Detecting first recepticle on a circuit
canadian_...@hotmail.com
circuit? I have an older house - the two upstairs rooms are on the same
circuit and are not grouned. Id like to add a GFCI plug on the first
recepticle on that circuit, so every recepticle downstream is
protected.
The brute force method would be to guess which recepticle is the first,
remove the outgoing wires, and test every other outlet for power -
rinse (hook back up the wires), repeat, until ive found the recepticle
that has power and all the others that dont. :) However this will take
awhile - most arent easily accessible - behind furnitire, beds etc.
I have at my disposal the standard home repair tools - volt meter, etc.
Thanks!
Mikepier
ensure it is protected.
Nehmo Sergheyev
Nehmo -
I don't know exactly how to do it in practice, but in theory…
1.
Unplug everything on the circuit.
At the circuit breaker box, with the breaker off, connect what would
have been the hot wire of the circuit to the neutral. Leave the neutral
connected normally.
Measure between one slot and the other at each receptacle.
At each receptacle, the measurement of the resistance and inductance
will be different. They will be lowest at the first, and highest at the
last.
14 gauge wire only has a resistance of 2.6 ohms per 1,000 feet, so the
difference in resistance will be difficult to measure. But the
inductance should be substantially different at each receptacle. At
higher frequencies, the measurement should be easy.
Or
2.
Get something that detects AC _current_ in a wire without electrically
connecting to the wire. Perhaps a pick-up coil attached to an amplifier
or perhaps a large coil simply connected to an earphone. I'm not used to
the commercial non-contact detectors, but one of them would work. You
want something that makes a different indication for a current flowing
wire and just a hot wire. After you have your detection tool, experiment
with it. Learn to detect a current-carrying wire.
With the circuit breaker on, plug-in a high-wattage lamp in what you
suspect to be the first receptacle. You should not be able to detect
current moving through the wires at any other receptacle. If you detect
current at a receptacle, it's at a position before the lamp receptacle.
Unplug the lamp and plug it in what you suspect to be the last
receptacle. You should be able to detect current at every receptacle.
Note I'm making a distinction between a receptacle with current going
through the wires connected to it and a receptacle that's just hot. All
of them should be hot. The electromagnetic field will be much stronger
around a current carrying wire.
Or
3.
Get a really high-wattage load, perhaps a big electric heater, something
with a high enough wattage to heat its supply wires detectably - but not
dangerously. Use the same system as the current detector. Plug in the
load at the (believed) last receptacle. Check the earlier receptacles
for warm wires. You get the idea.
4.
Fire the circuit up with DC (use a rectifier by the circuit breaker
box). Put a low-resistance load on the circuit at some receptacle. With
a sensitive voltmeter, measure between a hot slot of one receptacle and
the hot slot of another. The existence and the polarity of this tiny
voltage drop will show the relative position of the receptacles. If you
draw a diagram, you'll understand.
You could do this with the regular AC too, but you wouldn't get the
polarity info. You still could figure out which receptacle is first.
You're testing for a voltage drop across a load, which in this case is
just a piece of wire between receptacles. The voltage drop will not be
much.
[I crossposted]
--
(||) Nehmo (||)
Pop
<canadian_...@hotmail.com> wrote in message
news:1139708815.1...@g43g2000cwa.googlegroups.com...
: Is there a simple way to figure out which is the first
That's probably the onlyh accurate, positive way to do it though.
Usually it'll be the box that is the least wire distance from the
breaker box, so some logic might help as opposed to a WAG at
where to start. If you can see much of the wiring leaving the
breaker box, that might give a hint, too; depends.
Pop
jale...@sympatico.ca
For broad protection, GFCI circuit breakers may be added in many panels
of older homes to replace ordinary circuit breaker. For homes protected
by fuses, ...
canadian_...@hotmail.com
afaik, those breakers are pretty expensive. But ill check today and
possibly pick one up.
Thanks for the comments all. Nehmo - your post alluded to a method I
had considered, but im not skilled enough to know exactly what to do :)
What you say makes sense, but I think ill either go with a breaker, or
the method I talked abut.
Thanks all for comments.
Philip Edward Lewis
I've thought about gfci-ing some circuits by doing this:
Install the box/outlet near the main panel.
Unhook the wire from the breaker.
Add a new wire that goes from the breaker to the new (gfci) outlet.
