I was in my workshed which is about 60 ft from the house drilling some aluminum. I got a faint tingle in my hand, I touched the case of my drill a couple times and didn't feel any thing, so I started to drill again. I noticed the tingle again, I went through this a few times until I decided there's a problem. The tingle was at a tiny red spot on my finger, I later removed a small metalic sliver. If not for the sliver I probably would not have noticed the missing ground, for I don't know how long. The drill motor is a 3 wire system, hot, neutral and ground. I had it plugged into a GFCI. I unplugged the drill and pushed the test button. The GFCI didn't pop. I retrieved my DVM and tested from the drill case the the dirt outside the door, it was about 80v. I then tested from the Hot to the ground at the receptacle, that was about 20 v. I moved to another Receptacle closer to the house, same thing no ground connection. I moved up to a receptacle on the outside of the house on the same line, again no ground connection. Inside the garage, no ground connection. I opened the circuit breaker box and checked the ground wire, it is good. So, in my attic between the CB box and the garage there must be a connection box where the ground has opened up. Followup tomorrow evening. Mikek
The "test" button on the GFCI should work even if there is no ground to the GFCI. So you may have more than one problem here.
Don't discount the idea that the ground is open at one of the receptacles. In three houses I've worked on (one from 1965, two from
1969), if two or more NM cables come into a receptacle box, the ground wires are just twisted around each other for an inch or two, with no wire nut. Usually the contact between wires is OK but sometimes the twist is not very strong. One of the ground wires is longer than the others, and it goes to the green screw on the receptacle. When I swap a receptacle in a box like this, I usually add a green wire nut with a hole in the top for the long ground wire (Ideal "Greenie" or equal), to help make sure the ground stays connected.
Besides, checking the receptacles is probably easier than fooling around in the attic. :)
A good tool for quickly checking grounds is a 100 W incandescent lamp in a socket that has insulated wire leads. Connect the wires live to neutral to calibrate your eyes, then go from live to ground. If the brightness drops off a lot, the ground has high resistance. (If there is a GFCI in the circuit, going from live to ground should also pop the GFCI.)
GFCIs work independently of the safety ground in a 3 wire system - so will still trip if a few mA of current is passing to any local ground like soil, wet concrete or metal plumbing.
However, a missing safety earth conductor is never good as the metal cases of 3 wire appliances can become live and nothing blows.
BTW:
I have not seen a 3 wire, hand held drill in quite a while.
Buy one (or two) and walk it around to every outlet in the house. Also check power strips which I've seen miswired.
The life you save may be your own.
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Re: checking in receptacle boxes, I thing I have it somewhat isolated. The CB box and the garage are on opposite ends of the house, and as far as I know, the garage is on a breaker by it's self. But it also looks like there is a connection box between the CB box and the garage, or at least a break in the ground wire. It seems a little odd, I'll figure it out this afternoon. Mikek
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Depending on the grounding arrangements, this can sometimes still happen even if there isn't a complete disconnection or any serious leakage current.
The sensation of electrical shock is entirely dependent on the current density in the susceptible tissues, rather than the voltage applied. Human tissues are very conductive, but dry skin usually acts as a partial insulator so low voltages don't create enough current to cause any sensation.
With a sliver of metal puncturing the skin and leading directly into the underlying tissue, probably quite close to nerve endings, a very low voltage would develop enough current to be easily detectable. Tests have suggested that A.C. voltages below the 2v level can be detected by the tongue when the feet are in a wet, conductive environment.
This is a particular problem where the neutral and earth conductors are bonded ("P.M.E." in the UK) because the small voltage dropped along the neutral will apear on any bonded "earthed" metalwork. In farms and other wet environments, this can lead to animals receiving shocks from licking handrails, feeding troughs - and from milking machines through the milk lines directly to their teats.
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the GFCI. So you may have more than one problem here. "
I suggest you recheck that.
A GF interrupter works by a current transformer with the windings set to re ject differential mode signals. It transforms common mode current into a vo ltage which is used to "trip" the circuit open.
A GFCI or GFI will work withou a proper ground, but the test button will NO T because it tests by inserting a resistor from the hot to the ground (not neutral) which upsets the balance of current, which is the same thing that appens when current is going through a person to an earth ground, or anythi ng other than THAT neutral. (yup, each GFI circuit requires an isolated neu tral for that reason)
There is, in short (no pun intended) no other way for the test button to wo rk because if the only wires that are available are hot and neutral, there is no way to induce common mode current through the transformer.
that I got at Radio Shack (looks discontinued there), that not only tests GCFI's, but has an array of LED's on the back that test for outlets wired in the proper Hot/Com/Gnd sequence.
