Electrical box ground wiring.

[David Farber]

While trying to troubleshoot why some kitchen electrical outlets in this
junction box weren't working, I did a bit of research. Apparently, there is
supposed to be a ground connection (other than the screw going through the
frame of the outlet to the box) from the GFCI outlet to the junction box.
(see photo:
http://webpages.charter.net/mrfixiter/images/Home/Junction_box.jpg ) Can I
just run some wire from the green screw terminal on the GFCI outlet to the
box? Where would I attach it to the box? By the way, the problem with the
outlet was that the breaker tripped in the GFCI. There are three pairs of
wires in the photo. One is the incoming AC. One feeds another GFCI outlet
down the line. The last pair goes to a switch in the same junction box which
turns on some lights in the kitchen.

Thanks for your reply.
--
David Farber
Los Osos, CA

 

Those things work with or without a ground. It could be nuisance tripping, it happens with anything. If that is the case it is defective. To be sure disconnect the load side and see if it still trips.

If it does and there is nothing plugged into it, it is bad, if it does not trip, it is something off the line coming out of it that it is supposed to protect, and actually is probably doing its job.

The way to find out all what runs off it is to disconnect the OUTPUT neutral and with the branch circuit turned off, go to every neutrl around. I have wired them to protect lights, you have to for the over the sink lights. In some places you can't even do that, you have to install a GFCI breaker and run all new to the kitchen or sometimes bath. The NEC does ot necessarily require it, but some rehab codes do.

But who cares. You want the thing to work.

Take the load off and see what happens.

 

>"This was the first time this GFCI has tripped. "

If it continues to work it was a nuisance trip. they are quite sensitive. A little spray of water into anything runniong off it can trip it. In fact certain funny loading appliances can make it trip due to certain harmonics on the power line, depending on how they are designed, even if they are not plugged into it sometimes.

I though you meant it kept on tripping.

 

[David Platt]

While trying to troubleshoot why some kitchen electrical outlets in this
junction box weren't working, I did a bit of research. Apparently, there is
supposed to be a ground connection (other than the screw going through the
frame of the outlet to the box) from the GFCI outlet to the junction box.
(see photo:
http://webpages.charter.net/mrfixiter/images/Home/Junction_box.jpg ) Can I
just run some wire from the green screw terminal on the GFCI outlet to the
box? Where would I attach it to the box? By the way, the problem with the
outlet was that the breaker tripped in the GFCI. There are three pairs of
wires in the photo. One is the incoming AC. One feeds another GFCI outlet
down the line. The last pair goes to a switch in the same junction box which
turns on some lights in the kitchen.

Well, let's see.

Having a ground-wire connection to the GFCI itself is a good idea, if
a good ground is available. It's not (I believe) strictly required -
a GFCI can be used on a two-wire circuit.

In your case, it does appear that the outlet box is probably grounded;
I see what appear to be bare ground wires entering at the back. These
wires *should* be securely bonded to the junction box - this would
probably be done right at the back, where the screws and wire clamps
are located. I can't tell if those ground wires are in fact securely
bonded to the box, or whether they're just sitting there.

If you're going to ground the GFCI, you'd run a wire from the green
screw terminal, to a connection point with one of those ground
wires... e.g. if the existing bare ground wire is screwed to the box
at some point, you'd want to connect the ground wire to that screw or
to another box-mounted screw not too far from it.

Now, the lack of a ground wire from the GFCI shouldn't tend to cause
the GFCI to "trip" mistakenly. A proper GFCI operates by measuring
"current imbalance" between the hot and neutral wires. If more flows
through one than through the other, then it's almost certain that some
current is flowing to ground (somewhere) rather than back through
neutral... and this is a Bad Thing (shock hazard, or shock occurring).

A GFCI's protection does *not* depend on measuring current flowing
through its own ground wire. That's why they can be used to protect
two-wire circuits, where there isn't even a good ground connection
available... this makes them useful for retrofitting older house
circuits for improved safety.

Having a good ground on a GFCI circuit is actually likely to make the
GFCI trip sooner, rather than later, if an electrical fault exists.
For example, if you have an appliance with a grounded case, and a leak
or short develops between "hot" and the case, the GFCI will trip
instantly. If the case isn't grounded through the third prong
(e.g. if there is no ground prong, or if it's cut off or defeated with
a "cheater", or if it's plugged into a 3-wire outlet with no actual
ground) then the fault won't result in current flow to ground... until
somebody touches the case and also touches something grounded. At
that point they'll get a shock, and (knock on wood) the GFCI will trip
fast enough to protect them from anything more than a scare.

