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Electrically flummoxed.
April 4, 2014 5:22 AM   Subscribe

Half of my house has lost power. The breakers are fine. You're not my electrician - I just want to understand what the problem is or might be.

The first problem came right before I left for work yesterday, when at least one circuit in the house went out; I was getting ready to leave, figured I'd tripped a circuit breaker and would fix it later. When I got home, the problem had resolved itself - the lights that had gone out were back on.

When I went to bed last night (so nothing really on or running appliance-wise), the power went out again for all of the upstairs outlets in my 2-story house, and about half of the first floor. This morning - we do not venture into the basement at night, because SPIDERS - I went to the basement and checked all the breakers - all are in the 'on' position. I tried turning them off and back on, to no avail.

Any ideas about what the problem might be? I'm happy to call an electrician, I'd just like to have a better idea of what's going on.
posted by amy lecteur to Home & Garden (16 answers total)
 
Are all of the lights that went out plugged into outlets? Are any of your outlets GFCI? https://www.youtube.com/watch?v=K555qzFPSCE I have some in my house and was unaware that they can also be linked with other outlets. If the GFCI outlet trips, power will be lost to those outlets it is linked with.

If fixture lights are out too, then feel free to ignore the previous paragraph.
posted by studentbaker at 5:34 AM on April 4


When something similar happened at my old apartment it turned out to be an outside breaker.
posted by dortmunder at 5:36 AM on April 4 [3 favorites]


Something similar has happened to me and its probably nothing inside your house. Call your service provider. To confirm, see if any of your neighbors are having the same problem.

Apparently, electricity enters your house on two separate 120V legs. If one of the legs fails (again, somewhere in the service lines, outside your house), you will be left with only half power. Unplug any of your 240V appliances, until full power is restored.
posted by jindc at 5:38 AM on April 4 [4 favorites]


You call the Power Company. In my condo in Florida, we had two large electrical cables that fed the whole building. One night we all lost power in one-half of the house. One of those cables had loosened. It was fixed within an hour.

Start with the power company, then move to an electrician if they rule out line issues.
posted by Ruthless Bunny at 5:38 AM on April 4


I'm with the GFCI hypothesis-- I've had 2 outlets go out due to being downstream of a GFCI I accidentally test-tripped in my kitchen, and this was my first awareness that GFCI takes out the entire length of its particular circuit, rather than just the GFCI-equipped outlet.

GFCI is usually installed in any outlet near faucets, and anywhere a person is likely to have plugged appliances near running water, so check your bathrooms, powder rooms, kitchen, laundry room and spider-ridden basement.
posted by Sunburnt at 5:50 AM on April 4


If one of the legs fails (again, somewhere in the service lines, outside your house), you will be left with only half power.

If your breakers are labeled, you can pursue this idea by checking whether all of circuits that are down are on the same side of the breaker box (i.e. left or right).
posted by jon1270 at 5:59 AM on April 4 [1 favorite]


Re: GFCI and overhead lights: In my apartment the bathroom GFCI outlet is in fact upstream to the overhead fixtures, and tripping the GFCI will put those out as well. (I have been told this is not so up to code, but apparently it still happens.) So I'd check the GFCIs even if the overhead fixtures are working.

Also, if you noticed any lights flickering before this happened, it's possible a GFCI outlet failed entirely.

That being said, I doubt one GFCI could take down half of your house, so it sounds like the power supply line is the more likely culprit.
posted by pie ninja at 6:00 AM on April 4


I am an electrician.

It definitely sounds to me like you lost a leg. There are two hot wires going into your main breaker. Each one carries 120V, together they give you the 240V for your appliances. One of those two hot wires is out.

Several things could cause this, including a problem in the transformer on the street, your main breaker going bad, and a loose tap at the weather-head.

With a volt meter, you can check this in about 2min. But, if you do not know what you are doing, I would not suggest testing your main - as it is carrying enough power to kill you.

Personally, I think you should call an electrician first. If you call the power company yourself, and are not sure what you are talking about, the power company may not make this a priority because they might think the problem is on your side of the meter, and you might have to wait. If you call an electrician, he will be able to tell what is up - and if it is the power company, you will be better positioned to get them out there quickly.
posted by Flood at 6:05 AM on April 4 [10 favorites]


If your breakers are labeled, you can pursue this idea by checking whether all of circuits that are down are on the same side of the breaker box (i.e. left or right).


