Shock and sparks from electrical box

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Old 11-28-15, 04:19 PM
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Shock and sparks from electrical box

I just purchased my first home, which was built around the 1950s. I was in the garage one day and went to turn off the garage light. When i touched the metal box housing the light switch, I received a small electrical shock. Kind of a similar feeling to when you lick a 9v battery. Not painful, but a cause for concern.

This is the lighting setup in the garage:
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I turned that light one/off 40 times since I got that small shock, and couldn't recreate the problem or figure out what caused it. Fast forward three weeks, and I was trying to move my goalie gear into the garage and I bumped that fixture with my bag. A few sparks went flying. I then hit the metal piping a few times with my goalie stick and it happened again:
https://www.youtube.com/watch?v=oFGtVnldKyA&feature=youtu.be
After this happened, I killed the power at the fuse box and made a closer inspection. I notice that there is some burn marks where the metal conduit meets the box that looks dangerous:Name:  IMG_3661.jpg
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I opened the box behind the light bulb and noticed a few things: there seems to be way more wiring crammed into that box than is comfortable and that the wire connections to the light are exposed. The red/black live wire connection is extremely exposed, and likely making contact with the metal casing:
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Is this something I can handle myself, or is it a problem for an electrician to solve? I believe that covering the exposed hot wires with some time of insulation/electrical tape would likely solve the problem, but I am very concerned about the lack of grounding there seems to be. I shouldn't receive a shock from touching the light switch.

Any advice/insight on this electric problem and how to fix it would be much appreciated. Thanks!!
 
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Old 11-28-15, 04:30 PM
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Welcome to the forums.

Your video is private.

Yes..there are too many wires crammed into that box. You can put on a 4" round box extension ring to give you extra room.

Is that circuit serviced from the conduit ?
Is there a ground wire in the conduit from the house ?

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Old 11-28-15, 04:56 PM
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Thanks for heads up on video, made it public.

I'm kind of inexperienced on home repairs, but I'm assuming the circuit is serviced from the conduit. The conduit is coming from inside the house. The metal piping above the light bulb/electrical box goes towards the garage door. These are the wires inside the conduit; 2 yellow, 1 black, 1 white. From everything i have been reading, a ground wire should be green or exposed copper wire, so I'm not sure there is ground wire in there:
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Not sure if these help, but here is a photo of the below the light/electrical box:
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At the bottom on the outside of the garage is this metal box, which is directly on the other side of the wall of the 2 outlets near the floor. Again, I dont know electrical stuff very well, I assume this is going into the ground?:
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Last edited by dan5050; 11-28-15 at 07:51 PM.
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Old 11-28-15, 05:37 PM
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Typical 1950s wiring was before the safety ground was in general use. But conduit does provide the safety ground, provided it is electrically intact from the fuse box to the end of the conduit.

It looks like a live wire has come into contact with the box, and that the fitting between the box ad the conduit is loose.

I would call an electrician, because other things look wrong (a red and a black wire going to the lamp).
 
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Old 11-28-15, 06:00 PM
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(a red and a black wire going to the lamp).
I also see at least one white wire on the lamp.... it may have a receptacle on it.

Your conduit system is grounded by the fact that it's run underground. Your video shows the BX cable and connector shorting to the box. That would suggest the problem is not at that light but where the wire goes to.... garage door opener. That BX does not have a solid ground so at this time it may still be live.

If you plan on servicing the wiring. Turn the power off and check the receptacle at the garage door end first.
 
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Old 11-28-15, 07:46 PM
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I loosened removed the screw holding the conduit to the box so I could get a better look at whats going on. It was secured properly before.

I let the light hang far away from the electrical box and turned the circuit back on at the circuit breaker. I tapped the pipe, fairly hard, between the light switch and and the light/electrical box, and nothing happened, no sparks.

I then took a wooden stick and pushed the light fixture back toward the electrical box and wiggled it around a bit, which blew the circuit. So its the hot wire touching the metal electrical box causing this problem. Is there any way its a short somewhere else? How would this be caused by a short by the garage door opener?

This is seeming more and more like a problem for an electrician to deal with.
 
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Old 11-28-15, 08:13 PM
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The flex should have had a redhead to insulate the wires from the sharp edge of the conduit. It looks like the knockout is too large for the fitting, but that might be the angle of the photo.
 
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Old 11-28-15, 08:15 PM
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Yes.... pushing the light fixture into the metal of the box will cause a short but not at the BX cable.

You've shown us the BX going to the garage door opener as shorting at the box. If the conduit is actually at ground potential... that would mean the BX armor is hot.

OR.... the conduit is not grounded and the BX going to the garage door opener is actually grounded. The first scenario is the most likely one.

You'll need a meter to actually confirm what the problem is.
 
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Old 11-28-15, 09:02 PM
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I think i misspoke about what cable goes to garage before. This pic should clear it up. The conduit is going into the light bulb/electrical box. From there wires go up to the garage door opener and then down to the light switch and some outlets.

I got a small shock from the light switch, so that area is definitely not grounded properly, correct? it seems like nothing is safe with this setup.

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Old 12-21-15, 05:22 PM
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problem resolved. There was some old asbestos wire which connected the interior garage light to an outdoor exterior garage light that was on the other side of the wall. The wire was corroded. We replaced it and no more sparks.
 
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Old 12-21-15, 05:26 PM
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No more sparks is a good thing. Thanks for stopping back and letting us know how you made out.
 
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