I only have a basic understanding of home electrical wiring. I can understand how a light circuit works, including a 3-way circuit, but that's about the extent of it.

Last summer, I think I pretty well screwed up some outlets. We have a freezer in our garage, plugged into an outlet by the door to the garage. I also had a power strip plugged into that outlet for when I needed access to more outlets, as that was a convenient spot but the freezer covered the outlet up.

I also have a battery-powered lawn mower, and the battery has a quick charger. I made the mistake of plugging both of these things into the same outlet, and I assume the draw was too much to handle, because I came home one day to find water dripping out of the freezer That outlet - and a couple others on the outside of the house - do not work anymore.

I checked the breakers and they're all on. I've tripped and reset every GFI outlet I can find. What's puzzling to me is that there's a second outlet inside the garage - just in an awkward location for the freezer - and that one works, as do the ones that the garage doors are plugged into in the ceiling. Every switched light in the house also works. It's just three power outlets on the exterior of the house and in the garage.

What might have happened? How do I fix it?

Well it's done differently in different parts of the world BUT here at least (simply)

1) Power points and light are separate circuits (i.e. breakers) always
2) Power is usually split into more than group however for a small townhouse like ours we have just two circuits which equates to opposite sides. A larger house might have a couple more, maybe 4 or 5..

So 3 out of a lot doesn't sound like a breaker to me but more like a break in the wiring elsewhere which I can only guess to be burnt out wiring (which would not be a good thing) as a result of a slight overload. I presume the 3 are all in fairly close proximity to each other?

Is this an old place i.e. the wiring may be suspect?

If it was only one, I'd suspect the physical power point. 3 (assuming they stopped working at the same time) tends to suggest upstream from the powerpoint.

There's really not that much too it for the actual wiring usually. The line, neutral and earth should all just run back to the circuit board via some junction boxes. Work your way back from there.

If you have a lot of breakers (i.e. the 3 might be on just one exclusive one) then perhaps it has burnt out. Slightly tedious but do you know that each breaker is actually switching something else on/off. i.e. turn them on/off individually and work out what each one does.

Be sure. I've seen some old/crappy breakers that are worn-out enough so that they might look like they're on, but you still need to flip them fully off and then back on again to get them to work. Obviously if that turns out to be the case, you should replace the breaker. But that's easy to do on modern-ish breaker panels.

If it's true that the breaker is good, then I agree with the assessment that you might have burnt out the wiring in the wall. This is bad, in particular because that exactly the sort of thing that was supposed to trip the breaker. It's kinda the whole point of having a breaker in the first place. Again, breaker replacement is needed once you get the wiring fixed.

Another possibility is that the failure is completely unrelated to the freezer and the mower charger, and it's not a burn-out, it's something else, and it's just a coincidence that it looks like a burn-out and a bad breaker. Consider this possibility. Since that section of the wiring connects to outdoor outlets, who knows what could have happened. I once owned a house where the siding was so gappy that we had, um, "residents" in the outer walls a lot of the time. Remy takes a wrong turn, and bad stuff can happen to the wiring...

I just fixed a problem almost exactly like this. In my case, it was that the wire had come undone from the first outlet, as the person who installed it was lazy and just poked the wire into the hole in the back of the outlet, rather than using the screws on the side. The outlets were apparently wired like Christmas lights, where if one goes out, everything else down the line goes out. My breakers looked fine as well, and nothing was burnt inside the outlet either. If the outlet is burnt, here is how to fix it.

It really sounds like there's another GFCI outlet in the chain that you haven't found yet. But it could also be loose/bad wiring as Heather suggested.

It's probably not worth buying something of this ilk, but if you happen to be able to borrow one it's probably a decent idea. http://www.grainger.com/product/AMPROBE-Wire-Tracer-1WXE8

I'm with Mark. I suspect there's another GFCI outlet in some obscure location. Check the ceiling of the garage where the garage door opener plugs in or some similar obscure place.

Same EXACT thing happened in my garage and it took me forever to find the gfci outlet and reset. I assume you can get significantly cheaper wire tracers. I wonder if my network wire toner would work over that gauge wire...it a super cheap Chinese-made brand-less POS, but it's worked to trace network wires perfectly every time, even through walls.

And if a GFCI outlet indeed tripped, consider that it might have done so for a reason. Maybe the reason was all the stuff you had plugged in was just too much for the circuit, and you just need to reduce the number of items on that outlet. But, maybe, it was a genuine *ground* fault somewhere that needs to be fixed. Remy taking a wrong turn or snacking on the wrong bit could cause a ground fault, right?

I've had several variations on this problem in my garage, which indeed did once nuke everything in the garage freezer.

CAVEAT: I'm not a licensed electrician. If you follow my advice and electrocute yourself, it's not my fault. Don't mess around with 120V.

