Wallwart safety hazard you'd never consider.

Uhh... that sure looks like you got the chain across the 115VAC, that can happen to any plug!

This doesn't make sense to me. I'm going to try to replicate the result using a wall transformer and length of chain.

Ok here it is "mapped out".

And a similar situation. on an RS power supply I have. This has happened twice. The first time, the green wire ran next to another transformers cord. That extra transformer was not connected to a load. My polarity on the RS supply may have been inverted from whats shown, so diodes are left black.

Hard to believe this has happened twice, I've never seen or hard of it before myself.  I'll just have to take it on faith as I have no experience with this issue, and I don't know anyone else that has either.  Any wallwart that is sold in this country is supposed to meet UL requirements, and I'm dead certain that a short across the secondary blowing up your outlet isn't considered a passing score.   I checked at least a dozen wallwarts here, all are UL listed.

I don't have a solid theory why, just wild guesses. The warts fuse didn't blow either, so high volt low amp is what was happening.

This LG is  UL too. I just managed to creat a perfect storm this time. With the radio shack unit, it was no where near as dramatic. I just heard the thermal breaker click and investigated, finding a single diode was very hot and the bell wire was hot also. So the field of a diode has been on my mind.

My percious aversion was based on meltdowns and "sudden deaths" in my past, when I'd chaulk it up to my own inexperince.  I thought it had happened many years before, memorably with foil holiday ribbon but doubted my conclusion and chaulked it up to care lessness and shorted plug prongs, though I got no ac shock. This time, I have no doubt. I suspect using telescoped stranded cores without enough sheilding is to blame with these Wart's cords.

The side by side cords from wall warts Ive not had issue with that I recall.

I wonder if a clip on magnet filter might stop it.... I'm wishing I had a scope too.

President Bush (who referred to the devices as "energy vampires") said that wall warts consume an estimated 4 percent of all the electricity used in the average U.S. home. Extrapolated to a national scale, that's a total of about 52 billion kilowatt hours, or the energy produced by 20 average-size power plants.

Made in china !!!!

gunrunnerjohn posted:

Uhh... that sure looks like you got the chain across the 115VAC, that can happen to any plug!

Exactly!

The chain shorted across the AC plug... you can see the chain image on the white outlet, and the notches where the short arced on the two plug legs...No way that was a low voltage short, and it can't be induction because the low voltage side is DC!

IMHO, of course!

I'd like to see a pic of that wallwart upside down with the male plugs facing straight up alongside the outlet cord

I'll admit I'm a bit puzzled.  I have (I think) possibly experienced the hot power supply on a laptop power brick.  It's too darn tempting to fold up the unneeded length of each end (AC input and DC output to the laptop), especially with the handy straps these all come with so you can wrap up the cord to place it in a carry bag neatly!  I've never seen any fireworks, but this post got me to unwrap the little I had wrapped up on mine to see if there is a difference in heat I notice on the brick, as I have wondered if the heat was normal in the past.

As to the Wall-warts, I think considering modern ones transformers is probably not accurate in most cases for modern (figure last 10-15 years?) ones.  The small ones used for small chargers for cell phones, iPods, etc are I believe now using semiconductors instead of wound coil transformers like would be found in the old days (think up to probably 90's to maybe middle of the next decade?)  I used to be into hand held radio scanners in the 90's, and the wall warts that used to be sold to either power the radio or charge the batteries internally used to have some heft to them, because they actually had a large transformer winding and then converted to DC for what the radio wanted.  More recent models I had (figure 7-8 years ago, but I don't know the switch-over point for the tech) were extremely light, much like a modern cell phone charger or the LG unit shown.

The old Radio Shack desktop power supplies I am pretty confident do have a transformer coil in them to step down the voltage before converting to DC.

Based on size alone, I would guess there is not a large step down transformer coil inside that LG enclosure.  Assuming you are no longer planning on using it (I hope!), feel free to prove me wrong by cracking it open for a look.

Same as Eddie said, all IMHO.

