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GFCI didn't trip.. welder gave me a very small shock

M

Michael Shaffer

Jan 1, 1970
0
I was changing the rod on my arc welder and put my elbow down on the wet
ground and I must have completed the circuit because my thumb got
tingly. I guess I was asking for it because the ground was wet and my
gloves were wet. Anyways, shouldn't the GFCI of tripped or not?
 
E

Ecnerwal

Jan 1, 1970
0
Michael Shaffer said:
I was changing the rod on my arc welder and put my elbow down on the wet
ground and I must have completed the circuit because my thumb got
tingly. I guess I was asking for it because the ground was wet and my
gloves were wet. Anyways, shouldn't the GFCI of tripped or not?

No. The GFCI looks at the power going out of the wall, to the primary
coil of the welder transformer/power supply, and back into the wall - if
out does not equal in, it trips. But a GFCI cannot tell what's happening
on the secondary of the welder - no difference to it if you are getting
zapped or steel is getting welded. You'll just have to depend on your
brain.
 
B

Bob Weiss

Jan 1, 1970
0
Michael Shaffer wrote:
Anyways, shouldn't the GFCI of tripped or not?


Nope.

The welder is essentially an isolation transformer. The GFCI is only
looking for a ground fault on the primary side of the transformer. You
got a shock from the secondary side, and a primary GFCI won't do a thing
to prevent it, as you discovered....

Bob Weiss N2IXK
 
T

Tm

Jan 1, 1970
0
| Michael Shaffer wrote:
| Anyways, shouldn't the GFCI of tripped or not?
|
|
| Nope.
|
| The welder is essentially an isolation transformer. The GFCI is only
| looking for a ground fault on the primary side of the transformer. You
| got a shock from the secondary side, and a primary GFCI won't do a thing
| to prevent it, as you discovered....
|
| Bob Weiss N2IXK

Is it a total isolation? Or is there a ground-to-ground connection between
primary and secondary?

It's total. But that is not relavent to the GFCI issue.

Tm
 
B

Beachcomber

Jan 1, 1970
0
| The welder is essentially an isolation transformer. The GFCI is only
| looking for a ground fault on the primary side of the transformer. You
| got a shock from the secondary side, and a primary GFCI won't do a thing
| to prevent it, as you discovered....
|
| Bob Weiss N2IXK

Is it a total isolation? Or is there a ground-to-ground connection between
primary and secondary?

What everyone says is true about the secondary... It won't trip.
But does the GFCI work itself? There should be a test switch and a
reset button on it to simulate a ground fault.

Results?
 
J

John G

Jan 1, 1970
0
|
| |>
|> | Michael Shaffer wrote:
|> | Anyways, shouldn't the GFCI of tripped or not?
|> |
|> |
|> | Nope.
|> |
|> | The welder is essentially an isolation transformer. The GFCI is only
|> | looking for a ground fault on the primary side of the transformer. You
|> | got a shock from the secondary side, and a primary GFCI won't do a thing
|> | to prevent it, as you discovered....
|> |
|> | Bob Weiss N2IXK
|>
|> Is it a total isolation? Or is there a ground-to-ground connection
| between
|> primary and secondary?
|>
|
| It's total. But that is not relavent to the GFCI issue.

It can me. If there is a ground or neutral connection between primary
and secondary, it can form an additional path, creating a common ground
for the otherwise separately derived system. A ground fault can then
flow from a hot wire on the secondary, to real ground, to the ground or
neutral wire, to the power connection coming into the transformer, and
over the ground wire between primary and secondary completing the circuit.
It is then a potential shock path. If the ground clamp comes loose on
the working object, you may still have a circuit if that object touches
ground in some way (like through human contact).

If that connection is not present, you can be raising the voltage float
on the secondary system due to capacitive coupling. Think of it as being
in a ground fault loop in series with a capacitor.

