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I recently renovated my home and re-did all the electrical from the service drop on down. Everything appears to be working correctly so far except one circuit.

I have a NEMA 14-30R receptacle wired up for an oven. It’s 10/3 NM-B (3 conductors and 1 ground). When I plugged in the oven for the first time it did not turn on.

I checked the voltage on the receptacle and I get ~240v between the two hots, ~120v between both hots and the ground, but I get ~110v between one hot and the neutral, and ~130v between the other hot and the neutral.

The asymmetry seems strange… and I wonder if that might be the cause of the oven not powering on. Before I open up the load center and start testing everything, I just wanted to get a sanity check on this.

Is that likely the problem or is that fine?

Update

I opened up the panel and did some tests—here’s what I found.

The service coming in is fine.

The reading at the terminals for the breakers are the same as the readings at the receptacle.

The breaker is fine—I swapped it with another 30A and there was no change in readings.

The receptacle is fine—I took it off and tested the wire ends and there was no change in readings.

I checked the connection for the neutral wire and it is not loose. I loosened it and re-torqued it just to be sure. The wire was deformed from the mounting screw, but other than that it looked fine.

Update #2

I just figured it out—it was a lost neutral, although the cause was somewhat unusual. I’ll post an answer with the explanation shortly.

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    If you check random 120V receptacles around the house, do you get 120V or do you get some 110V and some 130V, or perhaps more variance than that? You might have a loose or bad neutral connection somewhere. What do you get in the panel? Aug 10, 2023 at 3:14
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    I checked a few 120v receptacles and they all read 120v. I also checked a 3-prong 50A receptacle I have, and that gets 120v between both hots and the ground, although that’s technically not the same as what I was tesing with the 4-prong receptacle. I haven’t opened up the panel yet to check. I tried googling the problem and couldn’t come up with anything, so I thought I’d try and create the resource to save future people some time. Aug 10, 2023 at 3:17
  • it could be one hot is just ghost voltage
    – Traveler
    Aug 10, 2023 at 3:25
  • @manassehkatz-Moving2Codidact has nothing to do with OP question
    – Traveler
    Aug 10, 2023 at 4:34
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    Symptoms look to me like your neutral is bad.
    – brhans
    Aug 10, 2023 at 12:18

1 Answer 1

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After trying all sorts of various things I finally stumbled onto what the problem was.

I’m using a Leviton load center, specifically the LP422-BPD.

Leviton does something sort of different with their load centers and breakers—the hot and neutral wires of a branch circuit connect to terminals in the load center next to the breaker, but not on the breaker itself.

Here’s an image from the manual of what that looks like:

enter image description here

This has all sorts of benefits, like being able to finish roughing in the panel without the breakers, installing breakers is as easy as just snapping them in, changing breakers is easier, changing breakers from a standard breaker to a GFCI/AFCI breaker is easier, et cetera.

If you’re installing a 1-pole breaker then the hot and neutral terminals in the slot are both used.

If you’re installing a 2-pole breaker with a 2-wire branch circuit then both hot terminals and neither of the two neutral terminals are used.

If you’re installing a 2-pole breaker with a 3-wire branch circuit then both hot terminals and one neutral terminal is used, but there is a specific neutral terminal of the two that you have to use—you can’t just use either.

Here’s the image from the manual:

enter image description here

This is because the 2-pole breaker itself only has three contact points. You can see what I mean in this photo of it. At the bottom there are four slots/grooves that contact the terminals, but only three have metal contacts in them.

enter image description here

When I was wiring the panel up I assumed either neutral terminal was fine to use and by chance I chose the wrong one, causing the lost neutral 🥲

I hope this helps someone else!

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  • Nice detailed answer :)
    – brhans
    Aug 13, 2023 at 18:11

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