Electrical box ground wiring.

[David Platt]

In article <m1pcre$oe1$1@reader1.panix.com>,
Cydrome Leader <presence@MUNGEpanix.com> wrote:

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.

Yup. In 20 years we've had that problem occur twice at our house,
with the usual weird symptoms (e.g. lights getting *brighter* when you
turn on something else). In both cases it was due to a squirrel
chewing through the neutral wire, in the drop between the pole-pig
transformer and our service panel.

In both cases, reporting a "low voltage / high voltage" situation to
the power company resulted in a rapid response... the last time
it happened there was a truck rolling up outside our door within about
20 minutes. PG&E considers this a problem which requires a rather
urgent repair, due to the potential for equipment damage, fires, and
so forth.

If the neutral isn't actually open, then a persistent 20-volt
neutral-to-good-ground differential would indicate a really huge
current draw on the circuit... probably well more than the wiring is
rated for. The National Electric Code seems to allow for only a 5%
voltage drop for a fully-loaded circuit.

 

[bud--]

On 10/17/2014 12:19 PM, David Platt wrote:

In article <m1pcre$oe1$1@reader1.panix.com>,
Cydrome Leader <presence@MUNGEpanix.com> wrote:

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.

Yup. In 20 years we've had that problem occur twice at our house,
with the usual weird symptoms (e.g. lights getting *brighter* when you
turn on something else). In both cases it was due to a squirrel
chewing through the neutral wire, in the drop between the pole-pig
transformer and our service panel.

If you live in an urban area with all-metal water distribution pipes
this can be masked somewhat. If you have an open service neutral the
neutral return path can become service panel neutral to the N-G bond, to
the water service pipe (earthing electrode), to adjacent houses through
the metal water distribution system, through their N-G service bonds,
and back to the transformer through the service neutral at those houses.

There was a thread where someone had significant current on the
conductor to the earthing electrodes and it turned out either he, or a
neighbor, had an open service neutral.

In both cases, reporting a "low voltage / high voltage" situation to
the power company resulted in a rapid response... the last time
it happened there was a truck rolling up outside our door within about
20 minutes. PG&E considers this a problem which requires a rather
urgent repair, due to the potential for equipment damage, fires, and
so forth.

I have seen other people say the same thing.

If the neutral isn't actually open, then a persistent 20-volt
neutral-to-good-ground differential would indicate a really huge
current draw on the circuit... probably well more than the wiring is
rated for.

High current should trip the breaker.

If you had a really long circuit you could possibly come up with a 20V
drop. A competent electrician would increase the wire size for really
long circuits.

The National Electric Code seems to allow for only a 5%
voltage drop for a fully-loaded circuit.

The NEC recommends, but does not require, 5%.

 

[Ron D.]

David:

You have an old box. Note the bare copper wires under the strain reliefs. You need to dig them out.

These http://www.zoro.com/i/G3705676/?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&gclid=CNqjrqqit8ECFSZo7AodHwgAKQ ground clips are eused in that situation.

They are a bit difficult to attach, but The secure a solid pigtail to the side of the box. e.g. the edge that's exposed.

What I use in this case is an ground Ideal Term-a-nut. See http://www.grainger.com/product/IDEAL-Wire-Connector-Nut-4YD75

So, you can dig out the bare ground. Install the term-a-nut and a solid pigtail. The solid pigtail goes to the ground clip and the free end of the term-a-nut (fork terminal goes to the green screw on the outlet),

With multiple GFCI's you would want to not series the GFCI. e.g. One GFCI protects the outlets down stream.

What can cause nuisance tripping is shared neutrals. The term is shared, but think of it as neutrals attached as "T-splices"

GFCI's do not need a ground, but if they don;t have one, they must be labeled that there is no ground.

You are not supposed to rely on the screw connection from the box to to the outlet, although some outlets are designed so it's OK.

Your house looks like it had original had two prong outlets and the upgrade wasn't done correctly. The conversion can be a pain, but the term-a-nuts make the job much easier.