-Dave

Most modern wall warts indeed do not use a full sized transformer.  However, they do have an isolated design with typically a small torrid transformer. There may be a small value capacitor that will allow you to measure some AC value at very high impedance coupling the line to the load, but it is designed not to allow any lethal current to flow.

Here's a typical design.

I have opened up many wall warts over the years and I cannot remember finding a fuse inside one of them, not to state that some don't exist. I have seen thermal breakers and some use an under size diode or bridge that just blows if you overtax the wart, I like these , usually easy to fix.  I have found fuses in the type of external power supplies that have their own cord running to the wall outlet. The ones with fuses seem to have screws holding the case together. I'm with EDDIEM ,if you look close you can see black marks on the edge of the power blades on the wart. To get hot like described it would need some powerful induction forces that such a small transformer is not going to provide. I have noticed that some extension cords do not allow male blades to completely seat in the female slots of the cord. Looks as though this is the case here. Wonder if there are melt marks on the plastic that match the beads, near the power blades.    Or, might those be, BLACK MAGIC BEADS ?

No melting, on the low volt cord is where I expected to find heat damage nor a break at the thick anti kink portion.

   Some pitting was on the high volt prongs edges, right at the air gap; no deposits except carbon. I.e. no weld material from the chain. The pitting wouldn't be conclusive anyhow, it occurs with arching the same way. The carbon build was heaviest on the inside face of the plug blades, but that is common to paths via air or other connection, means nothing either.

 I plugged it in and took a voltage reading, it seemed fine,  but it is in the trash now. 

The plug didn't hold to the socket well. In fact, had the chain lassoed the wart, it would have dislodged the prong seating, and it would have come unplugged at first lift of the chain. It was fully seated.

   The fuses in wall warts are normally very small and leg mounted, not the easy swap fuses you are used to seeing.

There are frequency loops; and voltage pulses, at low voltage that can occur, sometimes causeing semiconductors to misbehave depending on filtering and caused by anything from "static kitty" and a bad hair day, to if you're drawing on wye or delta at 440v. Movement and manipulation of electricity causes field change, mostly known and contained, but some things slip by, require shielding later, need a board or assembly moved etc.  I'd say I either saw 120v arcing to the chain along a random static trail or a feedback loop and high static voltage spikes.

It was sparking like the igniter on a gas stove or furnace, but faster.

  It was more likely unnoticed dog drool than the chain directly shorting out. Removal of the chain didn't disturb the cords either.

Adriatic posted:

..............................................

The plug didn't hold to the socket well. In fact, had the chain lassoed the wart, it would have dislodged the prong seating, and it would have come unplugged at first lift of the chain. It was fully seated....................

 

I still don't have a clue about the blue sparks you mentioned related to the chain on the low Voltage side, but this part I quoted makes me think you had just plain old arcing on the extension cord end because of the plug not making good contact with the socket on the extension cord (which I also hope you threw away at this point). 

I don't understand what "fully seated" means based on the statement that the plug didn't hold to the socket well.  Those 2 conditions seem mutually exclusive to me?  There is obviously supposed to be some friction at the plug/socket to make the electrical connection.

For the marks on the cord, I suspect that condition may fully explain it.  I learned a little about more modern circuit breakers (CAFCI - Combination Arc Fault Circuit Interrupting) when I had an event earlier this year.  For my short story, I noted that my alarm clock (20 years + old) had died.  Initially thought it had just met it's time.  then I noted other things in the same room were also not powered up (so went to check the circuit breaker).  Breaker wouldn't reset (did it's job!) and then I found a plug on a surge protector for a computer had become damaged.  It was one of those goofy rotating plugs meant to provide flexibility so you don't lose both ports of a 2 outlet plug with 2 items that have a ground prong. (see below)

Mind you I didn't regularly rotate this plug, I probably only unplugged it occasionally if I knew a long thunderstorm was in town, and possibly if I was going to be away for a trip or something.  When I took the plug out of the wall, it was literally in pieces.  These plugs have round traces on a flat surface that allow wiper contact when the plug rotates so the circuit completes.  I suspect this had some level of damage that caused an arc (due to an air gap) at some point and then physically degraded.  (or it got partially damaged  the last time I inserted it and just didn't arc immediately to trip the breaker).

