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Old 06-21-2010, 01:31 PM
Markxxx Markxxx is offline
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Electrical Outlet, Pop, Blows Out

Last night in the wee early hours, I was in bed reading and I heard a loud POP.

I thought it was a light bulb blowing or something. Anyway, I got up and looked around and couldn't find anything, then I noticed my electrical outlet had a black mark around one of the two places where you plug things in. It look like it had a burn mark around it.

It had a heating pad plugged into it at the time. But that was off.

Anyway I pulled the plug out and this morning called the landlord. He looked at it and then went and got a new outlet. It took him about five minutes and he replaced it.

I asked what caused that and he shrugged and said it was fixed. It does work. The heating pad still works to.

The heating pad was OFF at the time, and nothing else was plugged in. I lived in this flat for over 15 years with no problems. We have circuit breaker and only one time have the breakers ever tripped and that was during a storm.

So my question is, what causes something like that? Just bad wiring or does the wiring get loose over the years.

And frankly my landlord's a cheapskate, is that normally how you fix something like this? Just replace the outlet? I would hate to have the whole flat burn. Not that I really have anything worth anything but you know how it is.
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  #2  
Old 06-21-2010, 02:02 PM
engineer_comp_geek engineer_comp_geek is offline
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The metal contacts inside the outlet can just get old and break, and when they break they can touch one of the other bits of metal inside the outlet and short out the outlet, resulting in a POP, a puff of smoke, and (hopefully) the breaker blowing. The fix for this is just to replace the outlet.

Another thing that can happen is if you have a loose wire (either not tightened properly originally or it just worked loose over the years due to vibration) is that the wire connection may have overheated. The wire goes from the breaker to one outlet, then to another outlet, and so forth to the end of the circuit. You don't have one breaker for each outlet. So even though your heating pad was off, something else on the same circuit could have been drawing power and making the connection heat up. If it gets hot enough the outlet gets damaged, and can possibly catch fire, so shorting out and automatically shutting off the breaker is a good thing in this case. Did you get to see the old outlet? Did it look burnt? The fix for this is still pretty much the same. You just replace the damaged outlet and make sure the wires are nice and tight. You would also want to examine the wires for any signs of damage and repair as necessary.

Arc fault circuit interrupters (AFCIs) are really good for preventing fires when this sort of thing happens. I hope your landlord installed them. They aren't required though so you might have a hard time convincing him to put them in if he didn't. AFCIs are required for all new dwellings built these days, but they aren't required to be retrofitted into old ones.

Last edited by engineer_comp_geek; 06-21-2010 at 02:03 PM.. Reason: clarification
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Old 06-21-2010, 02:12 PM
Markxxx Markxxx is offline
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Quote:
Originally Posted by engineer_comp_geek View Post
Another thing that can happen is if you have a loose wire (either not tightened properly originally or it just worked loose over the years due to vibration) is that the wire connection may have overheated. The wire goes from the breaker to one outlet, then to another outlet, and so forth to the end of the circuit. You don't have one breaker for each outlet. So even though your heating pad was off, something else on the same circuit could have been drawing power and making the connection heat up. If it gets hot enough the outlet gets damaged, and can possibly catch fire, so shorting out and automatically shutting off the breaker is a good thing in this case. Did you get to see the old outlet? Did it look burnt? The fix for this is still pretty much the same. You just replace the damaged outlet and make sure the wires are nice and tight. You would also want to examine the wires for any signs of damage and repair as necessary.
Well the building is old and full of vibrations, so YES, that could've easily happened. I have two breakers for my house. One for the kitchen outlet and light and the other for the living room and bathroom. It's a studio.

I saw the old outlet. Of the two pluggers (places you plug things into) the left one was fine. the right one had a burn mark (it's the same color as when you snuff out a match.) around part of it.

I will fool with anything but electricity. Plumbing etc, I don't care, but electricity...

The thing was how quick it was. I never realized how easy it was to replace an outlet. The landlord turned off the breaker, took the new outlet out of a package then took the plate off. He then as he unscrewed one wire from the old burnt out socket he screwed it into the new electrical outlet.

The whole thing took like five minutes or less. I didn't realize it was so easy to change out an electrical outlet.

Last edited by Markxxx; 06-21-2010 at 02:12 PM..
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Old 06-21-2010, 02:14 PM
Carlarm Carlarm is offline
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My best guess is that your heating pad has an intermittent short, most likely right at the plug end. If so, even with it turned off, it could short out and cause a pop and scorch marks on the outlet. I would inspect this very carefully and discard it if the wire seems looser than it ought to be there. With your heating pad turned off and unplugged, hook an Ohm meter between the two prongs and wiggle wires at the plug end and at the controller end. If the resistance drops you've found the problem. If you don't have an Ohm meter (or multi-meter) ask around and you'll probably find someone who does.
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Old 06-21-2010, 02:34 PM
engineer_comp_geek engineer_comp_geek is offline
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Since the char mark is right by the outlet I think that's where the short occurred. I doubt that there is anything wrong with the heating pad Sounds like a simple case of metal fatigue to me. It happens in old outlets sometimes. Check your other outlets. If they feel loose when you plug something into them then they should be replaced too.

Quote:
Originally Posted by Markxxx View Post
The whole thing took like five minutes or less. I didn't realize it was so easy to change out an electrical outlet.
Yep, not much to it. You just need to make sure you put the wires in the right place (if you get them backwards the outlet will still work but will be dangerous) and you need to make sure the wires are screwed in tight.
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Old 06-21-2010, 08:24 PM
Markxxx Markxxx is offline
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Thanks for the answers. I just thought it'd be a lot more complex than that.

Still the whole thing is a bit unnerving, now I see why people in the old days used to insist on unplugging everything before they left home
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Old 06-22-2010, 06:05 AM
t-bonham@scc.net t-bonham@scc.net is offline
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Quote:
Originally Posted by Markxxx View Post
Still the whole thing is a bit unnerving, now I see why people in the old days used to insist on unplugging everything before they left home
That makes no difference.
A short can occur inside the receptacle itself, whether there is anything plugged into it or not (which is probably what happened in your case).

And is is not vibration that makes wires loose, but the fact that whenever something is on, electricity is flowing and warming up the wires so they expand slightly; when it is turned off, the electricity stops, the wires cool down, and they shrink. A few thousand of this on/off expand/shrink cycles and the wires can work themselves loose. Especially when the wires are made of a slightly different metal than the screw terminal that they are connected to. (Note -- this was much worse with aluminum wire -- it expands & shrinks much more than copper wire. That's why aluminum wire isn't used any more in house wiring.)
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Old 06-22-2010, 08:44 AM
Markxxx Markxxx is offline
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So you all are saying that even if NOTHING had been plugged into that outlet, it could've popped and blown?

Remember when Rhoda's (Mary Tyler Moore Show) flat burned up and Phyllis said, Rhoda probably left her iron plugged in. Then in a later scene we see this

Mary) Did they ever figure out what caused the fire
Phyllis) The fire department said it was caused by a short in the refridgerator plug
Rhoda) Careless of me to leave the apartment with the refridgerator running.

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Old 06-22-2010, 09:04 AM
johnpost johnpost is online now
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the receptacle spring contacts being loose and leaving a gap to the plug prongs is what caused the arc, if you saw the arc on the face. if it was a loose wire or component in the receptacle the arc blackening would be on the inside behind the faceplate (barring the receptacle actually falling apart).

in the old days people did unplug things. the longer the electrical path then the more chance for failure. people were worried about switches and insulation (which was and issue before modern plastics, frequently used materials for small appliance use would deteriorate) would fail and allow an arc to occur in the appliance.
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