mysterious voltage

[burnjob]

heh ... i am just replacing a ceiling fan and i turned the switch off before i started but to be 'a little' safer' i thought that i would grab my voltage meter and use it as a continuity tester and checking to see if the power was actually off ... anyway ... when i hooked up the voltmeter ... it registers 5 volts of current when the power to the switch is off (or the switch is in the 'off' position) ... so ... i replaced the switch incase there was a problem with it and the same thing happens ... 120 volts when on and 5 volts when off ... is there something wrong somewhere ? ... i think so but i don't know what it is ... thanks

[Wgoodrich]

No there is nothing wrong. You are reading voltage on the grounded leg [aka neutral] or neutral side of your circuit. Remember that this white wire you are touching also serves everything else that is on that same branch circuit. You are disconnecting the power to the light yet you still have a connected white wire to all other loads that is being fed power from that same branch circuit. The 5 volts is what you are getting from the use of that white wire of all other loads working on that same branch circuit.

This is normal. Remember that this white wire is not safe. If you break the white wire of a branch circuit then you just created an open grounded leg [aka neutral] or true neutral that is carrying the return path back to the panel completing the circuit or if a true neutral the unbalanced load of that same branch circuit completing that circuit.

Remember a white wire is insulated because it carries current. That current on the rest of that branch circuit is what you are reading. Turn off your breaker and you won't read the voltage of 5 volts.


Hope this helps

Wg

[burnjob]

ok i understand what you are saying but what i was checking was the red (power) lead coming from the switch to the ceiling fan and not the white (neutral) wire.
what is actually there is a 14/3 wire - black, red, white and ground - the black powers a separate light in the kitchen and the red is the one that i checked with the tester ... it goes into the bottom of the switch and goes from the top of the switch to the ceiling fan and there powers both the light (in the fan) and the fan.
the white wire is still nutted and is not open or exposed.
because i am replacing drywall the ceiling and wall is completely open and i have complete sight of the wire the whole way from the switch to the ceiling fan. that's why i originally thought that perhaps there was a problem with the switch because i didn't think it was right to be getting a reading from the power wire when the power was turned off at the switch.

[burnjob]

ok ... here's one more factor that i forgot to mention ... when i was testing it i was using the positive side of my volt/amp meter on the red wire and the negative side of the meter on the junction box that the fan hangs off of ... could there be stray voltage somewhere else that is not enough to kick a breaker but is enough to be picked up with my meter and is travelling through the ground wire ? ... but still in a way ... that doesn't make sense since the switch is in the off position and is not completing the circuit so i still shouldn't be able to read anything ... it is a brand new tester, the battery is good and it is zero'd ... i think that's all i can add for now
thanks

[dkerr]

Make sure the hot wire you are testing is not connected to the fan/light combo unit when you are checking for voltage. The switch wire,& the fan & light bulbs will give you an path to the neutral wire, which can give that 5 volts that yo are seeing if other things are using power elesewhere on the circuit. Remember the light bults or fan needs a neutral ad a hot to operate. In a light bulb case the hot and neutral feed thru a lighting element inside the bulb. In the fan motor case the hot and neutral feed thru a motor winding.

[Wgoodrich]

Disconnect the red wire from the fan wire from the red wire from the ceiling fan. Then test the red wire to your equipment grounding conductor. If you find the voltage disappeared then test from the lead of the fan to that same equipment grounding conductor. If you read the voltage on the fan wire but not the red wire when those two wires are separated then you are reading a discharge of a capacitor or you are again reading the voltage of a grounded leg [aka neutral] or true neutral through the motor windings of the fan that has current on that white wire from the other loads on teh same circuit passing through the fan windings.

Let us know what you find with that voltage test between the red [disconnected from the fan motor] and the bare and then the second test from the fan wire wire to the bare.

Wg

[burnjob]

sorry gentlemen but i did not mention that the fan was not connected at all at the time of testing ... i am replacing it so i had alread taken down the fan and had not yet put up the new fan ... so as far as i know ... there is absolutely no possible connection to any other source with the switch in the 'off' position

[Wgoodrich]

Sorry Don, looks like we were both posting a reply at the same time.

Wg

[burnjob]

is it at all possible for voltage to transfer from one hot wire to another if there are nicks or cuts or exposed points on both wires ?
not that i know of any ... but just a thought as the wiring is somewhere around 30 years old and i can not say that i know that every wire is free from defect or damage
hmmm ... if that was the case then i guess there would be a full transfer of voltage and not just 5 volts ... hmmm
what about magnetic fields ... considering that the box is also a junction box for other wires from other sources ... can a magnetic field be produced that would account for the voltage ?
just another shot in the dark ... i am almost ready to believe that aliens are responsible ... lol
thanks

[dkerr]

try this...

disconnect the switch wire at the switch itself , now with the wire coming from the switch disconnected and the wire from that switch disconnected at the ceiling location, you know at this point nothing is connected anywhere on that wire, so no power is coming or going on that one wire. Now check for power at the switch box between your switched (disconnected) hot and the electrical box (if grouded, if not then neutral) do the same at the ceiling location.

make sure your meter is set to red AC voltage and is in the 110 v range (or at or above that setting).

