Wall outlet exploded!

[parallax]

I have a 20-amp circuit in my kitchen that services three wall outlets, nothing else. The outlets themselves are the 20-amp type with 12 gauge wire in between and to the breaker box, so everything should be good from that perspective. Only one of the outlets had anything plugged into it--the dust buster charger and a charger for a remote. Everything has been working fine until today.

I got a new little TV for the kitchen--one of these new LED LCD types, and I wanted to test it out. I unplugged one of the adapters in the outlet and plugged in the TV adapter, which was not connected to the TV. As soon as I plugged it in, a big pop came from the outlet and smoke started pouring out. The breaker was tripped, so no immediate danger. I took the outlet out of the wall and disconnected the wires, and the outlet had a chunk blown out of its back, with soot all over the place (see attached pics). I cleaned and inspected the wires, and they seem to be fine. The adapter itself seemed OK as well and wasn't overheated.

What was the issue? I'm afraid to plug the adapter into another outlet because I don't want to take down another circuit. Do you think it's more likely a faulty adapter, or could it have been a defect with the outlet itself?

Thanks in advance.

[jwelectric]

That is the result of a ground fault or in other words the hot conductor came in contact with the metal of the device.
It would take the rest of the day for me to type in ever case that could have caused this.

[Thatguy]

As soon as I plugged it in, a big pop came from the outlet and smoke started pouring out. The breaker was tripped, so no immediate danger.
What was the issue?

Your mechanical force caused the grounded metal strip that now has a hole in it to move a fraction of an inch and touch a bare hot wire in the box, and for a few milliseconds more than 400 A flowed.
You need to find and insulate that wire, perhaps with approved heat shrink tubing.
If there are now little globs of metal that used to be part of that strap inside the box it is probably good practice to remove them.

You should also check ground integrity; connections may have been compromised. That test requires a hair dryer or toaster, an extension cord, clip leads and a DVM.

Since meters are mostly digital nowadays hardly anyone knows what parallax is.

[cacher_chick]

Looks to me like an energized wire was touching the back of the outlet. Look closely at the wires in the box for a spot of damaged insulation. This section of wire needs to be replaced.

You posted a nice picture of the outlet, can we see the box & wires too?

[SteveW]

For less than $10, you can buy an "outlet tester" (really should be called a "receptacle tester") that you plug into your new receptacle to check out the circuit (including the ground).

[220/221]

Yeah, the hot wire laying behind the receptacle had a nick or sclice in the insulation and was sitting there from day one, a fraction of an inch from a short circuit. When you pushed the plug in, it moved the recep back and, BAM. When you inspect the black wire(s) you will see the fault in the insulation.

Hey....it happens.

[Thatguy]

http://en.wikipedia.org/wiki/Arc_flash

Supercolliders take as much power as a town. In 2008 this one
http://en.wikipedia.org/wiki/Large_Hadron_Collider
shorted out, melting a half ton of copper extremely quickly.

Too bad they didn't get it on video!
I doubt anyone was hurt; they probably stay in a blockhouse when they run this thing.

[parallax]

Thanks, all!

Sure enough, I took a look at the black pigtail going to the outlet and found the point of "impact"....looks like the insulation was probably damaged there. Fortunately it was pretty easy to replace and carefully put it all back together. Back in business!