When there is a threaded hole in the box that can accept a ground screw, then other ways are possible.

So far, I've never tapped a ground hole.

 

[Ron D.]

I generally like the Term-a-nut process for wiring. One white, one black and one green. The parallel connections don't rely on the screw terminal pigtails.

Seasoned electricians pigtail the connections in the box with a wirnut.

The term-a-nuts I think can be purchased in stranded or solid. Not sure though. I use the stranded type.

 

[David Farber]

Ron D. wrote:

David:

You have an old box. Note the bare copper wires under the strain
reliefs. You need to dig them out.

These
http://www.zoro.com/i/G3705676/?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&gclid=CNqjrqqit8ECFSZo7AodHwgAKQ
ground clips are eused in that situation.

They are a bit difficult to attach, but The secure a solid pigtail to
the side of the box. e.g. the edge that's exposed.

What I use in this case is an ground Ideal Term-a-nut. See
http://www.grainger.com/product/IDEAL-Wire-Connector-Nut-4YD75

So, you can dig out the bare ground. Install the term-a-nut and a
solid pigtail. The solid pigtail goes to the ground clip and the
free end of the term-a-nut (fork terminal goes to the green screw on
the outlet),

With multiple GFCI's you would want to not series the GFCI. e.g. One
GFCI protects the outlets down stream.

What can cause nuisance tripping is shared neutrals. The term is
shared, but think of it as neutrals attached as "T-splices"

GFCI's do not need a ground, but if they don;t have one, they must be
labeled that there is no ground.

You are not supposed to rely on the screw connection from the box to
to the outlet, although some outlets are designed so it's OK.

Your house looks like it had original had two prong outlets and the
upgrade wasn't done correctly. The conversion can be a pain, but the
term-a-nuts make the job much easier.

When there is a threaded hole in the box that can accept a ground
screw, then other ways are possible.

So far, I've never tapped a ground hole.

Hi Ron,

I put a screw into the box and ran a wire from the screw to the GFCI's
ground. But first I checked the line voltage with the neutral wire on the
neutral side of the plug with a hair dryer running. Then I exchanged the
neutral wire with the new ground wire and checked the voltage again with the
hair dryer running. The voltages were exactly the same. That proved to me
that the ground wire is making a good connection back to the service panel.
Do you see an alternate explanation that would disprove my conclusion?

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

 

[Ron D.]

Yu might find this odd, but you can sometimes check connections, by measuring across the connection. e.g. At the service panel, you can measure from the wire (probe actually touching the wire) and the main bus.

So, your looking for small voltages in the range of millivolts. That sort of check can check the sanity of a breakers contact resistance too. You do have to do this test with a load.

There are "phantom voltages" that occur when high impedance meters are used to measure line voltage. Large resistance leakage paths sometimes "fool" a conventional DVM with an input Z of 10 meg ohms. One of Fluke's meters does have a low Z mode.

I typically use an Ideal Sure Test http://www.amazon.com/Ideal-Industries-61-165-SureTest-Analyzer/dp/B000LDKWSG

A very cool device.

=
The "shared neutral" causes grief with GFCI's and AFCI;s/ See http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http%3A%2F%2Fstatic.schneider-electric.us%2Fdocs%2FCircuit%2520Protection%2FMiniature%2520Circuit%2520Breakers%2FArc%2520Fault%2520Circuit%2520Interrupters-AFCI%2F0760DB0203R902.pdf&ei=W05DVMy2F5LlsATxv4HoAQ&usg=AFQjCNG8wV-QG3tr3UXmLMhJZMR-zPDMNQ&sig2=YDPwdo_aArHNardl81lP8g&bvm=bv.77648437,d.cWc&cad=rja for a better explanation.

 

[Michael A. Terrell]

"Ron D." wrote:

I generally like the Term-a-nut process for wiring. One white, one black and one green. The parallel connections don't rely on the screw terminal pigtails.

Seasoned electricians pigtail the connections in the box with a wirnut.

