klaatu wrote:
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.


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

"zxcvbob" wrote in message
...
klaatu wrote:
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.


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

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/

On Sun, 23 Jul 2006 16:43:19 -0700, klaatu
wrote:

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.

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).
--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

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.

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).

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.

John Gilmer wrote:
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).

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.

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
for general use." Thomas Alva Edison

John Gilmer wrote:
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).

The GFCI requires POWER to operate. That power comes from the circuit it's
protecting.


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

Modern GFCIs fail safe.

That's true. AND the protect against many wirkng errors.



They open when deprived of power and will
therefore open when the neutral fails upstream.

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.



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.

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

--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

On Mon, 24 Jul 2006 15:56:23 -0400, "John Gilmer"
wrote:

[snip]


One interesting thing was when I hit the "test" button with the power off,
it "clicked" and broke the connection between "line" and "load."


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

[snip]
--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

"Mark Lloyd" wrote in message
...
On Mon, 24 Jul 2006 15:56:23 -0400, "John Gilmer"
wrote:

[snip]


One interesting thing was when I hit the "test" button with the power
off,
it "clicked" and broke the connection between "line" and "load."


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

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.

"klaatu" wrote in message
...
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.

And what was the current path that would electrocute someone?
She wasn't touching a ground - just the water .

Bob

On Mon, 24 Jul 2006 21:26:28 -0400, "John Gilmer"
wrote:


"Mark Lloyd" wrote in message
.. .
On Mon, 24 Jul 2006 15:56:23 -0400, "John Gilmer"
wrote:

[snip]


One interesting thing was when I hit the "test" button with the power
off,
it "clicked" and broke the connection between "line" and "load."


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

Oh, it's just a spring!

When you "reset" you cock a spring.


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.

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.

--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

"Mark Lloyd" wrote in message
...
On Mon, 24 Jul 2006 21:26:28 -0400, "John Gilmer"
wrote:


"Mark Lloyd" wrote in message
.. .
On Mon, 24 Jul 2006 15:56:23 -0400, "John Gilmer"
wrote:

[snip]


One interesting thing was when I hit the "test" button with the power
off,
it "clicked" and broke the connection between "line" and "load."


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

Oh, it's just a spring!

When you "reset" you cock a spring.


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.

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.