I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

On Wed, 29 Nov 2006 00:22:47 -0600, wrote:

I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

Evidently the current flow through the fan to your hand, through your
body, throught your shoes to the ground was below the threshold of
the GFI. That path presented enough resistance to current flow to
limit it to a small enough value that the GFI didn't trip. Placing
the fan on the floor provided a lower resistance path so he current
was high enough to trip the GFI.

GFI's will allow a small amount of fault current to flow without
tripping. This reduces nuisance tripping, but still provides
protection against dangerous levels of current. There was enough
current to feel (which is very little) but not enough to be dangerous.

Seems like the GFI did its job, and you were smart to do the test you
did.

Paul

wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for
testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.

Dave

wrote:
wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for
testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.

Dave


The test you did doesn't prove GFCI breakers are more sensitive and
faster than GFCI outlets. It just proves that the particular pair you
had behaved that way.

To the OP, what were you standing on, type of shoes, etc or in contact
with when you got the shock? It does seem that the current you got
was less than the amount needed to trip the GFCI.

I would open up the fan and check to see that the metal casing is
actually grounded. Sounds like it's not. It should be.

wrote:
wrote:
wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for
testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.

Dave


The test you did doesn't prove GFCI breakers are more sensitive and
faster than GFCI outlets. It just proves that the particular pair you
had behaved that way.

To the OP, what were you standing on, type of shoes, etc or in contact
with when you got the shock? It does seem that the current you got
was less than the amount needed to trip the GFCI.

Yes, the test I did was anecdotal, but GFCI breakers are more
sensitive.

D

wrote:
I would open up the fan and check to see that the metal casing is
actually grounded. Sounds like it's not. It should be.


Since it's an old swivel type house fan, it's unlikely it has a
grounded cord to begin with. Also, even if it does, you can verify
that the case is grounded with a VOM, without taking it apart.

wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Two-prong plug on the fan, right?

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The GFI
sees that difference and trips.

--
Warren Block * Rapid City, South Dakota * USA

wrote:
wrote:

wrote:

wrote:

I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for
testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.

Dave


The test you did doesn't prove GFCI breakers are more sensitive and
faster than GFCI outlets. It just proves that the particular pair you
had behaved that way.

To the OP, what were you standing on, type of shoes, etc or in contact
with when you got the shock? It does seem that the current you got
was less than the amount needed to trip the GFCI.


Yes, the test I did was anecdotal, but GFCI breakers are more
sensitive.

D


Do you happen to know whether this is by design or is it just "always
that way"?

And if by design, why?

I wouldn't think it would be difficult for the designers to set roughly
equal sensing levels/times in both types.

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Warren Block wrote:

wrote:

I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.


Two-prong plug on the fan, right?

Irrelevant.

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.


The current through his body returns to ground (just like the garage
floor test that follows), not neutral.


Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????


The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The GFI
sees that difference and trips.



--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

CJT wrote:
Warren Block wrote:

wrote:

I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.


Two-prong plug on the fan, right?

Irrelevant.

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.


The current through his body returns to ground (just like the garage
floor test that follows), not neutral.



Certainly seems that the current through the GFCI should be unbalanced.
The only way it would be possibile for it to be equal would be if
you grabbed one part of the fan that was shorted to hot, and another
that was connected to neutral.




Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????


The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The GFI
sees that difference and trips.



--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

wrote:
wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I
touched it, I got a fairly good jolt on my fingers. The GFI did NOT
trip. WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the
garbage. But I can not understand why the GFI did not trip when my
fingers got shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better
for testing GFCIs than the test button on the outlet.

Baloney. GFCIs operate by comparing the current between the hot and neutral
leads. Period. Earth ground is not necessary for one to work properly.
It's a useful tester, but irrelevant to anything about the GFCI.

Pop`



Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.



Dave

Jeff Wisnia wrote:
wrote:
wrote:

wrote:

wrote:

I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for
testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.

Dave


The test you did doesn't prove GFCI breakers are more sensitive and
faster than GFCI outlets. It just proves that the particular pair you
had behaved that way.

To the OP, what were you standing on, type of shoes, etc or in contact
with when you got the shock? It does seem that the current you got
was less than the amount needed to trip the GFCI.


Yes, the test I did was anecdotal, but GFCI breakers are more
sensitive.

D


Do you happen to know whether this is by design or is it just "always
that way"?

