I have a Leviton GFI in my bathroom which I happened to test today
with my little 3 prong/3 lamp tester. The socket shows as being wired
correctly (2 yellow lights, no red) but pressing the 'trip' button on
my tester failed to trip the GFI (note when the trip button is
depressed all 3 lights (yellow-yellow-red) light up on the tester).
The test button on the GFI works fine though.

Still figuring that something must be wrong with the GFI, I replaced
it with a new one. The physical wiring is correct and again the tester
shows it is wired correctly. Also, the little green LED on the GFI is
lit presumably showing it is working. But again the trip button failed to
trigger the GFI even though again the manual test button on the GFI
worked.

My GFI tester worked fine triggering the other 13 or so GFI's in my house.

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?

I am stumped...

blueman writes:

I have a Leviton GFI in my bathroom which I happened to test today
with my little 3 prong/3 lamp tester. The socket shows as being wired
correctly (2 yellow lights, no red) but pressing the 'trip' button on
my tester failed to trip the GFI (note when the trip button is
depressed all 3 lights (yellow-yellow-red) light up on the tester).
The test button on the GFI works fine though.
CORRECTION, when I hold down the test button the lights show:
off, yellow, red
which in a normal situation would be signalling a Hot/Neutral reverse
but is probably just an artifact of the test button shunting current.

Still figuring that something must be wrong with the GFI, I replaced
it with a new one. The physical wiring is correct and again the tester
shows it is wired correctly. Also, the little green LED on the GFI is
lit presumably showing it is working. But again the trip button failed to
trigger the GFI even though again the manual test button on the GFI
worked.

My GFI tester worked fine triggering the other 13 or so GFI's in my house.

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?

I am stumped...

In article on Thu, 23 Jul 2009
23:32:52 -0400, blueman wrote:

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?


Your GFIs, both old and new, are fine. On a GFI, the tester built-in to
the receptacle works by shunting some current from hot to neutral.

Your hand held tester works a little differently - it shunts some
current from hot to ground. Either there is a grounding problem on that
circuit, or the hand held tester itself is faulty.

--
Seth Goodman

On Fri, 24 Jul 2009 05:24:09 -0400, Seth Goodman
wrote:

In article on Thu, 23 Jul 2009
23:32:52 -0400, blueman wrote:

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?


Your GFIs, both old and new, are fine. On a GFI, the tester built-in to
the receptacle works by shunting some current from hot to neutral.

Less incompletely, hot on the LOAD side to neutral on the LINE side.

Your hand held tester works a little differently - it shunts some
current from hot to ground. Either there is a grounding problem on that
circuit, or the hand held tester itself is faulty.

"blueman" wrote in message
...
I have a Leviton GFI in my bathroom which I happened to test today
with my little 3 prong/3 lamp tester. The socket shows as being wired
correctly (2 yellow lights, no red) but pressing the 'trip' button on
my tester failed to trip the GFI (note when the trip button is
depressed all 3 lights (yellow-yellow-red) light up on the tester).
The test button on the GFI works fine though.

Still figuring that something must be wrong with the GFI, I replaced
it with a new one. The physical wiring is correct and again the tester
shows it is wired correctly. Also, the little green LED on the GFI is
lit presumably showing it is working. But again the trip button failed to
trigger the GFI even though again the manual test button on the GFI
worked.

My GFI tester worked fine triggering the other 13 or so GFI's in my house.

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?

I am stumped...


*Pull out the GFI and use a pigtail socket and bulb to confirm that you have
a functional ground.

On Jul 24, 9:36*am, "John Grabowski" wrote:
"blueman" wrote in message

...





I have a Leviton GFI in my bathroom which I happened to test today
with my little 3 prong/3 lamp tester. The socket shows as being wired
correctly (2 yellow lights, no red) but pressing the 'trip' button on
my tester failed to trip the GFI (note when the trip button is
depressed all 3 lights (yellow-yellow-red) light up on the tester).
The test button on the GFI works fine though.

Still figuring that something must be wrong with the GFI, I replaced
it with a new one. The physical wiring is correct and again the tester
shows it is wired correctly. Also, the little green LED on the GFI is
lit presumably showing it is working. *But again the trip button failed to
trigger the GFI even though again the manual test button on the GFI
worked.

My GFI tester worked fine triggering the other 13 or so GFI's in my house.

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?

I am stumped...

*Pull out the GFI and use a pigtail socket and bulb to confirm that you have
a functional ground.- Hide quoted text -

- Show quoted text -

Suggestion/question?????.
GFIs trip when there is a certain amount of (milliamps) unbalance
between current flowing in the live and neutral conductors; true?
If the tester itself use say LEDs which take a very small amounts of
current maybe there is not enough (total) current flowing to unbalance
the GFI?
Not familiar with the circuit arrangement of the tester.
Or as suggested the ground is imperfect.

