POP! smoke....
February 17, 2005 6:43 AM   Subscribe

Electricityfilter: standard grounded outlet works fine with a lamp, radio, etc., but I plugged a Belkin surge protector into the outlet and it popped the circuit breaker.

The surge protector is fried, no reset. Reset the breaker, plugged a monitor into the same outlet (brave, I know) and it works fine. Purchased a less expensive 840 joule surge protector with a 15 amp breaker built-in and POP!...fried that, too. Same outlet now has a radio plugged in and it works fine.
posted by badger_flammable to Home & Garden (19 answers total)
 
to be frank - this is NOT a good situation. if you have a multimeter (if you don't, get one now - $15 at radioshack, or just get an electrician) and set it for AC 150 or 250 volts (basically anything above 120) and we're going to do 3 things:

1) test the voltage between the 2 vertical slots. it should be anywhere between 110 and 130 volts. any higher or lower, and i'd be concerned.

the next 2 tests will narrow things down a little more, even if the first test looked good.

2) test the voltage between the left slot and the ground hole. if memory serves me properly, this should 0 volts. if the wiring is reversed, you may see results on the order of test #1.

3) this test will really tell us if something's wrong. test the voltage between the right slot and the ground hole. the result should be roughly the same as that of test #1. if the wiring is reversed, it should be 0 volts.

to basically give "good, bad, worse" ideas based on these tests, i'll summarize:

"Good" - proper wiring
test 1: 110-130 volts - anywhere in this range is ok.
test 2: 0-2 volts - anywhere in this range is ok, though ideally it would be 0 volts.
test 3: 110-130 volts - basically, it should be the same as test 1.

"ok" - reversed wiring
test 1: 110-130 volts - anywhere in this range is ok.
test 2: 110-130 volts - basically, it should be the same as test 1.
test 3: 0-2 volts - anywhere in this range is ok, though ideally it would be 0 volts.

"BAD!" - crossed wiring in an outlet somewhere, or a short on that cicruit
(one or more tests may succeed, but if any one is bad, get it fixed right away)
test 1: anything below 110 volts or above 130 volts
test 2: anything other than 0-2 volts or 110-130 volts.
test 3: anything other than 110-130 volts or 0-2 volts.

if any tests between a slot and the ground hole give you a result less than 110 volts but greater than 2 volts, you have a serious short issue somewhere in your home's electrical wiring, and should have an electrician examine it immediately

please pose results of your tests so we can help you further!

good luck

-quad
posted by quadrinary at 7:36 AM on February 17, 2005


quadrinary's astutely described procedure can be simulated with a $15 "outlet tester" from Radio Shack.
posted by trharlan at 7:49 AM on February 17, 2005


(here)
posted by trharlan at 7:51 AM on February 17, 2005


good call trharlan. i guess i'm just a fan of detail!
posted by quadrinary at 7:55 AM on February 17, 2005


Are you saying that only three prong plugs caused a problem, or did some of these devices that worked have three prong plugs as well? If it is only three prong plugs I would suspect a short or miswiring that is putting voltage on the ground prong of the plug. quadrinary's test will show this. If that is the case I would rewire it (preferably having that work performed by an electrician) right away. Shorts can lead to fires.
posted by caddis at 8:51 AM on February 17, 2005


Actually, I quit using surge protectors a long time ago. About 5 tight overhand knots spread out over about two feet in the electrical cord seem to work better. The tech guys at a large university I used to teach at swore by it, and I've never lost a piece of equipment that has been protected this way. (I have lost a lot of pieces when I haven't done this.)

I would be interested to hear what the real tech experts here have to say about this, though.
posted by jhilton at 8:59 AM on February 17, 2005


Is this a new place? Try other outlets, see if they pop the surge protector too (now that you have one that is resettable). Get a tester and check it out that way too.

It is hard to imagine what the problem might be. Improper grounding (or just swapped wires in general) maybe. Maybe the link between neutral and ground at the utility has been broken, letting your AC float away from ground. You can check this previous thread for links that will teach you a bit about household electrical systems. I was a bit incoherent over there, but it is just as well that you are forced to think a little about how it all works (good excuse eh?).
posted by Chuckles at 9:00 AM on February 17, 2005


First, thank you all for the help.

Second, my dad is a semi-retired electrician and is on his way for a visit - should be here by Friday p.m.
...did some of these devices that worked have three prong plugs as well?

The monitor I tried was a three prong.

Is this a new place?
Nope. Been here for 9 years. Now that I think about it, the outlet in question has gone unused for that time, behind a bookshelf. I was just moving my computer from one room to another. The surge protector worked fine in the other room, and there is a similar surge protector in another room, apparently on another circuit since only 2 rooms and the closet in that part of the house lost power when the breaker flipped.
posted by badger_flammable at 9:38 AM on February 17, 2005


jhilton, the knot thing sounds way too optimistic... The knots would contribute to the inductance of the line cord a little bit, but it is highly unlikely that they would be helpful in any substantial way.

