While checking a another receptacle on the load side of a GFCI receptacle, I come up with the following:
Testing with a “Wiggy” across the hot and neutral, shows “nada”.
Testing with a “plug in” circuit checker shows “no ground”, I knew that.
Testing with a voltage meter across the hot and neutral shows 119+ VAC.
What’s up??
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Replies
You are using a very high impedence digital voltmeter. And it is measuring stray voltage.
So you're saying that the Wiggy is right?(dead circuit) what about the plug in checker? Not quite sure I follow you.
Yes, a dead circuit unless the wiggly is dead.You might have more than one problem.And if there is anything else plugged in to that circuit you can be seeing "feedback" through one of the open wires.Dan has a good idea.Also check at the GFCI.
Pardon my ignorance, but what's a wiggy? Is it similar to a Greenlee Volt Tick?
Thanks,
Scott.
It is wiggly and it is a brand name for a soliend tester.http://www.acehardware.com/sm-square-wiggly-voltage-tester--pi-1297996.htmlBut there are similar from other manufacturers.They have a soleniod that pulls agaisnt a spring and have a point to indicate the voltage.They are not a precision measuring device. But they draw enough current that they don't give false readings.
Wiggy is 'Square Ds' version of a solenoid voltage tester. IMHO it is the best commonly available brand of this sort of instrument.In my experience the solenoid voltage checker is the single best test instrument a HO or contractor can own. Simple, reliable and it tells you what you need to know. Too often I see would be troubleshooters grab a digital voltmenter and become confused. They get swamped by useless differences, 118v vs 122v, false readings of ghost voltages and never see the larger picture.Don't get me wrong. Voltmeters, digital and analog, True RMS and averaging, have a place but I typically do my initial assessment with a simple Wiggy. With practice you can tell voltage and often frequency, a big thing with VFDs, by feel alone. A big benefit when you are working in a confined and/or dark location. Also a boon for places where your hanging on by your toes.The other thing to practice is tsting you test instruments. Good practice for eelctrical contractors is to make sure your instruments 'read' a known voltage and do this first thing in the morning. Others, and in critical situations, need to check to see that the instrument reads before checking anything. In critical situations, where screwing up can easily get someone killed, it is best to check against a known voltage immediately before checking the circuit in question and then recheck against the known voltage to assure the instrument hasn't failed.I know of one situation where a defective instrument was used to check that a bus bar had been deenergized before maintenance was performed on it. The helper thought he had flipped the right breaker and the journeyman was being double sure checking the bars with his instrument. He got no reading and proceeded to position a wrench so he could check a connection for tightness. The rachet was uninsulated, he was not using gloves or mats, and he was kneeling on a concrete floor. Once 'captured' he couldn't get away. It was the last thing he ever did.Take it from me it looks silly, to the uninitiated, for a journeyman to check the voltage of something that is obviously working, to check the circuit in question and then return to a known good circuit but any good electrician will see it as a mark of professionalism. A commitment to safety.
I don't think checking the voltage is silly at all. I don't want to become the load. If I'm going to work on some circuit that I don't know about, I'm not going to trust someone else to make sure it's off when it's my life that could be over. He really should have verified the state of the buss bar. Sad to hear about this kind of thing, though.
"I cut this piece four times and it's still too short."
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69115
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Weight (lbs.)
69115
tester body is 6" (152 mm); leads are 28" (711 mm) long including 6" (152 mm) probe module
.65
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Measure everything again, but this time plug a table lamp (turned on) or some such into the other half of the outlet. You'll read nada/nada/nada.
Verify that the Wiggy works somewhere else(I doubt that it will). Otherwise, if you know that the ground is open, the voltmeter is right. Your circuit is across the hot and neutral, not the ground. 119 VAC is not stray voltage, especially when the ground is the only wire that's open. If the meter read mV, it would be stray voltage. The impedance of the meter doesn't matter, other than the fact that it will have very little effect on the circuit.
highfigh,
I beg to differ, there can be ghost voltage (aka phantom voltage; stray voltage is something different) up to line voltage (120v). It's just electrostatic voltage resulting from an energized cable or conductor being in contact with one that's not energized. It isn't always seen, because the cables have to be isolated from contact with anything that'll drain the electrostatic charge.
Long cable runs, low humidity, and contact with dry wood can lead to 120v of phantom voltage. I've observed it many times.
The impedance of the meter or tester matters. It's at the heart of whether the tester can discriminate between real voltage and phantom voltage. A digital multimeter, having high impedance (to protect electronic components from damaging voltage while measurements are made), will read the electrostatic voltage as "real".
In contrast, a low impedance tester, like a wiggy or other soleniodal tester, will present enough of a load that the current behind the ghost voltage is dissipated, and so no voltage is measured.
As far as the original posters situation, I suggest that he recheck his results, and the testers he used. And use a reference ground (an extension cord plugged into a known good ground). The results could be an open neutral and miswire.
