Finding an 'open' circuit in house wiring

jerry_njJanuary 13, 2011

I have a 120 vac duplex outlet to feed the cloths washer. It appears to be the only outlet on a 20 amp circuit breaker. That is there are no known other outages, lights in the laundry room work.

Problem: No power at duplex outlet

Check: verified no power with tester at duplex outlet and at the wires connected to the duplex outlet.

Check: verified circuit breaker was working, found power at the output terminal labeled as the washer circuit breaker

Next steps? The next most simple may be to check that all circuit breakers have power at their outputs, in case the CBs are mislabeled. If I can not find a faulty CB, trace the wire from the CB panel (in basement) to where it goes through the floor to the first floor laundry room. This will also verify I am checking the correct CB. Seems simple, if the CB is delivering power to the cable and the cable has no power at the outlet end, there must be a break in the wire, right?

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It is very unusual to simply have a break in the wire. More likely is a loose connection either at the breaker, the neutral bus, or at the receptacle.

    Bookmark   January 13, 2011 at 10:49AM
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Ron Natalie

If your house was wired to fairly modern codes, the laundry receptacles (typically only one given cheap builders) is required to be on a 20A circuit not shared with other rooms/uses.

Your methodology seems good. There may be (for some undetermined silly reason) a junction box between the receptacle and the panel. That would be a good place to look. I'd examine carefully all the exposed sections of the cable (including the areas inside the panel and the box with the receptacle) for damage. Just the other day I found a job where someone nicked the conductor near the receptacle (but was hidden inside the insulation.

    Bookmark   January 13, 2011 at 10:49AM
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Thanks I will make a more careful check on the wire connections.

The house is about 30 years old, and built by a custom contractor, proves nothing, with some deluxe features. I did not know it was "code" for a 20A 120 volt service to a laundry room. Of course there is also 240 volt service for the electric cloths dryer. The only thing connected to the troubled outlet is the washer (now running using an extension cord). I haven't checked but I'd guess the typical cloths washer doesn't draw more than 10 amps. But, if one is ironing from the same plug (duplex) the 20A could be best.

    Bookmark   January 13, 2011 at 11:50AM
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"verified no power with tester"

What kind of "tester"?

A digital meter?
Analog meter"
Voltage TIC?
A light bulb?

From what point to what point?
Hot to neutral?
Hot to ground?

Wires rarely break unless damaged (though over the years I have seen a few cables that were bad form the start).

A poor connection is a far more common cause, but you need to have tested with a load to really tell many times.

    Bookmark   January 13, 2011 at 1:58PM
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Is there a subpanel?
Could there be an outside GFI receptacle in the circuit, before the laundry receptacle? Maybe it's tripped.

    Bookmark   January 13, 2011 at 2:52PM
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Thanks for the good ideas. I used a "Square D" circuit tester. It is over 50 years old from the days I was an apprentice electrician...right out of high school. I has a mechanical indicator that comes down a scale so one can see a difference between 120 and 240 say. I used it across the duplex plug wire terminals, then I used my fingers just in case the tester wasn't working. At the CB box I used the tester to touch the CB lug screw and a ground wire randomly selected...not the return wire from the troubled outlet - could also be the problem - thinking an ohm meter to groudn on the return could provide some useful information. Now I can see I need to make sure the lug screw is tight, and better yet to get my test prob on the wire, not the lug screw. My old tester has a sharp test probe that can be used to pierce the wire insulation... I'll get back to this soon.

I am almost certain there is only one circuit run, from the CB box to the plug, but I'll have to trace that out physically to be sure. There is a ground fault CB feeding a bath room nearby. That breaker went bad and in replacing it some months back I may have "jiggled" the subject circuit loose. I like that idea and will focus on that for my next step.

    Bookmark   January 13, 2011 at 3:08PM
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"I used it across the duplex plug wire terminals, then I used my fingers just in case the tester wasn't working."

There is a troubleshooting method from the 1950's when men were men and ground fault protection was used by utilities on primary. If you threw your toaster in the kitchen sink and got killed, you should have known better.

    Bookmark   January 14, 2011 at 7:39AM
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I would use a Greenlee Circuit Seeker.

Plug the transmitter into the outlet. It sends a signal over the conductors.
The receiver(usually a probe) picks up the signal sent from the transmitter. The receiver generates a buzzing noise or activates a light when held close to the conductor with the signal. The stronger the signal, the brighter the light or louder the noise produced.

This will work fine as long as no other circuit is sharing a neutral.

    Bookmark   January 14, 2011 at 8:31AM
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Fox and hound circuit chasers can be fooled by broken conductors.

Enough of the signal can get past a small break in the wire to be picked up by the receiver.

Units with adjustable receive sensitivity are more useful for problems like this.

    Bookmark   January 14, 2011 at 9:57AM
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Thanks, I have looked with interest at the rf (I assume) signal generator and tracer. This is the second time in my life I think I would use one if I had one....didn't consider their weak points.

As for the toaster, AMen, I did take care, however, to be sure the path of least electrical resistance was between my index finger and thumb on the same hand.

    Bookmark   January 14, 2011 at 10:24AM
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One simple test I use on a circuit that no longer has power is a continuity test between the neutral and gound wire. If the circuit makes it back to the panel, there should be continuity. If not, then something has interrupted the neutral path back to the panel. Could be a tripped AFCI/GFCI, nine neutrals under an orange wire nut,etc. While there are a number of variables that can affect this simple test, nine times out of ten it gives me an excellent place to start troubleshooting.

    Bookmark   January 16, 2011 at 10:50AM
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Thanks, the ohm test sounds like a good check that at least the neutral wire has continuity to ground (at the CB box, assumed). The circuit isn't critical, so I didn't get to looking at it even with a weekend...where does the time go?

    Bookmark   January 16, 2011 at 10:09PM
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Hoping someone here can help. We had a massive electrical surge here two nights ago - tripped several breakers, took out 4 surge protectors (rated 330V), the microwave oven, and a few assorted ac adapters that were plugged directly into outlets. Thankfully, the devices that the surge protectors were designed to protect actually all survived. It also completely blew out GFI 1 (see attached), which I replaced with a new one, and tripped at least one other one.

The remaining situation after cleaning up the mess is that one circuit off a subpanel (see attached drawing) is still partially dead. GFI 1 has line and load power, but GFI 2 has neither. Also the neutral on GFI 2 is 0 ohms to ground, I think indicating that the outage is not being caused by another GFI outlet in the circuit (I haven't found one anywhere either).

Any thoughts?

    Bookmark   July 16, 2012 at 10:10AM
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Friendly reminder to new poster, mattero'... results-wise, you should post this in your own new thread, rather than hijacking/cold-starting a thread that's lain dormant for 18 months. ;')

    Bookmark   July 18, 2012 at 1:58AM
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I agree, a new thread "GFI Trouble Shooting" or similar will attract people knowledgeable in your subject. That said, there is clearly some expert inputs in this thread and as they all get your response you may get something helpful.

Moving forward, I admit I do not understand your diagram. Are you saying you have GFI circuit breakers in your main power box, or are you saying you have remote GFI (such as the GIF receptacle) that in the case of GFI2 has multiple non-GFI receptacles daisy-chained to?

    Bookmark   July 18, 2012 at 11:58AM
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"you have remote GFI (such as the GIF receptacle) that in the case of GFI2 has multiple non-GFI receptacles daisy-chained to" - this is it exactly. GFI1 receptacle has no load on it (other than its own duplex outlet) and is live and working, but GFI2 protects multiple other non-GFI outlets and has no line power to it.

    Bookmark   July 18, 2012 at 2:20PM
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