Question - electrical short

[Jethro]

I did a stupid thing - but I am curious.

Someone lent me his air compressor on which he had a 3-prong male plug. He had clipped off the ground, leaving the other two. I carelessly plugged the thing into a wall receptacle without paying any attention. That's the stupid part.

I turned my back on the receptacle to flip the compressor on switch on. I heard a strange sound, turned around, and a little black smoke was coming out of the receptacle where I had plugged the male plug in. Needless to say, I immediately removed the plug. When I did, one metal prong pulled out of the plug remaining in the receptacle. I turned the circuit breaker off and removed the prong.

I think I must have plugged the thing in backwards, since the ground was missing on the plug to prevent that. Dumb! Anyway, I now am curious as to why the goof did not trip the 15A breaker. I think it should have. Maybe the breaker is bad?

Agree?

I will replace the compressor plug of course.

Thanks

Jethro

[RBM]

Sounds like something shorted inside the male plug. Breakers don't always trip as quickly as we'd like them to

[Jethro]

It sure surprised me. I feel if I had not been 'right there', that I would have had a fire! Now if I haven't damaged the compressor.

Thanks

Jethro

[hallerb]

What you did shouldnt of mattered, the compressor is likely defective, locked up etc but not enough to trip breaker, or receptable was bad and its time just happened at that moment.

Thats why I avoid loaning or borrowing tools, WAY too much hassle:(

[RBM]

I wouldn't worry about the compressor. What happened was likely just localized in the plug.

[Steve Barker]

Sounds like his plug just fried out. Nothing to do with being "backwards". It didn't trip the breaker, because there was no short. Only an open. Put on a new HD plug and go on.

[Steve Barker]

They don't break unless there is a short, or overload. Burning a bad connection in half doesn't necessarily mean either.

[Ralph Mowery]

For the compressor it does not mater which way it is plugged in as far as damage to the compressor goes. It is usually safer to plug it in the correct way. If designed correctly the hot wire will go to the compressor's on/off switch , then to the pressuer switch and motor and back to the neutral wire. This makes it slightly safer but if the plug is reversed the compressor will work just fine if it is in good operating condition. The

120 volt circuit is alternating current and as far as the electricity is concerned it makes no differance, unlike DC that is found in the cars and maybe a few other places.

[Jethro]

Not short huh? Then why the smoke and black soot? Anyway I changed the male plug to a new 3-PRONG plug and now all is well and working. Thanks for comments

Jethro

[Steve Barker]

A bad connection will heat up and fry out. That doesn't mean it was a short circuit. When a light bulb burns out, it's not a short, it's an open.

[Doug Miller]

Absolutely not true -- there definitely *is* a difference between hot and ground in an AC circuit. About a 120V difference.

[Doug Miller]

An arc -- for example, if the wire in the power cord was frayed in (or at) the plug, and attached to the blade of the plug by only a few strands. Plug it in, and those little strands vaporize; current arcs over the gap, and poof! smoke and black soot.

[Ralph Mowery]

Please reread the post. I did not mention anything about the ground. It has already been established the ground pin has already been cut off. I simply said it does not make any differance which way a plug is inserted in the socket if the ground pin is cut off. The compressor would not be harmed. That only leaves the hot and neutral pins to connect and electrically it does not mater which way the plug is put in, the compressor will still run just as well either way if it is not defective.

[Doug Miller]

Pardon me -- I misspoke. I meant to say, "... between hot and neutral".

You imply they are interchangeable. They absolutely are not.

While that is true, it does *not* mean that there is no distinction between hot and neutral. There absolutely is a difference.

[Ralph Mowery]

Maybe you can enlighten me . What hapens if I cut off the ground pin of any modern device and plug it in the socket, then pull it out and reverse the plug ? Motors do not run in reverse, and light bulbs do not suck the light out of the room. The main issue is safety if the plug is reversed.

There were some electronic devices made many years ago (usually using tubes) that had a hot chassie and could be very dangerous to reverse the plug, but many of them were made before sockets had seperate ground pins.

[Doug Miller]

Well, yes, there is that little thing... just safety... that's all.

Please tell me that you don't attempt to do any of your own residential electrical wiring.

[Goedjn]

Breakers clear a circut when they detect overcurrent. If you don't have an AFCI, they don't give a damn about arcs.

[Jethro]

Well then, I guess I indeed could have burned the house down - there was smoke and the plug was super hot.

Jethro

[Mark Lloyd]

3-prong plugs would be somewhat safer if they were designed to enforce polarization even with the ground prong removed (since people will do that, or modify a 2-wire extension cord to accept a 3-prong plug).

That sounds less like a short than a loose connection. The current was flowing THROUGH that compressor, and was probably never high enough to trip the breaker. Sparks in the loose connection melted that prong so that it came loose, and heated the rubber or plastic in the plug enough to make it smoke. Plugging it in the wrong way PROBABLY did not contribute to this, it was just an old plug that needed to be replaced.

[Larry]

The smoke and black soot only indicates that something was burning. It is quite possible to generate enough heat for that without getting anywhere near to the amperage that will trip a circuit breaker. For sake of argument, suppose an electric hotplate or electric heater was plugged in; either generates enough heat to start a fire without trippig the breaker.