Ground fault protection of a welding system would be a good idea. It can
potentially be a difficult design to protect it, given the way it is used.
But it would not be impossible. For example, the ground can be connected
between primary and secondary, and a current sensor placed on it to check
for any fault currents at the 4 milliamp level to protect humans. And
additional current sensor on the actual welding leads could smooth out
the current spikes first, and then see what difference remains.
http://ka9wgn.ham.org/ |
----------------------------------------------------------------------
-------
What a lot of drivel.
The OP said he put his wet gloves and person across the output which is
probably 100 volts or some such with a current rating of MANY AMPS.
No GFCI or other device will protect him from stupidity.
It was designed to weld steel. it will most likely do a good job of
welding a stupid person.
If you can detect that the load is a person and not a piece of steel
then maybe you can save him.
 
O

Old Nick

Jan 1, 1970
0
On 15 Jun 2004 08:55:09 GMT, [email protected] vaguely
proposed a theory
.......and in reply I say!:
remove ns from my header address to reply via email


(1) but is not in the purview of earth fault cuiscuit breakers.

(2) one constantly stated advantage of trannies over other voltage
reduction circuits, You cna _only_ get the volstage. SUPTA
Ground fault protection of a welding system would be a good idea. It can
potentially be a difficult design to protect it, given the way it is used.
But it would not be impossible. For example, the ground can be connected
between primary and secondary, and a current sensor placed on it to check
for any fault currents at the 4 milliamp level to protect humans. And
additional current sensor on the actual welding leads could smooth out
the current spikes first, and then see what difference remains.

*******************************************************

Sometimes in a workplace you find snot on the wall of
the toilet cubicles. You feel "What sort of twisted
child would do this?"....the internet seems full of
them. It's very sad
 
J

Joel Corwith

Jan 1, 1970
0
Beachcomber said:
What everyone says is true about the secondary... It won't trip.
But does the GFCI work itself? There should be a test switch and a
reset button on it to simulate a ground fault.

I've run into units in which the test switch trips the unit, but a GFCI
tester doesn't. I don't trust the test buttons anymore.

Joel. phx
 
L

Louis Bybee

Jan 1, 1970
0
Joel Corwith said:
I've run into units in which the test switch trips the unit, but a GFCI
tester doesn't. I don't trust the test buttons anymore.

Joel. phx

Had you considered the possibility that your GFCI Tester was defective, and
the test button on the GFCI was functioning properly?

If you have the skills to work with live circuits safely (there is the
potential for a lethal shock) you could construct a circuit that could tell
you if the GFCI was functioning as intended.

With all live components insulated, and enclosed in a box you could assemble
a circuit where a three conductor cord with the appropriate male plug on the
other end was brought into the box with a 6.8k resistor connected to the hot
wire to limit current to approximately 18 ma. The other lead of the resistor
would be connected to a 100k pot. From the wiper of the pot a connection
would be made to a shrouded banana receptacle. A second shrouded banana
receptacle would connect to the ground conductor. With a multi meter
connected to the banana receptacles, and set to the current mode you could
read the current flowing in the circuit when plugged into the GFCI device.

With the pot adjusted to one extreme approximately 1 ma would flow. At the
opposite extreme approximately 18 ma would flow. With nothing else connected
to the GFCI except your test circuit (either the other receptacle on the
GFCI, or to the load terminals) you could slowly increase the current
flowing to observe where the device tripped. Recording that reading, and
reconnecting the other loads to the GFCI would allow you to repeat the test
and subtract to determine the approximate leakage of the load normally
connected to the GFCI device. I believe a GFCI device designed for
convenience outlets is specified to trip between 4 & 6 ma.

Measuring the current load your tester places on the GFCI circuit could also
indicate it's place in the puzzle.

Louis
 
L

Louis Bybee

Jan 1, 1970
0
Louis Bybee said:
Had you considered the possibility that your GFCI Tester was defective, and
the test button on the GFCI was functioning properly?

If you have the skills to work with live circuits safely (there is the
potential for a lethal shock) you could construct a circuit that could tell
you if the GFCI was functioning as intended.

