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Hot or neutral, which is what?
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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
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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".
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Neon testers are really, really inexpensive.
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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.
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Neon bulbs require at least about 90V to light, but draw very little
current. Maybe that helps.
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"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!)
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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.
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would you do?
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I'd run a lead to the nearest water pipe or sink faucet.
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Do you own a circut test lamp?
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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.
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