So, if your GFCI is tripping, then I don't expect that grounding the
GFCI more securely is likely to change this. You may actually have a
current-leak-to-ground on one of the circuits you are protecting. Or,
possibly, interference from a strong local radio transmitter is
"falsing" the GFCI - it does happen.

 

[David Farber]

David Platt wrote:

While trying to troubleshoot why some kitchen electrical outlets in
this junction box weren't working, I did a bit of research.
Apparently, there is supposed to be a ground connection (other than
the screw going through the frame of the outlet to the box) from the
GFCI outlet to the junction box. (see photo:
http://webpages.charter.net/mrfixiter/images/Home/Junction_box.jpg )
Can I just run some wire from the green screw terminal on the GFCI
outlet to the box? Where would I attach it to the box? By the way,
the problem with the outlet was that the breaker tripped in the
GFCI. There are three pairs of wires in the photo. One is the
incoming AC. One feeds another GFCI outlet down the line. The last
pair goes to a switch in the same junction box which turns on some
lights in the kitchen.

Well, let's see.

Having a ground-wire connection to the GFCI itself is a good idea, if
a good ground is available. It's not (I believe) strictly required -
a GFCI can be used on a two-wire circuit.

In your case, it does appear that the outlet box is probably grounded;
I see what appear to be bare ground wires entering at the back. These
wires *should* be securely bonded to the junction box - this would
probably be done right at the back, where the screws and wire clamps
are located. I can't tell if those ground wires are in fact securely
bonded to the box, or whether they're just sitting there.

If you're going to ground the GFCI, you'd run a wire from the green
screw terminal, to a connection point with one of those ground
wires... e.g. if the existing bare ground wire is screwed to the box
at some point, you'd want to connect the ground wire to that screw or
to another box-mounted screw not too far from it.

Now, the lack of a ground wire from the GFCI shouldn't tend to cause
the GFCI to "trip" mistakenly. A proper GFCI operates by measuring
"current imbalance" between the hot and neutral wires. If more flows
through one than through the other, then it's almost certain that some
current is flowing to ground (somewhere) rather than back through
neutral... and this is a Bad Thing (shock hazard, or shock occurring).

A GFCI's protection does *not* depend on measuring current flowing
through its own ground wire. That's why they can be used to protect
two-wire circuits, where there isn't even a good ground connection
available... this makes them useful for retrofitting older house
circuits for improved safety.

Having a good ground on a GFCI circuit is actually likely to make the
GFCI trip sooner, rather than later, if an electrical fault exists.
For example, if you have an appliance with a grounded case, and a leak
or short develops between "hot" and the case, the GFCI will trip
instantly. If the case isn't grounded through the third prong
(e.g. if there is no ground prong, or if it's cut off or defeated with
a "cheater", or if it's plugged into a 3-wire outlet with no actual
ground) then the fault won't result in current flow to ground... until
somebody touches the case and also touches something grounded. At
that point they'll get a shock, and (knock on wood) the GFCI will trip
fast enough to protect them from anything more than a scare.

So, if your GFCI is tripping, then I don't expect that grounding the
GFCI more securely is likely to change this. You may actually have a
current-leak-to-ground on one of the circuits you are protecting. Or,
possibly, interference from a strong local radio transmitter is
"falsing" the GFCI - it does happen.

Hi David,

I should have been clearer in my description. After noticing that the power
was off to the outlet, I pushed the GFCI reset button but I didn't hear a
click. At that point I figured either the GFCI hadn't tripped and there was
an internal problem, or it had tripped and there was something wrong with
the resetting mechanism. I removed the outlet from the wall and that's when
I noticed the missing ground connection. Regarding the GFCI, there was
nothing wrong with it. I read on a message board that you may have to apply
quite a bit of force to get it to reset. I tried again and it finally reset.
This was the first time this GFCI has tripped.

I looked again at the ground wiring you see in the picture. It exits the box
through a hole in the top of the box. If it's secured to anything outside
the box I can't tell. Is there some official test to perform to check if a
junction box is grounded?

Thanks for your reply.
--
David Farber
Los Osos, CA

 

[David Platt]

I should have been clearer in my description. After noticing that the power
was off to the outlet, I pushed the GFCI reset button but I didn't hear a
click. At that point I figured either the GFCI hadn't tripped and there was
an internal problem, or it had tripped and there was something wrong with
the resetting mechanism. I removed the outlet from the wall and that's when
I noticed the missing ground connection. Regarding the GFCI, there was
nothing wrong with it. I read on a message board that you may have to apply
quite a bit of force to get it to reset. I tried again and it finally reset.
This was the first time this GFCI has tripped.

