# Extensive Burn From Light Switch



## oldfrt (Oct 10, 2007)

At the school where my wife works,a teacher was 
received a severe burn to her hand when switching on a light.
Claims of a flame coming out of the switch were verified from witnesses.

I've never seen/heard of an actual flame coming from a switch before and wanted to hear what would cause this.
All the breakers were circa 70's,and the one in question failed to trip.
Inspectors found lose wire,and believe it contacted metal box,but flames?

Any input?


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## plummen (Jan 9, 2010)

i had that happen also years ago.squirrels ate through wiring in attic for outside light on deck,shot flames from switchbefore tripping breaker.i did inherit 2 baby squirrels from that job i had to raise with a bottle for several weeks! :laughing:


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## 480sparky (Feb 1, 2009)

It wasn't a flame, but an arc made of high-temperature plasma.


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## Warren (Feb 19, 2005)

Not sure about a switch, but a few months ago I was inside of an existing house doing some demo. I plugged in a short extension cord and started sawzawing out some framing. There was no working light in the room and it was a bit hard to see. After about 3 seconds of cutting, I noticed that that things seemed brighter. I glanced over to see the connection of my cord/tool was on fire. When I released the trigger it subsided a little and I quickly unplugged it and disposed of the cord. I have ssen smoke a few times from a cord end but never flames!


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## oldfrt (Oct 10, 2007)

480sparky said:


> It wasn't a flame, but an arc made of high-temperature plasma.


No one has come up with an explanation yet,but our 82 year old Fire Marshall is investigating.:laughing:

Thought it sounded a little far fetched,but since the witnesses were 5th graders........:sad:


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## 480sparky (Feb 1, 2009)

oldfrt said:


> No one has come up with an explanation yet,but our 82 year old Fire Marshall is investigating.:laughing:
> 
> Thought it sounded a little far fetched,but since the witnesses were 5th graders........:sad:


 
Short circuits creates arcs, not flames. However, since it happened unexpectedly, I have no doubt everyone said it was flames since we're all familiar with an 'electrical fire'.

Click here to see a real electrical arc. I realize it's a bunch of kids doing something stupid, but it shows what a 120v arc can do and what it looks like.


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## neolitic (Apr 20, 2006)

480sparky said:


> It wasn't a flame, but an arc made of high-temperature plasma.





480sparky said:


> Short circuits creates arcs, not flames. However, since it happened unexpectedly, I have no doubt everyone said it was flames since we're all familiar with an 'electrical fire'.
> 
> Click here to see a real electrical arc. I realize it's a bunch of kids doing something stupid, but it shows what a 120v arc can do and what it looks like.


When someone's been shot, it maybe 
too much to expect an exact description
of the bullet. :laughing:


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## 480sparky (Feb 1, 2009)

neolitic said:


> When someone's been shot, it maybe
> too much to expect an exact description
> of the bullet. :laughing:


I doubt anyone would (or even could) describe the bullet.

"Yes, officer..... It was 138-grain..... Winchester...... center-fire...... hollow point.......... .45-calibre. I know cause I saw it with my own eyes!"

Most likely, they'd describe the gun and the sound it made being fired. :w00t:


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## neolitic (Apr 20, 2006)

480sparky said:


> I doubt anyone would (or even could) describe the bullet.
> 
> "Yes, officer..... It was 138-grain..... Winchester...... center-fire...... hollow point.......... .45-calibre. I know cause I saw it with my own eyes!"
> 
> Most likely, they'd describe the gun and the sound it made being fired. :w00t:


Which sounds like the teacher's
description....
*FIRE!!!*


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## JonM (Nov 1, 2007)

They are closing the school until Wednesday so they can chance all the breakers, outlets and switches 

http://www.rep-am.com/articles/2010/02/20/news/doc4b803c9e5ecfd311008776.txt


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## woodchuck2 (Feb 27, 2008)

I am going to agree with 480 on this one. Electricity will arc when shorted, same as a welder does when striking the rod to start a bead, you dont see a welder starting a fire unless the material being welded is contaminated with a combustable substance. The only time i have ever seen "fire" was from the melting of the switch/recepticle and the insulation on the wire itself. I did however drill into a wire once that was inside a finished wall while running a new circuit, the hole was temporarily bright enough that i thought i drilled right through the wall and was looking into the hologen light on the floor on the other side . I tore the wall apart in fear of a fire and was lucky enough to pull the 3-wire back into the basement and repair the circuit.


