Why is there voltage on the neutral and can I remove it?

[AdamTeeScott]

I work on some old houses with plaster walls/ceilings and I occasionally run into knob and tube wiring. Occasionally some of the homes have BX cables run to the electrical boxes, or it will be half and half.

In any case, when I am trying to determine which conductor is the hot wire in an old ceiling box, for example, because the insulation is not colored, I tend to pick up voltage imbalances on the neutral conductor, some as high as 65 volts, which triggers my non-contact voltage tester.

Where would such an imbalance come from when nothing is plugged in and turned on and how, if possible, can I dissipate it, cancel it, 86 it, get rid of it, etc.?

 

[ActionDave]

Welcome to the forum.

A regular digital meter will give you all kinds of crazy voltage readings sometimes. That 86V may be what's known as phantom voltage. A low Z meter or a wiggy can be a big help sorting this out.

Using an extension cord plugged into a known properly wired receptacle and testing each mystery conductor against it is a good method for those tough troubleshoots.

 

[gadfly56]

Welcome to the forum.

A regular digital meter will give you all kinds of crazy voltage readings sometimes. That 86V may be what's known as phantom voltage. A low Z meter or a wiggy can be a big help sorting this out.

Using an extension cord plugged into a known properly wired receptacle and testing each mystery conductor against it is a good method for those tough troubleshoots.

Sometimes not. I was changing a light fixture in an upper room of my 1929 cape-style home to add an outlet. Since I was working solo, I used one of those screw-in adapters to plug in a clock radio. I cranked it up to max, went downstairs and loosened fuses until the radio dropped out. Went back upstairs and start blithely taking apart the old fixture when I got bit. Now I take out my meter and there's still 77 volts on it. Go back and forth loosening additional fuses until the 77 volts goes away. Finished the change out, put everything back and made a note to contact an electrician for a panel change. Had an electric dryer to hook up so I needed it anyway.

 

[ramsy]

Sometimes not. ..Go back and forth loosening additional fuses until the 77 volts goes away. ..made a note to contact an electrician for a panel change.

A new fuse box does not fix multi-wire branch circuits, with 2 breakers sharing same neutral, nor J-box hots tied to multiple breakers on same service leg.

However, the tools & methods ActionDave generously suggested can identify both scenarios.

 

[gadfly56]

A new fuse box does not fix multi-wire branch circuits, with 2 breakers sharing same neutral, nor J-box hots tied to multiple breakers on same service leg.

However, the tools & methods ActionDave generously suggested can identify both scenarios.

I did not mention there were apparently multiple circuits under some of the fuses. When the new panel went in, that problem did go away, probably more from cleaning up the circuits as anything else.

 

[GoldDigger]

I work on some old houses with plaster walls/ceilings and I occasionally run into knob and tube wiring. Occasionally some of the homes have BX cables run to the electrical boxes, or it will be half and half.

In any case, when I am trying to determine which conductor is the hot wire in an old ceiling box, for example, because the insulation is not colored, I tend to pick up voltage imbalances on the neutral conductor, some as high as 65 volts, which triggers my non-contact voltage tester.

Where would such an imbalance come from when nothing is plugged in and turned on and how, if possible, can I dissipate it, cancel it, 86 it, get rid of it, etc.?

Good odds that it is phantom voltage, measured by a high impedance meter. But if the neutral is in fact connected to the neutral bar at the main panel you cannot have phantom voltage on it.
Either the neutral is open somewhere (switched neutral?) or it is not in fact a neutral.

 

[Sahib]

You may check if it is a phantom voltage or not by a test lamp across it: if it lights up even if dimly, the voltage is real caused by faulty circuit upstream.

 

[ptonsparky]

Many older homes did have switched neutrals. It was a common practice.

 

[cowboyjwc]

Also in those older homes the wiring all turns black, so you could have a neutral and hot swapped down the line, but then it should have 120 volts on it. Could also just have really unbalanced loads in your panel. Also remember you're tied to the same neutral that your neighbor is.

 

[jumper]

Many older homes did have switched neutrals. It was a common practice.

And oh so painfully did I learn that one day years ago while atop a ladder. Did not stay atop the ladder....

 

[al hildenbrand]

And oh so painfully did I learn that one day years ago while atop a ladder. Did not stay atop the ladder....

:lol: Boy Howdy! ! That brings back some old memories.

All the suggestions offered in these responses above are spot on. To re-emphasize: As convenient as a noncontact volt sniffer is, the only reliable method to verify wires in ungrounded wiring methods from the first half of the 1900s is with a known ground extended on a good wire of some kind to a low impedance meter (not a digital meter).

There are short cuts, but this is the most assuredly reliable.

 

[JFletcher]

Welcome to the forum!

I work on some old houses with plaster walls/ceilings and I occasionally run into knob and tube wiring. Occasionally some of the homes have BX cables run to the electrical boxes, or it will be half and half.

In any case, when I am trying to determine which conductor is the hot wire in an old ceiling box, for example, because the insulation is not colored, I tend to pick up voltage imbalances on the neutral conductor, some as high as 65 volts, which triggers my non-contact voltage tester.

Where would such an imbalance come from when nothing is plugged in and turned on and how, if possible, can I dissipate it, cancel it, 86 it, get rid of it, etc.?

Could be phantom or induced voltage, could be live. Might be because you have neutrals of different circuits tied together, or even hots of the same leg. For safety, turn off breakers/remove fuses until it goes away before working on such a circuit.

Last time I saw an odd voltage on a 120V circuit, it was around 45V, and it was due to a failing breaker - it had been used as a switch to turn on/off the sign light at a beauty salon for who-knows-how-many-years.

 

[K8MHZ]

:lol: Boy Howdy! ! That brings back some old memories.

All the suggestions offered in these responses above are spot on. To re-emphasize: As convenient as a noncontact volt sniffer is, the only reliable method to verify wires in ungrounded wiring methods from the first half of the 1900s is with a known ground extended on a good wire of some kind to a low impedance meter (not a digital meter).

There are short cuts, but this is the most assuredly reliable.

I have had good luck with my old Greenlee no-contact 'sniffer'. If I hold the conductor in my hand close enough to where I place the tester, it can tell hots from the others 90 percent of the time. If I do not hold the conductors, the tester will show hots that are not.

 

[macmikeman]

When in doubt, turn off the house main, replace the wiring with new.

 

[mopowr steve]

:lol: Boy Howdy! ! That brings back some old memories.

All the suggestions offered in these responses above are spot on. To re-emphasize: As convenient as a noncontact volt sniffer is, the only reliable method to verify wires in ungrounded wiring methods from the first half of the 1900s is with a known ground extended on a good wire of some kind to a low impedance meter (not a digital meter).

There are short cuts, but this is the most assuredly reliable.

Another method is to hold one terminal of a plain ole neon tester between your fingers and with the other lead touch the wires your testing. The hot one will make the neon glow faintly.

 

[Sahib]

Another method is to hold one terminal of a plain ole neon tester between your fingers and with the other lead touch the wires your testing. The hot one will make the neon glow faintly.

I think one problem with neon tester is it glows for induction also. Another is it gives a shock on wet condition.

 

[Sahib]

how, if possible, can I dissipate it, cancel it, 86 it, get rid of it, etc.?

One way is to ground it but it is a violation after GEC.

 

[kwired]

One way is to ground it but it is a violation after GEC.

Nothing necessarily wrong with temporary grounding while working on something.