Painted outlets....

[mrcaptainbob]

Grandson's 'new home was inspected by the city. One of the 'gigs' was to replace those outlets that had paint on them. Seems a bit over the top, but then, it's not that big of a deal. Inspector was a good guy.... However....removing two of those outlets was a VERY good idea. Don't know what possessed the person to have done this, but there was a jumper wire from the ground (yes, the outlets were grounded...) to the neutral screw. So that 'over-the-top' request turned out to be a God send. Then there was, and still is, this really strange issue. Two switches in the same box were to control the porch light and, well, something else. We had no idea what. I figured it was the wall outlet behind the couch. To find which was hot I separated all the wires in the box, which was four sets. I found the one hot. While the wires were all separated out and the breakers were all on, I checked that outlet with one of those plastic probes that beep if current is detected. It beeped. After a lot of go-back-and-forth with testing I found by using a real tester that shows how MUCH voltage that that outlet, even not connected, to display 4.4(+/-) volts!! Where does that come from?? Well, I finished by connecting the two known circuits to the known hot. The fourth and unknown circuit is wire nutted dead in the box. No idea where that goes. And that unused wire's neutral (still unconnected) has continuity to the first hot wire's neutral. Strange stuff. But it's working.

[Nestor]

Mr. Captain Bob:

If I understand you, you're saying that a duplex receptacle in a metal (?) junction box was providing 4.4 volts AC even though there were no wires connected to it?

I wouldn't have a clue either.

This is just a SWAG (Scientific Wild A$$ed Guess), but maybe put your tester back in that outlet, and have someone phone your grandson's house. See if the voltage you read shoots up to 90 volts when the phone rings.

I don't know what voltage telephone wiring operates on when the lines are not in use, but I know that the ring signal is a full 90 volt signal, and can give you a pretty good jolt from a tiny wire like that.

I'm thinking maybe a nail or drywall screw is connecting a telephone wire to the metal jacket of the armoured cable going to that junction box.

[HayZee518]

wierd voltage

it is normal to have some leakage at outlets. 4.4 volts isn't much. if you've ever taken apart an outlet or switch, there isn't much, as far as insulation, between the neutral and hot bus inside. grease from manufacturing process will present some leakage between parts. this is more prevalent with switches, as there is moving parts inside. carbon tracking from arcs when a circuit is broken will be there but the resistance is so low that it isn't a dead short. Now, paint on the outside doesn't really matter because it is dry. the solvents used in paints have evaporated leaving just the pigment. AND I doubt the paint dripped inside between the two poles.

[Nestor]

Yes, but Captain Bob is claiming that this 4.4 VAC is coming out of a receptacle that's not even connected. Read the fine print:

After a lot of go-back-and-forth with testing I found by using a real tester that shows how MUCH voltage that that outlet, even not connected, to display 4.4(+/-) volts!! Where does that come from??

If the outlet isn't connected, that's 4.4 volts more than there should be in that receptacle. That can't be explained by "leakage".

Captain Bob: Are you SURE that receptacle was not connected?

[HayZee518]

outlet

Nestor -
take a new work metal box and fasten it to a 2x4. wire it up the way its supposed to be wired. connect it to a 15 amp single pole breaker and turn it on.
Now, measure the voltage from neutral to box ground and hot to box ground and neutral to the hot. what do you get?

[mrcaptainbob]

4.4 volts....

Well, I have seen the meter jump on wires where they're just being held in my hand. Although minimal voltage, it's still surprising (shocking??!!) to see any reading coming from something that's not connected. In the case of these two wires, to the best of my knowledge they were not connected to anything at the time of reading. They were metal boxes nailed to 2x4 house studs. I tested all four sets of wire in there and got readings of 120 on the supply, zero on two and 4.4 on the one. And the wall outlet was the only other that was 4.4. Again, since it would not light the lamp by itself, but would when connected to the hot lead, I assumed it was the correct wire. Still baffles me. I am not a fan of not 'knowing' the route of wires.....
HayZee....what think you of that finding of the ground jumpered to the neutral?

[Nestor]

Instead of me doing any wiring, I vote we put that 4.4 volts in the same bag as crop circles, the Burmuda triangle and UFOs.

[HayZee518]

wierd stuff

theoretically the neutral and bare ground are at the same zero potential when connected or not connected to a load. in a multiwire circuit the neutral carries the unbalanced load. in a balanced load zero current flows in a neutral. a bare ground within a cable assembly also carries a zero potential because at the panelbox it is connected to the neutral bus. a plug in polarity tester might indicated neutral and ground reversed in your case with a jumper between the neutral and ground screw.
an induction tester will detect a voltage on a wire not connected to anything at the load end because there is still a magnetic field around the conductor. this might also explain why your meter has a reading NOT connected to anything. an EMF or electro motive force exists in free air, more so if you are near a power line.