Take the old wire, and feed it from the gfci outlet.
Does anyone know if this is acceptable by NEC code?
I cannot think of a reason that it wouldn't be, but then, I'm no
expert. There might be some "exposed wiring" issues.
If it is allowed, perhaps you could have an electrician do that for
you.
--
May no harm befall you,
flip
Ich habe keine Ahnung was das bedeutet, oder vielleicht doch?
Remove origin of the word spam from address to reply (leave "+")
Sev
First, just try to trace the likely wire route by seeing where circuit
exits panel, get up in attic and see if I can see where run drops down
etc. Taking guess from this which is first receptacle in circuit-
after turning off power- and testing to make sure it's off!- pull out
this recep and disconnect black wires, then reconnect this recep, but
not run which continues to rest of circuit- cap loose wire. Turn
power back on and test to see if this recep is live, but rest of
circuit dead. Of course if it is dead you probably reconnected run to
rest of circuit and capped line from panel. This could be laborious if
your guesses are wrong/ if it is difficult to trace wire route.
Usually it is not that hard, but that does depend on how your house is
wired/ whether attic has decking etc. It is easier if you begin by
testing to see exactly which receps are on that circuit- turn it off
and test them all to see which live/dead.
canadian_...@hotmail.com
The recepticle is 15 bucks.
Gonna go that route :)
Thanks for responses all.
volts500
> canadian_...@hotmail.com writes:
> >afaik, those breakers are pretty expensive.
> Is there a posibility of sticking a new outlet near the breaker panel?
>
> I've thought about gfci-ing some circuits by doing this:
> Install the box/outlet near the main panel.
> Unhook the wire from the breaker.
> Add a new wire that goes from the breaker to the new (gfci) outlet.
> Take the old wire, and feed it from the gfci outlet.
>
> Does anyone know if this is acceptable by NEC code?
> I cannot think of a reason that it wouldn't be, but then, I'm no
> expert. There might be some "exposed wiring" issues.
Yes, it's acceptable, and in fact, it's exactly what many electrical
contractors do to save the customer money when it looks like it will
take a lot of time to find the first outlet, as in this case. In most
cases one only needs to try to visualize what the quickest, easiest,
and most practical way to run the circuit; usually yields a clue as to
where the first outlet is located.
John Larkin
If you go to RatShack and buy one of their little amplified speaker
boxes (looks like an old transistor radio) and a telephone pickup
coil, that combo can ge used to hear 60 Hz magnetic fields near wires.
So connect some load gadget to the various outlets one at a time.
Something that has nasty current harmonics, like a PC or a tv set, is
best... makes the current distinct and more audible. Now you can trace
the wires in the walls and figure where the current is going. You may
wish to kill other breakers in the house, or have somebody cycle your
test load, if things get confusing.
John
canadian_...@hotmail.com
I think I might have to go this route anyway.
Ive done about half the recepticles - Im confused because each
recepticle is at the end of the line - ie wire comes in, but not out.
Becasue of this im guessing that there is a central junction box (es)
in the attic or ceiling with drops down to each recepticle.
As an fyi - there are hardwired ceiling lights on the circuit as well,
although none of the recepticles are switched (they are always live).
Many people have suggested getting in the attic. I'm going to try this,
but its not going to be that easy. My house is a 1.5 story and the
attic is very small - only a couple feet in the best of places, with
lots of fiberglass - so mucking around in there will not be pleasent.
Couple questions:
1) If I do as suggested and put the GFCI by the panel - will each
recepticle be covered if its like I describe above? I can visualize
quite easily a series of recepticles with the first being a GFCI and
how they would all be covered. However in my case it seems a bit more
complicated - ie lights, a junction box spreading to each recepticle,
etc. Would this till be ok? Is there any situation where putting a GFCI
as the first recpeticle on a circuit would NOT protect ones downstream?
2) Once Ive hooked up the GFCI, is there any way to CONFIRM each
recepticle is covered? Ie something i can safely do to try and trip the
GFCI (and something safe incase its not on the same circuit as the
GFCI). Hopefully what ive said here makes sense.
Thanks for the responses all, very helfull.
Fred Bloggs
>
>>Is there a simple way to figure out which is the first recepticle on a
>>circuit? I have an older house - the two upstairs rooms are on the
>
> same
>
>>circuit and are not grouned. Id like to add a GFCI plug on the first
>>recepticle on that circuit, so every recepticle downstream is
>>protected.
