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What (if anything) does this mean?


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I was at a house this morning where the complaint is high electrical usage. I ended up finding amp readings in a small panel that I don't understand. In the photos, the neutral wire shows about 1.5 amps on it, with the A and B phases showing almost nothing. There are a couple of 120 breakers in the panel for garage lights, and another for a well pump, which was not running. Nothing at all drawing on this panel as far as I could tell.

I'm wondering if there is somehow an electrical "leak" going on here, because I'm accustomed to seeing a more logical relationship between these three readings. For instance, in my shop right now, there is 5 amps on the A phase, .9 amps on the B phase, and 4.1 on the neutral.

The panel in the photos is in the garage. The service is overhead and comes down the exterior wall of the garage directly behind this panel. The meter, a large disconnect, and a trough are mounted on the exterior wall. There is a conduit going to the house carrying a 400-amp service to a pair of panels there. Not sure if it matters, but there are *big* conductors on the exterior, very close to where my amp clamp is. I normally don't think this will influence the reading at all.

No doubt some of you guys can clear this up for me. Thanks in advance.

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tn_201631195752_b%20phase.jpg

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The neutral conductor is carrying the difference between the 'A' leg and the 'B' leg. That's normal. When they are the same, they cancel out perfectly and the neutral current is zero.

There's an exception to that rule that involves power factor values that are less than one but that's not a major player in this picture.

I don't see anything wrong with those amps.

Marc

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Hey, Marc, the neutral is carrying 10 times the current shown on the hot wires.

David, you may have some kind of a backfeed from the other panels finding a path to ground through that neutral you measured.

Even so, those readings are not where the power loss is. But that may be a clue to the problem.

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Check for open neutrals. I think John is on the right path with backfeed to ground.

When I was a kid we had a high usage condition at my mom's house. After a while we would get zapped on appliances and the kitchen sink would arc when the water was turned on. The neutral on the three wire overhead was contacting a lightning rod. It resolved itself when the arc finally cut through the neutral.

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Electric baseboard heat and electric hot water in this 1970 house, as is common here, but it has been unoccupied and (owner says) minimally heated during this winter. I'm going to recommend they have an electrician check this out. Hopefully they can find someone with the right troubleshooting skills.

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