voltage tester was picking up voltage on a detached wire

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Coppersmith said:
If the detached wire is laying next to an energized wire, the magnetic field from the energized wire is cutting across the detached wire and inducing a voltage on it just as if it were a very small transformer.
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Capacitive coupling to adjacent wires is much more likely, especially as that can happen even when the energized wire is not carrying any current.
 
michaelkingdom said:
Home inspectors have a state SOP which supersedes the Nachi SOP. Our great Florida SOP says we need to inspect the panel interior. Our SOP is also the minimum we need to do, not the maximum. We are allowed to go beyond the SOP.

I use an outlet tester on all outlets, trip all gfcis, test for power at the dryer outlet. When I open the panel I look for double taps which I understand are a non-issue for many electricians but we are trained to ID them and call them out. I even prewarn the homeowner, "the electrician may tell you this is a silly call but it is part of our job."

As far as checking if there is voltage on a wire that is almost touching the panel enclosure, if it was energized and then made the panel energized and the homeowner touches it the first question that gets asked is "who looked into the panel last...the home inspector. Let's call him and find out why he didn't warn us about this wire."

We do some evaluation in our process to try to find out causes of issues. We are not required to but it makes good sense to go a step further if it will save you or the customer time, money and injury.
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checking for voltage with non-contact tester is very similiar to not checking at all
 
Klein NCVT-2

Klein NCVT-2

readydave8 said:
checking for voltage with non-contact tester is very similiar to not checking at all
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I have noted this type of Stick Tester to have a very limited utility and to be quite misleading and as thus dangerous if relied on in the wrong ways.This particular unit will sometimes " fail " to show power on a fully energized line. I have found they can be used in certain service situations as a preliminary sort of tool and also sometimes with ON-OFF verification. They are highly limited and not what they have been cracked up to be.
 
You rub it across the hair on your arm to make sure it's working, then you hold it near the conductor.
 
Whenever your non contact sensor does strange stuff replace the battery. I've been using these for over a decade and I've gotten to where I can tell a false reading and almost always it's a weak battery and/or moisture/corrosion in the works.
 
i not reading all the posts. its magnetic coupling. had this issue many many years ago. UF wire that was in ground for like 30+ years, ran from a switch to pole light outside with about 70ft of wire. emf reader in socket says "yep", put bulb in says "nope". hmmm, started to dig wire up near pole, about 20ft away found a splice, hot wire corroded away in the splice but both ends were still somewhat close. no current allowed means no light. those emf readers can lead to some false beliefs.
 
FionaZuppa said:
i not reading all the posts. its magnetic coupling. had this issue many many years ago. UF wire that was in ground for like 30+ years, ran from a switch to pole light outside with about 70ft of wire. emf reader in socket says "yep", put bulb in says "nope". hmmm, started to dig wire up near pole, about 20ft away found a splice, hot wire corroded away in the splice but both ends were still somewhat close. no current allowed means no light. those emf readers can lead to some false beliefs.
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No current allowed means no magnetic coupling. (Although this may depend on what the source circuit of the coupling was.)
 
These work by sensing a changing electric field. They capacitively couple. It's why they can't read through a grounded conductor.

I do have one that will magnetically couple and is useful for detecting a loaded circuit inside a conduit or metallic cable, but I only know of the one manufacturer who makes that version.
 
K8MHZ said:
This, from the NACHI site:

IV. The inspector is not required to:

  1. insert any tool, probe, fingers, nose or device into the main panelboard, sub-panels, distribution panelboards, or electrical fixtures.

​
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FIFY:D

GoldDigger said:
Capacitive coupling to adjacent wires is much more likely, especially as that can happen even when the energized wire is not carrying any current.
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Number one condition most of the time.

michaelkingdom said:
Thanks guys. Could you elaborate on this shirt/arm hair test? The sensitivity on mine starts at 50V.
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Static electricity developed when rubbing across your shirt can be in the thousands of volts range - but at such a low current capacity you don't necessarily feel it, or is just a little snap when you do feel something.
 
GoldDigger said:
No current allowed means no magnetic coupling. (Although this may depend on what the source circuit of the coupling was.)
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maxwell equations. because the e-field flips at 60Hz, you have a mag field that flips too.

a coupling of some sort (E or B) in the broken wire must be there for one of these no-touch detectors to buzz "live" on a conductor downstream of a break.
 
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ActionDave said:
No I'm not dead sure, but I'm reasonably sure it's phantom voltage.

One thing I am dead sure about is, live or dead, advising someone hook up a light bulb to piece of fully sheathed romex sticking out of a panel at someone else's house is not a helpful suggestion.
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Especially when any good voltage tester will load up the circuit enough to "bleed" off any ghost voltages and accomplish what the suggester is trying to accomplish. The only thing a non-contact tester is good for is a preliminary test to increase caution. The problem can be that it actually makes someone less cautious when it gives a false negative.
 
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