The breaker boxes with which I am familiar alternate the bus bars that connect breakers on each side, so that every other breaker on each side gets power from one 120v leg, and the others get power from the other leg. That is, the one-side-or-the-other-of-the-breaker-box idea doesn't apply.

But it does sound like one of the 120v legs is wonky. Don't run the dryer or electric stove until you get it sorted out.
posted by BillMcMurdo at 6:06 AM on April 4 [3 favorites]


Previously. In my case, it was that a leg went out.
posted by MrMoonPie at 6:45 AM on April 4 [1 favorite]


Another previously, bad outside wiring on a single phase.
posted by kiltedtaco at 6:50 AM on April 4


Yeah, you lost one of the two outside legs feeding your house. Loose wire, or the step down transformer (those big can things mounted on the poles) is failing. Typically those cans will feed multiple houses, so ask your neighbors and use that info to determine if the problem is the can or just the feed to your house.

And seconding what BillMcMurdo said above -- while half of the breakers will be on one leg and half on the other, it's not necessarily a left/right situation or even alternating as you go down. My own panel has them bunched in groups of 4. There may be a diagram inside the breaker panel door that shows how that particular panel is structured.
posted by intermod at 11:48 AM on April 4


Current update: electric company has come and gone, and it wasn't anything outside. Have checked all my gfci's, all are fine. My next call will be to an electrician, except today is my birthday, and people are having me over, so I need to leave soon. Further updates, details and best answers once I'm no longer typing on this accursed phone.
posted by amy lecteur at 12:01 PM on April 4


Sure sounds like a dropped leg; bet you find a burned main lug connection in your panel. However does your (if it's electric) stove work? If so you don't have a completely dropped leg.

Do you have a single breaker panel or does you house have two? Half a house without power is sometimes caused by a sub panel tripping it's feeder or main.

And because you can get 12 devices on a single 15A circuit (24 on a multi wire branch circuit) the failure of a single breaker can take out several rooms in a house depending on how they are wired. EG: a single breaker can feed three small bedrooms and a MWBC can feed four medium size bedrooms plus a hall.

jon1270: "If your breakers are labeled, you can pursue this idea by checking whether all of circuits that are down are on the same side of the breaker box (i.e. left or right)."

Breaker panels aren't split like that if only because 240V breakers couldn't have the two poles next to each other. Instead the circuits alternate as you work your way down the rows with breakers across from one another generally on the same circuit. There is some weirdness with tandems, piggybacks, half height breakers (some panels are filled with half height breakers), etc. but I can't think of a single panel with more than a handful of circuits (IE: any panel with two rows) where the left side is one leg and the right side is another.
posted by Mitheral at 12:12 PM on April 5 [1 favorite]


I yield to Mitheral on this one. It's been a few years since I opened up the box I'm thinking of, and I probably got something mixed up in my memory.
posted by jon1270 at 1:58 PM on April 5


So...eight years and some expense later, I'm finally back (with power and online, thank the internet gods) to offer best answers and, hopefully, a modicum of experience and knowledge for future Askers.

From the fantastic advice above, recognizing that a leg was out, I initially gambled and called the electric company first - and while they weren't able to fix the problem, I'm glad I started with them, because the technician looked at the exterior situation, declared most of what he saw outdated, then quite happily replaced every piece of hardware between the meter and the electric pole, including the meter itself. No dice fixing the issue, but it's kind of nice to know everything there is up to date.

When that didn't work, I called an electrician, but it took several days for us to sync schedules. I'll explain the problem as best I can: on the outside of my house, the electric company's meter protrudes from the top half of a grey metal box, and the lines from the power pole enter that box from the top. The bottom half of that box contains a breaker switch like the ones in my basement breaker box. When we opened it up, there were visible scorchmarks inside, on one side. So yes, the issue was as diagnosed above, that one leg was out - but the problem was between the meter and where the two legs enter the house. The electrician replaced that exterior breaker switch, the box housing it, and the wiring that runs from that exterior box to my indoor breaker box. All better.

I have no idea how I missed the previouslies, other than not looking past the first couple of pages of search results and being generally, well, flummoxed when I first posted the question. For future reference, the dead leg's circuits followed no regular pattern inside the breaker box.

Thanks, everyone.
posted by amy lecteur at 1:37 PM on April 13 [1 favorite]


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