*Pull out the GFI and use a pigtail socket and bulb to confirm that you have
a functional ground.- Hide quoted text -

- Show quoted text -

A GFI's operation has nothing to do with the ground. It monitors the
current flowing throught the hot and neutral.

In article , Mike rock wrote:
*Pull out the GFI and use a pigtail socket and bulb to confirm that you have
a functional ground.


A GFI's operation has nothing to do with the ground. It monitors the
current flowing throught the hot and neutral.

If you'd read the entire thread, you would have seen that the OP stated that
the GFCI trips normally when he presses the test button on the GFCI, but fails
to trip when he presses the test button on his plug-in tester -- and you would
have also seen an explanation of why this is so: the plug-in tester shunts
current to *ground*, and *cannot* trip the GFCI unless there is a functional
ground at the outlet.

(Doug Miller) writes:

In article , Mike rock wrote:
*Pull out the GFI and use a pigtail socket and bulb to confirm that you have
a functional ground.


A GFI's operation has nothing to do with the ground. It monitors the
current flowing throught the hot and neutral.

If you'd read the entire thread, you would have seen that the OP stated that
the GFCI trips normally when he presses the test button on the GFCI, but fails
to trip when he presses the test button on his plug-in tester -- and you would
have also seen an explanation of why this is so: the plug-in tester shunts
current to *ground*, and *cannot* trip the GFCI unless there is a functional
ground at the outlet.

Yes - that now explains almost everything.
But how does the GFI test button work? Does it really just test if the
breaker works or does it have a way of testing that the current
monitoring part works? (I'm not sure how it would do that since
without shunting current to ground, it really has nowhere else to
shunt it and create a current imbalance between hot and neutral).

On 2009-07-24, blueman wrote:

But how does the GFI test button work? Does it really just test if
the breaker works or does it have a way of testing that the current
monitoring part works?

The GFI uses a current transformer to detect a downstream imbalance
between hot and neutral current. The test button has access to the
hot and neutral both before and after this current transformer. So it
shunts a small amount of current from the hot after the transformer to
the neutral before the transformer (or vice versa, I don't know),
which creates an imbalance in the current transformer.

Cheers, Wayne

"John Grabowski" writes:

"blueman" wrote in message
...
I have a Leviton GFI in my bathroom which I happened to test today
with my little 3 prong/3 lamp tester. The socket shows as being wired
correctly (2 yellow lights, no red) but pressing the 'trip' button on
my tester failed to trip the GFI (note when the trip button is
depressed all 3 lights (yellow-yellow-red) light up on the tester).
The test button on the GFI works fine though.

Still figuring that something must be wrong with the GFI, I replaced
it with a new one. The physical wiring is correct and again the tester
shows it is wired correctly. Also, the little green LED on the GFI is
lit presumably showing it is working. But again the trip button failed to
trigger the GFI even though again the manual test button on the GFI
worked.

My GFI tester worked fine triggering the other 13 or so GFI's in my house.

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?

I am stumped...


*Pull out the GFI and use a pigtail socket and bulb to confirm that
you have a functional ground.

BINGO - no *functional* ground.

Though not clear why the gfi tester didn't read it as an open ground
unless there was some "inducted" current flow from ground to neutral
in the cable sheathing. Also, interestingly, a digital (not analog)
ohmeter read 120v between hot and ground again maybe consistent with
inducted current. But as always resistive loads (i.e. bulb on a
pigtail) tell the truth.

This all does make me worry though about the accuracy of the low-end
GFI tester I have -- i.e., how many open grounds are there lurking
somewhere in the house that the tester has failed to detect...

I fixed the problem by tracing upstream where I found that the ground
wire had broken off in the box. Problem solved & thanks for the help.

blueman writes:

"John Grabowski" writes:

"blueman" wrote in message
...
I have a Leviton GFI in my bathroom which I happened to test today
with my little 3 prong/3 lamp tester. The socket shows as being wired
correctly (2 yellow lights, no red) but pressing the 'trip' button on
my tester failed to trip the GFI (note when the trip button is
depressed all 3 lights (yellow-yellow-red) light up on the tester).
The test button on the GFI works fine though.

Still figuring that something must be wrong with the GFI, I replaced
it with a new one. The physical wiring is correct and again the tester
shows it is wired correctly. Also, the little green LED on the GFI is
lit presumably showing it is working. But again the trip button failed to
trigger the GFI even though again the manual test button on the GFI
worked.

My GFI tester worked fine triggering the other 13 or so GFI's in my house.

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?

I am stumped...


*Pull out the GFI and use a pigtail socket and bulb to confirm that
you have a functional ground.

