2

A light that has a 2 wires (and a ground) coming in from an outlet. The 2 wires are unused.

From the other side there are two wires coming up to the box. 1 of these wires connects to the light and the other connected to the ground wire from the first bundle. A third wire connects the bundle to the other side of the light.

I understand what is going on here - the people who setup the light (for whatever reason) used the ground as the neutral, not sure why since they had 2 other wires they could have used.

Anyway, when I was trying to figure out what was going on I disconnected all the wires at the switch & up in the light box. When I disconnected the ground coming from the outlet the 2 wires from the switch box showed hot from my cheap voltage meter - they were not connected to anything on the other side...

Why were they hot?

  • Stray voltages can naturally appear due to inductive coupling with live wires. Measure the current on the wire. The proper way to measure voltage in this situation is with an analog multimeter or an electrician's multimeter with low-Z mode. – user71659 Jan 30 '18 at 19:39
1

Edit: OK so it's not the light. But it's a ground fault somewhere. One presumes it is in the circuit, but grounds can be crossed over amongst circuits in the same panel, especially in a ground retrofit situation. So it could be anywhere wired which feeds the hot ground wire.

There should be no intentional current whatsoever on a safety ground. (though there can be micro-currents due to coupling or the tiny, tiny amount of leakage which is allowed.)

Unexpected currents like this are why grounds must be pigtailed, so you don't have to sever a ground to replace a device.

Obviously, bootlegging neutral from ground is the picture postcard definition of a ground fault.

If your previous homeowner did it one place, good chance he did it lots of places.

It's hot because when you interrupt/sever a current return, current is no longer able to return. Normally it flows freely back to the panel, and that pulls it down to near earth voltage. But current can't go any further so it's "piling up" right there.

  • That sounds good - but I have disconnected all the wiring in the light switch so there is no way for the hot to go through the light switch -- that is what weirded me out and why I asked the question. – Anthony Nichols Jan 30 '18 at 15:36
  • @AnthonyNichols oh, dear! Well, that's worse then. – Harper Jan 30 '18 at 17:15
  • Small amounts of ground currents are unavoidable due to coupling and are allowed. Without measuring the actual ground current, you cannot conclude there's a fault. – user71659 Jan 30 '18 at 19:45
  • @user71659 would this current add up to enough to make a DVM indicate 120V? That is the situation the OP is reporting and that is the context in which I am answering. – Harper Jan 30 '18 at 21:30
  • @Harper Yes. If there is no sink for the current, then a capacitive coupling with a 120 V line will lead to a 120 V stray or ghost voltage. – user71659 Jan 30 '18 at 21:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.