Outdoor Outlet burned up

[alvinamorey]

A relative called me and said they had a breaker that kept tripping. I went and looked and found an outdoor outlet that was in a suitable outdoor box with a protective cover (that closes over the outlet). The face of that cover was all black and charred, the foam in the cover was burned on half of the cover as if it had burned. When I opened the box I found the outlet was all charred from the side by the hot wire to the cover plate. I could see that water had been entering the box and corrosion on the screws. From what I was able to gather, the corrosion allowed a certain amount of electricity to arc over the box cover which in turn caused carbon tracking on the outlet itself, and at one point it must have gotten quite hot to burn away the foam on that side of the cover.

Does this seem to make sense as far as what happened? The breaker would trip as soon as I turned it on as in a dead short, yet there was no noticable direct short such as a bared wire touching the box. Therefore it appears it was only the carbon on of the burned away outlet and corrosion that formed the short to the box. I find this hard to believe and it looks as if could have been a serious fire hazzard. It sure looks like it actually burned under the cover.

I am just asking if anyone can explain how this occurred. Obviously water was leaking into the box. I replaced the outlet with a new GFI outlet and installed a new cover. The box itself was still ok. Besides the gasket that came with the new cover, I applied silicone around the top and sides of the cover to insure no more water leakage. Those gaskets dont seem to be adaquate in my opinion.

Alvin

[RBM]

That happens just as you described. You did mention "outdoor box" if you are referring to an outdoor weatherproof box such as type "FS" or Bell box, the threaded knockouts must be sealed with suitable compound to exclude water entry and by current code the covers should be "while in use" type, which prevents water entry when something is plugged in

[alvinamorey]

Yes, it's a outdoor weatherproof box. I'm not sure what type, as in "FS" or "bell box". Just the common ones made to be mounted outdoors on the surface of the siding with screw in hole plugs. The water was obviously leaking from the gasket under the cover plate which was deteriorated from age. Those foam type gaskets are pretty weak if you ask me. Thats why I applied a bead of silicone around the whole cover. The cover I used is just the spring loaded snap shut type. This outlet is only used to power lawn tools and nothing is ever left plugged in during rain. The thing was installed years ago before they even required GFIs outdoors. I used a GFI this time.

Alvin

[N8N]

The breaker should have been a GFCI type breaker so yes, it should have tripped immediately. Also if there was arcing and burning going on the receptacle itself may have become shorted internally from a contact falling against another when the plastic support burned away.

nate

[Phisherman]

I know that outdoor receptacles can deteriorate over time and needs regular inspections. A guy I know had serious fire damage to the side of his house. The electrical box to his hot tub corroded, shorted, and caught fire. Gaskets, silicon, or other weather stripping can fail.

[RBM]

I would recommend sealing the screw in plugs with silicone, as water goes right through them

[tony]

Well my friend it is all depend how you use it I have used silicon many times I also have equipment that runs @ 160 deg. F and 95% RH (relative humidity) been in service for years with no leaks first of all, all silicones are not same two surface must be clean wash in soap and water second if surface is glossy it should be clean and prime with silicon primer and silicon applied with minimum of 1/16th thickness I can sure you it will hold

[alvinamorey]

I do believe there was a small fire inside this box on my relative's house, but fortunately it was encased in a metal box and went out. This metal box was hooked to metal conduit so it was quite safe. If it was a newer style plastic box it could have caused a fire.

It also tripped the breaker which in turn knocked out a few basement lights. Those lights were what they called me to fix. At first I thought there was a bad switch for those lights but soon discovered there was no power. After opening several boxes in the basement, and disconnecting things one by one, I discovered the problem was the wires going to that outlet.

[Mark]