OK, understood. Yes, those trip/reset arrangements can be "stiff". I
think they may put a lot of tension on the springs inside, to make
sure that the disconnect opens reliably and quickly.

I looked again at the ground wiring you see in the picture. It exits the box
through a hole in the top of the box.

It's fairly common for romex cable (heavy, flexible in-wall wiring) to
have two insulated connectors (hot/black and neutral/white), and one
bare ground wire between them. That's what you may be dealing with
there.

If it's secured to anything outside
the box I can't tell. Is there some official test to perform to check if a
junction box is grounded?

Yes, it can be done, but it's a bit tricky.

The simplest sort of tester is a small plug-like device you connect to
the outlet, which has several LEDs or neon bulbs inside. What you
would want to see, usually, is a couple of lights lit (indicating
that a voltage differential exists between line/neutral and
line/ground), and one or more other lights not lit (e.g. the "hot and
neutral are reversed" light). This will catch a couple of common
wiring faults (no ground at all, and ground/neutral reversal).

These simple testers are cheap, some even come with a "deliberately
trip the GFCI by leaking a bit of current" button, and they're a good
thing to have in your home-repairs drawer.

Gardner Bender GFI-3501 is one such (currently $8 at Home Depot);
there are many other brands.

These won't necessarily tell you that you have a *good* ground on the
circuit, though, because this sort of tester is designed to draw
almost no current at all through the circuit. It may tell you that
ground is connected, when its only connection to the actual building
ground is through corroded conduit and when the "ground" won't
actually carry much current reliably during a fault.

And, it won't catch the case in which ground and neutral have simply
been connected together at the outlet (i.e. no "real" ground). This
is a code violation and can be a safety issue.

Doing a *good* test for these faults usually requires measuring
voltages between the three terminals, while also pulling a substantial
current load on the circuit. Other tests would require powering down
the circuit (e.g. at the main breaker) and measuring resistances.
It's probably best to have a professional electrician perform these
sorts of tests, if you have doubts about the circuit.

 

A GFCI outlet should trip if there is a voltage difference between the ground wire and neutral. Any flow there indicates a potential problem and should cause it to trip off. Without a ground connected, this effectively prevents the GFCI from working properly. The holes at the rear of the box are for ground screws. You should connect the ground to there. Also, it looks like the ground wire is "grounded" to the box by being folded back into the entry hole with contact at that point. This installation was not likely done by an electrician. Proper grounding is necessary for proper functioning of the GFCI outlet.

Dan

 

[Michael A. Terrell]

dansabrservices@yahoo.com wrote:

A GFCI outlet should trip if there is a voltage difference between the ground wire and neutral. Any flow there indicates a potential problem and should cause it to trip off. Without a ground connected, this effectively prevents the GFCI from working properly. The holes at the rear of the box are for ground screws. You should connect the ground to there. Also, it looks like the ground wire is "grounded" to the box by being folded back into the entry hole with contact at that point. This installation was not likely done by an electrician. Proper grounding is necessary for proper functioning of the GFCI outlet.

Wrong. An imbalance between line and neutral is supposed to trip it.
The imbalance is current going to the ground conductor, or another path
t ground that causes the imbalance. GFCI are supplied with labels for
two prong, ungrounded outlets. Since most of what is plugged into a
protected circuit is two wire, they would be useless if they are like
you describe.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[Jerry Peters]

David Farber <farberbear.unspam@aol.com> wrote:

David Platt wrote:
While trying to troubleshoot why some kitchen electrical outlets in
this junction box weren't working, I did a bit of research.
Apparently, there is supposed to be a ground connection (other than
the screw going through the frame of the outlet to the box) from the
GFCI outlet to the junction box. (see photo:
http://webpages.charter.net/mrfixiter/images/Home/Junction_box.jpg )
Can I just run some wire from the green screw terminal on the GFCI
outlet to the box? Where would I attach it to the box? By the way,
the problem with the outlet was that the breaker tripped in the
GFCI. There are three pairs of wires in the photo. One is the
incoming AC. One feeds another GFCI outlet down the line. The last
pair goes to a switch in the same junction box which turns on some
lights in the kitchen.

Well, let's see.

Having a ground-wire connection to the GFCI itself is a good idea, if
a good ground is available. It's not (I believe) strictly required -
a GFCI can be used on a two-wire circuit.

