel. I assume this goes to a ground rod but in case it was ran all the way back i determ it. This time I turn on a light and measure from the #12 in the mud to the egc in the circuit 120v.
After I quickly shut off all the power to the building I began tracing the neutral all the way back and found I dropped it at the weather head of the other building. After crimping the neutral back on I still have .5v between the neutral and egc? I also temporally re-termed the water pipe and mysterious bare wire at the water tank, this made no difference. I left it and decided .5v is acceptable. Would you agree?
I realize a 3 wire system is no longer acceptable, but it was for a long time. This is the way I understand it. It was okay to feed a separate building with 3 wire as long as there were no other connections to the main panel. You bond the neutral and ground again and all fault current then must go back on neutral. You still must drive a ground rod, so if you drop a neutral as I did, electricity is going to find a path back to the source and directly though the earth is the only one left. Is this correct?
Was the path I took to find the problem logical or were there cues I should have picked up on sooner? My background is not in troubleshooting but I enjoy and hope to become more efficient.
sorry for such a long post. feedback is welcome
I string the #12 wire that has one end stuck in the mud inside for further measurements.
There is a metal water pipe coming into the building that I assume connects between the other buildings onsite since I don't want any other paths back to the other buildings I determ the wire from the water pipe. I plug in my shop vac to a recep and measure from the #12 in mud to the egc in the circuit, 57v. My thinking is there are parallel paths back to the source. The only other path I could think of is the #6 leaving the panel. I assume this goes to a ground rod but in case it was ran all the way back i determ it. This time I turn on a light and measure from the #12 in the mud to the egc in the circuit 120v.
After I quickly shut off all the power to the building I began tracing the neutral all the way back and found I dropped it at the weather head of the other building. After crimping the neutral back on I still have .5v between the neutral and egc? I also temporally re-termed the water pipe and mysterious bare wire at the water tank, this made no difference. I left it and decided .5v is acceptable. Would you agree?
I realize a 3 wire system is no longer acceptable, but it was for a long time. This is the way I understand it. It was okay to feed a separate building with 3 wire as long as there were no other connections to the main panel. You bond the neutral and ground again and all fault current then must go back on neutral. You still must drive a ground rod, so if you drop a neutral as I did, electricity is going to find a path back to the source and directly though the earth is the only one left. Is this correct?
Was the path I took to find the problem logical or were there cues I should have picked up on sooner? My background is not in troubleshooting but I enjoy and hope to become more efficient.
sorry for such a long post. feedback is welcome