Dudnt work that way- it is qwite posble there is no furst recept-icle.
Put in a brak-er.
volts500
> Great idea guys re GFCI right at the panel..
>
> I think I might have to go this route anyway.
>
> Ive done about half the recepticles - Im confused because each
> recepticle is at the end of the line - ie wire comes in, but not out.
Then you won't be able to install a GFCI receptacle at the first
outlet. Go with the GFCI receptacle at the panel.
> Becasue of this im guessing that there is a central junction box (es)
> in the attic or ceiling with drops down to each recepticle.
Possibly, or you may have knob and tube wiring.
> As an fyi - there are hardwired ceiling lights on the circuit as well,
> although none of the recepticles are switched (they are always live).
>
> Many people have suggested getting in the attic. I'm going to try this,
> but its not going to be that easy. My house is a 1.5 story and the
> attic is very small - only a couple feet in the best of places, with
> lots of fiberglass - so mucking around in there will not be pleasent.
>
> Couple questions:
>
> 1) If I do as suggested and put the GFCI by the panel - will each
> recepticle be covered if its like I describe above?
Yes, it will be OK.
> I can visualize
> quite easily a series of recepticles with the first being a GFCI and
> how they would all be covered. However in my case it seems a bit more
> complicated - ie lights, a junction box spreading to each recepticle,
> etc. Would this till be ok?
Yes if you install the GFCI at the panel.
> Is there any situation where putting a GFCI
> as the first recpeticle on a circuit would NOT protect ones downstream?
Yes. The way your house is wired as you described. There's not a
line/load available.
>
> 2) Once Ive hooked up the GFCI, is there any way to CONFIRM each
> recepticle is covered?
Yes, trip the GFCI and verify that all outlets on that circuit go dead.
You also want to make sure that you do _not_ have a ground connection
between any of the downstream outlets. It's possible that the ground
is hidden or that BX cable was used.
canadian_...@hotmail.com
between any of the downstream outlets. It's possible that the ground
is hidden or that BX cable was used. "
Thanks for your responses Volts500.
It is NOT knob and tube from everything Ive seen so far.
Can you elaborate a little on what you mean by " make sure you do not
have a ground connection between any downstream outlets ".
About half of the outlets have NO ground (not even to the box).
The other half use a newer cable and are grounded to the box. That
ground is connected to the outgoing ground as well which I presume
leads to the next outlet.
However when I test the outlets with a tester, it reads "open ground" -
ie not grounded back to the panel.
Are you saying:
1) Remove the outlet to ground connection for each outlet? Ie dont
hookup a ground to the outlet? If so, what should I do with that ground
wire? Cap it off? Should it be hooked to the junction box?
2) Or something else?
Also
Could you explain why I _dont_ want a ground connection between any of
the downstream outlets?
Much thanks.
canadian_...@hotmail.com
Opps - I didnt mean "junction" there. I just meant to the actual box
obviously.
volts500
I think Tom Horne did a good job of explaining the reasons for not
connecting the ground on downstream outlets in a previous thread. In
your case in may be best to use isolated ground receptacles as he
suggested in the "replacing older electrical outlets" thread. You
should be able to find that thread a few pages back in this newsgroup,
or google it. Also, the non-grounded three prong receptacles need to be
marked "no ground" with the stickers that come with the GFCI
receptacle. Also, the instructions that come with the GFCI receptacle
should help a lot.
Nehmo
> GFCI breaker to fir my panel up here in canada is $115 bucks.
> The recepticle is 15 bucks.
Nehmo -
The problem with GFCIs is that they're prone to naissance trips.
Usually it's inconvenient to walk all the way to the circuit breaker
panel to investigate the condition of the GFCI. A better location is
right at the receptacle. And to aid the troubleshooting, a GFCI
equipped with an indicator light is helpful http://snipurl.com/mhtb .
The best arrangement is to have a GFCI at every receptacle in the
protected area. In that way, when a GFCI trips, the power interruption
is limited to one duplex receptacle.
Nehmo
Nehmo
Mikepier
.
> You also want to make sure that you do _not_ have a ground connection
> between any of the downstream outlets. It's possible that the ground
> is hidden or that BX cable was used.
>
I thought GFI's operation had nothing to do with the ground. It trips
when it detects a current imbalance between the hot and neutral,
regardless if theres a ground or not. I could be wrong though.