(the surge strip has been discarded, and once I deduced what happened, I replaced the outlet as well - this solved the breaker tripping)

In my case, I believe the CAFCI probably protected me from having an electrical fire.  You can bet I will avoid these rotating plugs like the plague in the future.

Not a 100% same correlation to your story, but seemed close enough to perhaps add some relevant experience that might add to the discussion.

-Dave

ADRIATIC, was that receptacle GFCI protected? I would think that GFCI protected receptacles in a train room would be sensitive enough to trip at the slightest short like this. You only need the first receptacle for that room that is closest to the breaker box to be a GFCI and the rest of the standard receptacles down stream from it will be protected. Just be sure that the amp rating of the GFCI receptacle that your installing matches the amp rating of the breaker that is supplying the power to it. Or, you can also just install a GFCI breaker for that room, but their not cheap. For those who are reading this comment, and never installed a receptacle and want to add a GFCI to your train room, plug a light into the first receptacle in the string of that room and it will go out when you find the breaker that is feeding it. Remove the old receptacle and when installing the GFCI attach your white wire (neutral) to the silver screw side and your black wire (common) to your gold screw side. Your wire ends do not get wrapped around the screw under the screw head like a standard receptacle, they get pinched under the flat plate under the screw. Then your bare ground wire goes under the green ground screw. Now push your receptacle into the box like your done, to get all the wires to bend and fit, then pull it back out just enough to re-tighten the screws and wrap some electrical tape around it to cover the screw heads. GFCI's are much wider then standard so make sure you use the tape. When finished apply the little stickers that say "GFCI Protected" to the receptacles down stream. Turn your breaker back on and test it with the buttons provided. GFCI's were made to save lives so their a great addition to a home.

AlanRail posted:

President Bush (who referred to the devices as "energy vampires") said that wall warts consume an estimated 4 percent of all the electricity used in the average U.S. home. Extrapolated to a national scale, that's a total of about 52 billion kilowatt hours, or the energy produced by 20 average-size power plants.

We cut consumption where I live so the utilities got the commissions to allow them to raise rates to keep profits up.

Dave Zucal posted:

ADRIATIC, was that receptacle GFCI protected? I would think that GFCI protected receptacles in a train room would be sensitive enough to trip at the slightest short like this.

You have to remember that a GFI only trips on a path to ground, basically it's checking to see if there is any difference in the current coming to the outlet and neutral return.  Any difference indicates that there is current flowing where it doesn't belong.

The CAFCI, OTOH, will trip for a ground fault, but also if any arcing is detected between hot and neutral.

I, like everyone else here have never heard of this phenomenon before. It sure looks like the chain just got caught between the 2 blades. I wouldn't think that induction would cause that kind of damage.

Ground fault protection does NOT blow on a short.  It blows when the current in the hot (black) wire or an AC circuit is unequal to the current flowing in the neutral (white circuit).  If there is a difference that exceeds 10 miliamperes ()+/-), there could be some current flowing through you that is hazardous to you.

A GFCI breaker is designed to open if either (1) there is such a difference or (2) the current being drawn exceeds the rated current.  Note that there are GFCI breakers that allow more than a 10ma differential, but these do not provide adequate protection to a human, only to equipment.  For example, the current NEC requirement for breakers on vessel shore power circuits in marinas does not protect people; it's too high.

I agree John, but I would still be interested in knowing if this happened with a GFI protected circuit. I have a GFI protected outlet outside the house that is so sensitive it will pop on a dense foggy morning. If I were ADRIATIC, I would play Sherlock Holmes and try to re-enact the event to get to the bottom of how this occurred. He may have a receptacle that is wired backwards.

  This was not on a GFI circuit thats for sure. Yea, that would have done the trick Id bet; GFI.

This house as built doesn't yet have grounded outlets & wire everywhere, just by windows, utilities, and bath,. The UL extension cord is on a 7amp industrial breaker strip (?Dayton). There are only 5 wall mount gfi here,  I put them in anywhere near the water & outside.

