Managed to catch this almost-disaster

[spitfire557]

Not necessarily related to my garage, but instead my basement.

We run a dehumidifier in our basement 24/7, and have been for months on end. We also use a short (25 ft maybe?) extension cord and have that plugged into a standard receptacle. I happened to be down there tonight and unplugged the extension cord from the outlet and immediately noticed some burn marks.

Turns out the outlet/plug overheated and was slowly burning away the outlet. Surely this could have been a disaster had I not noticed.

Now my question for the more electrical savvy - is this as simple as a faulty outlet? It looks like the majority of the burn started at the plug. It was tough to get a photo, but the wiring does not look burned at all.

I checked the outlet and it's sitting steady at 123 volts. The extension cord is rated for 13 amp, and the dehumidifier advertises a max draw of 5.6 amps. Nothing else was plugged into this outlet.

 

[yamatitan]

You had a bad/loose neutral connection, my guess would be the male end of started slipping out of the plug making bad contact causing resistance/heat. Change the outlet and make sure to check your connections and it should be fine. Wouldnt hurt to check all neutral connections in the circuit back to the panel.

 

[topcok88]

So the neutral side of the outlet is shows signs of burning up. What I can’t tell for sure is if the outlet is wired correctly in the first place.

Edit: It almost appears the outlet is wired backwards? Can’t say that is the cause but it looks suspicious enough.


Sent from my iPhone using The Garage Journal mobile app

 

[ard]

Im gonna guess the machine crimp INSIDE the plug (where the wire attaches to the prong) was poor...arc'd for a good long time, heating the prong and then heating the outlet.

Prolly would have just eventually melted enough to open the circuit or close it and trip the breaker.

 

[spitfire557]

My dad seems to think the circuit may have gotten overloaded (his best 9pm non-electrician guess). I traced it out and the only thing on this (15amp) circuit is three basement receptacles (only one of which was being used - this one) and our washing machine. So I doubt it was overloaded.

Took the receptacle out and it definitely looks like it originated from within the outlet. FYI it is a 20amp "spec grade" receptacle, no clue on age.

 

[spitfire557]

So the neutral side of the outlet is shows signs of burning up. What I can’t tell for sure is if the outlet is wired correctly in the first place.

Edit: It almost appears the outlet is wired backwards? Can’t say that is the cause but it looks suspicious enough.


Sent from my iPhone using The Garage Journal mobile app

Oddly enough there is no "white wire" or "black wire" labeling on the back of this outlet. When looking at it from behind though, the neutral was wired to the right side, which seems standard to me.

 

[Innovate1]

Outlets sometimes loose their grip on the prongs over time. I would be checking your other outlets. If a plug slips in and out with little resistance the outlet needs to be changed. Just a guess but that may be what caused the overheating. Or maybe the screw wasn't tight.

 

[checkthisout]

Im gonna guess the machine crimp INSIDE the plug (where the wire attaches to the prong) was poor...arc'd for a good long time, heating the prong and then heating the outlet.

Prolly would have just eventually melted enough to open the circuit or close it and trip the breaker.

Yup.

 

[ard]

Yup.

OP- cut open the plug, let us know what you find

Edit. My bad..he did post that the wire looks black (due to burning) but is actually white.

Its a 20A outlet (not the usual 15A)...the smaller 'prong' is the 'Line' or '+' or black. The other one (that will accept a prong that is vertical or horizontal (ie | or --) is the neutral or white. ( Edit: This is not permitted on a 15A circuit (which is what I think OP siad it is...)

However, that is NOT the cause of the overheating.

 

[pbon]

Both wires are black in this case, as the OP noted, but said the white wire was on the correct side.

 

[spitfire557]

Perhaps the photo is deceiving. The wiring is standard 12 AWG Romex. The wire on the burned side is actually the white neutral. It looks black in the photo because of the burn.

 

[redidbull]

I'd buy one of those plug in testers to make sure everything is correct. Also use a 15 amp outlet with just the 2 vertical slots with no horizontals. Jim

 

[tyme2par4]

Oddly enough there is no "white wire" or "black wire" labeling on the back of this outlet. When looking at it from behind though, the neutral was wired to the right side, which seems standard to me.

For future reference, the white wire goes to the silver screw, and the black or hot wire goes to the brass screw.

It definitely looks like a bad connection. How old is the outlet? The contacts can get corroded or wear out after a while.
As an EV owner, I have to keep a close eye on my outlets because charging at 12A for 10 hours puts a toll on even high quality outlets.

 

[sberry]

So here we got a grade outlet but had a problem anyway,,, lots of help that was.

 

[tonyciambrone]

I were going to leave something on an extension cord 24/7 (which I wouldn't) I would at least put in a TR receptacle. They seem to grab plugs better than the regular ones.

But really I don't ever think permanent extension cords are a good idea

 

[Bretny]

Time for a new outlet and to run a circuit for your dehumidifier. Run a 20a. 15a is a joke today.

 

[spitfire557]

For future reference, the white wire goes to the silver screw, and the black or hot wire goes to the brass screw.

It definitely looks like a bad connection. How old is the outlet? The contacts can get corroded or wear out after a while.
As an EV owner, I have to keep a close eye on my outlets because charging at 12A for 10 hours puts a toll on even high quality outlets.