I did google around a bit to see what people have to say about it. Nobody with any authority suggests using knots. One person pointed out (correctly!) that the knot will be a point of high resistance, so it is no wonder that spot burns when hit by lightning. That doesn't mean it helps protect equipment.

badger_flammable, Please let us know what you find out!
posted by Chuckles at 9:53 AM on February 17, 2005


Actually, I quit using surge protectors a long time ago. About 5 tight overhand knots spread out over about two feet in the electrical cord seem to work better. The tech guys at a large university I used to teach at swore by it, and I've never lost a piece of equipment that has been protected this way. (I have lost a lot of pieces when I haven't done this.)

I was about to call you out for posting a frivolous, non-helpful answer in a way that didn't make it obvious that it was frivolous and non-helpful, until I read this:

I would be interested to hear what the real tech experts here have to say about this, though.

No, this won't do a thing. Electricity is not water; tying knots in the "hose" won't slow it down.

Reminds me of this guy I remember from GEnie who recommended plugging everything into 50-foot extension cords "to keep the surges further from the equipment."
posted by kindall at 10:20 AM on February 17, 2005


Electricity is not water; tying knots in the "hose" won't slow it down.

Sure it will. You're creating a coil inductor, which, thanks to phase change issues, will have impedance. This will result in a restriction in the amount of current carried. In this case, "slow it down" is actually a very accurate description of what happens.

However, there isn't going to be much, and it'll be completely useless to a DC surge, like a lightning pulse. Inductors work by using magnetic fields creating changing currents. In AC, the current is *always* changing. In DC, it isn't -- an inductor, to AC, is a pure conductor to DC. Furthermore, you're putting strain on the cable, which may well result in the conductors cracking, causing oxidation, more resistance, and fires. In short, *never* tie a knot in a conductor. Period.

Good surge suppressors combine inductors, capacitance, and varistors. The inductors help suppress minor AC surges, the capacitors act to boost sags, and the varistors act a a "crowbar" fuse.

Varistors have resistance that changes as a function of applied voltage. So, at the rated voltage, they have very high resistance, but at surge voltages, they conduct. The trick is to connect a varistor (usually a MOV, metal oxide varistor, bigger ones use gas discharge tubes.) between the hot leg and the earth ground. If a surge hits, the MOV conducts and shorts the surge to ground.

If it's a big one, the MOV also melts, which is why good surge suppressors have the "protected" LED on them, to tell you that the MOV is still functional (it lights on the small amount of current that leaks through the MOV in high-resistance mode at normal current.) Every so often, though, they take a surge, melt, and fail short, rather than open.

Which, cleverly enough, is a perfect segue back to the original subject.

Before you follow quadrinary's or tharlan's advice, (both of which are correct,) I would get a meter. Set it on the resistance (ohms) function. Unplug everything from the surge protector (and unplug the surge protector itself, though that shouldn't be an issue here) and meter the two flat blades on the plug. It won't matter which one you put the positive and negative leads on. Then, meter each blade against the round ground pin.

What you should see is infinite resistance. What I'm betting you'll see is something close to zero. In short (err...) I'm guessing the short is in the strip itself, and the reason your breaker popped is that you plugged a dead short into a plug.

Or, in simpler terms -- the surge suppressed, having proudly fought for the resistance, has shuffled off this mortal coil and has been inducted into the heavenly choir. I suggest a funeral with full honors, and a new surge suppressor.
posted by eriko at 11:39 AM on February 17, 2005


Sure it will. You're creating a coil inductor, which, thanks to phase change issues, will have impedance. This will result in a restriction in the amount of current carried. In this case, "slow it down" is actually a very accurate description of what happens.

However, there isn't going to be much, and it'll be completely useless to a DC surge, like a lightning pulse.


Yeah, what I said: realistically, a few knots is not going to have any measurable effect. Certainly not like a knot in a hose would.
posted by kindall at 12:06 PM on February 17, 2005


I'm guessing the short is in the strip itself

Except surge protector #2 produced the same result.
posted by badger_flammable at 12:38 PM on February 17, 2005


It is a puzzle. The surge suppressor shunts over-voltages to ground. If the voltage was high, say the outlet was somehow miswired for 240 then that would explain blowing the circuit breaker and perhaps frying the surge protector. However, I would think that the other devices, at least some of them, would not like 240, but instead they worked fine.

There are three wires in the surge protector, hot, neutral and ground. Neutral usually just passes right through. The varistors are wired between hot and ground. If the neutral and hot wires were reversed at the outlet and there was voltage on the ground this might allow reverse current through the varistors and hence the shut-down. However, this seems so unlikely.

Please do report back here what you father finds.
posted by caddis at 2:05 PM on February 17, 2005


great reply, eriko. thx, even if it ultimately proves to not be the cause.
posted by five fresh fish at 2:45 PM on February 17, 2005


Frack, and I missed that there were two strips.

