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-   -   Explosion (http://www.diychatroom.com/f18/explosion-150094/)

squarenuts 07-13-2012 12:42 AM

Explosion
 
I suffered some burns today when an explosion occurred as I plugged a kitchen stove into a 3 prong 220 wall outlet.

as soon as contact was made, a powerful and very bright blast ejected the plug and left my hand, the plug, and a little bit of the wall scorched.

The receptacles for the two live prongs are now joined by some melting damage.

The corresponding prongs have lost a little mass, about pencil eraser size round at the base, presumably vaporized.

I do not know the amperage at this time, will get that info tomorrow.

All the wiring appeared to be in order, a more thorough investigation had to be put off as I sought professional medical consultation.

WHAT HAPPENED?

What kind of temperatures could we be talking about?

Thanks
(cross posted here: http://www.diychatroom.com/f45/explo...93/#post964552 )

k_buz 07-13-2012 12:58 AM

There was something wrong with either the range or the receptacle. From the size of the arc flash, it sounds like either one of those two shorted out phase to phase.

mpoulton 07-13-2012 03:05 AM

Sounds like a dead short in the stove. The circuit was almost certainly on a 50A breaker, but the instantaneous fault current is MUCH higher - probably on the order of 1000A for about 1/5 second until the breaker trips. Temperature? Somewhere around 10,000-30,000 Fahrenheit is typical for most atmospheric arcs. The temperature of the plasma is less important than the radiant heat from it, which is what does the damage. It's pretty unlikely that there was any danger of really serious injury from this kind of incident though. The available fault current is just not high enough to cause an arc flash like this:
http://www.youtube.com/watch?v=W6Im7...1&feature=plcp
(Note: the incident in this video is reported to have been fatal for one of the workers.)

wkearney99 07-13-2012 09:53 AM

All the more reason never to connect a heavy appliance like that without shutting off the breaker first. Sure sounds like the stove has a dead short in it, or someone mis-wired that outlet some time in the past, for a likewise mis-wired stove that used to be connected to it.

gregzoll 07-13-2012 10:08 AM

Always have the breaker off, when plugging this stuff in, after inspecting it for proper operation. Then have someone standing away, with someone else flipping the breaker.

Yep, dead short.

Yoyizit 07-13-2012 12:04 PM

Supposedly for resi. work you need level 2 arc flash gear.

And from your burn you can maybe tell how many watts/sq. cm. per second your skin got radiated with. Sunlight is 1 kw/sq. meter but it takes many minutes to get a sunburn.

Maybe the breaker didn't trip, in which case you got 3kA to 10kA or so through the arc.

mpoulton 07-13-2012 01:33 PM

Quote:

Originally Posted by Yoyizit (Post 964805)
Supposedly for resi. work you need level 2 arc flash gear.

And from your burn you can maybe tell how many watts/sq. cm. per second your skin got radiated with. Sunlight is 1 kw/sq. meter but it takes many minutes to get a sunburn.

Maybe the breaker didn't trip, in which case you got 3kA to 10kA or so through the arc.

I highly doubt many residential panels have enough fault current to require any specific arc flash PPE. The hazard calcs rarely indicate a need for it in 120/240V panels, and when they do it's almost always a huge commercial service (800A+).

M Engineer 07-13-2012 01:46 PM

Quote:

Originally Posted by mpoulton (Post 964878)
I highly doubt many residential panels have enough fault current to require any specific arc flash PPE. The hazard calcs rarely indicate a need for it in 120/240V panels, and when they do it's almost always a huge commercial service (800A+).

But a Hazard/Risk Category 0 still requires PPE (long sleeves, long pants, safety glasses, hearing protection and gloves)

Yoyizit 07-13-2012 04:28 PM

Quote:

Originally Posted by mpoulton (Post 964878)
I highly doubt many residential panels have enough fault current to require any specific arc flash PPE. The hazard calcs rarely indicate a need for it in 120/240V panels, and when they do it's almost always a huge commercial service (800A+).

I never even knew about arc-flash until Mike Holt's forum talked about it.

An electrician long gone from this forum told me about level 2 gear for resi work.

Here's one that would have killed me:
a 17 year old was tree trimming, a branch fell onto a power line and enough current went through him to kill him.
I would have cut branches near power lines and my only worry would have been that the falling branch would break the line and PoCo would have come after me.
I guess I was assuming that tree sap is non-conductive except for lightning.

This kid is probably owed my thanks. He might have saved the life of my "future self".

mpoulton 07-13-2012 05:15 PM

Quote:

Originally Posted by M Engineer (Post 964886)
But a Hazard/Risk Category 0 still requires PPE (long sleeves, long pants, safety glasses, hearing protection and gloves)

Of course. I meant "specific extra PPE for the elevated arc flash category".

andrew79 07-13-2012 07:20 PM

we use the "space suit" all the time at my work. but we're also dealing with 1000A breakers. Being as we have the suit on site already we'll generally use it any time we're working on anything 100A and up.

stickboy1375 07-13-2012 07:41 PM

Andrew, isn't the fact that you guys have guards around your main service lugs part of this safety practice? Im talking residential panels now...

andrew79 07-13-2012 08:05 PM

i haven't had a new residential panel open in so long i forget what it looks like, the upper edge of the main has a guard in all the new panels i've done at work. you actually have to slide it out of the breaker to get at the lugs, basically unless you drop something into the hole from the top there's no way to hit the lugs on the main breaker.

and then you pop of the cover for the breakers and the busbar is exposed so go figure :laughing:

andrew79 07-13-2012 08:08 PM

1 Attachment(s)
heres a picture of a seimens tub at home depot here in canada, there is a gaurd at the top, nowhere near as well built as those used in commercial industrial applications but it's there nonetheless.

TarheelTerp 07-13-2012 08:27 PM

Quote:

Originally Posted by squarenuts (Post 964553)
I suffered some burns today when an explosion occurred as I plugged a kitchen stove into a 3 prong 220 wall outlet.

WHAT HAPPENED?

was this a new or old stove? who installed the cord?
had you seen this stove work before you plugged it in?
had you seen another stove work where you plugged in this one?


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