Bud--
>
>
> I think Tom Horne did a good job of explaining the reasons for not
> connecting the ground on downstream outlets in a previous thread. In
> your case in may be best to use isolated ground receptacles as he
> suggested in the "replacing older electrical outlets" thread. You
> should be able to find that thread a few pages back in this newsgroup,
> or google it.
Chris Lewis
I think that most people would find that GFCI's don't false trip very
often. If at all. I've never had one of mine trip when it wasn't clear
it _probably_ had a good reason. False trips are suggestive of
electrical boxes getting damp, bad extension cords, or oddities in
old wiring (intermittent neutral-ground shorts) etc.
By putting in more GFCIs, you're increasing your probabilities of
GFCI failure _and_ false tripping.
I'll bet that if you did a good sized survey, you'll find _more_ trouble
(including out-and-out GFCI failure) if you put an GFCI in every
receptacle box than you would with a judiciously placed single GFCI outlet
(or breaker).
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
Rich Grise
Well, as long as I have your attention, it makes absolutely no difference
whatsoever which outlet on a main line has a GFCI - each one only protects
itself and what's plugged into it, and couldn't care less what's happening
downstream:
[view in fixed font, with wrap off]
.
. Mains Hot -------+-------------+-------------+
. Mains Neut. -----|--+----------|--+----------|--+
. | | | | | |
. ------ ------ ------
. | GFCI | | GFCI | | GFCI |
. ------ ------ ------
. P.C P.C P.C
Where "P.C" means "Protected Circuit".
What has been suggested, (sorry, don't remember by whom - jalegris?) is to
use a GFCI circuit breaker, which goes on the left:
.
. -------
. Mains Hot --| GFCI |----+-------------+-------------+
. Mains Neut.--| C.B. |----|--+----------|--+----------|--+
. ------- | | | | | |
. Ordinary Ordinary Ordinary
. Outlet Outlet Outlet
That's "on the left" in my attempt at a diagram - in real life, it goes in
the breaker panel.
Or, of course, you could upgrade your wiring - it will increase the resale
value of the house considerably! :-)
Good Luck!
Rich
w2aew
That's not exactly true. The GFCI receptacles have a LINE input and
and LOAD output. Any receptacles connected to the LOAD output
terminals of the GFCI are also protected circuits.
Keith Williams
rich...@example.net says...
> [crossposted, s.e.d dropped from followups]
> On Sun, 12 Feb 2006 07:38:58 -0800, canadian_woodworker wrote:
>
> > Yea, ive read that page before.
> >
> > afaik, those breakers are pretty expensive. But ill check today and
> > possibly pick one up.
> >
> > Thanks for the comments all. Nehmo - your post alluded to a method I had
> > considered, but im not skilled enough to know exactly what to do :) What
> > you say makes sense, but I think ill either go with a breaker, or the
> > method I talked abut.
> >
> > Thanks all for comments.
>
> Well, as long as I have your attention, it makes absolutely no difference
> whatsoever which outlet on a main line has a GFCI - each one only protects
> itself and what's plugged into it, and couldn't care less what's happening
> downstream:
Not true. GFCI outlets have a gazinta and a gazouta. Anything
attached to the gazouta side is also protected by the GFCI. The
feed-through is usually rated at 20A, which is likely the same as
the branch circuit. If he can find the first outlet he can protect
the whole circuit with a $10 GFCI outlet, rather than a $25 GFCI
breaker. He won't have to go into the basement (or outside, in my
case) to reset the GFCI either.
> [view in fixed font, with wrap off]
> .
> . Mains Hot -------+-------------+-------------+
> . Mains Neut. -----|--+----------|--+----------|--+
> . | | | | | |
> . ------ ------ ------
> . | GFCI | | GFCI | | GFCI |
> . ------ ------ ------
> . P.C P.C P.C
>
> Where "P.C" means "Protected Circuit".
>
> What has been suggested, (sorry, don't remember by whom - jalegris?) is to
> use a GFCI circuit breaker, which goes on the left:
> .
> . -------
> . Mains Hot --| GFCI |----+-------------+-------------+
> . Mains Neut.--| C.B. |----|--+----------|--+----------|--+
> . ------- | | | | | |
> . Ordinary Ordinary Ordinary
> . Outlet Outlet Outlet
>
> That's "on the left" in my attempt at a diagram - in real life, it goes in
> the breaker panel.
