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Old 02-06-2017, 10:29 PM   #1
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Changed out a rusted out old subpanel today, was ungrounded. Fed by a 200a 3ph 240 delta panel. This panel fed milking equipment and lighting for a barn, it also fed a detached outbuilding with quadplex, and a well pump panel with triplex.

New panel is 100a 3ph, fed with #2, #6 ground. Bonding jumper in new subpanel is not used.

Got everything landed in the new panel, energized it, and started testing. Voltages checked out fine, noticed the riser for the outbuilding feed had no ground. Put the ammeter on the ground wire from main panel to sub panel and there was 2a. Shut off the 100a breaker feeding the outbuilding, the 2 amps on the ground goes away. Turn 100a breaker back on, 4 amp surge then goes back to 2a.

The only load on inside the outbuilding is a freezer. The subpanel in the outbuilding has a ground rod, attached to the ground bar. It also has no bonding jumper. Screwed in the bonding jumper, it arced with the can, so that came back out.

Look up at the mast of the first building, both the ground and neutral of the quadplex is tied to the neutral from the sub panels mast. Big ugly splitbolt where the 4 wires are all tied together, aluminum to copper.

My question is, how is that current going back on the ground I ran 15ft from the new subpanel to the main panel? Could the neutral/ground splice be high resistance, now the current is going back via ground rod then to a water pipe or something?

Going to take the bucket truck out later this week to take a look at it.
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Old 02-06-2017, 10:35 PM   #2
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This is an ungrounded system?

I can't quite tell by your description...
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Old 02-06-2017, 10:42 PM   #3
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This is an ungrounded system?

I can't quite tell by your description...
The service / panel that fed the one I replaced is grounded. The panel I pulled out had no ground ran with the feeders to it. I pulled new feeders and a ground.
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Old 02-06-2017, 10:49 PM   #4
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[B]Look up at the mast of the first building, both the ground and neutral of the quadplex is tied to the neutral from the sub panels mast. Big ugly splitbolt where the 4 wires are all tied together, aluminum to copper./B]

So the neutrals and grounds are splice together outside of the main?
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Old 02-06-2017, 10:54 PM   #5
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So the neutrals and grounds are splice together outside of the main?
Yeah, that overhead that is fed by the panel I changed, years ago someone spliced together the ground and neutral of the guadplex to the neutral that goes down the mast. Copper to aluminum under a split bolt.

Going to run a egc up to the weatherhead and separate the grounds and neutrals in a few days. Too steep of a metal roof to climb in the rain.
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Old 02-06-2017, 11:05 PM   #6
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You may also want to go through the buildings if that doesn't solve it. I've had similar situations, typically they've spliced the neutrals and grounds (Bootlegs) and that is causing the current on the ground.
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Old 02-06-2017, 11:28 PM   #7
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Kinda hard to paint a picture..but yea undo the quadplex splice.. 250.142 objectionable current.. its creating a parallel path for the neutral to "return" on metal parts. Id double check the freezer with a gfci as well to see if im dealing with faulty equipment
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Old 02-06-2017, 11:51 PM   #8
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Heres a hastily drawn diagram of the situation.



Just not understating how there could be current on the ground between panel 1 and 2, when the 3rd panel dosent have a ground going to panel 2, only a neutral, and panel #2 does not have a bonding jumper.
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Old 02-07-2017, 01:02 AM   #9
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Heres a hastily drawn diagram of the situation.



Just not understating how there could be current on the ground between panel 1 and 2, when the 3rd panel dosent have a ground going to panel 2, only a neutral, and panel #2 does not have a bonding jumper.
Look at your picture again. The ground and neutral are in parallel from that overhead splice. Think of all the equipment that has a EGC and is connected to concrete. And most likely that splice is corroded as hell. Bet the cows knew there was current there.

Last edited by backstay; 02-07-2017 at 01:06 AM.
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Old 02-07-2017, 01:06 AM   #10
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Just out of curiosity, see if there is any current on the wire going to the ground rod on the out building. I'd suspect that splitbolt connection.

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Old 02-07-2017, 05:28 AM   #11
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The overhead splice in your picture between the middle and outbuilding is wrong the same way the bonding jumper in the subpanel is wrong. In fact it's one of those things you are surprised and lucky there weren't worse problems. But yeah you should be seeing current on the ground anywhere between the main panel n-g bond and the no-good bond.

The only thing that I'm kind of scratching my head about, is why all the current on the ground goes away when you turn off the breaker in the middle panel to the outbuilding. Doesn't the improper ground create a parallel path for all the loads in the middle panel as well? (Lighting and milking equipment if I read you right). If that's the case, if the lights are on, shouldn't you still see some current on the ground to the main?
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Old 02-07-2017, 06:50 AM   #12
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Turn ff the power and lift all neutrals, unplug all equipment and megger the neutrals to ground.

With power on check for zero sequence on each circuit and feeder.

Look for any obvious neutrals that are grounded.
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Old 02-07-2017, 07:05 AM   #13
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Old 02-08-2017, 09:17 PM   #14
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Solved the issue today, there was a neutral tied to a ground in a 30a disconnect fed by the middle panel.
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