Monk goof

Did anyone else see the GFI goof on Monk Friday? The ground wire was cut in the box that caused an electrocution when water and a hair dryer got on the floor. Seems to me that a GFI would trip with no ground. Mine do.
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klaatu wrote:

I caught that when they first showed it, but then later they said a wire was loose and I assumed it was the neutral wire. (I'm still not convinced that it wouldn't trip) What would happen if you wired the hot wire to the "LOAD" side and left the neutral disconnected? Would that energize the hot side of the receptacle even if the device was tripped?
Bob
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I guess they can't all be PhDs in math like the Simpsons Writers http://www.sciencenews.org/articles/20060610/bob8.asp
http://www.mathsci.appstate.edu/~sjg/simpsonsmath/
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wrote:

It should have nothing to do with a ground connection to the GFI.
I have had several GFIs without a ground connection for several years. They definitely do trip when something goes wrong (including wet fire ant mounds over holiday light cords in the yard).
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Mark Lloyd
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The GFCI requires POWER to operate. That power comes from the circuit it's protecting.
SO: if you have a properly operating and properly connected GFCI and you disconnect the NEUTRAL "line" wire, the electronics in the GFCI no longer are powered. The HOT "load side" wire will still be HOT. You would cross the HOT output of the GFCI to GROUND and the devide will not trip. (You may trip a breaker but the GFCI would not do anything except, perhaps, smoke.)
Open neutrals can be as (or more) dangerous than open grounds. The open neutral will permit crosses between HOT and neutral which will NOT trip a breaker. An open neutral will cause the light to go out but leave every WHITE wire in the room just as dangerous as the BLACK or RED wire.
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John Gilmer wrote:

Modern GFCIs fail safe. They open when deprived of power and will therefore open when the neutral fails upstream. The newer ones can also detect a neutral to ground fault without a load on the circuit by injecting a detecting current onto the neutral.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
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That's true. AND the protect against many wirkng errors.

MAYBE some GFCIs do open when there is no power but that certainly isn't true of most of those out there.
Think about it: if it opens when the power goes away then it must re-close where the power is restored (or folks would be running about resetting all the GFCIs in the house after a 1 second power outage.)
I don't think the contacts are rated to "switch" the load every time there is a power glitch.
In the "interest of science" I arranged an experiment of a "out of the box" GFCI that "Meets All New UL943 Safety Standards" to include: Ground Fault (duh!); Correct line/load wiring; and GFCI Electronics Integrity.
As received it was "tripped" so there wasn't any continuity between line and load.
Using a cord set salvaged from an old and forgotten lamp, I connect 120 volts to the "line" side. I hit the reset button and it "clicked."
When I removed the power there was still continuity between corresponding "line" and "load" wires.
One interesting thing was when I hit the "test" button with the power off, it "clicked" and broke the connection between "line" and "load."
The GFCI does protect against a LOT of stuff. BUT it doesn't protect against a neutral that is connected AFTER the unit is reset.
How could ths happen?
It might happen if the "romex" neutral is accidentally cut by a missplaced nail. The nail might even maintain the circuit for a time before something shifts and the neutral is open.
Most likely, however, is that someone wiring another circuit accidentally forgets to connect a white wire. He might even even mistake a neutral for a "switch loop" white wire.
Or, someone might have been careless and placed two white wires under the same screw in the CB box (happens all the time.) That's a "no-no." Worse than putting two grounds on the same screw (which wasn't a 'no-no' but it might be now.) Down stream someone else replacing or re-arranging a circuit will end up taking off another neutral in the addition to the one associated with his target.

Quite true. That particular feature has been around for quite a time.

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On Mon, 24 Jul 2006 15:56:23 -0400, "John Gilmer"
[snip]

I suppose there's some power stored somewhere. Does this happen when power is disconnected for an hour?
[snip]
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wrote:

Oh, it's just a spring!
When you "reset" you cock a spring.
These GFCIs do fail occasionally (it pays to test them when you get "a round tuit") and when you find a bad one, you can go ahead and take it apart. Among other things you will see the dual "sensing" cores (one is actually the current injector so that neutral/ground faults can be sensed.)
Since my "new" GFCI's aren't in service yet, they will not fail for some time.
I have some 10 or 12 GFCIs in various places and I still don't have them in ALL the locations (including the kitchen near the sink) where they should be! If they have an expected life of 15 years I will have a "victim" to take apart sometime within the next year or so.
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On Mon, 24 Jul 2006 21:26:28 -0400, "John Gilmer"

So the "test" button just releases a spring? That's something a ground fault wouldn't be able to do, so the "test' button is not really useful for testing the GFCI.

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wrote:

When there is no power applied the test button does cause (by mechanical action) the unit to trip. (At least in the unit I experimented with.)
I would hope that when power is applied the test function works "properly."
If you have more than one or two GFCIs in your place you should get a GFCI "tester" which provides a real ground fault. These things are just a "circuit tester" (3 neon lamps) and a push button.
Frankly, in spite of all the GFCIs I have in my place, I don't believe any have even functioned in a manner that would have prevented my getting a shock. They have tripped but not beause human flesh came between HOT and GROUND.
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John Gilmer wrote:

Are you sure about that? It could all be mechanical with electro- magnetic sensing. Current in either the "hot" series coil or the neutral coil that's not opposed by and equal current in the other coil trips a spring-loaded mechanical switch.
(I don't know if they could get the required level of sensitivity with a purely magnetic system.)
Bob
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And what was the current path that would electrocute someone? She wasn't touching a ground - just the water .
Bob
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