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Old 10-30-2009, 08:46 PM   #1
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power on or off

i was changing outlets when i came across 3 outlets on the same circuit. i turned off the breaker, tested with an inductance tester and it beeped like crazy when it was near a hot wire, i plugged in a radio, no power, used an outlet anylyzer, no power and tested with a neon tester and it did not light up. thinking it was the inductance tester, i tested an outlet i already changed and shut off the breaker, no beeps from the tester. does this make sense?

p.s. there are no other wires in the box that could be on another circuit. it only beeped when it was near the hot slot or the hot screw.


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Old 10-30-2009, 09:23 PM   #2
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Stick and inductance tester in your ear and it will some times beep. Any magnetic field will cause it to beep including feedback on a neutral. Use it only to warn you to use a real tester.


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Old 10-30-2009, 10:13 PM   #3
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when joking around at work, I tell plumbers it is a gay detector. Then run the tester up and down their arm. It will tic like crazy.

anyway, some testers are more sensitive than others and they often tic on induced power on a wire. If you could check that wire with a DMM, it most likely would have shown some voltage. Very little but voltage just the same. It is induced from other hot wires that run parallel to the wire you are testing and actually induce a voltage on your wire.

the wires could run along with each other right when coming out of the breaker panel or as they pass through studs together.

Last edited by nap; 10-31-2009 at 01:42 PM.
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Old 10-31-2009, 08:27 AM   #4
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You are picking up inductive voltage on a circuit with no loads attached.

Try plugging in a lamp or radio (has to be switched on), and see if it still beeps. Chances are, with the loads draining any phantom voltage, you won't get any beeping unless the power has been restored.

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Old 10-31-2009, 11:51 AM   #5
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When doing electrical work in a home, it is best to turn off the main power to the entire house.

There are some situations where two or more breakers may provide power to the wiring in one electrical box.

For example outlets where a switch controls one outlet (for a lamp) and the other outlet is always on. It is possible that these are on two separate breakers. (Possible...) So best to be safe and turn off the main power.
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Old 10-31-2009, 01:31 PM   #6
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Originally Posted by bryan1282 View Post
does this make sense?
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Old 11-01-2009, 07:29 AM   #7
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Billy -- Isn't it a little hard to see what you're doing and run power tools with power cut to the whole house? Sure, go ahead and do that when you can but much of the time it's not an option. So I tell people to just get in the habit of not assuming that because you think you've turned the right breaker off, you're good to go. Check at the jbox with a multimeter! I was replacing a 50 A stove receptacle, switched off the 50 A breaker marked range and discovered that the labels (and breakers) for the dryer and range had been switched (the 50A marked stove was feeding the dryer. the 40 A marked dryer was feeding the range). Also I've more than once found circuits fed by two breakers (on same leg of course). All that could be reasons to do as you say and just cut power to the whole house, but again that isn't always an option. -- Cheers
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Old 11-01-2009, 09:24 AM   #8
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Originally Posted by philS View Post
Billy -- Isn't it a little hard to see what you're doing and run power tools with power cut to the whole house?...
I think it is a good idea to give that advice to others - homeowners doing their own electrical work. Use a flashlight if necessary.

And this would be for those replacing switches, outlets, light fixtures, etc. mainly. Those who might not be familiar with multi-wire branch circuits and similar situations.

And there can be weird grounding situations where a ground wire is energized by another circuit*. (You would not believe some of the handiwork I have seen! )

So I would say turn off ALL power if possible.

If that won't work, turn off all breakers except one (for power tools and lights) and double check that power is in fact off for what you are working on. That would be safer than turning off just one breaker.

*I've seen new additions where all the new wiring added came with a ground wire and all the grounds were inter-connected with the new wiring, but the grounds were never connected to the main panel!

So there is a bunch of ground wiring which is "floating". A malfunctioning appliance on one circuit could energize the entire ground network. So you turn off just one breaker in all this wiring, yet the dangerous hot ground situation is still there via power supplied by another breaker!

You can get something like this in an appliance and the bare wire is touching the "grounded" metal of the appliance...

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Old 11-02-2009, 11:00 PM   #9
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Seen this hundreds of times, when current cross bleeds from one circuit to another, (cant recall exact term for this..) especially when circuits are obviously sitting next to each other. If you plug in your appliance (i.e. radio) and your not getting power. Chances are your safe to assume the circuit is not live. I'd dare stick my fingers on it to see...then again I used to run in burning houses and building for a living...when everyone else was running out.


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