AC electrical puzzlement

[Doug Garson]

Glad you found it. I'm not an electrician so I'm having trouble understanding how a bad neutral connection leads to a hot neutral. Can any of the Sparkies explain it? I would have thought you would need a short between the hot and neutral to cause the neutral to become hot.

[Tom M King]

It only makes the loose neutral hot when something is plugged into an outlet on that circuit. The connection is made inside whatever is plugged in. The breaker would trip if there was a short, but in this case the loose neutral now can carry the hot load but there is no real short because the now energized neutral is not bonded. Nothing works when plugged in downstream because there is no bonded neutral to complete the circuit. That's why I asked to start with if anything was plugged into that circuit.

I've seen this exact thing twice before on old back stabbed device circuits.

[Dan Friedrichs]

Glad you found it. I'm not an electrician so I'm having trouble understanding how a bad neutral connection leads to a hot neutral. Can any of the Sparkies explain it? I would have thought you would need a short between the hot and neutral to cause the neutral to become hot.

Imagine a load like a heater (which is just a piece of resistive wire) is plugged in, but the neutral connection is broken at the panel. The 120V flows from the hot, through the heater, to the neutral, causing the neutral to have 120V on it.


Glad you found it, Curt. When we bought our last house, one of the first things I did (before moving furniture in) was replace all the old receptacles and light switches with matching, higher-quality versions, and use screw terminals (no backstabs). Only took a few hours and not that much cost.

[Tom M King]

Both of the such circuits that I found like that were in a rental house I bought cheap because it was considered a tear-down for many reasons. It also had one circuit that nothing would work on some outlets unless something was plugged into one receptacle in that circuit. I didn't bother to even think about that one. I just pulled all the devices and replaced every one of them. I think that work was originally done in 1974. Everything works fine now in it.

[Doug Garson]

Tom, Dan, thanks for the responses, makes sense, I wasn't aware that a loose neutral could be that dangerous. As far as I know, none of the outlets or switches in my house are back stabbed, any I've done or looked at are connected using the side screw terminal.