Outlet blew up in my face!

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Old 10-22-09, 07:46 AM
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Outlet blew up in my face!

I'm no expert on electrical wiring, but I know enough to be able to do the simple things round the house, like moving or adding new outlets, replacing old outlets with GFI units, etc. Having been zapped more than a few times through my life I also tend to be a bit wary of getting another dosage of electricity, though living in the USA, as I do these days, and dealing with its voltage is certainly easier than dealing with the double dosage one gets in my home country of Australia.

Still, the other day I got the bejesus scared out of me and I've been left wandering what I could have done differently and what actually happened. Maybe someone might be able to give me some pointers.

I recently remodeled our living area, part of which involved tearing out some old wood paneling and replacing it with drywall. In order to do the job I had to unscrew the numerous outlets from their boxes and leave them loose until the drywall had been secured, finished, and painted, after which I went round and began securing the outlets back in place. As I usually do I made sure that all of them were isolated on the main board, and after each had been secured and covered over by the faceplate I went around with my little tester (the kind that you insert into an outlet or place near a live wire, waiting for the telltale light flash to indicate whether the unit is active or not) to see if all was well. Everything seemed fine. So I then went round each of the outlets a final time with a floor lamp, plugging it in to each outlet to ensure that all were working fine. All went well until I came upon one particular outlet - when I plugged the cord in to it the outlet practically exploded out at me with an electrical flame that burned the tips of two fingers, burnt off about a quarter of an inch of one of the lamp's two pins, left black marks all round the outlet on the new wall, and basically gave me a near heart attack!

Something obviously shorted out, but I don't understand how. If there was already a problem in the box, surely it should have tripped the breaker before I inserted the plug, right? How could inserting the plug have completed some kind of short circuit - especially in such dramatic fashion? And why didn't the breaker flick off before the electrical flash occurred?

Finally, how could I have done anything differently to somehow know that there was a short circuit in place? The only thing I can think of that I could have done differently was to plug the lamp in first before switching the breaker back on - the fact that the breaker didn't trip when I switched it back on was what led me to believe that all was okay.

Is there any kind of tester that can tell me if there's a potential problem like this - the last thing I want to do is go around plugging things in hoping like hell they don't explode in my face - that's not the way most people would choose to test outlets!

Like i said, I'm still puzzled how it happened, not least because the outlet was perfectly fine before and I did nothing to it other than unscrew it while I was doing some work around it.

Any thoughts would be much appreciated.
 
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Old 10-22-09, 08:10 AM
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The breaker didn't trip before the flash because there was no reason up to that point. Perhaps the receptacle shifted enough and shorted to the metal box or the grounding conductor.
 
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Old 10-22-09, 11:00 AM
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Possibly the wiring in the floor lamp was short-circuited when you inserted the plug. Constant movement of the floor lamp may have caused the short. Invest a few dollars in a reliable plug-in receptacle tester.
 
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Old 10-22-09, 11:37 AM
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hi again

Actually, the lamp was fine - I'd been using it only a few minutes earlier elsewhere. I've since replaced the plug and it's working fine again.

I asked the electrician at Home depot if there was some kind of tester I could get that would prevent me going through this again, but he said there isn't one that could have helped in a situation like this. I don't know enough about the subject to be sure if he was wrong or right.
 
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Old 10-22-09, 12:02 PM
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What you described implies an "external" short that occured outside the outlet-box when the plug was inserted; the receptacle was "sealed" with a wall-plate at the time.

Was the wall-plate metal , and was it burnt when the short ( or Ground ) occured?.
 
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Old 10-23-09, 02:06 PM
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No, it was a standard plastic face plate. To be exact, it was the larger of the two pins that got fried to a point where about 1/4 of an inch got burned away.

As I said, is there any kind of tester that could have warned me beforehand that there might be a problem with the outlet? The little light flickering unit I used indicated that all was fine, insofar as power was available.
 
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Old 10-23-09, 02:50 PM
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Originally Posted by timbo59 View Post
No, it was a standard plastic face plate. To be exact, it was the larger of the two pins that got fried to a point where about 1/4 of an inch got burned away.

As I said, is there any kind of tester that could have warned me beforehand that there might be a problem with the outlet? The little light flickering unit I used indicated that all was fine, insofar as power was available.
Was the plug on the lamp an 'add on' or factory sealed type? Just briefly reading this I would say a fault occurred with the plug. Hot to neutral short in the plug could have caused the severe result you experienced. The lamp you say is working after the new plug is installed.

I realize you were testing the outlets with the lamp just a short time before the incident but I would take a look at the internal part of that lamp plug.
 
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Old 10-23-09, 04:41 PM
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What did you find when you pulled the outlet out? Is it repaired now?

Got any pics?

This also could have happened if the outlet was miswired at 240V, such as if it was a split receptacle using both legs of your panel before you changed it. However, I would have expected your lamp to burn brighter until it burns out if this were the case. Yours sounds like a dead short right at the receptacle.


Was your lamp cord a 3-prong one (usually only 2 prongs for a lamp)?
 
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Old 10-25-09, 12:29 PM
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If one of the prongs on the cord-plug melted away, it means the prong was conducting a large fault-current , most likely a short-circuit current , not a Ground-Fault current which occurs when the "live" conductor makes contact with a metallic surface.

The severity of the fault-current calls into question the ability of the circuit-breaker to react safely and swiftly to a defect in the circuit under protection.

Could you please determine the make / brand of the breaker?. Till then we can play a"guessing game". My guess is a Federal Pacific.
 
 

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