In your case, it does appear that the outlet box is probably grounded;
I see what appear to be bare ground wires entering at the back. These
wires *should* be securely bonded to the junction box - this would
probably be done right at the back, where the screws and wire clamps
are located. I can't tell if those ground wires are in fact securely
bonded to the box, or whether they're just sitting there.

If you're going to ground the GFCI, you'd run a wire from the green
screw terminal, to a connection point with one of those ground
wires... e.g. if the existing bare ground wire is screwed to the box
at some point, you'd want to connect the ground wire to that screw or
to another box-mounted screw not too far from it.

Now, the lack of a ground wire from the GFCI shouldn't tend to cause
the GFCI to "trip" mistakenly. A proper GFCI operates by measuring
"current imbalance" between the hot and neutral wires. If more flows
through one than through the other, then it's almost certain that some
current is flowing to ground (somewhere) rather than back through
neutral... and this is a Bad Thing (shock hazard, or shock occurring).

A GFCI's protection does *not* depend on measuring current flowing
through its own ground wire. That's why they can be used to protect
two-wire circuits, where there isn't even a good ground connection
available... this makes them useful for retrofitting older house
circuits for improved safety.

Having a good ground on a GFCI circuit is actually likely to make the
GFCI trip sooner, rather than later, if an electrical fault exists.
For example, if you have an appliance with a grounded case, and a leak
or short develops between "hot" and the case, the GFCI will trip
instantly. If the case isn't grounded through the third prong
(e.g. if there is no ground prong, or if it's cut off or defeated with
a "cheater", or if it's plugged into a 3-wire outlet with no actual
ground) then the fault won't result in current flow to ground... until
somebody touches the case and also touches something grounded. At
that point they'll get a shock, and (knock on wood) the GFCI will trip
fast enough to protect them from anything more than a scare.

So, if your GFCI is tripping, then I don't expect that grounding the
GFCI more securely is likely to change this. You may actually have a
current-leak-to-ground on one of the circuits you are protecting. Or,
possibly, interference from a strong local radio transmitter is
"falsing" the GFCI - it does happen.

Hi David,

I should have been clearer in my description. After noticing that the power
was off to the outlet, I pushed the GFCI reset button but I didn't hear a
click. At that point I figured either the GFCI hadn't tripped and there was
an internal problem, or it had tripped and there was something wrong with
the resetting mechanism. I removed the outlet from the wall and that's when
I noticed the missing ground connection. Regarding the GFCI, there was
nothing wrong with it. I read on a message board that you may have to apply
quite a bit of force to get it to reset. I tried again and it finally reset.
This was the first time this GFCI has tripped.

I looked again at the ground wiring you see in the picture. It exits the box
through a hole in the top of the box. If it's secured to anything outside
the box I can't tell. Is there some official test to perform to check if a
junction box is grounded?

Thanks for your reply.

There are usually threaded holes in the back of metal outlet boxes for
ground wire attachment.

See those 2 holes in the center of the box near the sides? They should
be for grounding the box. Try an 8-32 screw. Also it doesn't appear
that the ground wire is *firmly* bonded to the box. It looks like it's
just sort of pushed in with the romex under the clamp.

 

[David Platt]

A GFCI outlet should trip if there is a voltage difference between the
ground wire and neutral. Any flow there indicates a potential problem
and should cause it to trip off. Without a ground connected, this
effectively prevents the GFCI from working properly.

I believe that your description of how a GFCI works, is incorrect.

Everything I have read about them, says that they trip when they sense
a *current* imbalance, between "hot" and "neutral". They do not sense
voltage differences between ground and neutral. They can operate
without any ground connection at all.

Basically, they run these two wires through an inductive transformer
core in a "balanced" arrangement, and have a secondary sense wire in
the same core. If the current flow in hot and neutral is the same,
the fields around the two conductors are equal but opposite in phase,
they cancel out, and no current is induced in the sense wire. If
there's any hot-to-ground current flow "downstream" of the sensing
transformer, then the current flow in the neutral wire is reduced, the
two currents don't cancel out entirely, a current is induced into the
sense wire, and the GFCI detects this current and trips.

Citation: http://www.cpsc.gov//PageFiles/118853/099.pdf from the
U.S. Consumer Products Safety Commission. This fact sheet
describes the current sensing design, and specifically points out that
a GFCI can be used to protect a two-wire circuit which has no ground
connection at all. All of the other references I have seen, agree
with what the CPSC is saying here.