And if by design, why?

I wouldn't think it would be difficult for the designers to set roughly
equal sensing levels/times in both types.

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

I have to claim 'just in my experience' based on a few cases, I did
read something awhile ago and can't find the darn thing.

One common sense reason to claim the breaker 'more sensitive' though is
that the breaker will 'see' more wiring and equipment, and so the
background leakage the breaker sees will be higher than that which an
outlet will see (even if chained to a few more outlets).

Since the background leakage will be higher, the amount of fault
current required to hit the magic number of total leakage current
(usually 4-6mA) will be less.

Dave

Warren Block wrote:
wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I
touched it, I got a fairly good jolt on my fingers. The GFI did NOT
trip. WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Two-prong plug on the fan, right?

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or
the fan motor and you.

GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground. Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Pop`



Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the
garbage. But I can not understand why the GFI did not trip when my
fingers got shocked ????

The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The
GFI sees that difference and trips.

On 29 Nov 2006 07:24:10 -0800, wrote:


wrote:
I would open up the fan and check to see that the metal casing is
actually grounded. Sounds like it's not. It should be.


Since it's an old swivel type house fan, it's unlikely it has a
grounded cord to begin with. Also, even if it does, you can verify
that the case is grounded with a VOM, without taking it apart.


The first way to check if the case is grounded is by looking at the
plug. It has to have 3 prongs to be grounded.

If it is a two prong plug, and it sounds like that is what it is, It
will not be grounded.

This was a problem. Most likely you can flip the plug in the
receptacle and the "shock" will go away.

The hot is connected to the case in one situation and connected to the
switch for the motor lead in the other.

They came out with polarized plugs to assure that the hot is connected
to the load first.

wrote:
CJT wrote:
Warren Block wrote:

wrote:

I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI
outlet.

I plugged it in, and reached to flip the metal switch. When I
touched it, I got a fairly good jolt on my fingers. The GFI did
NOT trip. WHY? I thought that was the whole purpose of having
them.
This GFI was just purchased and installed, and the test button
works fine.


Two-prong plug on the fan, right?

Irrelevant.

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground
fault. It can't tell if it's just the fan motor between hot and
neutral, or the fan motor and you.


The current through his body returns to ground (just like the garage
floor test that follows), not neutral.



Certainly seems that the current through the GFCI should be
unbalanced. The only way it would be possibile for it to be equal
would be if
you grabbed one part of the fan that was shorted to hot, and another
that was connected to neutral.

No. I understand why you think that way, but it's not so. The current on
each line under ideal conditions will be exactly equal. Current is not
"lost" inside the fan motor. It's too much to go into here, but here's a
link might help you get started:
http://www.reliance.com/mtr/mtrthrmn.htm

Pop`






Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again,
and the GFI tripped instantly. For the heck of it, I put a piece
of wood under it (on the floor) and the GFI did not trip. This
proves that fan motor has leakage to the metal housing, so it goes
in the garbage. But I can not understand why the GFI did not trip
when my fingers got shocked ????


The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The
GFI sees that difference and trips.



--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Pop` wrote:
wrote:
wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I
touched it, I got a fairly good jolt on my fingers. The GFI did NOT
trip. WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the
garbage. But I can not understand why the GFI did not trip when my
fingers got shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better
for testing GFCIs than the test button on the outlet.

Baloney. GFCIs operate by comparing the current between the hot and neutral
leads. Period. Earth ground is not necessary for one to work properly.
It's a useful tester, but irrelevant to anything about the GFCI.

Pop`



Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.



Dave

I've had a few GFCI outlets where the test button was flaky, and if you
chain outlets, the built-in test button can't test the overall circuit.

The other functions of the tester are just good all-around capabilities
to have if you're messin' with your wirin'.

Dave

Pop` wrote:
wrote:
CJT wrote:
Warren Block wrote:

wrote:

I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI
outlet.

I plugged it in, and reached to flip the metal switch. When I
touched it, I got a fairly good jolt on my fingers. The GFI did
NOT trip. WHY? I thought that was the whole purpose of having
them.
This GFI was just purchased and installed, and the test button
works fine.


Two-prong plug on the fan, right?

Irrelevant.

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground
fault. It can't tell if it's just the fan motor between hot and
neutral, or the fan motor and you.


The current through his body returns to ground (just like the garage
floor test that follows), not neutral.