The outlet tested as wired correctly with an outlet tester. And I’m not sure on age of outlet, we just bought the home last year.

I’ll replace the outlet and keep an eye on it.

 

[spitfire557]

The outlet tested as wired correctly with an outlet tester. And IÂ’m not sure on age of outlet, we just bought the home last year.

IÂ’ll replace the outlet and keep an eye on it.

Also, I’ll be sure to plug the humidifier directly into the outlet from now on.

 

[rlitman]

...As an EV owner, I have to keep a close eye on my outlets because charging at 12A for 10 hours puts a toll on even high quality outlets.

I work at a data center. We have many hundreds of things plugged in for years on end, many of which are continuously running pretty close to 80% of the breaker rating. I regularly scan everything with a thermal camera, and in the 10 years I've been here, I have found (and replaced) ONE plug/connector pair that scanned warm (it happened to be an L6-30). This one plug was not hot enough to feel with your hand, but based on the thermal camera images, we decided to find a maintenance window and replace it.

In comparison, over the same time frame I've replaced about a dozen current carrying wires with failed end crimps, and repaired several burned up bolted connections.

Yes, continuous use will separate the good from the bad, but it isn't the initial cause of outlet failure. What kills outlets is frequent plugging/unplugging, and that's something that just doesn't happen in a data center. We plug things in, and leave them alone.

I was recently at a hotel, and the outlets on the nightstand were ludicrously loose. I can only assume that every night that room has been occupied, someone plugs in a phone charger or the like. The now loose connector will become even more loose if high currents are drawn through it, because its abnormally high resistance will cause local heating that anneals the metal, leading to accelerated loosening. It's a vicious cycle.

The only good answer when NEMA plugs are called for, is to regularly replace outlets that see regular plugging. They're effectively consumables.

 

[ard]

Still dying to see what the crimp looks like inside that plug where it attaches to the blade....

 

[wyliesdiesels]

So the neutral side of the outlet is shows signs of burning up. What I can’t tell for sure is if the outlet is wired correctly in the first place.

Edit: It almost appears the outlet is wired backwards? Can’t say that is the cause but it looks suspicious enough.


Sent from my iPhone using The Garage Journal mobile app

That would not cause the burn up.

The burn up was caused by a high resistant connection.

My dad seems to think the circuit may have gotten overloaded (his best 9pm non-electrician guess). I traced it out and the only thing on this (15amp) circuit is three basement receptacles (only one of which was being used - this one) and our washing machine. So I doubt it was overloaded.

Took the receptacle out and it definitely looks like it originated from within the outlet. FYI it is a 20amp "spec grade" receptacle, no clue on age.

An overloaded circuit would cause the breaker to trip not burning.

The issue you have here was a high resistant connection.

Oddly enough there is no "white wire" or "black wire" labeling on the back of this outlet. When looking at it from behind though, the neutral was wired to the right side, which seems standard to me.

There isnt on most outlets. Neutral goes to silver screw and hot goes to brass screw

OP- cut open the plug, let us know what you find

That is mis-wired. The black wire should be on the other side...

Its a 20A outlet (not the usual 15A)...the smaller 'prong' is the 'Line' or '+' or black. The other one (that will accept a prong that is vertical or horizontal (ie | or --) is the neutral or white.

However, that is NOT the cause of the overheating.

The neutral wire has turned black due to the burning.

And there is no positive and negative in AC electricity

So here we got a grade outlet but had a problem anyway,,, lots of help that was.

Even spec grade outlets can wear out. The tangs on the inside get loose and open up

 

[Zeke]

Oddly enough there is no "white wire" or "black wire" labeling on the back of this outlet. When looking at it from behind though, the neutral was wired to the right side, which seems standard to me.

The color of the screws tells you neutral and hot, e.g., silver vs. gold.

My take after studying the photo is that the wire was loose and wire torsion had it touching near the front side just at the edge of the lug base. With poor connectivity the neutral side of the plug overheated. I've seen this many times.

 

[spitfire557]

Still dying to see what the crimp looks like inside that plug where it attaches to the blade....

I’ll cut it apart later tonight and post some pictures.

 

[Mr. T]

Hard to tell from the pic but it kind of looks like the neutral wire’s insulation was under the terminal screw. That would make for a smoky receptacle after a while.

Either way, definitely looks like the termination was bad somehow.

 

[Zeke]

Hard to tell from the pic but it kind of looks like the neutral wire’s insulation was under the terminal screw. That would make for a smoky receptacle after a while.

Either way, definitely looks like the termination was bad somehow.

Didn't see that until you mentioned it. So, between us the tip of the wire was the only connectivity. I say that because of the clean base at the edge as opposed to the black elsewhere under the wire loop.

 

[American Locomotive]

Look at the heat discoloration on the screw, and the pattern of the burnt plastic. It's all radiating out from the screw area. IMO, there was bad/sloppy screw connection to the incoming wire, and that's what caused the issue.

There's nothing wrong with using an extension cord - 5.6A is not a high current draw. Our dehumidifier has been running off an extension cord for years without a single problem.