All the train power is on strips with breakers most are 7amp. But one is 10a for 7 small transformers on a 15amp box breaker.

The old train room has its own newer box with two 20a lines.

The easiest thing was to toss it and be mindful of it. 

A possibility is the chain is not a good conductor. Unless you pulled it very tight.

I think the chain was caught between the the 2 prongs on the transformer when you plugged it in. (You didn't notice it). But didn't short because the small links between the 2 prongs were not a good connection (to cause a short).  Every time you shook the chain you were creating a connection in the links (causing them to spark). Which was creating a connection on the outside (long) part of the chain.  It was trying to short out taking the longer part of the chain.

You thought something else was happening on the low voltage side of the transformer.

Even on a chain hung light fixture you have to run a separate stranded ground wire to the light because the chain is not a reliable connection.

I think you were playing with a hot chain.

This is the only logical thing I think could have happened.

FWIW - GFI's are 5ma and usually trip at 6ma on my testers. A Good GFI tester has milli-amp scales.

AFCI and GFIs are worth every penny.

BobbyD posted:

We cut consumption where I live so the utilities got the commissions to allow them to raise rates to keep profits up.

Likewise, our county convinced everyone to conserve water and then the water utility convinced the county to raise rates to cover fixed costs. Net result we pay more for less.  

The chain was draped down and over the cord, the plugs were never disturbed. The plug was seated and always unseated easily (prongs make contact, then give a slight push to seat fully).  The chain is tempered, but light fixture chain diameter. It would have unseated the plug at least partially to get there. After unplugging the other end, I found it fully seated.

...Ok, all thats being seen is the carbon on the white plug and bare where arcs happened....consistant with what youd see that I described too. It sure looked like somthing should have been caght there. You can see the carbon is stronger going towards the low volt too.

I had to look hard as to why else the focus is on doubt. If you are looking at the circular shape at the blade base, that is die cut in both blades equally, not pitting. The pitting is the "flower shape" on ONE blade's divot. Minor pitting normal for arcing. There is anodizing missing from the chain, but no metal loss, and it doesn't have as much carbon on it as the plug does. Instead, it has cabon amounts similar to what was on the low volt cord. And why were there carbon trails for an inch along the low volt cord too? Just the cord, not the floor.

Question: Was the low voltage side connected to anything? A load?

I'm curious if the low voltage side, if connected to a load might have been sharing a connection with the grounded side of the 120 volt AC source.  Possibly reverse polarity would cause problems.

Your right, beware of these cheap adapters.

I'm not an expert by any means,  but the posted image CLEARLY shows that the chain was in direct contact with the prongs of the transformer.  

I've yet to read here of anyone else duplicating your claims.  I personally think that your claims are akin to yelling fire in a theater.  

We are all users of these devices in our homes, thus we would tend to take these types of claims much more seriously.  

The most prudent thing you could do is to RECREATE the incident and post a video of the results.   Only then you would have a valid reason to alert the community here.   

  I see.

Well there could have been a fire had I not SEEN what was happening, and IMO you have conveniently chosen not to address all the facts.

 The big missed point being carbon along the low volt cord indicates arcing along it. That small amount of carbon matches the chains carbon.   Why doesn't the amount of carbon on the plug more closely match the chain? How did the chain avoid the heaviest of the carbon deposits.

I did not rule out an unkown 110v short. I ruled out the chain. A loose wire strand from trimming, dog drool; way more probable because of what I saw and how reacted; with deliberation.

Looking into standard specs, the short length of that cord requires no shielding, though shielding wouldn't hurt it, a cheaper unshielded cord was likely used. With backfeed, that would not be enough insulation to stop a backfeed loop.

When those phones "blew up" and accelerators stuck there was plenty of nay saying too. Someone is first...and sometimes maybe the only person.

  I dont think anyone here is an expert, that would mean a doctrate in electrical physics just to start. But I do have a lot of experience in electrical, electronics, and confidence in my eyes and actions. 