[An episode of "CSI", years ago, got this wrong... the lead story was
a murder which was arranged by tampering with a drill that was
plugged into a GFCI - cutting off the ground prong on the plug and
then arranging for a current leak. In fact, a GFCI would have
tripped under these circumstances, even with an un-grounded tool case
and even if the ground connection on the GFCI itself had been cut.]

 

[Maynard A. Philbrook Jr.]

In article <m1ke0l$5fj$1@dont-email.me>, farberbear.unspam@aol.com
says...

Hi David,

I should have been clearer in my description. After noticing that the power
was off to the outlet, I pushed the GFCI reset button but I didn't hear a
click. At that point I figured either the GFCI hadn't tripped and there was
an internal problem, or it had tripped and there was something wrong with
the resetting mechanism. I removed the outlet from the wall and that's when
I noticed the missing ground connection. Regarding the GFCI, there was
nothing wrong with it. I read on a message board that you may have to apply
quite a bit of force to get it to reset. I tried again and it finally reset.
This was the first time this GFCI has tripped.

I looked again at the ground wiring you see in the picture. It exits the box
through a hole in the top of the box. If it's secured to anything outside
the box I can't tell. Is there some official test to perform to check if a
junction box is grounded?

Thanks for your reply.
--
David Farber
Los Osos, CA

The ground wire is connected to the ground screw of the duplex, your
outlet in most cases, if not, it's connected to the metal box and when
the duplex is screwed into the box, it then gets connected to ground.
You can also have it both ways which is better but takes longer to
install.

Ground wires are part of the romix wire so it gets connected to your
main ground in your home back at the sub panel box, where your breakers
live. In there the ground wire is attached to the same bus strip as the
neutral wire.. Somewhere around there you should have a real earth
ground connecting to the sub panel.

Although a GFCI will trip with an older non grounded system, it's not
advisable, because in order for this to happen, the circuit has to
become
unbalanced and if it is the appliance that is shorting, you maybe
touching it at the time. Grounds are there to isolate you from the
high potential when things go wrong. Having no ground plug means the
appliance is not grounded.


As for the reset on the GFCI outlet, for most units your power has to
be on before it'll reset.

jamie

 

"As for the reset on the GFCI outlet, for most units your power has to
be on before it'll reset. "

I have found this not to be true. However, to test, it does require power.

Also, I stand corrected her or in the othe rgroup, that the ground is not even reqquired for the test button to work, originally I thought it was.

All of them I ever installed were properly grounded so whatever. I thought it took current to the ground for test. It does not, it simpley takes it to BEFORE the GF circuit and that causes the imbalance that makes it trip and prove itsel

 

[Michael A. Terrell]

jurb6006@gmail.com wrote:

"As for the reset on the GFCI outlet, for most units your power has to
be on before it'll reset. "

I have found this not to be true. However, to test, it does require power.

Also, I stand corrected her or in the othe rgroup, that the ground is not even reqquired for the test button to work, originally I thought it was.

All of them I ever installed were properly grounded so whatever. I thought it took current to the ground for test. It does not, it simpley takes it to BEFORE the GF circuit and that causes the imbalance that makes it trip and prove itsel

The test button does nothing without a connection to ground. It
causes an imbalace between line and neutral by diverting a few mA to
ground form neutral.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[Michael A. Terrell]

"Maynard A. Philbrook Jr." wrote:

In article <m1ke0l$5fj$1@dont-email.me>, farberbear.unspam@aol.com
says...
Hi David,

I should have been clearer in my description. After noticing that the power
was off to the outlet, I pushed the GFCI reset button but I didn't hear a
click. At that point I figured either the GFCI hadn't tripped and there was
an internal problem, or it had tripped and there was something wrong with
the resetting mechanism. I removed the outlet from the wall and that's when
I noticed the missing ground connection. Regarding the GFCI, there was
nothing wrong with it. I read on a message board that you may have to apply
quite a bit of force to get it to reset. I tried again and it finally reset.
This was the first time this GFCI has tripped.

I looked again at the ground wiring you see in the picture. It exits the box
through a hole in the top of the box. If it's secured to anything outside
the box I can't tell. Is there some official test to perform to check if a
junction box is grounded?

Thanks for your reply.
--
David Farber
Los Osos, CA



The ground wire is connected to the ground screw of the duplex, your
outlet in most cases, if not, it's connected to the metal box and when
the duplex is screwed into the box, it then gets connected to ground.
You can also have it both ways which is better but takes longer to
install.

Ground wires are part of the romix wire so it gets connected to your
main ground in your home back at the sub panel box, where your breakers
live. In there the ground wire is attached to the same bus strip as the
neutral wire.. Somewhere around there you should have a real earth
ground connecting to the sub panel.