It could be a GFCI in the first outlet on the circuit, as well.
> Or, of course, you could upgrade your wiring - it will increase the resale
> value of the house considerably! :-)
Maybe.
--
Keith
Charlie Edmondson
One of the 'recent' innovations is to build the GFCI circuit breaker
into the 'first' outlet in the chain. On that outlet, the two sets of
connections are isolated from each other, so that all downstream outlets
are then protected. This allows you test and reset the circuit from
inside, without having to go find the breakerbox. It has become
standard in the NEC to do it that way now.
But, the only way to really tell which outlet is first is to pull each
one out, and buzz out each side. Takes a while, but is the only sure
way to find out. Unless, of course, you took pictures of the wiring
before they put up the sheetrock!
Charlie
Nehmo
> I think that most people would find that GFCI's don't false trip very
> often. If at all. I've never had one of mine trip when it wasn't clear
> it _probably_ had a good reason. False trips are suggestive of
> electrical boxes getting damp, bad extension cords, or oddities in
> old wiring (intermittent neutral-ground shorts) etc.
Nehmo -
GFCI nuisance trips are common. This article, Think Like a GFCI
http://www.ecmweb.com/mag/electric_think_gfci/ discusses some causes:
harmless leaks, capacitive leaks, cumulative (the fed outlets added
together), and fluorescent fixtures may generate switching transients.
Even legitimate tripping is a pain to correct when the reset button is
in the panel box in the basement.
Chris Lewis -
> By putting in more GFCIs, you're increasing your probabilities of
> GFCI failure _and_ false tripping.
Nehmo -
No.
Cumulative leaks on downstream outlets would be eliminated because
there would be no downstream outlets. And as I said before, any
tripping incident is localized, allowing for easy troubleshooting,
which is even more easy if the GFCI receptacles have indicator lights.
I repeat: the ideal arrangement is a GFCI at every receptacle that
needs protection.
Mark Lloyd
>Great idea guys re GFCI right at the panel..
>
>I think I might have to go this route anyway.
>
>Ive done about half the recepticles - Im confused because each
>recepticle is at the end of the line - ie wire comes in, but not out.
>Becasue of this im guessing that there is a central junction box (es)
>in the attic or ceiling with drops down to each recepticle.
>As an fyi - there are hardwired ceiling lights on the circuit as well,
>although none of the recepticles are switched (they are always live).
>
Mine are like that. In most cases, wires to each receptacle and switch
come from a junction box at the ceiling light fixture. The whole thing
would look something like a giant octopus on top of the room with
tentacles hanging down all over. In that case, maybe you could put a
GFCI in a box next to the existing ceiling one. The other rooms use
pigtails so each receptacle has it's own connection (no others depend
on it).
>Many people have suggested getting in the attic. I'm going to try this,
>but its not going to be that easy. My house is a 1.5 story and the
>attic is very small - only a couple feet in the best of places, with
>lots of fiberglass - so mucking around in there will not be pleasent.
>
My attic looks like that.
>Couple questions:
>
>1) If I do as suggested and put the GFCI by the panel - will each
>recepticle be covered if its like I describe above? I can visualize
>quite easily a series of recepticles with the first being a GFCI and
>how they would all be covered. However in my case it seems a bit more
>complicated - ie lights, a junction box spreading to each recepticle,
>etc. Would this till be ok? Is there any situation where putting a GFCI
>as the first recpeticle on a circuit would NOT protect ones downstream?
>
Something that won't work on shared neutral circuits.
>2) Once Ive hooked up the GFCI, is there any way to CONFIRM each
>recepticle is covered? Ie something i can safely do to try and trip the
>GFCI (and something safe incase its not on the same circuit as the
>GFCI). Hopefully what ive said here makes sense.
>
Ground each hot connection, through a resistor (just like the test
buttons do). The resistor limits current in case the GFCI doesn't
work.
>Thanks for the responses all, very helfull.
--
Mark Lloyd
http://notstupid.laughingsquid.com
"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin
Mark Lloyd
wrote:
A GFCI doesn't use ground. It responds to unintended ground
connections (indicated by a difference brethren hot and neutral
currents), like when you touch a defective power tool and become part
of the circuit.
