How to identify breaker for a currently dead circuit?
There is a circuit in my house which has become unpowered, but I can't find a breaker for it. None of the breakers in the service panel are tripped (yes, I know what that looks like), and the two labelled "not in use" don't affect this unpowered line (I've cycled them both a couple of times).
The circuit has two GFCI outlets on it; both are unpowered and the TEST buttons have no effect (I've tried RESET, of course). The circuit also has an overhead fluorescent panel, and an outside security light, neither of which are working.
I thought I could use a circuit tracer (a.k.a. breaker finder) for this, but what I've read so far indicates that they only work on active lines (i.e., so you know which breaker to turn off).
Does anyone have a non-obvious suggestion for how I can find where this circuit is turned off? Or could I use a circuit tracer for this, even though it's unpowered?
The circuit has two GFCI outlets on it; both are unpowered and the TEST buttons have no effect (I've tried RESET, of course). The circuit also has an overhead fluorescent panel, and an outside security light, neither of which are working.
I thought I could use a circuit tracer (a.k.a. breaker finder) for this, but what I've read so far indicates that they only work on active lines (i.e., so you know which breaker to turn off).
Does anyone have a non-obvious suggestion for how I can find where this circuit is turned off? Or could I use a circuit tracer for this, even though it's unpowered?
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I'll bet that one, and similar, showed up in my Google search, but I didn't even bother to read the ones that cost hundreds of dollars. The cheaper DIY ones (~$50) talked only about plugging into energized lines.
But is it possible these are going thru a light switch somewhere?
I believe these are all on the same circuit because they all stopped working around the same time (within a few days I had need to use them all). At the very least, the garage GFCI used to work fine, and now it doesn't reset, nor does the TEST button cause a trip (the sure sign that it's unpowered).
Cheap versions are fairly widely available, but they require that the circuit have power. The pro units are able to inject a signal whether the wire is powered or not, so they're more useful for finding breaks.
(I had to use one early this year to find the place where a contractor accidentally cut a cable. They did make good once that was pointed out, but I shouldn't have had to find the problem for them. Especially after they had brought a pro in to look for it. Sigh.)
Hey, on a slightly off-topic note -- exactly how did you use a circuit finder to get the location of a break? When I try to design something like that, I'm coming up with either using coax and a scope to send pulses down the line and look for reflections, or some sort of differential resistance measurement. I know that can't be right. Is this worth a separate Question (and a free BA for you)?
To find the break, I traced the wire back from the light that wasn't working through the attic to where it went down to the basement, picked it up there (I was unduly lucky; it happened to be a relatively unusual color, which made that a bit easier), and then followed it back until I stopped getting signal. (Well, actually I first confirmed that the signal wasn't reaching the circuit breaker, so I knew the problem was definitely between breaker and switch.)
. orksecurity's directional receiver method is more common in a residential setting.
. Measuring the resistance/impedance sounds to me like it would require near perfect wiring, but I'm no engineer.
Besides all the kitchen lights which were out, there was also a GFCI on the other side of a shared wall which was dead. That latter one was "in series" ("upstream" in electrician's parlance) with the rest of the circuit, and it had failed, killing power to everything else.
With that dead GFCI replaced, everything now works normally. And I've learned a useful practical lesson in troubleshooting!
Apparently the fault turned out to be with a GFCI outlet on the same circuit, which failed in such a way that it disabled power to everything downstream from it. When the electrician removed that outlet and connected the two hots to each other and the two neutrals to each other, the downstream line all came back to normal.
Other devices designed for cable tracing include telephone line and Cat5 type cable testers (from computer supply store - around $30), and there's also a tone generator for tracking telephone/ network/ cable lines, etc.
Maybe you could feed the signal through a big diode or at least a fuse, just in case the power is on or comes on when you flip the breaker. Would be best to make your own plug to fit in the receptacle, as you would not want to send the signal through the common wire (as it would connect to all breakers).
Maybe you should find out what the different 'breakers are connected to (anyway)?
Could any wire have been chewed by e.g. rodents?
L
That's why I'm confused. The previous homeowner did a terrific job of labelling the entire service panel. Every breaker is identified, and those identifications are all correct (tested when we moved in).
The problem I have now is that none of the labels relate to this particular set of outlets and switches, and neither to either of the labelled "Not in Use" breakers.
"Could any wire have been chewed by e.g. rodents?"
Crap. I sure hope not. Finding out is going to mean an adventure into our three attic crawlspaces. Time to dig out the old Tyvek suit :-(
The rodent explanation wokrs. If it's wired into any of the breakers they should either affect something also or they're not the problem?
L
There are a pair of outlets inside the kitchen for some undercounter lights: one is a true GFCI, the other has the sticker saying "GFCI protected" in series with it. The other GFCI is on the other side of the same wall, in the garage, and is in parallel.
They also put the switch for the extra overhead light in the same box as the switch to the disposal. But those switches are on completely different circuits, as they should be.
I've flagged Keydogstony's answer with the "sticky flag," because he addressed my underlying problem (but I don't relish climbing around the crawlspace in a Tyvek suit).
With the mains off, maybe connect a 9V battery to the end of the cable that you can identify (one electrode to each line), then prod around the potential far-ends of the cable with an LED to see if you can make it light up (maybe use two LEDs with the opposite-polarity legs twisted together, to save a false-negative due to accidentally-reversed current).
Oh, wait, US properties have a breaker per socket, don't they? No ring-mains?
(If the problem is inside the main fuse-box, UK regulations require the attentions of a properly-certified electrician, either to do the work or to certify the work you did as safe to connect to the mains.
Bloody safety elves...)
As I'm NOT a trained electrician, and 100A at 120V is not something to mess with, I don't intend to remove the service panel with power energized.
With continued reflection, and very helpful input from all y'all :-), I'm becoming convinced that I have an open wire somewhere up in the attic. Sigh...