7 years of vending, & games, including monitor repair, and deep trouble shooting some frequency and static trailing issues from communications, to high voltage application. There was industrial hvac applications for 4 years and 3 more years with low voltage mixed with high voltage on machine controls. One press avg 150 solinoids...relays at first, then solid state. I was the youngest certified theater stage technician in the country at 15 years 10months, running 440v carbon arc spotlights (note that is a 440 arc under my control, plasma shape and all) and I weld with every heliarc option out there. Sparks get my attention, they dont cause panic.

  This page makes the danger clear without going too in depth; backfed voltage isn't something to play with* ...and SOME wallwarts can become a flyback.

  Any experienced electrition can tell you stories of dead spots and voltage spikes without apparent explainations because of wire to wire induction. Fixing precludes finding exact causes; mostly by simply changing connection points and wire paths

   A 120v wallwart has about 180v floating on the board, maybe more. That much voltage can arc easier than you may think, but not easier than I KNOW. Unsual, you bet; but something to be aware of. Cycles/frequency can play games outside of normal expectations alone and arcing eliminates predictability. The arc would most likely project from the point formed at that rounded die cut or from the disc center of the magnetic field therr, and because the field poles would be split evenly, that directional arcing you think is chain produced would occur without it right along that 180° line, and unlikely to reproduce on the other flat edges.

  If I was prepared for possible high voltage feedback, from what I suspect as a flyback loop scenereo,.maybe I would play. Or a piece of wire or solder may have shorted INSIDE. But it might also be akin to that high voltage line in the old TVs, and I'm not up for an unkown flyback charge.

  The most prudent thing for ME to do is not to recreate this scenero, but to fix things by moving on to a new power supply, avoid crossing wires close to possible strong electric fields, and mention it, here and to LG.... that's done. 

  Do what you want, but I don't think I've been accused of crying wolf since I read "phasing transformers was uneccessary worry" and whole heartedly disagreed.

Don't like it, block me.

*   http://www.reliableplant.com/R...sting-safety-voltage

pops3301 posted:

Question: Was the low voltage side connected to anything? A load?

I'm curious if the low voltage side, if connected to a load might have been sharing a connection with the grounded side of the 120 volt AC source.  Possibly reverse polarity would cause problems.

Your right, beware of these cheap adapters.

The adapter was under load. There was a phone plugged in via usb.

I don't mind being questioned, or fully thought out opinions that at least partially address all possibilites and all the factual occurances, vs assumtion a result can have only one cause.

Adriatic has been one of the sounder citizens of this forum.  So I am unwilling to dismiss his conclusions as the ravings of another nut.  I wonder if the links of a chain---or more specifically, a chain such as his---could act as a coil and have a current induced in them.  Not much voltage is necessary to induce a substantial current in a closed circuit with no resistance.

That being said, the carbon tracks across the prongs and the receptacle do indicate that something crossed them.  One must be careful since, wiht some extension cords, a plug doesn't go in all the way and something can go between plug and receptacle, causing a short.  If fine enough, like a thin bare wire, there won't be enough current to pop a house breaker before the wire burns up.

I'm afraid the evidence in this case is simply too strong that the chain, or some other metallic object, shorted the plug right at the outlet.

The carbon tracking on the outlet, the burnt spots on the plug that EXACTLY match the carbon tracking, and the marks on the chain that conveniently line up with the plug all suggest that's really what happened.

Adriatic posted:

The insulation on the wires is fine. No melting, still putting out to spec. The unsheild cored wire vs side by side it acted with the transformer field on the chain was in it creating a high voltage feedback, so got near red hot, lifted anodized areas, and has carbon streaking on it too(arrow area) Luckily the chain is on a knife with an impact plastic handle and sheath...I was insulated from any shock. You can see the arcing that happened seperatly on the ac line.

The unsheild cored wire vs side by side it acted with the transformer field on the chain was in it creating a high voltage feedback.

I don't have a PhD in anything, but I do have 40+ years of Electrical Engineering background that tells me that the above described scenario is less likely than lightning striking you twice!  If that kind of energy was dissipated in the small wire on the secondary, there would be SERIOUS damage to the wire and the insulation.  The fact that there's no melting or any obvious sign of damage on the secondary wire, other than carbon tracking, suggests that the marks on the wire are simply from the short and carbon bits from the short across the prongs. 