The problem with connecting grounds (when no connection to earth
exists) is not specific to GFCIs. If you have 2 receptacles connected
this way, and an appliance plugged into one has a short from hot to
ground (one that's not quite enough to trip the breaker), the ground
connection at the other receptacle is now hot. You can get
electrocuted by touching what was supposed to be a safety ground.
Mark Lloyd
wrote:
That's when they're ALL first receptacles. Seems to be a common
situation here.
Mark Lloyd
And write down your test results, to avoid forgetting and redundant
retesting. You could also mention what to do if you see only one pair
of wires to the receptacle, maybe even short wires going to a soldered
junction.
Mark Lloyd
I suppose you have fewer than 7 2/3 receptacles :-)
Chris Lewis
> Chris Lewis -
> > I think that most people would find that GFCI's don't false trip very
> > often. If at all. I've never had one of mine trip when it wasn't clear
> > it _probably_ had a good reason. False trips are suggestive of
> > electrical boxes getting damp, bad extension cords, or oddities in
> > old wiring (intermittent neutral-ground shorts) etc.
> Nehmo -
> GFCI nuisance trips are common.
There are many ways that nuisance trips can occur, but they are by
no means _commonly_ occuring.
> This article, Think Like a GFCI
> http://www.ecmweb.com/mag/electric_think_gfci/ discusses some causes:
> harmless leaks, capacitive leaks, cumulative (the fed outlets added
> together), and fluorescent fixtures may generate switching transients.
The article deosn't say anything about how common these actually occur,
and you're misinterpreting how "harmless" some of these things are.
There's no such thing as a harmless leak. Even a neutral-ground intermittent
is potentially a serious problem if it causes the grounding circuit
to corrode. It's not supposed to carry current _unless_ there's a fault.
Continuous current, especially in the presence of moisture, can easily
cause grounding connections to eventually fail. So that tiny little leak
can cause a full grounding failure later on that kills you.
The GFCI is trying to tell you something.
If you follow the guidelines of where to use GFCIs, nuisance trips
are virtually non-existant. I've never seen one. And I've installed
quite a few.
Cumulative leaks is not likely to be an issue. Leakage in properly
installed and dry systems is _extremely_ low. Vastly lower than the milliamps
needed to trigger a GFCI. Not enough, even when multiplied by 10 or 15
to be an issue. And if it was, you still have issues with ground circuit
corrosion.
The other point I was trying to make is that by multiplying the GFCIs by
a factor of 10, you're multiplying the possibility of GFCI burnout (by
line-side spikes etc) by a factor of 10. Which in the long run outweighs
the issue of nuisance trips.
From a reliability standpoint, it's better to have fewer than more of
these things.
Nehmo
> GFCI's on every outlet, but it's overkill. Or should I say underkill?
You will note the confusion people in this newsgroup have about GFCIs.
And this confusion is not limited to those people. Experienced
electricians often don't even know what's inside of a GFCI. And
everyday-people, people who typically use receptacles, sometimes are
completely bewildered by them and how they should be used.
When ordinary Smo discovers a downstream receptacle to be dead,
sometimes that's the end of the troubleshooting. Smo simply concludes
there is something wrong with the electricity, and he or she leaves it
to somebody else to make the repair.
However, if the receptacle Smo is using has a reset button on it, Smo,
seeing the button right there, may try it, and he or she may succeed in
repairing the electric problem.
So a multiple-GFCI installation has a troubleshooting advantage. This
equates to an installation that is up and working a higher proportion
of its life. Thus, the multiple installation is superior. However, it
costs more.
In new construction, the labor cost of installing a GFCI receptacle is
equivalent to that for a regular receptacle. The cost difference in
materials isn't substantial. Consequently, new construction (on all but
the cheapest of projects) should have a GFCI at every receptacle where
GFCI protection is needed.
In retrofits, each replaced receptacle is an added cost. And in some
older houses, the old small boxes won't accommodate a GFCI. So an
inexpensive way to protect all the outlets on a circuit is to just use
the GFCI on the first outlet.
Jasen Betts
> Well, as long as I have your attention, it makes absolutely no difference
> whatsoever which outlet on a main line has a GFCI - each one only protects
> itself and what's plugged into it, and couldn't care less what's happening
> downstream:
you can get outlets that proviide proteted output terminamls
on the back to connect protect to other downstream standard outlets
. Mains Hot ------+ +----------+-------------+
. Mains Neut. ----|-+ | +--------|--+----------|--+
. | | | | | | | |
. ------ Ordinary Ordinary
. | GFCI | Outlet Outlet
. ------
. P.C
note: ground connection present but not shown
--
Bye.