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## Electric_Light (Nov 25, 2007)

School, light switch. Probably a 277v leg from a 480v system. The service panel is larger and so is the transformer(probably hundreds if not thousands of kVA) feeding the service, so the fault current could be quite high. Also, 277v can sustain a longer arc than 120v. 

The available fault current is a few magnitudes greater than what a residential distribution transformer can provide.

A case study I read (would love to link, but can't locate it now) articulated an electrician who was injured when he shorted across bus bars in a panel in the electrical room of a high rise building. He received severe burns from vaporized tools. It discussed a legal action against the breaker manufacturer for failing to interrupt. (not sure if it failed to trip, or if the fault current was beyond its capacity though) The power was interrupted when the power company side fuse popped. 

Sparky messed up. He shorted out the panel. Things vaporized, he got injured.
The entire building had an outage for hours. 
Lawyers' eyes sparkled


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## protechplumbing (Oct 10, 2008)

I had an old receptacle blow up in my face when I plugged my drill into it. My hand was burned pretty good. My face and forearms were sunburned and I was blind for about a minute from the huge arc that it made. It arced like the baddest welder I've ever seen for like 10 seconds before the breaker finally tripped.

One of my many fun encounters with electricity.


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## newenergy (Mar 5, 2008)

One time a wire got pinched in about a 450 volt solar array and the wire insulation caught fire and pretty much instantaneously was a pretty decent sized flame.


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## administr8tor (Jan 18, 2010)

newenergy said:


> One time a wire got pinched in about a 450 volt solar array and the wire insulation caught fire and pretty much instantaneously was a pretty decent sized flame.



That sounds expensive?


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## newenergy (Mar 5, 2008)

administr8tor said:


> That sounds expensive?


It was just a little wire - not close enough to the modules to affect them. The arrays can be pretty high voltage, but are current limited and while a short can make a good arc it doesn't blow up the modules or anything. That string was probably like 7 or 8 amps max.


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## Cole82 (Nov 22, 2008)

480sparky said:


> Short circuits creates arcs, not flames. However, since it happened unexpectedly, I have no doubt everyone said it was flames since we're all familiar with an 'electrical fire'.
> 
> Click here to see a real electrical arc. I realize it's a bunch of kids doing something stupid, but it shows what a 120v arc can do and what it looks like.


 Saw this video today and made me think of your post Sparky

http://www.break.com/index/tree-branch-catches-fire-on-power-lines.html


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## stp57 (Dec 12, 2007)

Maybe the teacher was wearing the same stuff that Michael Jackson was wearing when he went up in flames?:blink:
Steve


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## Electric_Light (Nov 25, 2007)

480sparky said:


> Short circuits creates arcs, not flames. However, since it happened unexpectedly, I have no doubt everyone said it was flames since we're all familiar with an 'electrical fire'.
> 
> Click here to see a real electrical arc. I realize it's a bunch of kids doing something stupid, but it shows what a 120v arc can do and what it looks like.


That outlet is probably fed from a leg of the college's on-premise 208/120v 3phase transformer which is probably fed from 12470 or 7200v primary.

The available fault current is a several magnitudes greater than what's available from a residential transformer in yards which is often about 2 feet on each side. 

The breaker responds to over-current, but it doesn't limit current.

Such transformers look something like this and can weigh as much as a large SUV providing with a capacity in the range of several thousand kVA


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## sundance 2 (Mar 5, 2010)

sounds like to me yes a plasma spark but schools have 277 and 120 sounds like maintance men not calling an electrician 277 through a 120 switch makes a big spark some where they tied something in wrong im sure everything was grounded at the switch. most likley it was in the hallways or a lighting fixture sundance


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