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587

I was replacing some outlets in my kitchen with GFCI outlets and encountered something weird. With the breaker off, one outlet still showed 8v on my multimeter. If I plugged in a low power LED to create a current draw, the LED wouldn't light up but my multimeter now showed 0v on that outlet.

I'm guessing this was some type of negligible phantom current from induction? I've seen induction before with radio comms where you have a LOT more coils of copper, but never with a piddly 20amp circuit for a garbage disposal.

And to answer the obvious question, yes, the breaker was off. I mapped every outlet and switch in my house years ago because I like staying alive. After I saw those 8v on my multimeter I flipped all the breakers that even run near that room, just to rule out something weird like crappy insulation on a separate circuit running alongside the one I was working on.

I was replacing some outlets in my kitchen with GFCI outlets and encountered something weird. With the breaker off, one outlet still showed 8v on my multimeter. If I plugged in a low power LED to create a current draw, the LED wouldn't light up but my multimeter now showed 0v on that outlet. I'm guessing this was some type of negligible phantom current from induction? I've seen induction before with radio comms where you have a LOT more coils of copper, but never with a piddly 20amp circuit for a garbage disposal. And to answer the obvious question, yes, the breaker was off. I mapped every outlet and switch in my house years ago because I like staying alive. After I saw those 8v on my multimeter I flipped all the breakers that even run near that room, just to rule out something weird like crappy insulation on a separate circuit running alongside the one I was working on.

(post is archived)

[–] • 2 pts (edited )

"Phantom" voltage isn't uncommon. I put an incandescent light on the circuit to remove any phantom voltage when I encounter it. I've seen it make readings as high as 60V, but it wasn't "real" since literally zero power could be delivered at that voltage. My multimeter has a setting for testing batteries that puts a very small load on the circuit to see the "real" voltage. It's helpful in these situations too.

[–] • 1 pt

I would change that breaker. It could be damaged or corroded.

[–] • 1 pt

Maybe you have a neutral wired into another circuit. Or bad breaker

[–] • 1 pt

Most multimeters have a very high internal resistance of about 10 MegOhms on their voltage ranges. Those are not suited for meaningful voltage measurements on house wiring. Use one with a Lo Z input or use something similar to this: https://www.benning.de/products-en/testing-measuring-and-safety-equipment/test-equipment-voltage-tester/voltage-tester-duspol.html

That voltage could be inductively or capacitively coupled from a neighboring cable, for instance. Nothing to worry about, IMO.

[–] • 1 pt

^ This. I have a Fluke 88 and get the same type of behavior on 110.

[–] • 0 pt

A worn/corroded breaker can allow a few volts to leak even when in the off position

[–] • 0 pt

I replaced the entire panel 2 years ago, so I doubt it's a faulty breaker.

[–] • 1 pt

Then it's almost certainly induction = wires laying right next to each other.

[–] [deleted] • 0 pt

Maybe. You're seeing voltage but no current which fits the symptoms of induced voltage.

[–] • 0 pt

I've run into that problem. Incandescent bulb fixed it.