Jasen
ehsjr
>
>
> Well, as long as I have your attention, it makes absolutely no difference
> whatsoever which outlet on a main line has a GFCI - each one only protects
> itself and what's plugged into it, and couldn't care less what's happening
> downstream:
>
> [view in fixed font, with wrap off]
> .
> . Mains Hot -------+-------------+-------------+
> . Mains Neut. -----|--+----------|--+----------|--+
> . | | | | | |
> . ------ ------ ------
> . | GFCI | | GFCI | | GFCI |
> . ------ ------ ------
> . P.C P.C P.C
>
> Where "P.C" means "Protected Circuit".
Right - when wired as drawn above. But GFCI receptacles
can be wired to protect downstream receptacles/wiring as
well. They are marked with a line and load side. The
wiring on the line side of the GFCI receptacle is not
protected by the GFCI. The GFCI contained receptacle,
and everything on the load side is:
--------- --------
Mains Hot -------| GFCI |------| Regular|--- etc
Mains Neut. -----| Recpt. |------| Recpt. |---
--------- --------
Line Load
>
> What has been suggested, (sorry, don't remember by whom - jalegris?) is to
> use a GFCI circuit breaker, which goes on the left:
> .
Cheaper to install a GFCI receptacle in the first position
on the branch, and equally effective for ground fault
protection as a GFI circuit breaker. But you can't do
that on a multiwired branch with a shared neutral. For
such a branch circuit, you wire only to the line side,
and the GFCI receptacle feeds nothing down stream. Or
you could feed a non-shared neutral circuit downstream
through the GFCI receptacle, which implies adding
an extension to the existing multiwire.
Ed
Mark Lloyd
>In Canada, GFCI outlets have input and output terminals so you can
>protect a whole chain of downstream outlets with just one GFCI. You
>could put a GFCI on every outlet, but that's overkill. Or should I say
>underkill?
Is that different from the LINE and LOAD terminals?
Rich Grise
> In retrofits, each replaced receptacle is an added cost. And in some
> older houses, the old small boxes won't accommodate a GFCI. So an
> inexpensive way to protect all the outlets on a circuit is to just use
> the GFCI on the first outlet.
It seems I've learned something today. It sounds like you're describing
an outlet and circuit breaker in one box.
So, when any outlet on the "output side" trips it, the whole string
goes out? Does the first one still work? I.e., does it have two reset
buttons?
Thanks,
Rich
Ken Taylor
disconnecting its own load and allt he downstream ones.
Cheers.
Ken
Nehmo
device. Inside of this device is the GFCI circuitry. The connecting
slots for a plug and the downstream (labeled "load") connectors are
_both_ downstream from the circuitry.
If the GFCI is tripped, everything goes off.
There *are* two buttons, but one is "test" and the other is "reset".
Peter Bennett
wrote:
>On Mon, 13 Feb 2006 16:01:47 -0800, Nehmo wrote:
>
>> In retrofits, each replaced receptacle is an added cost. And in some
>> older houses, the old small boxes won't accommodate a GFCI. So an
>> inexpensive way to protect all the outlets on a circuit is to just use
>> the GFCI on the first outlet.
>
>It seems I've learned something today. It sounds like you're describing
>an outlet and circuit breaker in one box.
Not quite - it just has a GFCI trip, no overcurrent trip, so it does
not replace a normal circuit breaker.
>
>So, when any outlet on the "output side" trips it, the whole string
>goes out? Does the first one still work? I.e., does it have two reset
>buttons?
The GFCI outlet, and any outlets connected to its "load" terminals,
will switch off on a fault (or test). There is a single reset button
to restore power to the GFCI outlet and any downstream outlets.
>
>Thanks,
>Rich
--
Peter Bennett VE7CEI
email: peterbb4 (at) interchange.ubc.ca
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq
John Fields
wrote:
>On Mon, 13 Feb 2006 16:01:47 -0800, Nehmo wrote:
>
>> In retrofits, each replaced receptacle is an added cost. And in some
>> older houses, the old small boxes won't accommodate a GFCI. So an
>> inexpensive way to protect all the outlets on a circuit is to just use
>> the GFCI on the first outlet.