The term-a-nuts I think can be purchased in stranded or solid. Not sure though. I use the stranded type.

Are they legal in every jurisdiction? A lot of things aren't allowed
under local codes.


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

 

[Ron D.]

On Monday, October 20, 2014 12:31:24 AM UTC-4, Michael Terrell wrote:

"Ron D." wrote:


Are they legal in every jurisdiction? A lot of things aren't allowed

under local codes.

I can buy them locally at a real electrical supply house, so I would suppose they are legal in mine. They are not much different than a wire nut.

 

[Cydrome Leader]

Ron D. <Ron.Dozier@gmail.com> wrote:

David:

You have an old box. Note the bare copper wires under the strain reliefs. You need to dig them out.

These http://www.zoro.com/i/G3705676/?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&gclid=CNqjrqqit8ECFSZo7AodHwgAKQ ground clips are eused in that situation.

They are a bit difficult to attach, but The secure a solid pigtail to the side of the box. e.g. the edge that's exposed.

I have to ask. How the hell do you attach or use those things?

 

[Cydrome Leader]

bud-- <null@void.com> 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.

Maybe you can explain this one-

A friend's apt has a ceiling fan in a room that trips the GFCI in the
bathroom if you exercise the fan speed or light switch fast enough.
They're on separate circuits as far as I can tell, but the wiring is old
and crappy to start with so I'm not even going to take off some covers to
look around.

I still have no idea how this happens. Anybody seen un-connected devices
trip a GFCI outlet?

 

[Cydrome Leader]

Michael A. Terrell <mike.terrell@earthlink.net> wrote:

"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.

Well, technically, a GFCI device doesn't need a ground prong or a ground
to function. Notice I say GCFI devive, not receptacle. Take for instance
hair dryers or electric blankets these days. They have a GFCI module in
the plug, which is polarized, but not grounded.

On the other hand, if you're installing a GFCI outlet, they all have
ground prongs, and to not ground it would be improper. Downstream outlets
could be old receptacles with no ground prong, if you're doing some sort
of retrofit or hacky upgrade. I have no doubt both have been done by
people at home, but a real electrician would do the same might be a
different story. Anybody know what the NEC says about this?

 

[David Platt]

In article <m29cvg$acr$2@reader1.panix.com>,
Cydrome Leader <presence@MUNGEpanix.com> wrote:

Well, technically, a GFCI device doesn't need a ground prong or a ground
to function. Notice I say GCFI devive, not receptacle. Take for instance
hair dryers or electric blankets these days. They have a GFCI module in
the plug, which is polarized, but not grounded.

On the other hand, if you're installing a GFCI outlet, they all have
ground prongs, and to not ground it would be improper. Downstream outlets
could be old receptacles with no ground prong, if you're doing some sort
of retrofit or hacky upgrade. I have no doubt both have been done by
people at home, but a real electrician would do the same might be a
different story. Anybody know what the NEC says about this?

Ummm... as I pointed out a week or so ago, the Consumer Products
Safety Commission *specifically* points out that you can use a GFCI
receptacle on a circuit which has no ground. It will protect its own
jacks, and any other outlets which are wired "downstream", against
ground faults.

This is an accepted and approved method for adding safety to a
two-wire circuit which has no ground wire accessible.

I agree, it's not as good a solution as re-wiring with a good
ground... but it's a lot better than leaving a two-wire circuit
without ground-fault protection!

The CPSC (and I believe the NEC) requires that any GFCI outlets which
don't have an actual ground, must be installed with a sticker which
says so, so that the user is aware that the ground prong is "open".

 

[Michael A. Terrell]

Cydrome Leader wrote:

Well, technically, a GFCI device doesn't need a ground prong or a ground
to function. Notice I say GCFI devive, not receptacle. Take for instance
hair dryers or electric blankets these days. They have a GFCI module in
the plug, which is polarized, but not grounded.