Certainly seems that the current through the GFCI should be
unbalanced. The only way it would be possibile for it to be equal
would be if
you grabbed one part of the fan that was shorted to hot, and another
that was connected to neutral.

No. I understand why you think that way, but it's not so.


What is not so? The above is absolutely correct. The only way the
current would be balanced is if it was all flowing between hot and
neutral. With the fan situation, the only way the current could be
balanced with some of it flowing through the person, would be for the
person to be touching something that is on the hot, while at the same
time touching something on the neutral, which seems very unlikely.
The more likely scenario from what was described was that the person
touched the fan switch, which would mean the likely path is from the
fan throught the person and to ground.



The current on
each line under ideal conditions will be exactly equal. Current is not
"lost" inside the fan motor. It's too much to go into here, but here's a
link might help you get started:
http://www.reliance.com/mtr/mtrthrmn.htm

Pop`



Nothing that I said implies or requires that any current be lost.
Maybe you're the one that should learn to read, Eh?

In article X_jbh.13329$J5.6832@trnddc04, "Pop`" wrote:

GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground.

Definitely not correct, as will be explained below...

Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Take that simplicity one more step, and ask yourself this question: if the
current returning on the neutral conductor is less than the current being
supplied on the hot conductor, what happened to the rest of the current?

Answer: it *must* be going *some*where, and that somewhere is presumably
earth ground, possibly through a human being.





Pop`



Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the
garbage. But I can not understand why the GFI did not trip when my
fingers got shocked ????

The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The
GFI sees that difference and trips.







--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

CJT wrote:
Warren Block wrote:

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.

The current through his body returns to ground (just like the garage
floor test that follows), not neutral.

Pretty clearly not the case since the GFI didn't trip. Unless it's
faulty. Or are you saying it's impossible to get shocked between hot
and neutral?

--
Warren Block * Rapid City, South Dakota * USA

Terry wrote:
On 29 Nov 2006 07:24:10 -0800, wrote:


wrote:
I would open up the fan and check to see that the metal casing is
actually grounded. Sounds like it's not. It should be.


Since it's an old swivel type house fan, it's unlikely it has a
grounded cord to begin with. Also, even if it does, you can verify
that the case is grounded with a VOM, without taking it apart.


The first way to check if the case is grounded is by looking at the
plug. It has to have 3 prongs to be grounded.

If it is a two prong plug, and it sounds like that is what it is, It
will not be grounded.

This was a problem. Most likely you can flip the plug in the
receptacle and the "shock" will go away.

The hot is connected to the case in one situation and connected to the
switch for the motor lead in the other.


Good grief! If that were true, don;'t you think there would be an
awful lot of people dead from decades ago? I don;t know of any
appliances with a metal case, where if you simply plugged the cord in
one way vs the other, you could wind up dead, because the case is now
hot.




They came out with polarized plugs to assure that the hot is connected
to the load first.

Warren Block wrote:
CJT wrote:
Warren Block wrote:

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.

The current through his body returns to ground (just like the garage
floor test that follows), not neutral.

Pretty clearly not the case since the GFI didn't trip.

It's not clear, since the current required to feel a shock may be below
the threshold that will trip the GFCI.




Unless it's
faulty. Or are you saying it's impossible to get shocked between hot
and neutral?

--
Warren Block * Rapid City, South Dakota * USA

wrote:

Warren Block wrote:
CJT wrote:
Warren Block wrote:

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.

The current through his body returns to ground (just like the garage
floor test that follows), not neutral.

Pretty clearly not the case since the GFI didn't trip.

It's not clear, since the current required to feel a shock may be below
the threshold that will trip the GFCI.

A web search said about 5 mA to make a GFI trip, so I see what you're
saying. I thought they were much more sensitive than that, but if they
were they would probably trip too often.

--
Warren Block * Rapid City, South Dakota * USA

Terry wrote:

snip
They came out with polarized plugs to assure that the hot is connected
to the load first.

I think you have that backwards.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Pop` wrote:

wrote:

CJT wrote:

Warren Block wrote:


wrote:


I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI
outlet.

I plugged it in, and reached to flip the metal switch. When I
touched it, I got a fairly good jolt on my fingers. The GFI did
NOT trip. WHY? I thought that was the whole purpose of having
them.
This GFI was just purchased and installed, and the test button
works fine.


Two-prong plug on the fan, right?

Irrelevant.