>
>It seems I've learned something today. It sounds like you're describing
>an outlet and circuit breaker in one box.
---
Not a circuit breaker, per se.
The GFCI will trip if there's a difference between the current into
the load and the current returning from the load, but it won't trip
if the load current (and the return current) are higher than the
circuit is rated for, since that's the job of the upstream breaker.
---
>So, when any outlet on the "output side" trips it, the whole string
>goes out?
---
Yes.
---
>Does the first one still work?
---
Yes, but it works by switching itself (as well as all of the
downstream sockets) off of the mains.
---
>I.e., does it have two reset buttons?
---
No, just one.
--
John Fields
Professional Circuit Designer
cs_po...@hotmail.com
> But, the only way to really tell which outlet is first is to pull each
> one out, and buzz out each side. Takes a while, but is the only sure
> way to find out. Unless, of course, you took pictures of the wiring
> before they put up the sheetrock!
Well, if you had a fast scope, and a pulse generator, and pulled the
end out of the breaker box and drove it like an RF transmission line,
you might learn something by plugging a simple "nightlight" load into
each outlet while watching the scope.
If it's on the first floor and the basement is unfinished, you might be
able to get a good idea just by looking up.
Joe Soap
news:1140978884.1...@v46g2000cwv.googlegroups.com:
> Well, if you had a fast scope, and a pulse generator, and pulled the
> end out of the breaker box and drove it like an RF transmission line,
> you might learn something by plugging a simple "nightlight" load into
> each outlet while watching the scope.
Or maybe use a Time Domain Reflectometer.
--
Joe Soap.
JUNK is stuff that you keep for 20 years,
then throw away a week before you need it.
hol...@noshit.com
Connect the recepticle to your testicle and you will know !!!! :)
David Combs
Joe Soap <m...@privacy.net> wrote:
>In response to what <cs_po...@hotmail.com> posted in
>news:1140978884.1...@v46g2000cwv.googlegroups.com:
>
>> Well, if you had a fast scope, and a pulse generator, and pulled the
>> end out of the breaker box and drove it like an RF transmission line,
>> you might learn something by plugging a simple "nightlight" load into
>> each outlet while watching the scope.
>
>Or maybe use a Time Domain Reflectometer.
And just what is that, and what does it do?
Thanks,
David
Jeff
voltage with a digital voltmeter. Plug with highest voltage should be the
first.
"David Combs" <dkc...@panix.com> wrote in message
news:dv9351$7h1$1...@reader2.panix.com...
Joe Soap
$qk4.1...@bgtnsc05-news.ops.worldnet.att.net:
>>>Or maybe use a Time Domain Reflectometer.
>>
>> And just what is that, and what does it do?
If you type "Time Domain Reflectometer" into the Googlebox, and hit Return,
all will be revealed.
Tomi Holger Engdahl
From http://www.epanorama.net/links/measuring.html#line
Time Domain Reflectometry measurements (sometimes called Time Domain
Spectroscopy techniques) work by injecting a short duration fast rise
time pulse into the cable under test. The effect on the cable is
measured with an oscilloscope. The injected pulse radiates down the
cable and at the point where the cable ends some portion of the signal
pulse is reflected back to the injection point. The amount of the
reflected energy is a function of the condition at the end of the
cable. If the cable is in an open condition the energy pulse reflected
back is a significant portion of the injected signal in the same
polarity as the injected pulse. If the end of the cable is shorted to
ground or to the return cable, the energy reflected is in the opposite
polarity to the injected signal. If the end of the cable is terminated
into a resistor with a value matching the characteristic impedance of
the cable, all of the injected energy will be absorbed by the
terminating resistor and no reflection will be generated. Should the
cable be terminated by some value different from the characteristic
impedance of the cable the amount of energy reflected back to the
cable start point would be the portion of the pulse not absorbed by
the termination. Also any change in the cable impedance due to a
connection, major kink or other problem will generate a reflection in
addition to the reflection from the end of the cable. By timing the
delay between the original pulse and the reflection it is possible to
discern the point on the cable length where an anomaly exists. The
cable type governs this signal propagation speed. For example normal
Category 5 cable propagation speed is 66% the speed of light, and for
most coaxial cables this value is between 66% and 86%.
One circuit example for TDR signal generator:
http://www.epanorama.net/circuits/tdr.html
--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/