- Any semi-modern up-to-code wiring will require that there's a GFCI on every circuit. It's there. Look for it. I think my house has precisely one non-GFCI outlet, hidden in a strange corner in the attic. And even then, I'll bet I just never found the GFCI.

- It's reasonably typical for electrical plug boxes to be wired sequentially. The first one on the chain is typically where they put the GFCI outlet. That outlet and every one after it has one wire (three conductors) in and one wire (three more conductors) out. As Heather mentioned, it can get crowded in there, and and things don't always get screwed down properly.

- Furthermore, GFCI outlets, unlike standard ones, have an "upstream" and a "downstream" side, i.e., the path to the circuit breaker and the path to the rest of the outlets on the chain. Older GFCI outlets will happily let you install them backwards, and you won't be protecting any of the downstream outlets. Newer ones flat out don't work if you wire them up backwards. (Of course, you have no idea if your original electrician got it wrong, and of course the two wires aren't labeled. If you've got a multimeter, make sure the bare leads are poking out and not touching anything else, then energize the circuit and probe them. Carefully. Then turn the circuit off again.)

- Another way that electricians can screw up is by installing the GFCI somewhere other than at the head end of the chain. They only protect "downstream" outlets. If you're in a modern up-to-code house, you can get a cheap electrical outlet tester (here's one from Home Depot; note the red "test" button). A proper home inspector goes to each and every outlet in your house, plugs that thing in, hits the "test" button, and is expecting a GFCI somewhere to pop. If it doesn't, and instead your circuit breaker pops, then the house is not up to modern code.

- If you want to be paranoid, then replace that GFCI once you find it. They tend to wear out after ten years. We had one in our bathroom that had a quiet 60Hz buzz. I replaced it. No more buzz.

INTERESTING.

My house, which is quite modern (built within the last 5-7 years or so) has always had a low frequency hum, at 60hz and at all the harmonic nodes above and below 60hz, which is so faint that I can only hear it when I'm scrutinizing the noise floor of things I've recorded with sensitive mics in my recording studio. I've never been able to track down its source, and kinda wondered if it was neighbors, or just a pervasive constant noise from Aurora Avenue (though it never changes pitch or volume) or if it was a variation of The Hum. I wonder if maybe it's just a crappy GFCI outlet somewhere near the studio, and I just need to track it down and replace it.

Very interesting, thanks.

NFPA 70 (which is the most recent I have) seems to only require them for
* bathrooms
* kitchens
* outdoor plugs
* garage or "ground level" work areas

and even the executive summary from the NFPA states nothing more:

http://www.nfpa.org/safety-information/f...it-interrupters

Hmmm. Maybe my electrician went above and beyond by putting so damn many GFCI outlets in and around the house. Given how cheap and shoddy the work was in some places, I'm hard pressed to imagine how the extra GFCI outlets were anything other than required.

Yeah, I dunno. I looked when we moved in this place; some of the work here was less than ideal and I wanted to know that it was up to code. It seems to be.

A problem with GFCI is false tripping. Something one really does NOT want to occur on say, a freezer or NAS circuit.

Pretty decent idea for most parts of the home though.

Our master bathroom was out a couple days ago. It might have been obvious to be that something had been chained off the GFCI that the hot tub was on, but we quickly established that wasn't it. In the process of tracking it I tried tripping the GFCI by the sink, before finding the panel had one tripped breaker, but then the bathroom still didn't work... turned out both the GFCI by the sink and the upstream breaker had gone.

One more theory for Tony's 60Hz hum: fluorescent bulb transformers, including CFL bulbs. I'm slowly but surely banishing these things from my house, but of the remaining ones, some of them buzz.

Indeed. I have already banished them for the most part, except in a couple of cases, but when I was hunting for the hum, I turned off all lights of all kind and still the hum was there.

Have you determined whether the recorded noise is accoustically induced or electrically coupled? If you enclose the microphone in accoustic absorbent material so the mic cannot 'hear' anything, does the recording still show the same amount of hum noise?

Do not use the microphone 'mute' switch for this test as this may alter the electrical properties of the microphone feed to the recording equipment.

Mechanically coupled noise can be weird to trace. Microphone mountings can conduct vibration into the mic from the surfaces the mic stand is attached to.

I've walked around the room with the mic in my hand and the headphones on. The sound changes as I move around the room, but not enough to help me narrow its location down exactly . It seems to be coming from all the walls and floor. As if the whole house's frame is quietly resonating to a distant low frequency Diesel engine of some kind. That's what it sounds like anyway.

I'm relatively sure it's not hum in the gear itself, otherwise the noise would be the same as I moved the mic around. Also I've been through several different bits and brands of gear and the noise never changes.

60Hz audio has a wavelength of about 5m. In theory you should be able to use two microphones and locate the source by the phase shift, if you've got an oscilloscope. (Something like: start with the two mics close to each other, check that the hums are in phase, and try moving one mic so that they stay in phase. If you find yourself moving the mic in an arc, the centre of that circle is the source of the hum. If you find yourself moving it in a straight line, the source is distant and its direction is perpendicular to the line. If the hum is in phase everywhere in the room, you're in the resonator situation.)