BINGO - no *functional* ground.

Though not clear why the gfi tester didn't read it as an open ground
unless there was some "inducted" current flow from ground to neutral
in the cable sheathing. Also, interestingly, a digital (not analog)
ohmeter read 120v between hot and ground again maybe consistent with
inducted current. But as always resistive loads (i.e. bulb on a
pigtail) tell the truth.

This all does make me worry though about the accuracy of the low-end
GFI tester I have -- i.e., how many open grounds are there lurking
somewhere in the house that the tester has failed to detect...

Actually it is kind of ironic that while the GFI tester didn't detect
a floating ground in its normal mode, it (indirectly) signalled a bad
ground by failing to trip the GFI when the test button was pressed.

Do better quality GFI testers do a better job of testing for
*functional* grounds?

Also this led me to experiment and I noticed that if the ground and
neutral pin on the GFI tester are both wired to neutral then the GFI
tests ok which in some ways is electrically understandable since
ultimately the neutral and hots are bonded at the service
entrance. However, it is not a code ground.

Do better quality GFI testers have a way of testing for functional
ground vs. neutral used as ground? (perhaps as a proxy they could
measure resistance between neutral and ground???)

Much safer, now. Good job.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"blueman" wrote in message
...

I fixed the problem by tracing upstream where I found that
the ground
wire had broken off in the box. Problem solved & thanks for
the help.

On Jul 24, 4:01*pm, "Stormin Mormon"
wrote:
Much safer, now. Good job.

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"blueman" wrote in message

...

I fixed the problem by tracing upstream where I found that
the ground
wire had broken off in the box. Problem solved & thanks for
the help.

Thanks for posting the outcome. A broken ground; glad the OP found it.

BTW: I agree with the person who posted;
Quote: "If you'd read the entire thread, you would have seen that the
OP stated that
the GFCI trips normally when he presses the test button on the GFCI,
but fails
to trip when he presses the test button on his plug-in tester -- and
you would
have also seen an explanation of why this is so: the plug-in tester
shunts
current to *ground*, and *cannot* trip the GFCI unless there is a
functional
ground at the outlet.".

It seemed obvious the question was why didn't the 'test' feature of
the 'tester' work as expected!

Interesting thread and as often makes one think (and learn!). Thanks
for posting the original question.

stan writes:

On Jul 24, 4:01*pm, "Stormin Mormon"
wrote:
Much safer, now. Good job.

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"blueman" wrote in message

...

I fixed the problem by tracing upstream where I found that
the ground
wire had broken off in the box. Problem solved & thanks for
the help.

Thanks for posting the outcome. A broken ground; glad the OP found it.

BTW: I agree with the person who posted;
Quote: "If you'd read the entire thread, you would have seen that the
OP stated that
the GFCI trips normally when he presses the test button on the GFCI,
but fails
to trip when he presses the test button on his plug-in tester -- and
you would
have also seen an explanation of why this is so: the plug-in tester
shunts
current to *ground*, and *cannot* trip the GFCI unless there is a
functional
ground at the outlet.".

It seemed obvious the question was why didn't the 'test' feature of
the 'tester' work as expected!

Interesting thread and as often makes one think (and learn!). Thanks
for posting the original question.

Your welcome
And I learned a lot too -- it is always sobering to learn the
limitations of your test equipment (or any other limitations).

I wonder how many professionals (e.g., electricians, home inspectors,
city inspectors) let alone DIY'ers realize that:

1. A GFI tester can show the circuit being fine even though there is
no functional ground. Similarly a (digital) multimeter can read the
full 120V hot-to-ground. Both presumably due to induced currents.

2. The test button on a GFI can work also without a functional ground.

It all makes sense retrospectively, but probably not something that
most people think about...

blueman wrote:
I have a Leviton GFI in my bathroom which I happened to test today
with my little 3 prong/3 lamp tester. The socket shows as being wired
correctly (2 yellow lights, no red) but pressing the 'trip' button on
my tester failed to trip the GFI (note when the trip button is
depressed all 3 lights (yellow-yellow-red) light up on the tester).
The test button on the GFI works fine though.

Still figuring that something must be wrong with the GFI, I replaced
it with a new one. The physical wiring is correct and again the tester
shows it is wired correctly. Also, the little green LED on the GFI is
lit presumably showing it is working. But again the trip button failed to
trigger the GFI even though again the manual test button on the GFI
worked.

My GFI tester worked fine triggering the other 13 or so GFI's in my house.

Any idea what could be happening here?
Why would both the old and new GFI show as being wired correctly and
yet fail to trip?

I am stumped...
Hmm,
I'd measure Ohmage between ground and neutral with a meter on that
outlet. Reading should be very close to zero Ohm.