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?
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.
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.