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground
fault. It can't tell if it's just the fan motor between hot and
neutral, or the fan motor and you.


The current through his body returns to ground (just like the garage
floor test that follows), not neutral.


Certainly seems that the current through the GFCI should be
unbalanced. The only way it would be possibile for it to be equal
would be if
you grabbed one part of the fan that was shorted to hot, and another
that was connected to neutral.


No. I understand why you think that way, but it's not so. The current on
each line under ideal conditions will be exactly equal. Current is not
"lost" inside the fan motor. It's too much to go into here, but here's a
link might help you get started:
http://www.reliance.com/mtr/mtrthrmn.htm


I believe you need to rethink that in the case where there's a path
to ground that does not include the neutral (e.g. the case being
discussed).

Pop`






Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again,
and the GFI tripped instantly. For the heck of it, I put a piece
of wood under it (on the floor) and the GFI did not trip. This
proves that fan motor has leakage to the metal housing, so it goes
in the garbage. But I can not understand why the GFI did not trip
when my fingers got shocked ????


The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The
GFI sees that difference and trips.



--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .






--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Warren Block wrote:

CJT wrote:

Warren Block wrote:


The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.

The current through his body returns to ground (just like the garage
floor test that follows), not neutral.


Pretty clearly not the case since the GFI didn't trip. Unless it's
faulty.

.... or insensitive, which is the issue.

Or are you saying it's impossible to get shocked between hot
and neutral?



--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

On 29 Nov 2006 06:58:59 -0800, wrote:


wrote:
wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for
testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.

Dave


The test you did doesn't prove GFCI breakers are more sensitive and
faster than GFCI outlets. It just proves that the particular pair you
had behaved that way.

To the OP, what were you standing on, type of shoes, etc or in contact
with when you got the shock? It does seem that the current you got
was less than the amount needed to trip the GFCI.

Cement garage floor, leather shoes that were somewhat wet from walking
to the garage after a rain storm. I ONLY felt the shock on my
fingers. I was not touching anything with my other hand or other body
parts.

Mark

On 29 Nov 2006 07:15:42 -0800, wrote:

I would open up the fan and check to see that the metal casing is
actually grounded. Sounds like it's not. It should be.

It's NOT. This is probably a 1940's or 50's fan. No ground wire to
the outlet. Just the old 2 prong plugs which is all that was used on
that old stuff. When I get a box of stuff at those auctions for a
couple bucks, I dont waste too much time fixing the bad stuff unless
it's really valuable. I really did not need another fan anyhow, but
there were lots of other goodies in the box. I always test all the
stuff as soon as I get home and discard the bad stuff so it's not
laying around.

On 29 Nov 2006 11:01:28 -0800, wrote:


Terry wrote:
On 29 Nov 2006 07:24:10 -0800, wrote:


wrote:
I would open up the fan and check to see that the metal casing is
actually grounded. Sounds like it's not. It should be.


Since it's an old swivel type house fan, it's unlikely it has a
grounded cord to begin with. Also, even if it does, you can verify
that the case is grounded with a VOM, without taking it apart.


The first way to check if the case is grounded is by looking at the
plug. It has to have 3 prongs to be grounded.

If it is a two prong plug, and it sounds like that is what it is, It
will not be grounded.

This was a problem. Most likely you can flip the plug in the
receptacle and the "shock" will go away.

The hot is connected to the case in one situation and connected to the
switch for the motor lead in the other.


Good grief! If that were true, don;'t you think there would be an
awful lot of people dead from decades ago? I don;t know of any
appliances with a metal case, where if you simply plugged the cord in
one way vs the other, you could wind up dead, because the case is now
hot.


There were more electricution deaths in the past. Much of that old
stuff was more dangerous than the newer stuff. I cant begin to count
the number of times I got shocked when I was younger (in the 60's and
70's). Most of the time people are not killed, just shocked....
It was leakage, not direct short in most instances......
Those old metal encased power tools, as well as "hot chassis" radios
and tvs were the worst. I'd say the most shocks I got when I was
younger were from the old metal electric drills. Now they are plastic
cased, have 3 prong plugs or polarized plugs. Much safer....
Electricity is much safer these days.

