DIY Electrical Fool

[Jamech]

It's me.
I'm trying to wire a ceiling fan with lights and control lights with one switch and fans with another. I've run 14-2 from a 15amp breaker to the box for the 2 switches.Connected black to the top of one switch and plug in jumpered between the backs of the 2 switches to power both switches.I've run 14-3 out to the fan box,connecting red to the bottom of one switch and black to the bottom of the other and tied the whites together and the coppers and the switch green screws all together. measuring the voltage at the fan box with a Fluke 77 I have 120v at red and black as i turn on their switches but i have ~45 volts at the wire that is off when I turn on the other switch on both switches. What have I done wrong.
Thanks
Jamech

 

[Aceman]

You're reading ghost voltage.

Have you tried to turn on the fan and light yet?

 

[Nostraquedeo]

Yeah, use an analog meter and you will most likely not see that voltage.

 

[Jamech]

Thanks for the quick replies. The fan is not up just wire hanging down(with breaker off when not testing!!!). I thought maybe the Fluke was the problem, wish I had a Simpson 260 here at home. Almost 50v seems like a lot of ghost voltage but i'm a real rookie on home wiring.

 

[2LTim]

Jamech:
A better name for mysterious voltage would be "Induced Voltage." Whenever you have a wire carrying a current, and another wire running parrellel to it, the magnetic field surrounding the loaded wire "Induces" a voltage into the extra wire. The higher the current in the active circuit, and the longer the distance the two wires run together, the higher the induced voltage. This is why you never want to run low voltage wiring, i.e. network cables, phone wires, cable or speaker wires along side high voltage wires.
If you would add any type of a load to the extra wire (a light bulb will do it) your induced voltage will dissapear.
As for me, I would prefer the Fluke to an old Simpson any day. 50 volts AC will not typically hurt you, but you will probably feel it, not any curent to speek of. If the Simpson used all of the available current to try to make the needle move and you see no voltage, you will probably spend hours trying to figure out why you are getting that funny little tingling feeling when your Fluke told you right off that you have something there. Then you have places like Garage Journal to get an explaination for what is going on.
Tim

 

[Jamech]

Thanks Tim
Don't multimeters have high resistance so as not to effect circuit measurements, reistance that is measured in Ohms per volt. I have seen differences in measurements between analog meters and digital meters but never really understood why. Your explanation of magnetically induced voltage is definitely right on. Would the current available with this induced voltage be very low?

Jamech

 

[oleguy]

the old simpson 260 is one of the best analog meters out there.the 360 is the digital version.the 260 has a 20000 ohms per volt input.

 

[MrMark]

you are seeing capacitively coupled voltage because you have parallel runs of conductors and the one with the "phantom" voltage is not grounded (not hooked up). It is free to float. A typical non-contact test light (a device that works on capacitive coupling theory) would give you a false positive here too. Induction has to do with inducing a current in a wire by a changing magnetic field surrounding the wire. I wouldn't worry about it.

 

[gmhill33]

Jamech:
This is why you never want to run low voltage wiring, i.e. network cables, phone wires, cable or speaker wires along side high voltage wires.
Tim

What if they are in two different pieces of PVC pipe, is it ok then?

Thanks,
Gary

 

[MrMark]

With coax, you are worried about distortion of the RF waveform that exists between the center conductor and the grounded braiding. The PVC pipe is not a shield. Line voltage should be separated from the coax, and phone too, by 12 inches or so on parallel runs. Crossings are made at 90's and try to maintain 6 inches separation on crossings as well.