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?
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.
On Tue, 12 Dec 2006 16:36:35 -0500, "Charles Schuler"
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.
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!)
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.
Just as McDonald\'s is where you go when you\'re hungry but don\'t really
care about the quality of your food, Wikipedia is where you go when
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.
Asking Iran and Syria to help us succeed in Iraq is like your local fire
department asking a couple of arsonists to help put out the fire.
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.
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