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Re: Detecting first recepticle on a circuit

canadian_woodworker

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. > > 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.

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

  1. 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

  1. 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.

  1. 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  (||)
Reply to
Nehmo Sergheyev
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from google on GFCI circuit breaker

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, ...

formatting link

Reply to
jalegris

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.

Reply to
canadian_woodworker

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

Reply to
John Larkin

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

Reply to
Fred Bloggs

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

Reply to
Rich Grise

Rich,

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.

Reply to
w2aew

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.

It could be a GFCI in the first outlet on the circuit, as well.

Maybe.

--
  Keith
Reply to
Keith Williams

In Canada, at least, it CAN make a difference depending on where you put the GFCI outlet - it has input and output terminals. By connecting it as the first in a chain you can protect all the other downstream outlets. That's what the OP is trying to do. Of course, you could put GFCI's on every outlet, but it's overkill. Or should I say underkill?

-- Joe Legris

Reply to
jalegris

Hi Rich, 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

Reply to
Charlie Edmondson

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
Reply to
Jasen Betts

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 (||)
Reply to
Nehmo

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

Reply to
jalegris

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

Reply to
ehsjr

Is that different from the LINE and LOAD terminals?

--
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
Reply to
Mark Lloyd

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

Reply to
Rich Grise

Not in any I've seen. The outlet with the protection circuit trips out, disconnecting its own load and allt he downstream ones.

Cheers.

Ken

Reply to
Ken Taylor

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 (||)
Reply to
Nehmo

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        
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html 
Newsgroup new user info: http://vancouver-webpages.com/nnq
Reply to
Peter Bennett 

--
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.
Reply to
John Fields

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