Cliff
A unenergized circuit in contact with one that is energized is not electrostatic voltage. The voltage is there because of the contact. Long runs(I assume you mean wires that are parallel) will result in capacitive coupling. Dry wood does not conduct electricity. Neither does dry air. They are dielectric and resist current flow. Static electricity is stored charge, nothing more. That's why it's called STATIC electricity. Generally, if the voltage reading is near line voltage, there is something in contact with the live wire, even if it's a thin strand if wire. You can also have a situation where the voltage reading is high and won't drive any current. Proximity to a live wire will indicate this(broken wire in insulation, loose terminal, screw fell out and the wire is still in position, etc). If the voltage looks odd and you want to test for a live circuit, a test light will work. Not the LED type, though. They don't draw enough current. Just so we're clear, voltage is potential energy(electrical pressure, if you will) and current is electron flow. 1 ampere = 1 coulomb per second, IIRC (6.24 x 10 to the 18th power x the charge of one electron). You can read voltage on a live wire that's not connected to a load. You can't measure current on this specifically because there is no load. No load, no current unless there's a short circuit. Since the reading in question is on the load side of the GFCI recepticle, I would be looking at the whole circuit. I don't remember seeing anything about it tripping, so it may be an open neutral. Light bulbs show the GFCI a load that is very similar to a short(a bulb is about 1 ohm until the filament heats up and then the resistance increases) and most of the times I have seen lights connected to GFCI recepticles, they tripped. I would like to see more info about the age of the house, type of wiring, other electrical issues, etc. I think there could be more to this problem.
"I cut this piece four times and it's still too short."
Edited 3/29/2005 9:45 pm ET by highfigh
"most of the times I have seen lights connected to GFCI receptacles, they tripped. "
This will come as quite a surprise to the millions of guys who plug their trouble lights into their GFCI protected garage receptacles.
I should have been more clear about this. I have seen lighting circuits wired to the load side of GFCI recepticles and they tripped immediately, even with no shorts to ground or neutral. I have a GFCI in my garage with my trouble light plugged into it too, but mine is flourescent.
"I cut this piece four times and it's still too short."
Really got you guys going didn't I! Gonna stop by the site and check this out again.
The reason the ground is open is that there is none. This is an outdoor circuit that was wired 25 yrs ago, under concrete! I have a suspicion that the nm/cable has died.
We've had a rough winter with much more than usual frost heave!
And the wiggy is alive and well!
Edited 3/30/2005 6:04 am ET by POPEYE87
Thanks for putting that in there when you originally wrote about the problem. Like I said, it would be helpful to have more info. Are you saying that we were overthinking this?
"I cut this piece four times and it's still too short."
I was right. Multiple problems.And I suspect that reason that you are measuring a "full" 119 volts with the digital VM is that there is a high impedence connection. Which would agree with the probably failure.Some place the wire is broken and corroded, but there are copper salts and/or water that is "making" the connection. Might be a couple of hundred thousand ohms of resistance. Not enough to operate a wiggly. But enough to for a DVM with 20 meg ohm input impedence.And enoguh to operate the neon bulb in the tester. And if the test only indicated that it had a bad ground and it is like mine then the fault is in the neutral side, BTW, if you put the test in a good receptacle and compared the lights you will probably find that while the one for hot was lite that it was not as bright as it should have been.When I replied the first time I started to mention the high impedence. I consider it "stray voltage", but you can also get false readings from capactively couple from other circuits or inductivaly coupled."This is an outdoor circuit that was wired 25 yrs ago, under concrete! I have a suspicion that the nm/cable has died."Outdoor and underground (even if in conduit) are not suppose to have NM cable. UF (underground feeder) is what is used. One of differences is that there is no paper wraping i the UF which can atract mositure.
Edited 3/30/2005 9:01 am ET by Bill Hartmann
pardon my blunder, it was in fact UF cable.
After rechecking the circuit I've concluded that the neutral wire was toast.
Nada results on the "simple" but overlooked test of plugging in a "appliance".
Both branches of this outdoor circuit had no ground wire in the UF cable and the installer had run a jumper from the neutral terminal on the receptacles to the ground terminal on the receptacle!!!!
And no, I don't think this was an overworked topic, especially when it can be a life threatening situation. I thank you you all for your input. I've learned a few things here at this forum and will hopefully continue to!
> I should have been more clear about this. I have seen lighting
> circuits wired to the load side of GFCI recepticles and they tripped
> immediately, even with no shorts to ground or neutral. I have a GFCI
> in my garage with my trouble light plugged into it too, but mine is
> flourescent.What you have probably seen is circuits with crossed neutrals. If the neutral is connected to ground or to the neutral of another circuit then the GFCI will trip immediately, even before lights are turned on.
But the circuit had no issues after the lights were removed and the panel was inspected with hot/neutral/ground removed and tested. In the last case, I kind of think the wires were buried and they didn't use direct burial cable or the conduit was breached.
"I cut this piece four times and it's still too short."
I can't quite parse that. However, I'm quite certain that simply removing the light bulbs in a properly-wired circuit would not make a GFCI start "holding", when it wouldn't with the bulbs in place.
No, it is not electrostatic. But, it is quite possible for a piece of wire that is not connected at either end to show a voltage. This is exactly how an antenna works, by picking up RF energy and 60 hertz power lines can put out quite a bit of RF energy that a high impedance volt meter can read. Unless you run your "antenna" near a high voltage power line, you won't pick up any significant energy, but the voltage is still there.Having said that, 119 volts is too close to line voltage to dismiss it as coincidence and I'm not going to stick my finger on it without more information!
An antenna works by picking up a small signal and then the tuning circuit resonates because it's tuned to that frequency(pilot). The antenna is definitely connected on one end- the tuner input. As I said, wires that are parallel can be influenced by another wire and the voltage difference, proximity and wire size make the difference between it being a large or small effect. If an unterminated wire is next to a high voltage wire, there may be a readable voltage on it, but it won't matter because the wire is still unterminated. If the wire is terminated on at least one end and it's close to a high voltage conductor, there will be some effect, depending on what the wire is used for.
"I cut this piece four times and it's still too short."
If you plug in a toaster, and it makes toast, your wiggy is toast too.