Both red and black wires hot

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  #1  
Old 03-08-15, 09:56 AM
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Both red and black wires hot

I have two circuits where I have a run of 3 wire where both the red and black wires are both hot. If I switch of both there is no current. If I have the red off and the black switch on, both have power. If I turn the red switch on the black off they both have power. Both of these runs of 3 wire are home runs and were run from the same spool of wire. I checked every possible junction box to make sure that black and red were not connected.

Did I get a bad batch of wire?

Any other investigation steps I can conduct?

Thanks
 
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  #2  
Old 03-08-15, 10:18 AM
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Welcome to the forums.

You need to use an actual meter, preferably an analog meter to check your wire.

You are most likely using a non-contact tester which only tells you that there is dangerous voltage in the area. If you have two wires next to each other and one is hot..... that probe will show the dead one as live. The voltage is inductively picked up by the dead wire.

This is normal and doesn't present any problem.
 
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Old 03-08-15, 10:24 AM
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Sounds like you are using a non contact tester. We could actually start a forum about people who chase wild gees because they believe the hype on the package they come in. They are really only good as a general indicator there may or may not be voltage on the line. If you were using an analog (not digital) multimeter apologies for this reply.
 
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Old 03-08-15, 11:00 AM
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Bad wire is way down on the list. Standard test after running a new circuit would be along these lines: (use an analog meter)

- Black to Neutral = 120V; Black to Ground = 120V
- Same for Red; Check voltage to neutral and ground

Chances are you are done and it's wired correctly

I use a digital meter and it's common to see voltage on a multi-wire circuit with one leg off.
Not always, but you can sometimes see anywhere between 7 - 14V, or more.

These are false readings.
 
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Old 03-08-15, 11:11 AM
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I was using a contact tester, but I had the wired separated as far as possible to prevent picking up current from the other line.

I tested one of the circuits (digital meter). With the red switch off and the black on the voltage on the black wire is 120v, the red wire is 39v.
 
  #6  
Old 03-08-15, 11:24 AM
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My digital meter is expensive, but it will still detect induced voltage sometimes. If your digital meter is not as good as mine, it is probably more prone to induced voltage.
Sounds like you are OK.
You can pick up a cheap analog meter, probably better for your situation. Readings will be more accurate.
One problem with a non-contact tester is you can't check voltage to ground.
 
  #7  
Old 03-08-15, 12:43 PM
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the red wire is 39v
99% likely induced voltage. You can confirm with a cheap ($8-$15) analog multimeter.

See also: http://support.fluke.com/find-sales/...105317_A_w.pdf
 
  #8  
Old 03-08-15, 12:48 PM
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I wire the fixtures and they work perfect. I'm definitely going to pick up a analogy meter the next time at Homedepot.

I was just short of cutting drywall and pulling a new wire.

THANKS!!!!!!!!!!!!!!!
 
  #9  
Old 03-08-15, 07:16 PM
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If you connect a small wattage incandescent lamp (25 watts is plenty) across the two points where you are touching the voltmeter probes, a voltage, if it is induced voltage, will be drained off to be indistinguishable from zero.

The more sensitive (and probably more expensive) a voltmeter or multimeter is, the more likely it will report induced voltage. If you took two voltmeters of different sensitivity and used them one at a time to measure the same circuit, any induced voltage will be reported as higher on the more sensitive meter.

I have never seen a voltmeter that had a push button or dial setting to impose an additional load across the two circuit points it was testing, in effect doing the same thing as your connecting a smal incandescent lamp across the two test points. But perhaps such a meter (probably yet more expensive) exists.
 
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Old 03-08-15, 08:02 PM
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I was using a contact tester, but I had the wired separated as far as possible to prevent picking up current from the other line.
If you read this forum regularly, you'll soon notice that about twice a week someone posts a problem similar to yours, but they are trying to use a non-contact tester for troubleshooting. That is the reason for the quick responses and questions about your tester. These testers have their place, but not when troubleshooting a problem. They are, however, a big moneymaker for the box stores and thousands of them are sold every week for around $8 to $15.
 
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Old 03-08-15, 08:09 PM
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I have never seen a voltmeter that had a push button or dial setting to impose an additional load across the two circuit points it was testing,
Actually there is a high end Fluke that has a similar function. See my previous link: http://support.fluke.com/find-sales/...105317_A_w.pdf But a $10 analog meter does the same for a lot less.
 
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