Although a GFCI will trip with an older non grounded system, it's not
advisable, because in order for this to happen, the circuit has to
become
unbalanced and if it is the appliance that is shorting, you maybe
touching it at the time. Grounds are there to isolate you from the
high potential when things go wrong. Having no ground plug means the
appliance is not grounded.

As for the reset on the GFCI outlet, for most units your power has to
be on before it'll reset.

jamie

Sigh, why do you post so much crap?

GFCI are allowed on non grounded outlets. If the device is 'shorted'
it will trip a circuit breaker. If it has developed a fault path to the
case, you won't trip it unless you are touching the defective device and
a suitably grounded item.
--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[Cydrome Leader]

David Farber <farberbear.unspam@aol.com> wrote:

David Platt wrote:
While trying to troubleshoot why some kitchen electrical outlets in
this junction box weren't working, I did a bit of research.
Apparently, there is supposed to be a ground connection (other than
the screw going through the frame of the outlet to the box) from the
GFCI outlet to the junction box. (see photo:
http://webpages.charter.net/mrfixiter/images/Home/Junction_box.jpg )
Can I just run some wire from the green screw terminal on the GFCI
outlet to the box? Where would I attach it to the box? By the way,
the problem with the outlet was that the breaker tripped in the
GFCI. There are three pairs of wires in the photo. One is the
incoming AC. One feeds another GFCI outlet down the line. The last
pair goes to a switch in the same junction box which turns on some
lights in the kitchen.

Well, let's see.

Having a ground-wire connection to the GFCI itself is a good idea, if
a good ground is available. It's not (I believe) strictly required -
a GFCI can be used on a two-wire circuit.

In your case, it does appear that the outlet box is probably grounded;
I see what appear to be bare ground wires entering at the back. These
wires *should* be securely bonded to the junction box - this would
probably be done right at the back, where the screws and wire clamps
are located. I can't tell if those ground wires are in fact securely
bonded to the box, or whether they're just sitting there.

If you're going to ground the GFCI, you'd run a wire from the green
screw terminal, to a connection point with one of those ground
wires... e.g. if the existing bare ground wire is screwed to the box
at some point, you'd want to connect the ground wire to that screw or
to another box-mounted screw not too far from it.

Now, the lack of a ground wire from the GFCI shouldn't tend to cause
the GFCI to "trip" mistakenly. A proper GFCI operates by measuring
"current imbalance" between the hot and neutral wires. If more flows
through one than through the other, then it's almost certain that some
current is flowing to ground (somewhere) rather than back through
neutral... and this is a Bad Thing (shock hazard, or shock occurring).

A GFCI's protection does *not* depend on measuring current flowing
through its own ground wire. That's why they can be used to protect
two-wire circuits, where there isn't even a good ground connection
available... this makes them useful for retrofitting older house
circuits for improved safety.

Having a good ground on a GFCI circuit is actually likely to make the
GFCI trip sooner, rather than later, if an electrical fault exists.
For example, if you have an appliance with a grounded case, and a leak
or short develops between "hot" and the case, the GFCI will trip
instantly. If the case isn't grounded through the third prong
(e.g. if there is no ground prong, or if it's cut off or defeated with
a "cheater", or if it's plugged into a 3-wire outlet with no actual
ground) then the fault won't result in current flow to ground... until
somebody touches the case and also touches something grounded. At
that point they'll get a shock, and (knock on wood) the GFCI will trip
fast enough to protect them from anything more than a scare.

So, if your GFCI is tripping, then I don't expect that grounding the
GFCI more securely is likely to change this. You may actually have a
current-leak-to-ground on one of the circuits you are protecting. Or,
possibly, interference from a strong local radio transmitter is
"falsing" the GFCI - it does happen.

Hi David,

I should have been clearer in my description. After noticing that the power
was off to the outlet, I pushed the GFCI reset button but I didn't hear a
click. At that point I figured either the GFCI hadn't tripped and there was
an internal problem, or it had tripped and there was something wrong with
the resetting mechanism. I removed the outlet from the wall and that's when
I noticed the missing ground connection. Regarding the GFCI, there was
nothing wrong with it. I read on a message board that you may have to apply
quite a bit of force to get it to reset. I tried again and it finally reset.
This was the first time this GFCI has tripped.