I bought it a number of years ago when I discovered a bass-ackwards wired outlet at the old house. Anytime I see a peculiarity with electrical I first test the outlet. ...Jim Thompson
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I love to cook with wine. Sometimes I even put it in the food.
Yes, I'm on my way to lowes/Home Depot to get one of those, and a non contact voltage tester to help trace the wire. I'll shut down all but that one. I'm outta here, Mikek
I bought the gadget, it tells me that I have, HOT and NEU REV. I know that is not correct. btw, I did check it on a few other outlets that check ok. So, I did this, I drove a rod into the soil, I measured from the HOT (shorter slot) to the rod, 123V. I measured from neutral, (the longer slot), to the rod, 1.6V. Then I measured from the ground pin to the rod, 91V. So, I measure 91Vac on the ground wire, that means I has to be open between the house and the workshed. I don't know why it has 91 Volts on it though. I did recheck the outlet on the outside of the house and it is OK. My previous in the garage measurements were in error, everything in the garage is OK, except the outlets are 40 years old and make poor connection on the slots. With the info I now have, I'm confident it is a repair gone bad. About 15 years ago I installed a tripod for an antenna. My first few shovels of dirt found and cut the pvc conduit between the house and work shed. So. I installed a box and repaired the wires. I moved the tripod a few feet. We have had 10 or 15 inches of rain during the last 7 to 10 days, I had a little standing water in the area where the repair was made. I suspect I'll have the shovel out in the morning. Damn! Mikek
PS. I also bought the non contact voltage tester, it's pretty neat, get it within an inch of an ac cord and it beeps. I measured 2-1/2" from my soldering iron ac cord when it beeped, this is when off.
You just _know_ how it will be... rain in the morning >:-} ...Jim Thompson
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I love to cook with wine. Sometimes I even put it in the food.
I wouldn't mind putting of the repair! I brought the original job that started all this (cutting some slots in a 2" square aluminum tube) into the garage and got it done. I can take it to the boat in the morning and check the fit, and make adjustments if needed. I'm adding a short extension on the rear of my pontoon boat, (my business office :-). I bought 60 feet of 2" square tube with 1/8" wall and cut it all to size. I bought a TIG welder and when I get my helmet delivered, I'll start practicing *tigging! Then I'll finish my project. For those questioning my 3 pin drill motor, I found an ad in Popular Mechanics, Jan 1966, so it must have been manufactured in 1965 or before. It is almost 50 years old, WOW. See page 10.
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I used it instead of my cordless because it is powerful, it would have taken much longer with my cordless.
Mikek
I always wanted to learn to weld aluminum. Now I'm going to do it.
I've got one here that the test button works with no ground, I'm guessing the test passes between the protected hot and unprotected neutral (or vice versa) It's a GFCI power strip.
The advantage of doing it this way is that the test-button won't trigger upstream GFCI breakers.
but for hardwired GFCI outlets the advantage may swing the other way.
Sure. Consider the following guts of a GFCI. It is shown in the "tripped" or open condition. Use a fixed-width font such as Courier.
/ A B C /I Live ---*--*----@@@@@---*---o I o--- Live | ===== I +--+ +-@@@@@-+ I | | | I | ------------- I GFCI +---|measure and| I GFCI "line" | compare |.....I "load" side +---| current | I side | ------------- I | | | I +--+ +-@@@@@-+ / | ===== / Neutral ---*--*----@@@@@---*---o o--- Neutral D E F
The @@@@@ things are the current transformers. The connections at B and E provide the extra juice needed (if any) for the "measure and compare current" box to work. The "measure and compare current" also contains the solenoid that operates the mechanical linkage (... and I) to the two switches to open up the connection to the "load" side. Note that there are no connections to ground in this anywhere.
Now, connect a 1200 ohm resistor from C to D. What happens?
Alternatively, connect a 1200 ohm resistor from A to F. What happens?
The test button is inside the GFCI, so it has access to the line both before and after the current measurement. It can grab some "unmetered" juice - before the current transformer - to test with.
I also got out my suicide cord and a brand new Leviton GFCI and tried it. I wired the black wire from the cord to the brass "line" terminal on the GFCI, and the white wire from the cord to the silver "line" terminal on the GFCI. I left the ground wire from the cord unconnected. I didn't connect anything to the "load" terminals or the ground terminal on the GFCI. I placed the GFCI on an insulated surface. I plugged my three-neon-lights tester into an outlet in my house and verified it was wired correctly. I plugged the suicide cord into that same outlet.
I pressed the "reset" button on the GFCI and it latched in. I pressed the "test" button on the GFCI and it tripped. I repeated this two more times with the same results.
The installation instructions for the GFCI include the line "Connect the grounding wire (only if there is a grounding wire)". The test procedure in the instructions does not change if the ground wire is not connected.