I had an old tube type short wave radio when I was a kid. I ran a
long wire out the house to garage for an antenna. That radio had a
"hot chassis" In other words, if the plug was in one way, the chassis
was direct to the 120VAC. If reversed, it was hooked to the neutral.
So one day I had it turned on and connected the antenna wire, then was
going to connect the ground wire (shortwave antennas need a ground).
As I connected this ground wire, the thin wire literally burned off
the insulation and left a nasty burn on my hand. The house filled
with smoke and my dad got really ****ed and was going to throw the
radio away. After he calmed down he called his brother (my uncle),
who was an electrician. He installed a polarized grounded plug on my
radio, and we never had another problem with it. The days of having
to reverse the plug are no longer an issue.



They came out with polarized plugs to assure that the hot is connected
to the load first.

Pop` wrote:

snipped


GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground. Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Pop`



And, don't forget that the more recent GFCI's will detect a leakage path
between the neutral and ground as well, and thus disconnect power when
there's a neutral to ground short.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

wrote:

Jeff Wisnia wrote:

wrote:

wrote:


wrote:


wrote:


I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched
it, I got a fairly good jolt on my fingers. The GFI did NOT trip.
WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the garbage.
But I can not understand why the GFI did not trip when my fingers got
shocked ????

head to home despot or lowesers (or better yet a local place) and
purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for
testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI
outlets. I converted a circuit from GFCI outlet to GFCI breaker, just
for fun I tested the GFCI outlet on the circuit with the GFCI breaker.
Breaker was faster than the outlet.

Dave


The test you did doesn't prove GFCI breakers are more sensitive and
faster than GFCI outlets. It just proves that the particular pair you
had behaved that way.

To the OP, what were you standing on, type of shoes, etc or in contact
with when you got the shock? It does seem that the current you got
was less than the amount needed to trip the GFCI.


Yes, the test I did was anecdotal, but GFCI breakers are more
sensitive.

D


Do you happen to know whether this is by design or is it just "always
that way"?

And if by design, why?

I wouldn't think it would be difficult for the designers to set roughly
equal sensing levels/times in both types.

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.


I have to claim 'just in my experience' based on a few cases, I did
read something awhile ago and can't find the darn thing.

One common sense reason to claim the breaker 'more sensitive' though is
that the breaker will 'see' more wiring and equipment, and so the
background leakage the breaker sees will be higher than that which an
outlet will see (even if chained to a few more outlets).

Makes sense to me...I've encountered more than enough cases of GFCI
breakers tripping because of cruddy conditions along the circuit to
become an advocate of just using GFCI outlets.

Since the background leakage will be higher, the amount of fault
current required to hit the magic number of total leakage current
(usually 4-6mA) will be less.

Dave



--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

On Wed, 29 Nov 2006 16:16:40 -0500, Jeff Wisnia
wrote:

Pop` wrote:

snipped


GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground. Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Pop`



And, don't forget that the more recent GFCI's will detect a leakage path
between the neutral and ground as well, and thus disconnect power when
there's a neutral to ground short.

Jeff

Ok, I thought I knew how GFCI outlets worked, and now I find out
that I didn't know how the test button worked. Fine, I'm ok with
that, but this doesn't make any sense. It seems as if
a nuetral-ground leak should look exactly like a hot-ground
leak, except probably smaller, as there's less resistance downstream
of the correct current path.

How would you tell the difference even if you wanted to?

--Goedjn

On Nov 29, 1:06 pm, "Pop`" wrote:

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or
the fan motor and you.GFI,

Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground. Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Ground Fault is the correct terminology. You don't have to have a
grounding wire to get a ground fault.

Current going to ground on a path other than the neutral causes a
imbalanced load on the neutral.

The white wire is the ground(ed) connector. The third prong and green
wire is the ground(ing) conductor.

Jeff Wisnia wrote:
Pop` wrote:

snipped



GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original
case may have been ground, but now, because of poor terminology, is
considered the Neutral conductor. How a GFCI operates has nothing to
do with the ground. Since it senses differences in current between
the hot/neutral conductors, any third wire earth ground is irrelevant
to its opeartion. Hot amps = Neutral amps, all OK. Not equal, it
trips. It's literally that simple.

Pop`



And, don't forget that the more recent GFCI's will detect a leakage path
between the neutral and ground as well, and thus disconnect power when
there's a neutral to ground short.

Jeff

How do they distinguish an undesired "short" from the deliberate
connection between ground and neutral at the breaker panel?