On the other hand, if you're installing a GFCI outlet, they all have
ground prongs, and to not ground it would be improper. Downstream outlets
could be old receptacles with no ground prong, if you're doing some sort
of retrofit or hacky upgrade. I have no doubt both have been done by
people at home, but a real electrician would do the same might be a
different story. Anybody know what the NEC says about this?

The NEC requires the protected outlets be marked as non grounded. The
labels come with the GFCI.


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

 

[Cydrome Leader]

David Platt <dplatt@coop.radagast.org> wrote:

In article <m29cvg$acr$2@reader1.panix.com>,
Cydrome Leader <presence@MUNGEpanix.com> wrote:
Well, technically, a GFCI device doesn't need a ground prong or a ground
to function. Notice I say GCFI devive, not receptacle. Take for instance
hair dryers or electric blankets these days. They have a GFCI module in
the plug, which is polarized, but not grounded.

On the other hand, if you're installing a GFCI outlet, they all have
ground prongs, and to not ground it would be improper. Downstream outlets
could be old receptacles with no ground prong, if you're doing some sort
of retrofit or hacky upgrade. I have no doubt both have been done by
people at home, but a real electrician would do the same might be a
different story. Anybody know what the NEC says about this?

Ummm... as I pointed out a week or so ago, the Consumer Products
Safety Commission *specifically* points out that you can use a GFCI
receptacle on a circuit which has no ground. It will protect its own
jacks, and any other outlets which are wired "downstream", against
ground faults.

This is an accepted and approved method for adding safety to a
two-wire circuit which has no ground wire accessible.

I agree, it's not as good a solution as re-wiring with a good
ground... but it's a lot better than leaving a two-wire circuit
without ground-fault protection!

The CPSC (and I believe the NEC) requires that any GFCI outlets which
don't have an actual ground, must be installed with a sticker which
says so, so that the user is aware that the ground prong is "open".

Ok- that would make sense- as stupid as a sticker may be, you need
something to indicate an abnormal condition. I've only see the industrial
versions of these warning tags though- never seen one screwed into a wall
in an old bathtoom, at least yet.

 

[bud--]

On 10/23/2014 1:26 AM, Michael A. Terrell wrote:

Cydrome Leader wrote:

Well, technically, a GFCI device doesn't need a ground prong or a ground
to function. Notice I say GCFI devive, not receptacle. Take for instance
hair dryers or electric blankets these days. They have a GFCI module in
the plug, which is polarized, but not grounded.

On the other hand, if you're installing a GFCI outlet, they all have
ground prongs, and to not ground it would be improper. Downstream outlets
could be old receptacles with no ground prong, if you're doing some sort
of retrofit or hacky upgrade. I have no doubt both have been done by
people at home, but a real electrician would do the same might be a
different story. Anybody know what the NEC says about this?


The NEC requires the protected outlets be marked as non grounded. The
labels come with the GFCI.

Trivial addition - downstream receptacles also need the "GFCI protected"
label.

As I think you have written, the NEC explicitly allows a (grounded) GFCI
receptacle to be used on an ungrounded circuit, and allows grounded
receptacles downstream, all with the label in your post. When used this
way, ground terminals are not to be connected together. Ungrounded
receptacles can also be used downstream.

The ground terminal on a GFCI connects only to the ground contacts for
what is plugged-in. There is no connection to the protection circuit.

==============================
A few changes from the 2011 NEC

If you are replacing a receptacle where it is now required to be tamper
resistant (child proof), the replacement has to now be tamper resistant
(most of a house).

Same with weather-resistant.

If you are extending an existing circuit in an area where AFCI
protection is now required, the entire extension is required to be AFCI
protected. (AFCI receptacles are now available.)

If you are replacing an ordinary receptacle in an area where GFCI
protection is now required, the new receptacle is required to be GFCI
protected. (Several ways to do it.)

If you are replacing an ordinary receptacle in an area where AFCI
protection is now required, the new receptacle is required to be AFCI
protected. (Also several ways to do it.) (Other than this, AFCI is
intended to protect the branch circuit wiring in addition to the
receptacle and what is plugged in.)