Peter

I have had situations where the electrical noise was coming from wiring or equipment below the floor or overhead, and as the microphone moved around the microphone cable followed (naturally) and the induced noise changed as the cable moved. Transformers used for lighting can sometimes leak a noisy magnetic field. As can a nearby outdoor utility transformer feeding your neighborhood or commercial facility.

Good (balanced) microphone cables are supposed to reject outside magnetic/electrical interference, but this may not be 100% effective. Cable shielding can also be helpful but can be overcome if the cable is not perfect or the noise source is relentless.

Were you testing with a wired microphone? Balanced audio connection?

Thanks for all the responses, folks. I'm away on vacation so I'll need to check take in all this advice later. I could have sworn I looked for all possible GFCI outlets when this problem first occurred and tripped/reset them all. I would assume that if one of them was the cause of this problem, that it would also be dead, but they all seemed fine too.

I'm hoping it's not frayed cords.

And I'm interested in tracking down the source of Tony's hum, too! As previously established, my house also has a weird noise that I've asked you folks about. Funny thing is, I couldn't hear it the other night, but I can't recall if the absence coincided with the outlets going dead.

Balanced XLR, large-diaphragm condenser mic.

Agreed that it could be inductive noise from somewhere as opposed to vibrations, but there are times when I think I can faintly hear what I think is the same hum in the walls of the house with just my ears. Sometimes it stops suddenly and I only realize it stopped because it was suddenly gone.

But when I step outside I don't hear the hum. Or at least, there's possibly enough other environmental noise to cover it up.

Makes me think the vibration is coming through the ground, and that only the resonance of my 2-story house is making it audible.

It could be something in the house itself, but everything that vibrates (fridges, computers, hot water heater, furnace, etc) I've been able to rule out.

A friend had a pond with a submersible pump in it. Her neighbor could hear that pump throughout her house. It wasn't audible next to the pond outside, though.

Are you sure that it isn't the refrigerator?

The next time the noise appears, run quick and unplug the refrigerator and see if the noise goes away.

tanstaafl.

It occurs to me that linking to Lissajous curves is relevant here.

Exactly the kind of thing I'm suspecting. It feels and sounds like that sort of thing.

Doug, I already ruled out the fridges for sure.

Okay, that's really really interesting. Now I'm picturing some weird thing like a hidden exhaust fan or a sewage pump, running off of the circuit in question, that has now malfunctioned and blown out the circuit.

Well, you can stop thinking that. I was wrong about that noise. I don't know why I didn't hear it the other night, but I can hear it now, so it's not connected. Oh well!

So did you ever get the problem solved, Matt? I certainly hope so. I have a fair amount of experience tracing such problems, and have found hidden GFI outlets, but often I find that a loose or somewhat burnt connection is the problem. If it still isn't fixed, read on.

Turn off the breaker to the circuit and ensure that power is off by either testing with a meter or plugging in an appliance in the known working outlet. Then, pull the outlet cover and remove from the wall, exposing the wiring. If there are two or more bundles entering the outlet (each bundle typically has white, black, bare) then the outlet is midway in a chain of outlets. A single bundle means that it is at the end.

Check that ALL connections are robust. If the wires are poked into little holes in the back of the outlet (backwiring), it should not be considered robust. Remove the wires from the little holes and use the screws on the sides of the outlet.

You might also find that a wire is broken -- when it was being stripped, the conductor was gouged, and when the wire got bent this way and that when it was crammed into the box, it fatigued and eventually broke. Remove the broken-off bit, carefully strip the wire and connect.

If there are three (or more) cable bundles coming together in the box, there are probably wire-nuts holding the connections together (might be tape on top of the wire-nuts), and some little "pig tails" going to the outlet. Check all connections -- the wire-nuts can corrode, break, be loose, or be covering more tape. When reassembling a wire-nut connection, the conductors must be clean, and stripped so that when the wire-nut is installed, the conductors are not easily visible. Personally, I strip about an inch, twist the conductors together, cut off excess conductor to about 5/8", then cap with the wire-nut.

In any case, always make connections to the outlets using the screws on the sides. Insulation must not be under the screws, only bare conductor. The insulation should start within 1/8" of the screw. The bare conductor should be wrapped around the screw in the direction of tightening the screw. Tightened properly, they'll never fail. Unused screws should be snugged.

My guess is that you'll find *(or have already found)* the problem by inspecting no more than three outlets. Then, you'll lie awake at night wondering what condition the REST of the wiring in the house is like...

As mentioned earlier in this thread, a wire tracing device (sometimes called a "toner") is a fabulous tool. I have an Ideal that purchased years ago for phone and data networks, but now I use it mostly for tracing house wiring circuits. Fun to play with!