With all live components insulated, and enclosed in a box you could assemble
a circuit where a three conductor cord with the appropriate male plug on the
other end was brought into the box with a 6.8k resistor connected to the hot
wire to limit current to approximately 18 ma. The other lead of the resistor
would be connected to a 100k pot. From the wiper of the pot a connection
would be made to a shrouded banana receptacle. A second shrouded banana
receptacle would connect to the ground conductor. With a multi meter
connected to the banana receptacles, and set to the current mode you could
read the current flowing in the circuit when plugged into the GFCI device.

With the pot adjusted to one extreme approximately 1 ma would flow. At the
opposite extreme approximately 18 ma would flow. With nothing else connected
to the GFCI except your test circuit (either the other receptacle on the
GFCI, or to the load terminals) you could slowly increase the current
flowing to observe where the device tripped. Recording that reading, and
reconnecting the other loads to the GFCI would allow you to repeat the test
and subtract to determine the approximate leakage of the load normally
connected to the GFCI device. I believe a GFCI device designed for
convenience outlets is specified to trip between 4 & 6 ma.

Measuring the current load your tester places on the GFCI circuit could also
indicate it's place in the puzzle.

Louis
Another thought occurred to me after hitting send that could be your issue.

If the GFCI device were installed in a circuit where the ground was
defective or non existent, it would operate as you describe. The test button
on the unit would function normally, and the tester wouldn't (it needs the
functional ground wire).

Louis--
*********************************************
Remove the two fish in address to respond
 
J

John G

Jan 1, 1970
0
| What a lot of drivel.

Obviously you missed the point.

| The OP said he put his wet gloves and person across the output which is
| probably 100 volts or some such with a current rating of MANY AMPS.
| No GFCI or other device will protect him from stupidity.
| It was designed to weld steel. it will most likely do a good job of
| welding a stupid person.
| If you can detect that the load is a person and not a piece of steel
| then maybe you can save him.

So by using your reasoning, since it is possible for people to kill
themselves by sticking their fingers in a light socket, or sticking
paper clips into an outlet, then having ground wires and GFCI
protectors for other more common modes of electric shock is not needed.
I never said Grounds, GFCIs or any other protective system was not
required.
I just said you cannot protect a person from putting himself in place of
the EXPECTED load.
An this is what the OP did in the first place at the beginning of this
thread.
 
J

Joel Corwith

Jan 1, 1970
0
Louis Bybee said:
Had you considered the possibility that your GFCI Tester was defective, and
the test button on the GFCI was functioning properly?

Yes, except it was with a class of 12 who each had a tester (though not all
checked). Good point on the ground, however the ground did appear
functional, though a false ground is a possibility (although not probable
for the year of the structure).

Joel. phx
 
G

Gunner

Jan 1, 1970
0
What a lot of drivel.
The OP said he put his wet gloves and person across the output which is
probably 100 volts or some such with a current rating of MANY AMPS.
No GFCI or other device will protect him from stupidity.
It was designed to weld steel. it will most likely do a good job of
welding a stupid person.
If you can detect that the load is a person and not a piece of steel
then maybe you can save him.

I lit myself up pretty good one hot summer day, while laying in the
bilge of an aluminum boat, while wearing only shorts and a welders
leathers and welding underneath a brace below the steering gear. I
grabbed the rod without gloves to change out the stub. My bare and
sweaty back was in full contact with the hull..which was grounded to
my workpiece.

Lincoln buzzbox, straight AC

Gunner

That rifle hanging on the wall of the working-class flat or labourer's
cottage is the symbol of democracy. It is our job to see that it stays
there.
- George Orwell
 
G

Gunner

Jan 1, 1970
0
Hmmmmn, there was supposed to be a smiley somewhere around here.
<G>

Gunner

That rifle hanging on the wall of the working-class flat or labourer's
cottage is the symbol of democracy. It is our job to see that it stays
there.
- George Orwell
 
B

Ben Miller

Jan 1, 1970
0
Beachcomber said:
I've run into units in which the test switch trips the unit, but a GFCI
tester doesn't. I don't trust the test buttons anymore.

The GFCI circuit may have been ungrounded. External testers require a
ground, or they will not trip the GFCI. The internal test button does not
require a ground. The internal buttons are reliable, and there is no reason
not to trust them.

Ben Miller

Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com
 
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