Could some other scenario be possible?  Sure.  However, since you hold all the evidence, we have to go on the evidence you provided.  From that single picture you provided, it screams out that the chain was across the prongs of the plug on the extension cord and the secondary output wire was just a recipient of some ejected carbon from the 120V short.

Literally hundreds of millions, if not billions of wall warts are in use all over the country.  If this kind of failure were even a very very remote possibility, I'm sure this would be a highly publicized issue.

Can wallwarts fail?  Sure, I've had several failures, and I've even had some of the higher power ones do a little melting on the plug with poor connections.  And yes, those could have started a fire under the right circumstances in the right environment.

Concerning any event there is theory and then there is practical.  Theory has been hashed.  Now the challenge is to practically replicate the event. 

If it can not be replicated a short across the plug IMO is the obvious conclusion.

Many events can be over thunk.

Did the breaker pop?  What value breaker is on this line?

 Some folk here are looking at the issue correctly, weighing, and acknowledging even the small possibilities besides the appearant and likely.  Thats all I ask, and all I can ask.

I, however also have to beleive what I saw as well as my recall of the actions I performed at the time. Laying the chain down is the only point I was somewhat unattentive. Removal I had my eyes peeled; sparks. I even resited and urge to cradle the chain with my free hand as I lifted the shealth again fearing shock.

The carbon evidence on the black low voltage line not as appearant, I can't change that. I had hoped that carbon would show on the white towel when wiped but it wasn't enough to show well.

As a note, I've seen two people fly through the air being struck by lightning. My neighbor flew about 15ft up and about 35 ft distance. He was struck firmly twice (and survived a natural gas explosion...lucky?)   My buddy's family vears clear of him in storms, another dual strike victim, with a few close calls besides that. Between those two, they've been struck, or nearly struck, 6 times that I nearly experienced with them or actually saw. A relative has hit the Ohio lottery for millions twice. I had 14 close freinds die in just a few years, non over 45.

    The odds though steep, do work in my favor here because above a 0:1 ratio means it is possible.  

Tom Tee posted:

Concerning any event there is theory and then there is practical.  Theory has been hashed.  Now the challenge is to practically replicate the event. 

If it can not be replicated a short across the plug IMO is the obvious conclusion.

Many events can be over thunk.

Did the breaker pop?  What value breaker is on this line?

Breakers did not pop. 7a on the power strip 10a at the box.

A direct short should have popped one had it been high volt /high amp....maybe

I wanted to draw the same conclusions. But what I saw doesn't let me. Had the carbon been on the plug only, I would not have posted. For me the carbon on the low volt is proof what I saw was arc trails and not just a light reflection of the arcing at the prongs.

Im not expecting the world to stop using wall warts. I will continue myself, though more cautiously. I will keep wire and other metal further away from those warts though.

I just looked at what few wall warts I have. All of them are flush with the outlets. If I find any that aren't they will be junked. Maybe they changed the design on the ones I am using as they have a projection preventing this problem.

  The chain's link between spheres seems like the weak point in the high volt short theory to me too. I'd think that link would be lucky to pass 2 amps without distructive heat. I pulled on the chain to check for softening; but over hardening is still a possibily.

Like I said, Im not equipt to experiment with it safely imo, and the wart is now on its way to Mount Trashmore anyhow...(A real place....Ive not only seen it, I've skied it, lol)

I laid a 2x4 across the burners of my furnace last winter. Almost burned down the house. I'm still searching for a safer way to heat my home as winter is fast approaching.

I get it; you may be cold, but I'm not not quite so chilly with indefference.

Honestly, I meant no disrespect Adriatic. There are lots of hazards in the home if you don't refrain from creating one, be it accidentally or on purpose. I just don't think its the fault of the walwart, its obviously the chain put across the terminals.

Metal ,or any other conductor across  the terminals of a power source is always a no,no. Try putting the two terminals of a 9 volt on your tongue, it won't hurt you, but youll feel it.