I am also assuming that the switch wire feed is only serving the one fan/light combo location. And that there is only 1 switch involved and not 2 3-way switches.

[burnjob]

excellent idea ... i will give it a try and let you know what i find out ... thank you again for your assistance

[Anonymous]

Isn't he trying to read the voltage of an open wire here? I am thinking that the 5V is completely irrelevant, he has a wire that is open from the switch to tht fixture, it's got no reference to the ground of everything else. There's no current. It's the old Phantom!

[Wgoodrich]

If he is reading with the switch off yet the hot wire connected to the windings of the fan motor to the grounded leg [aka neutral] then he is reading the voltage of the current of other loads on that same branch circuit through the motor as a back feed tested from that hot wire of the fan to the equipment grounding conductor. This voltage if that wire from the switch is still connected to the the fan wire connected to the fan motor widings then the voltage is not coming from teh switch rather it is coming as a back feed through the motor windings from other loads on that branch circuit.

Remember that if you loose a white wire going from a panel to the end of this white wire in a multiwire branch circuit using a true neutral your equipment can still run at a reduced effeciency through the windings of other loads on that same branch circuit. Kind of like wiring a bunch of porcelean keyless light fixtures in series. If you have an open true neutral series affect can appear through the filiments of light bulbs and through heating elements and through motor windings.

A good example of this would be a blown main fuse in a fuse panel but when your 220 volt oven heating element is turned on your lights in the house start working [back feed].

In this case I do not see it being an open neutral or open grounded leg. I see it as only a back feed of other loads applied to the same multioutlet branch circuit back feeding this 5 volts through the motor and not the switch. If it was an open neutral or open grounded leg then that voltage would read much higher.

Wg

[Anonymous]

In Burn's fourth post he states that the fan was not connected at the time of his testing. I too suspected induced or "phantom" voltage.Check out this site:http://www.nema.org/engineering/papers/PhanBull88.html

[Wgoodrich]

joefixit, I see what you mean in the fourth post saying the fan was disconnected. I must have either spaced it in my mind or missed the post saying the fan was disconnected.

If this is a red wire and both ends are disconnected as Don advised in one test then the voltage is coming from obsorbing eddy currents from nearby conductors in my predictions. No other explaination other than a back feed on the bare or equipment grounding conductor and that would depict as you suggested a loose neutral. I don't see that being the case though if the hot wire was disconnected at both ends.

I am curious as to what he finds.

I have read the link you provided. Lots of info there some theory that may be accurate depending on that certain situation but unproven depending again on the situation but good reading.

Have you ever taken a voltage tester that is with a series of lights to depict the level of voltage and approached a neon light? Your voltage tester with the lights will start lighting up even though you are only pointing the tester in the air. The closer to the transformer of the neon light the more lights start lighting up. This is an example of eddy currents that capactence voltage feild floating around an energized conductor that emits even through the insulation of the wire. This may be what is being experienced in this post.

Wg

[burnjob]

well folks ... i too agree with you ... as strange as it is and with the little bit that i know about electricity (i say that because i am in no way a qualified electrician or engineer) i can only speculate that this mysterious 5 volts that i am reading has to be the result of interference from another source ... for example ... the eddy current created from another power source in close proximity to the wire that i am testing.

i agree that the number of "5" volts is irrelevant as it is only likely caused by another power source and in my mind the closest comparison i can make is that of school experiments with making our own coils and being able to read a current in the air when only in close proximity to the wire and not actually in contact with it.

my biggest concern here was that as this is my home and i did not string the wire in the walls i have no idea as to what may or may not have been done ... expecially if there were any small accidents where an insulator was nicked or cut during installation.

i think it only makes sense that if a wire is open on both ends - "yet" i can still obtain a voltage reading on it - and especially since it is an insignificant number of 5 volts - then it must be attributed to a field that is being created around or near it and not to anything else ... possibly even a current in a nearby wire which is not even wound around but only close to maybe even a staple is creating a magnetic field that in turn is creating an electric current in the wire that i am measuring ... again ... just theory

i am very grateful for the time and energy that you have spent in replying to my post(s) as initially it concerned me ... but as i read your replies i feel confident that it is nothing to be concerned about as it is probably only just as you have described as an eddy current caused by another power source.

thank you again for your extensive time and energy ... it is very much appreciated

[burnjob]

joefixit
thank you for this reference

http://www.nema.org/engineering/papers/PhanBull88.html

that i think explains it very logically and factually ... i think i will try the same test with a resistor which i am sure i can pick up at the local radio shack or electrical supplier ... would be interesting to see just for the curiousity of it
thanks again