Hmm. A *seriously* miswired outlet might have both legs of 120V on them, producing 240V at the outlet. But about the only way I'd see that is if someone replaced a high-current 240V outlet with a NEMA 5-15 outlet.

Most breaker boxes are built so that it is impossible to get 240V on a single breaker -- you need a double breaker (which has the switches tied together) to get both legs onto the wire. Is the breaker that's popping a double breaker? If so, that's A) the problem and B) a *seriously* whacked job, and needs to be fixed.

If it was a simple polarity issue, it shouldn't trip the breaker -- the varistors would see 120V, just 180 degrees out of phase. (Hot and Neutral, together, carry the 120VAC current. Ground is a safety ground.)

If the whole house was running high voltage, the strips would fail everywhere. I can see a radio (with a transformer and power regulator) and a lamp working on 240. Heck, a notebook wouldn't mind at all, if it's like most, with a 100-240VAC/50-60Hz power supply.

Half of me says 'Two Bad Strips', to be honest. If there is 240V on that outlet, then somebody screwed up and changed an outlet.

I'm echoing caddis -- let us know what your father finds.
posted by eriko at 5:24 PM on February 17, 2005


One problem I described above is properly called a loose neutral. That would be a serious problem! Read "What does it mean when the lights brighten" in the electrical wiring FAQ, part 2. It seems like you should have noticed some problems before this if it is a loose neutral...

I almost posted the 240V outlet idea myself, but badger_flammable said that when the breaker went it turned power off in a couple of rooms. It makes sense that someone would wire one outlet at 240 for an air conditioner, or something (it would be wrong, there are other NEMA receptacles for that job) but two rooms and a closet? It took me 20 minutes to find that NEMA chart, but isn't it cool!
posted by Chuckles at 6:19 PM on February 17, 2005


Long overdue, and I apologize...and I'm sorry in advance for my lack of technical description below. If you want more information, I can ask him specific questions and report back.

As expected, my electrician father arrived Friday with testers in hand.

First stop was the problem outlet. Voltage detector found all three holes with voltage. Next, a test of the adjacent outlet. Same result. Not good. Inspected for bare wires, none found.

To the breaker box next. Voltage, voltage everywhere.
He began removing the ground wires, one by one and testing. During one test, it popped the breaker and blew 2 out of 3 bulbs in a ceiling fan and fried my TIVO in one room. It also blew out a VCR in another room. Coincidentally (?!?) the TIVO and the VCR were in the first socket of separate surge protectors in separate rooms. The other things (TVs, DVDs, etc...) on the surge protectors were undamaged, but the surge protectors were dead. Lesson? Unplug stuff before testing.
By process of elimination, he discovered the problem on the range circuit (4 wire grounding). We unplugged the stove, checked the outlet and found no problem. He removed the back of the stove to find one of the wires burnt off, touching the back of the stove.

To be blunt, it is a wonder someone didn't get electrocuted when touching the stove.

We replaced the 4 wire plug and wire.

Apparently, the short at the stove was sending power back to the breaker box and through the entire house. Here is where the question shifted. Why did the surge protector work in a different room? Why did anything work in the entire house without frying or tripping the breaker? Why didn't the house burn to the ground?

This mystery is unsolved, so if you have any input, I (and others) would be interested.

As an understatement, I am relieved. I can only imagine what may have happened if I never moved that surge protector.
posted by badger_flammable at 8:41 AM on February 22, 2005


Thanks for the update! Your explanation doesn't really explain the problem though, so it sounds like there may still be a problem...

If either of the lives touched the stove chassis a breaker should have blown immediately. If the neutral touched the chassis nothing bad should have happened, you would never have had a problem. The ground conductor is supposed to touch the chassis. So your description above cannot be a complete description of the problem.

When you say your father-trician found voltage on all three wires in the outlet it is a little confusing because voltage is a relative measurement.

If you have three points you normally pick one arbitrarily and call it ground, then you can measure the voltage of the other two points relative to 'ground'. A good analogy might be elevation. Do you measure a mountains height relative to the centre of the earth? Relative to the ground next to it? Relative to sea level...

I assume he was using some kind of non contact voltage detector. This is How non contact voltage meters function. I understand the theory well enough for the purposes of this discussion, but I'm still not entirely clear on how they work in practice.

If current flows into the probe it must come from somewhere. The human holding the probe perhaps? well it has to get into the human too! Maybe the human is just such a large capacitor relative to ground that the probe sees the human as equivalent to ground...

The conclusion is, I think the ground connection in your place is not actually grounded at all (normally done by attaching the electrical ground to the city water supply where it enters the house). This would explain why a live wire touching the chassis didn't cause a blown fuse/breaker.

The father-trician probably addressed this too, but you didn't mention it in your description. For your own safety as well as my curiosity please check that with him...

Anyway, sorry to hear about the dead gear... Nothing I have said so far can explain how that happened... Maybe if somebody else is reading they can add some insight...
posted by Chuckles at 2:59 PM on February 23, 2005


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