Burnt outlet... too much current?

[96Firebird]

The outlet that I used to have a window AC plugged into is slightly burnt. I'm not sure if it is the hot or neutral, haven't really looked at it yet. It isn't horribly burnt, but noticeable.

Was this probably caused by too much current from the AC? Loose wire behind the outlet? I'll try to get some pics of the outlet, and hopefully figure out what the cause was before installing the AC again.

 

[herm0016]

Check for loose wires or backstab connections, replace outlet with a high quality 20 amp rated version ( not the 1 dollar one from a home center) check for corrosion on the plug of the a.c. unit.

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[Paperdoc]

I agree. If this were simply the AC pulling too much current, the breaker for the circuit would have tripped. The fact that you have visible burn marks says there was some event that caused substantial local heating at some time, and that usually means a poor connection at that point that cause high resistance and heat generation.

 

[herm0016]

YEP. When I buy a house I replace all the switches and outlets with the higher quality ones using the screw posts, This also allows me to check nearly every wirenut. In high current spots, like in the garage or on an AC I only use hospital / commercial grade outlets.

 

[mindless1]

How old was it and how many plug/unplug cycles? Usually it's just a matter of the outlet or device plug contacts becoming oxidized over time, and some loss of spring tension. Sometimes it's also a case where the device plugged into it, had the cord mashed back and it started fraying, creating heat that damages the outlet, but usually the damage is evident on the device plug itself before the outlet.

Like anything they tell you an "up to" rating on one but that's when it's new, not after aging or adverse conditions. I don't use fancy expensive outlets but I do keep spares around, sealed up in a ziplock bag so they stay away from excess air and moisture, and won't hesitate to install a new one before leaving something high current plugged into it long term, before any signs of a problem.

 

[stormkroe]

If damage is visible on the outside/face, that's where the problem is. As mentioned earlier, worn or oxidized jaws can give you less contact area, and a 5 amp draw can melt the plug facing right off without even disturbing the breaker from its nap. I've even seen the plastic guard from a tamper-resistant plug break off an jamb back into the receiving jaws, causing the plug to barely engage. The first batch of TR's were a joke and hard to plug into. Spec grade or higher isn't a bad idea, but construction grade is rated conservatively and works just fine when installed properly (no stab ins!)

 

[Raizinman]

I replaced a friends window A/C unit electrical outlet due to the same thing. What caused his problem was that his A/C unit didn't have enough tilt (leaning out). His was put in pretty level. On a windy day, the water drainage instead of going outside, drained inside right down the power cord into the electrical box. It wasn't a lot, and only happened on the right conditions (strong wind from the correct direction), but there was enough moisture where his outlet turned brown. Replacing the outlet was easy, finding the actual problem was much harder.

 

[mindless1]

^ And a lot of people don't realize you may need to run a coat hanger or whatever through the tray drainage path periodically to clear fungus out of it so the condensation drains into the back (to be blown off or drip outside) at a good rate.