I looked again at the ground wiring you see in the picture. It exits the box
through a hole in the top of the box. If it's secured to anything outside
the box I can't tell. Is there some official test to perform to check if a
junction box is grounded?

sort of. My tester is a 200 watt bulb, but larger would be better. Connect
one lead to hot and the other to the box of your ground. With the load on,
measure the voltage across the bulb. If it's not the same as the bulb
connected to hot and neutral, you have a faulty ground. The connectivity
and resistance should be as good as your neutral itself.

A plain volt meter test from hot to ground is not valid, and neither are
those little pocket testers. They don't run a real current through ground,
which is something that has to happen if your equipment faults. For old
installations like in that photo, you have no idea what's really going on
or how many times it's been messed with in the past, and how secure the
connections are now.

 

"If it's not the same as the bulb
connected to hot and neutral, you have a faulty ground. "

Not necessarily. There is some voltage on neutrals in some places. This is caused by heavy loading on one side of the 240 compared to the other. It can be worse if common neutrals are used.

Saw one place that had like 20 volts on the neutral because of two 110 volt window AC units that happened to be on one side of the line.

 

[Cydrome Leader]

jurb6006@gmail.com wrote:

"If it's not the same as the bulb
connected to hot and neutral, you have a faulty ground. "

Not necessarily. There is some voltage on neutrals in some places. This is caused by heavy loading on one side of the 240 compared to the other. It can be worse if common neutrals are used.

Saw one place that had like 20 volts on the neutral because of two 110 volt window AC units that happened to be on one side of the line.

Good point- there could be other serious problems with such a test.

But still, if you're in the US, have 20 volts on neutral relative to
ground, you probably have a bad neutral, which is also a big deal. This
problem could even exist outside your home, over at the distribution
transformer or wiring from there to your meter.

If your neutral "drifts" by 20 volts from ground, where it should be
bonded at the service entrance, and you have split phase 240 (120+120)
service you've got half the house with 100 volts at the oulets and other
side with 140 volts. That's not good for any devices or appliances you
have.

 

[bud--]

On 10/16/2014 8:27 AM, Michael A. Terrell wrote:

jurb6006@gmail.com wrote:

"As for the reset on the GFCI outlet, for most units your power has to
be on before it'll reset. "

I have found this not to be true. However, to test, it does require power.

Also, I stand corrected her or in the othe rgroup, that the ground is not even reqquired for the test button to work, originally I thought it was.

All of them I ever installed were properly grounded so whatever. I thought it took current to the ground for test. It does not, it simpley takes it to BEFORE the GF circuit and that causes the imbalance that makes it trip and prove itsel


The test button does nothing without a connection to ground. It
causes an imbalace between line and neutral by diverting a few mA to
ground form neutral.

The test button does not require a ground. The hot and neutral go
through a current transformer. The test button connects a resistor to
the hot ahead of the CT and the neutral downstream from the CT (or
vice-versa). Plug-in GFCI testes do not work without a ground.

I agree with everything else you have written here.

------------------------------
Interesting feature -
There is a second CT that tries to create a common-mode current on the
hot and neutral. If there is a plugged-in or downstream N-G connection
the GFCI trips.

 

[Michael A. Terrell]

bud-- wrote:

On 10/16/2014 8:27 AM, Michael A. Terrell wrote:

jurb6006@gmail.com wrote:

"As for the reset on the GFCI outlet, for most units your power has to
be on before it'll reset. "

I have found this not to be true. However, to test, it does require power.

Also, I stand corrected her or in the othe rgroup, that the ground is not even reqquired for the test button to work, originally I thought it was.

All of them I ever installed were properly grounded so whatever. I thought it took current to the ground for test. It does not, it simpley takes it to BEFORE the GF circuit and that causes the imbalance that makes it trip and prove itsel


The test button does nothing without a connection to ground. It
causes an imbalace between line and neutral by diverting a few mA to
ground form neutral.


The test button does not require a ground. The hot and neutral go
through a current transformer. The test button connects a resistor to
the hot ahead of the CT and the neutral downstream from the CT (or
vice-versa). Plug-in GFCI testes do not work without a ground.

I agree with everything else you have written here.

------------------------------
Interesting feature -
There is a second CT that tries to create a common-mode current on the
hot and neutral. If there is a plugged-in or downstream N-G connection
the GFCI trips.

The ones I've opened were as I described. They were very early
models, and failed in high humidity locations.
--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[David Farber]

"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:m1p3lk$ob4$1@reader1.panix.com...

