What happened is a plumber cut through the main water pipe to do a repair. He got the shock of his life and blew 2 garage door openers, a dish washer, and something else. The plumber said half the basement lights went brighter and half went dimmer.
It is a 3 flat residence, 200 amp, 240 volt, 1 phase, 3 meters outside, 3 - 100 amp main breaker panels inside. IMO the service is likely done without a permit. It is all in RMC conduit. The grounding conductor does not run all the way to the entrance of the incoming water service, it is connected within 10 feet of the breaker panels. Copper water pipes, no die-electric union, lead service. No driven rod.
From left to right facing the inside panels. Panel A has a #4 conductor connected to the water pipe. Panel B has a #8 conductor connected to the water pipe. Panel C has no wire connecting it to the water pipe. Panel A is connected to panel C via a 1/2 EMT pipe. Panel B is connected to panel C via a 1" EMT. All panels have the bonding screw connecting the neutral bus to the panel encloser (the back of the panel).
There is current flowing through both wires connected to the water pipe. This varies with tenet use, I think. On panel A I read .7 to 3.9 amps with a clamp on meter. The reading on the wire in panel B was less but I don't remember exactly. There is current flow on the neutral conductor in panel A, it was higher than the grounding conductor but I don't remember exactly. With the amp meter on the grounding wire in panel A, turning the main off in panel A has no affect on the reading. Turning the main off in either panel B or C changes the reading and flipping both off mains in B & C changes the reading to 0. I have indentified 5 breakers in panel B and 4 breakers in panel C that, when turned off change the reading. Some raise the amperage and some lower it.
There are no ground bushings on the service pipes. The service voltage is 113 on one phase, and 124 on the other phase, to ground (the neutral bus or the panel). I have checked the screw tightness at all neutral connections except the main service riser. The connection in the meter box was too close to the hot lug for the tools I had then. There is a hornets nest in the weather head. I did grab both wires and yank on them to see if they were loose. I'm going back with hornet spray today.
So what do I do? What tests should I run?
As I see it, I should run one #4 wire to the water service and connect it to all three neutral buss's and eliminate both of the other two. But I don't think that will fix the problem, just make a proper grounding connection.
I can't figure out why current is flowing on the grounding conductor. Shouldn't the current flow on the neutral conductor? Am I correct in thinking that installing one grounding conductor , instead of two, would increase the current flow on the one? Am I also correct in thinking that the problem is that it seems the resistance in the neutral is too high? That would allow the current flow on the grounding conductor? If that's correct how do I test that?
I typed everything I could think of to help, and I hope I didn't miss anything.
Thanks Mike
It is a 3 flat residence, 200 amp, 240 volt, 1 phase, 3 meters outside, 3 - 100 amp main breaker panels inside. IMO the service is likely done without a permit. It is all in RMC conduit. The grounding conductor does not run all the way to the entrance of the incoming water service, it is connected within 10 feet of the breaker panels. Copper water pipes, no die-electric union, lead service. No driven rod.
From left to right facing the inside panels. Panel A has a #4 conductor connected to the water pipe. Panel B has a #8 conductor connected to the water pipe. Panel C has no wire connecting it to the water pipe. Panel A is connected to panel C via a 1/2 EMT pipe. Panel B is connected to panel C via a 1" EMT. All panels have the bonding screw connecting the neutral bus to the panel encloser (the back of the panel).
There is current flowing through both wires connected to the water pipe. This varies with tenet use, I think. On panel A I read .7 to 3.9 amps with a clamp on meter. The reading on the wire in panel B was less but I don't remember exactly. There is current flow on the neutral conductor in panel A, it was higher than the grounding conductor but I don't remember exactly. With the amp meter on the grounding wire in panel A, turning the main off in panel A has no affect on the reading. Turning the main off in either panel B or C changes the reading and flipping both off mains in B & C changes the reading to 0. I have indentified 5 breakers in panel B and 4 breakers in panel C that, when turned off change the reading. Some raise the amperage and some lower it.
There are no ground bushings on the service pipes. The service voltage is 113 on one phase, and 124 on the other phase, to ground (the neutral bus or the panel). I have checked the screw tightness at all neutral connections except the main service riser. The connection in the meter box was too close to the hot lug for the tools I had then. There is a hornets nest in the weather head. I did grab both wires and yank on them to see if they were loose. I'm going back with hornet spray today.
So what do I do? What tests should I run?
As I see it, I should run one #4 wire to the water service and connect it to all three neutral buss's and eliminate both of the other two. But I don't think that will fix the problem, just make a proper grounding connection.
I can't figure out why current is flowing on the grounding conductor. Shouldn't the current flow on the neutral conductor? Am I correct in thinking that installing one grounding conductor , instead of two, would increase the current flow on the one? Am I also correct in thinking that the problem is that it seems the resistance in the neutral is too high? That would allow the current flow on the grounding conductor? If that's correct how do I test that?
I typed everything I could think of to help, and I hope I didn't miss anything.
Thanks Mike