Detecting first recepticle on a circuit

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jalegris

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.
--
(||) Nehmo (||)


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On Mon, 13 Feb 2006 16:01:47 -0800, Nehmo wrote:

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
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Rich Grise wrote:

disconnecting its own load and allt he downstream ones.
Cheers.
Ken
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The GFCI and duplex receptacle are combined in a discrete or single 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".
--
(||) Nehmo (||)


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wrote:

Not quite - it just has a GFCI trip, no overcurrent trip, so it does not replace a normal circuit breaker.

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.

--
Peter Bennett VE7CEI
email: peterbb4 (at) interchange.ubc.ca
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wrote:

--
Not a circuit breaker, per se.
The GFCI will trip if there\'s a difference between the current into
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Rich Grise wrote:

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
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Charlie Edmondson wrote:

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.
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Or maybe use a Time Domain Reflectometer.
--
Joe Soap.
JUNK is stuff that you keep for 20 years,
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And just what is that, and what does it do?
Thanks,
David
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Plug a large load like a hair blower into the plug, turn on and measure the voltage with a digital voltmeter. Plug with highest voltage should be the first.

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If you type "Time Domain Reflectometer" into the Googlebox, and hit Return, all will be revealed.
--
Joe Soap.
JUNK is stuff that you keep for 20 years,
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snipped-for-privacy@panix.com (David Combs) writes:

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
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On 26 Feb 2006 10:34:44 -0800, cs snipped-for-privacy@hotmail.com wrote:

Connect the recepticle to your testicle and you will know !!!! :)
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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
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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?
-- Joe Legris
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On 13 Feb 2006 17:15:50 -0800, snipped-for-privacy@sympatico.ca wrote:

Is that different from the LINE and LOAD terminals?
--
Mark Lloyd
http://notstupid.laughingsquid.com
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Rich Grise wrote:

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

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
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On Sun, 12 Feb 2006 09:43:39 GMT, "Nehmo Sergheyev"

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
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Dudnt work that way- it is qwite posble there is no furst recept-icle. Put in a brak-er.
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