Therefore, I stand by my statement that the "test" button on the GFCI should work even if there is no ground to the GFCI.
The GFCI is a Leviton catalog number N7599. The stickers on the GFCI say "LEVITON N7599 INSP. 1H42I 43644-04 Z 7" and "(UL) LISTED GROUND FAULT CIRCUIT INTERRUPTER CLASS A 2 POLE UNIT 20A 125V 60HZ ISSUE NO. B-511,882 LEVITON MFG. CO. INC. I"
The installation instructions are apparently Leviton document number PK-93750-10-00-2A.
Product link on Leviton's website:
Instruction link on Leviton's website (PDF):
See also this entry of the electrical wiring FAQ:
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NOTE: If you are using one of those "plug with three neon lights plus a button" testers on a GFCI, then I completely agree that those kinds of testers need a ground to work. They can't reach "inside" the GFCI, so the best they can do is dump some current from Live to Ground. That wasn't the original poster's situation, though.
Actually, probably NE-2s or similar neon lamps, not LEDs. These things are an excellent quick sanity check. I have one in my house-wiring toolbox. I know a guy that has an RV and he always has one plugged in to one of the kitchen outlets; not all RV park electrical boxes are wired correctly.
They can be fooled... the neon lamps only need a few mA, so they won't tell you if you have a high resistance connection somewhere. But if they say something is wrong, it often is.
The super-duper version is made by Fluke or Ideal and has a built-in voltmeter with LCD. It can also measure the voltage before and after it applies a high load to the circuit and calculate the percent voltage drop in the wiring. I watched the home inspector go around this house with one and you could watch the voltage drops build up the further along he got on each receptacle circuit. This is total overkill for fixing Mikek's (amdx's) problem, but I figured I would mention it.
The poor-boy super-duper version is a Kill-a-watt or equal, a small space heater, and a pad and pencil to do some cipherin'. :)
If this is at the GFCI in the shed, that may explain why the "test" button on that GFCI doesn't work. (Even with an open ground... see my recent response to jurb6006 for why the "test" button should always work.)
If you were using a digital multimeter, it probably has a very high input impedance, and it will sometimes see voltage that isn't really there. Swap a 100 watt light bulb for the meter and see what it does; you'll probably find that it lights hot-to-rod, but not neutral-to-rod or ground-to-rod.
That's a different rainy-day project for the spring or fall (when you can turn off the juice without interrupting the furnace or aircon). Buy "spec grade" outlets of the right color in boxes of 10 at your favorite big-box store and work around the house replacing them. (The "spec grade" stuff should cost about $1 apiece.) I have seen electrically- ignited house fires and I didn't like what I saw even a little bit.
Aha!
Call before you dig... except finding that particular wire is your baby, not the power company's. :)
Those are fun. If there is a place in your house where you know there is a live cable behind drywall or stucco or wood or whatever, you might try it there to see if the tester can "see" the cable through the covering.
I had an older one that wouldn't beep when you put it on the Netural side of a flat lamp cord (SPT-1 or SPT-2), but would if you put it on the Hot side. If you ran it along a round orange outdoor extension cord, it would beep when the Hot wire twisted close to that side but not everywhere.
Tip: When using one of these, always try it first on a circuit that you know is live to make sure it is still working. If you want to be really sure, test it on a known-live circuit, then test your unknown circuit, then test the known-live circuit again.
Yes I'm measuring with a high impedance DVM, and I understand the voltage reading would drop if I put a load on it.
I'm lucky and unlucky like that. That time I hit the conduit, the ONE conduit running through my yard. Another time I was ready to spend a weekend digging up a sewer line to install a cleanout, within three shovel fulls I hit the clean out cover. I had no clue it was there. I was one happy clam for the rest of the weekend.
Ya, I tried finding wire in the wall, I didn't have any luck. I bought the more expensive non contact because it said it worked down to 50 volts, the cheaper ones said 100 volts.
I bought the Sperry Wire Tracker at HD for ?? $26 and it has proved useful at finding ALL the wires in our home. Even the wires that went to an outlet but never come out through the drywall! The workman just drywalled over that outlet! It was for a built-in fridge, so I was happy to find the wired outlet and not have to pull new wires.
The principle works on injecting squeaky tones into the cable, you then walk along the wire with the portable unit listening for a response. If wire is isolated AND it's a quiet day, you can get about an 18 inch range to find/track a wire.
the test passes between the protected hot and unprotected neutral (or vice versa) It's a GFCI power strip. "
That makes sense, it's just something I didn't think of. I stand corrected.
The main point though is that it does not need a ground to work, as some pe ople hever tried to say. Not here, I just heard that a few times and though t it was a common misconcepton. You should hear some of the total BS some o f these people at DIY type stores (Lowe's, Home Depot) tell people.
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