David Farber <farberbear.unspam@aol.com> wrote:
David Platt wrote:
While trying to troubleshoot why some kitchen electrical outlets in
this junction box weren't working, I did a bit of research.
Apparently, there is supposed to be a ground connection (other than
the screw going through the frame of the outlet to the box) from the
GFCI outlet to the junction box. (see photo:
http://webpages.charter.net/mrfixiter/images/Home/Junction_box.jpg )
Can I just run some wire from the green screw terminal on the GFCI
outlet to the box? Where would I attach it to the box? By the way,
the problem with the outlet was that the breaker tripped in the
GFCI. There are three pairs of wires in the photo. One is the
incoming AC. One feeds another GFCI outlet down the line. The last
pair goes to a switch in the same junction box which turns on some
lights in the kitchen.

Well, let's see.

Having a ground-wire connection to the GFCI itself is a good idea, if
a good ground is available. It's not (I believe) strictly required -
a GFCI can be used on a two-wire circuit.

In your case, it does appear that the outlet box is probably grounded;
I see what appear to be bare ground wires entering at the back. These
wires *should* be securely bonded to the junction box - this would
probably be done right at the back, where the screws and wire clamps
are located. I can't tell if those ground wires are in fact securely
bonded to the box, or whether they're just sitting there.

If you're going to ground the GFCI, you'd run a wire from the green
screw terminal, to a connection point with one of those ground
wires... e.g. if the existing bare ground wire is screwed to the box
at some point, you'd want to connect the ground wire to that screw or
to another box-mounted screw not too far from it.

Now, the lack of a ground wire from the GFCI shouldn't tend to cause
the GFCI to "trip" mistakenly. A proper GFCI operates by measuring
"current imbalance" between the hot and neutral wires. If more flows
through one than through the other, then it's almost certain that some
current is flowing to ground (somewhere) rather than back through
neutral... and this is a Bad Thing (shock hazard, or shock occurring).

A GFCI's protection does *not* depend on measuring current flowing
through its own ground wire. That's why they can be used to protect
two-wire circuits, where there isn't even a good ground connection
available... this makes them useful for retrofitting older house
circuits for improved safety.

Having a good ground on a GFCI circuit is actually likely to make the
GFCI trip sooner, rather than later, if an electrical fault exists.
For example, if you have an appliance with a grounded case, and a leak
or short develops between "hot" and the case, the GFCI will trip
instantly. If the case isn't grounded through the third prong
(e.g. if there is no ground prong, or if it's cut off or defeated with
a "cheater", or if it's plugged into a 3-wire outlet with no actual
ground) then the fault won't result in current flow to ground... until
somebody touches the case and also touches something grounded. At
that point they'll get a shock, and (knock on wood) the GFCI will trip
fast enough to protect them from anything more than a scare.

So, if your GFCI is tripping, then I don't expect that grounding the
GFCI more securely is likely to change this. You may actually have a
current-leak-to-ground on one of the circuits you are protecting. Or,
possibly, interference from a strong local radio transmitter is
"falsing" the GFCI - it does happen.

Hi David,

I should have been clearer in my description. After noticing that the
power
was off to the outlet, I pushed the GFCI reset button but I didn't hear a
click. At that point I figured either the GFCI hadn't tripped and there
was
an internal problem, or it had tripped and there was something wrong with
the resetting mechanism. I removed the outlet from the wall and that's
when
I noticed the missing ground connection. Regarding the GFCI, there was
nothing wrong with it. I read on a message board that you may have to
apply
quite a bit of force to get it to reset. I tried again and it finally
reset.
This was the first time this GFCI has tripped.

I looked again at the ground wiring you see in the picture. It exits the
box
through a hole in the top of the box. If it's secured to anything outside
the box I can't tell. Is there some official test to perform to check if
a
junction box is grounded?

sort of. My tester is a 200 watt bulb, but larger would be better. Connect
one lead to hot and the other to the box of your ground. With the load on,
measure the voltage across the bulb. If it's not the same as the bulb
connected to hot and neutral, you have a faulty ground. The connectivity
and resistance should be as good as your neutral itself.

A plain volt meter test from hot to ground is not valid, and neither are
those little pocket testers. They don't run a real current through ground,
which is something that has to happen if your equipment faults. For old
installations like in that photo, you have no idea what's really going on
or how many times it's been messed with in the past, and how secure the
connections are now.

I was thinking exactly the same thing! Without a decent amount of current
going through the ground circuit, how can you tell if the ground connection
is really firmly attached? I was thinking of using a coffee maker as the
load. I'm going to the hardware store to get the appropriate sized ground
wire, attach it to the box, then measure the voltage difference with the pot
running off hot and ground, then hot and neutral.

Thanks to everyone for all your great replies.
--
David Farber
Los Osos, CA