Hot or neutral, which is what?

[# Fred #]

I just helped someone to replace an overhead light fixture in an old house with existing K&T wiring without wire termination ID. I referenced the light fixture terminal polarities to the nearest K&T ungrounded outlet but realized if that outlet is wired wrong so will my light installation. I have a non contact volt sensor but it was not working and also I was tempted to give the finger test but I'm getting old and my heart may not take the kick. I guess I should have referenced the polarities to a cold water pipe. What would you do?

[HotRod]

I wouldn't worry about it and go home and get a good sleep.

[RBM]

The finger test won't help, you need to use the two arm test from the wires to the nearest grounded thing, but I'd recommend something other than your body parts

[Jeff Wisnia]

If I had a long enough piece of wire handy I'd put the smallest bulb handy in the fixtur, connect its black wire to one of the two power wires and connect my piece of wire to the white fixture lead, then touch its other end to a water pipe and have someone switch on the power.

If the bulb lit I'd know the fixture's black wire was on the correct of power lead. If it didn't light I'd repeat the test with the black fixture lead connected to the other power wire.

Jeff

[Goedjn]

Do you own a circut test lamp?

[Charles Schuler]

Neon testers are really, really inexpensive.

[Jeff]

As others said use a neon bulb tester. Touch one lead to your hand and the other to the circuit. If it is the hot lead the tester will dimly light. I would still be sure to wear sneakers and not be touching anything grounded. Try first in a plug.

[John Grabowski]

I'd run a lead to the nearest water pipe or sink faucet.

[Colbyt]

If this is the biggest problem you ever encounter working on older homes you have gotten off real easy.

As Hotrod said, " go home and sleep well".

Colbyt

[maradcliff]

And not only that, but if you touch one lead to a hot wire and grab the other lead (of the neon tester) with your fingers, the neon will show a slight glow. It wont do that on the neutral. And you wont get a shock doing this. I do it all the time. To be totally honest, I really never understood why it lights when touched, but it works.

Go out and spend the 2 bucks for the neon tester and save lots of time and shocks too. Touching hot wires is not a good idea at anytime, even though I do see professional electricians do it.

I know what you are dealing with. On the old K+T the wires were often all the same color black, or if one was white, its too dirty now. Those cloth wires had a tar or wax like substance in the coating which seemed to discolor them over time. Once you ID them, put some white electrical tape on the neutrals.

[Jeff Wisnia]

[e-mail] wrote: esters are really, really inexpensive.

"It woiks" because your body has "free space capacitance"* which can accumulate a charge, like it does when you scuff your shoes on a carpet, and will get discharged when you "spark" to ground (or to another person's capacitance, sharing your charge with them). The value of your body capacitance varies from about 100 to 300 picofarads, depending on whether you are skinny or fat.

AC line voltage connected to one side of the the neon tester drives a minute current (less than a milliamp) in and out of your body's capacitance, and that current is enough to make the tester's bulb glow.

• The free space capacitance of an object is the sum mutual capacity of it to all the conducting objects of the universe. (Wow!)

Jeff

[David Nebenzahl]

[e-mail] spake thus:

Well, obviously it lights because some current is flowing through it (and your body). Apparently little enough to not give you a buzz.

Thanks but no thanks. The other day I was installing a circuit in a flooded basement, and I was paranoid to even touch boxes and cables with the circuits de-energized. (You know, wet shoes and all.) I prefer other ways of donating my body to science.

[Mark Lloyd]

Neon bulbs require at least about 90V to light, but draw very little current. Maybe that helps.

[clifto]

For years I've had a small screwdriver with a neon bulb in a translucent handle, and a little metal contact on top. To test for AC voltage, you hold your finger on the contact and shove the blade of the screwdriver into the outlet or onto the conductor being tested. The only time I came even close to sensing anything at all was when I used it at its maximum rated voltage, 600V. At that I might not have noticed the sensation had I not been aware it might happen.