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?
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
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
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.
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.
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, ...
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.
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.
If it is allowed, perhaps you could have an electrician do that for you.
I'm pretty unsophisticated- barely use meters- here's what I'd do. 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.
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.
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.
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.
Then you won't be able to install a GFCI receptacle at the first outlet. Go with the GFCI receptacle at the panel.
Possibly, or you may have knob and tube wiring.
Yes, it will be OK.
Yes if you install the GFCI at the panel.
Yes. The way your house is wired as you described. There's not a line/load available.
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.
" 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. "
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?
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 - 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
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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.
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