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

On Wed, 29 Nov 2006 18:06:47 GMT, "Pop`"
wrote:

Warren Block wrote:
wrote:
I just went to an auction and came home with a whole bunch of old
junk. One of them was an old metal framed swivel house fan. I am
always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I
touched it, I got a fairly good jolt on my fingers. The GFI did NOT
trip. WHY? I thought that was the whole purpose of having them.
This GFI was just purchased and installed, and the test button works
fine.

Two-prong plug on the fan, right?

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or
the fan motor and you.

GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground. Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Pop`



Just for the heck of it, I plugged the fan in again, and had the
switch already turned on. The fan ran just fine on a wooden table.
Then I set it on the cement garage floor and plugged it in again, and
the GFI tripped instantly. For the heck of it, I put a piece of wood
under it (on the floor) and the GFI did not trip. This proves that
fan motor has leakage to the metal housing, so it goes in the
garbage. But I can not understand why the GFI did not trip when my
fingers got shocked ????

The cement floor provided a current path to ground, so the amount of
current on the neutral was different from what was on the hot. The
GFI sees that difference and trips.






I think of "ground" being the ground connection that you DON'T want.
That is, the circuit being grounded through you.
--
26 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"Unlike biological evolution. 'intelligent design' is
not a genuine scientific theory and, therefore, has
no place in the curriculum of our nation's public
school classes." -- Ted Kennedy

CJT wrote:
Jeff Wisnia wrote:

Pop` wrote:

snipped



GFI, Ground Fault Interruptor is a misnomer. "Ground" in the
original case may have been ground, but now, because of poor
terminology, is considered the Neutral conductor. How a GFCI
operates has nothing to do with the ground. Since it senses
differences in current between the hot/neutral conductors, any third
wire earth ground is irrelevant to its opeartion. Hot amps = Neutral
amps, all OK. Not equal, it trips. It's literally that simple.

Pop`



And, don't forget that the more recent GFCI's will detect a leakage
path between the neutral and ground as well, and thus disconnect power
when there's a neutral to ground short.

Jeff

How do they distinguish an undesired "short" from the deliberate
connection between ground and neutral at the breaker panel?


A GFCI *outlet* does not monitor the wiring from it to the breaker, only
any wiring down-stream of the outlet (and items plugged into the outlet).

A GFCI *breaker* would monitor all of the branch circuit.

Warren Block wrote:
CJT wrote:
Warren Block wrote:

The amount of current on the hot line is the same as that on the
neutral. So as far as the GFI is concerned, there's no ground fault.
It can't tell if it's just the fan motor between hot and neutral, or the
fan motor and you.
The current through his body returns to ground (just like the garage
floor test that follows), not neutral.

Pretty clearly not the case since the GFI didn't trip. Unless it's
faulty. Or are you saying it's impossible to get shocked between hot
and neutral?


The threshold of sensation is three milliamperes. It takes six or more
to trip a Class A GFCI.
--
Tom Horne

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

Goedjn wrote:
On Wed, 29 Nov 2006 16:16:40 -0500, Jeff Wisnia
wrote:


Pop` wrote:

snipped


GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground. Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Pop`



And, don't forget that the more recent GFCI's will detect a leakage path
between the neutral and ground as well, and thus disconnect power when
there's a neutral to ground short.

Jeff


Ok, I thought I knew how GFCI outlets worked, and now I find out
that I didn't know how the test button worked. Fine, I'm ok with
that, but this doesn't make any sense. It seems as if
a nuetral-ground leak should look exactly like a hot-ground
leak, except probably smaller, as there's less resistance downstream
of the correct current path.

How would you tell the difference even if you wanted to?

--Goedjn

I didn't SAY that they tell the "difference". Since their only "output
means" is to open the circuit between the supply and load side of the
breaker for either kind of fault, hot to ground leakage or neutral to
ground shorts.

They will detect and "pop" if you make a connection between their
neutral output and ground, even with nothing at all connected to their
hot output.

Before you worry too much about how they can sense a connection between
two leads which should be at the same potential (neutral and ground) if
there isn't any current flowing in either of them, I'll tell you that
there will be, because the GFCI contains a current transformer which
adds a small in-phase voltage to both the hot and neutral output leads.

That voltage on the neutral lead will cause a small current flow if the
neutral gets connected to ground. The normal differential current
sensing portion of the GFCI responds to the current flowing in the
neutral which has not come from the hot output and "pops" the GFCI.

