Home wiring question Additional info 8/10

[bruceb58]

Re: Home wiring question

Re: Home wiring question

Believe it or not they asked me about how to do this when I first interviewed as a EE. I had no idea how it was done in a house at the time but answered the question correctly.

 

[rbh]

Re: Home wiring question

Re: Home wiring question

Now that I think about it, is this not a parallel series circuit???

 

[Tim Frank]

Re: Home wiring question

Re: Home wiring question

All the above notwithstanding, I would beg/buy/borrow an old analog steam-powered voltmeter and verify that 50 V. reading....I agree with Bruce re: some "inconsequential voltage" but don't think that Bruce would tag 50 V as that....

Sounds to me like the neutral may have been damaged/broken.

 

[Limited-Time]

Re: Home wiring question

Re: Home wiring question

Update: At lunch I checked the voltages between the hot (black) and ground 50v, and the neutral (white) and ground 0v. So I suspect there is a problem some where? Looking at the diagrams Bruce supplied it would seem to have to be in one of the switches.

 

[bruceb58]

Re: Home wiring question

Re: Home wiring question

All the above notwithstanding, I would beg/buy/borrow an old analog steam-powered voltmeter and verify that 50 V. reading....I agree with Bruce re: some "inconsequential voltage" but don't think that Bruce would tag 50 V as that....

Sounds to me like the neutral may have been damaged/broken.

I never said that!

50V is not inconsequential if its really there. Hard to imagine getting that from a capacitve effect.

To the OP, where are you measuring the hot lead? After the switches but before the load?

 

[bruceb58]

Re: Home wiring question

Re: Home wiring question

Now that I think about it, is this not a parallel series circuit???

Not really. I think what you are thinking of is when you have passive components such as caps, inductors and resistors in both series and in parallel and have to figure out impedance of the lump circuit.

 

[DianneB]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

If the light fell it is most likely you have damaged wiring. The chance of a switch going bad at the same time is ZERO unless one of the wires pulled the switch apart.

When anybody (who knows what he is doing) uses a white wire as a 'hot wire' it is SUPPOSED to be marked in some way to show it is not a neutral.

I have repaired WAY TOO MANY 'amateur jobs' in my life to have much tolerance for not-to-code work. Much of it is a danger to life and property (and will void your house insurance). If you aren't absolutely SURE you know what you are doing and what you are doing is up to code, DON'T DO IT! Go play with something that wont kill people or burn down your house!

 

[Tim Frank]

Re: Home wiring question

Re: Home wiring question

I never said that!

50V is not inconsequential if its really there. Hard to imagine getting that from a capacitve effect.

To the OP, where are you measuring the hot lead? After the switches but before the load?

Reread what I said :
"but I don't think that Bruce would tag 50 V as that...."

Exactly what I meant.... might have said it better as "but I don't think that Bruce would call 50 V inconsequential"

 

[bruceb58]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

OK...got it! I need to stop and read!

 

[joed]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

I believe the 50 volts to be a phantom voltage which is common when using a digital meter. The meter has a very high impedance and will pick up a voltage reading from capacitive coupling. There is really no voltage there.
Connect any incandescent light across the two wires and try it. You will probably measure zero volts.

 

[Limited-Time]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

Had the builder and original electrical contractor out today to check out the line. They verified the voltage. But as soon as a load was connected the voltage zeroed. So it seems there is voltage but no current. We crossed both the hot and neutral and hot and ground and nothing happened. No circuit trip, not even a spark. The electrical contractor went so far as to grab the bare lines, again nothing. So with their blessings I remounted and wired the fixture. still doesn't seem quite right to me.

 

[rbh]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

Had the builder and original electrical contractor out today to check out the line. They verified the voltage. But as soon as a load was connected the voltage zeroed. So it seems there is voltage but no current. We crossed both the hot and neutral and hot and ground and nothing happened. No circuit trip, not even a spark. The electrical contractor went so far as to grab the bare lines, again nothing. So with their blessings I remounted and wired the fixture. still doesn't seem quite right to me.

Induction from parallel lines????

 

[Tim Frank]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

Depending on the age of the fixture there might me a capacitor in the fixture....that could give a residual voltage reading.

 

[Limited-Time]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

Depending on the age of the fixture there might me a capacitor in the fixture....that could give a residual voltage reading.

The lines read the voltage with the fixture disconnected.

 

[j_martin]

Re: Home wiring question Additional info

Re: Home wiring question Additional info

I believe the 50 volts to be a phantom voltage which is common when using a digital meter. The meter has a very high impedance and will pick up a voltage reading from capacitive coupling. There is really no voltage there.
Connect any incandescent light across the two wires and try it. You will probably measure zero volts.

Actually any path that will allow .001 amp to ground will probably bring it down to 0 V. It takes .010 amps to feel it. That's what is meant by inconsequential.

hope it helps
john

 

[j_martin]

Re: Home wiring question

Re: Home wiring question

I never said that!

50V is not inconsequential if its really there. Hard to imagine getting that from a capacitve effect.

To the OP, where are you measuring the hot lead? After the switches but before the load?

Take an average digital multimeter. Put it on a low voltage range. Connect one lead to the nearest ground, like the center screw on an outlet cover. Pinch the other lead in between your fingers.

What you are reading is capacitive coupling to your body from the house wiring.

50 feet of conductor running within a fraction of an inch of an energized conductor, and with no load on it will have a lot of voltage on it, but will supply extremely low current.

hope it helps
John

 

[rbh]

Re: Home wiring question

Re: Home wiring question

Take an average digital multimeter. Put it on a low voltage range. Connect one lead to the nearest ground, like the center screw on an outlet cover. Pinch the other lead in between your fingers.

What you are reading is capacitive coupling to your body from the house wiring.

50 feet of conductor running within a fraction of an inch of an energized conductor, and with no load on it will have a lot of voltage on it, but will supply extremely low current.

hope it helps
John

I am thinking thats called induction, isn't it???

 

[generator12]

Re: Home wiring question Additional info 8/10

Old thread, but I couldn't resist chiming in.

An electrician uses something called a "wiggy" (named after the maker - "Wigginton". Others make them too, but that's the moniker.) This device is a low impedance measuring instrument that will force the circuit to provide a reasonable current in order for it to register a voltage. It's designed just for circumstances like this one, where a very high impedance measuring device (i.e., digital voltmeter or oscilloscope) will indicate voltage which is present due to inductive or capacitive coupling.

Yes, that's an actual voltage you're reading, but at the first sign of current flow it will be brought down to zero. If you touch the test lead on your digital voltmeter, you'll see it read a voltage. It's a real voltage, but has so little capacity that ANY level of current flow will dissipate it immediately.

Get a test light at the hardware store and recheck. (Same wires, same path) You will almost certainly note that it doesn't light.

(Yes, this IS experience talking.)

 

[bigdee]

Re: Home wiring question Additional info 8/10

bruceb58, joed, j_martin, generator 12 are all correct on this one. A digital multimeter can be confusing to a novice. The best tool for the average homeowner to use is a "wiggy"