[Nestor]

an induction tester will detect a voltage on a wire not connected to anything at the load end because there is still a magnetic field around the conductor.

No, can't be magnetism.

Magnetism is associated with CURRENT, not voltage. There is no magnetic field around your car battery's positive or negitive terminals, but there is around any of the wires in your car once current starts flowing through that wire. So, a non-contact voltage tester can't work on magnetism because there is no magnetic field around a wire unless current is flowing in that wire.

I'm no expert on this stuff, but my understanding is that a non-contact AC voltage detector detects the electric field around a wire that's charged.

Member in grade school when the science teacher demonstrated static electricity by rubbing a balloon in his/her hair and sticking that balloon to the wall, or by rubbing a glass rod in some fir and using it to pick up pieces of paper? Well, that's static electricity. And the fact that static electricity can make two pith balls repel or attract one another means that there's a static electric "field" around each pith ball that makes them attract each other or repel each other.

That is, the electric field of one pith ball interacts with the electric field of the other pith ball to make them move together or apart.



I expect you'd have a similar electric field around a copper wire that's charged up with electrons, just like a pith ball. And that electric field should get stronger and weaker 60 times per second just as the voltage applied to the wire does.

So, I suspect non-contact voltage testers detect the electric field around a wire with voltage in it, but no current.

How they do that is sumthin I don't know either.

It's just a guess, but it's my best guess.

[HayZee518]

induction voltage tester

ok, then - the name says it all "INDUCTION" voltage tester. What in your opinion is induction? What does induction mean? Induction comes from the word induce. When you induce a voltage you are putting in a voltage. A transformer produces power by induction - that is rising and collapsing magnetic fields. An induction coil in a radio increases or reduces voltage. Some have a movable iron core to short out the windings by moving a powdered ferrite core within the inductor. Ferrite is powdered iron filings held together by a binder [glue] a transformer just sitting there with no load connected doesn't induce anything in the secondary but there is a magnetic field around the primary or a voltage. and there is a minute current flow in the primary. Explain a coil for a TACO valve. there is a voltage and a current present to pull the sleeve or valve slug open. Watch Holmes on Homes on TV. Mike uses a no contact voltage detector on wires just hanging in a building - connected to nothing, but the detector beeps when it's near a hot wire.

[Nestor]

Hayzee:

I don't know how a non-contact voltage detector works.

I just know that without current flowing in a wire, you won't have a magnetic field around that wire.

That's not much to know... ...but I know that much for sure.

[HayZee518]

no contact voltage tester

Amplified electronic testers (informally called electrical tester pens, test pens, or voltage detectors) rely on capacitive current only, and essentially detect the changing electric field around AC energized objects. This means that no direct metallic contact with the circuit is required. The user must touch the top of the handle to provide a ground reference (through stray capacitance to ground), at which point the indicator LED will light up or a speaker will buzz, if the conductor being tested is live. Additional energy to light the lamp and power the amplifier is supplied by a small internal battery,
Bodily capacitance is the means why metal desk lamps, when touched, lights with the proper circuitry connected to them.

[Nestor]

I just thought non-contact voltage detectors were reverse engineered from alien technology at Area 51.

[HayZee518]

Area 51???

You're kidding! The theremin, a musical tone generator works because of bodily capacitance. You put your hands into a balanced field and unbalance it. This produces sound of varying frequency.
Well, with the no contact indicator, if you don't touch the metal clip, it won't work.

[HayZee518]

AC versus DC

In an AC circuit, magnetism is continually expanding and collapsing as in going from zero to 90 degrees, then down and through 180 degrees to 270 degrees and back up to zero degrees. One complete cycle equals 360 degrees. A sinusoidal waveform if you will. You can have voltage on a wire but NO current.
DC is current that starts at zero degrees then goes up to 90 degrees and stays there. It is called straight line DC. there is voltage present but no current. only way you get current flow is to feed the DC through a resistive, inductive or capacitive load. resistive - any thing that exhibits an opposition to current flow. an inductor or coil presents resistive and reverse induced current. a transformer produces induced current but of reverse polarity of 180 degrees. capacitive freely accepts electron flow and stores it until a critical value is reached, then discharges it. a dc power supply produces dc power. a pi filter in a power supply uses capacitance and an inductor.