Trust me it works... Or test it yourself with a neutral to ground short.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.98*10^14 fathoms per fortnight.

On Thu, 30 Nov 2006 00:14:03 -0500, Jeff Wisnia
wrote:

Goedjn wrote:
On Wed, 29 Nov 2006 16:16:40 -0500, Jeff Wisnia
wrote:


Pop` wrote:

snipped


GFI, Ground Fault Interruptor is a misnomer. "Ground" in the original case
may have been ground, but now, because of poor terminology, is considered
the Neutral conductor. How a GFCI operates has nothing to do with the
ground. Since it senses differences in current between the hot/neutral
conductors, any third wire earth ground is irrelevant to its opeartion. Hot
amps = Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Pop`



And, don't forget that the more recent GFCI's will detect a leakage path
between the neutral and ground as well, and thus disconnect power when
there's a neutral to ground short.

Jeff


Ok, I thought I knew how GFCI outlets worked, and now I find out
that I didn't know how the test button worked. Fine, I'm ok with
that, but this doesn't make any sense. It seems as if
a nuetral-ground leak should look exactly like a hot-ground
leak, except probably smaller, as there's less resistance downstream
of the correct current path.

How would you tell the difference even if you wanted to?

--Goedjn

I didn't SAY that they tell the "difference". Since their only "output
means" is to open the circuit between the supply and load side of the
breaker for either kind of fault, hot to ground leakage or neutral to
ground shorts.

They will detect and "pop" if you make a connection between their
neutral output and ground, even with nothing at all connected to their
hot output.

Before you worry too much about how they can sense a connection between
two leads which should be at the same potential (neutral and ground) if
there isn't any current flowing in either of them, I'll tell you that
there will be, because the GFCI contains a current transformer which
adds a small in-phase voltage to both the hot and neutral output leads.

That voltage on the neutral lead will cause a small current flow if the
neutral gets connected to ground. The normal differential current
sensing portion of the GFCI responds to the current flowing in the
neutral which has not come from the hot output and "pops" the GFCI.

Trust me it works... Or test it yourself with a neutral to ground short.

Jeff

What was confusing me was the implication that there's an
older type of GFCI that will trip on a hot/ground short,
but not on a nuetral/ground short. Was I inferring more
from "more recent GFCIs" than was intended?

Jeff Wisnia wrote:

Goedjn wrote:

On Wed, 29 Nov 2006 16:16:40 -0500, Jeff Wisnia
wrote:


Pop` wrote:

snipped


GFI, Ground Fault Interruptor is a misnomer. "Ground" in the
original case may have been ground, but now, because of poor
terminology, is considered the Neutral conductor. How a GFCI
operates has nothing to do with the ground. Since it senses
differences in current between the hot/neutral conductors, any third
wire earth ground is irrelevant to its opeartion. Hot amps =
Neutral amps, all OK. Not equal, it trips. It's literally that
simple.

Pop`



And, don't forget that the more recent GFCI's will detect a leakage
path between the neutral and ground as well, and thus disconnect
power when there's a neutral to ground short.

Jeff



Ok, I thought I knew how GFCI outlets worked, and now I find out that
I didn't know how the test button worked. Fine, I'm ok with
that, but this doesn't make any sense. It seems as if
a nuetral-ground leak should look exactly like a hot-ground leak,
except probably smaller, as there's less resistance downstream
of the correct current path.

How would you tell the difference even if you wanted to?

--Goedjn


I didn't SAY that they tell the "difference". Since their only "output
means" is to open the circuit between the supply and load side of the
breaker for either kind of fault, hot to ground leakage or neutral to
ground shorts.

They will detect and "pop" if you make a connection between their
neutral output and ground, even with nothing at all connected to their
hot output.

Before you worry too much about how they can sense a connection between
two leads which should be at the same potential (neutral and ground) if
there isn't any current flowing in either of them, I'll tell you that
there will be, because the GFCI contains a current transformer which
adds a small in-phase voltage to both the hot and neutral output leads.

.... which suggests it won't work unless/until something is drawing
current from the "hot" lead. I realize that's not much of a
restriction.


That voltage on the neutral lead will cause a small current flow if the
neutral gets connected to ground. The normal differential current
sensing portion of the GFCI responds to the current flowing in the
neutral which has not come from the hot output and "pops" the GFCI.

Trust me it works... Or test it yourself with a neutral to ground short.

Jeff



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