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amik59mg · Joined: 31 Oct 2004 Posts: 3 Location: Denver, CO

I have an old cabin recently purchased but 50 + years old...some old wiring....not grounded and some new. ....I recently plugged a mechanics worklight (3 prong plug ) into one of the interior outlets in order to see into the crawl space under the house. The protective "bulb cage" of the light came into contact with a metal gas pipe and created an arc....sparked and deformed the metal)( 0nly slightly ... like a buble weld)
on the cage and the pipe. It spooked me and I 'm wondering what the cause could be. The circuit breaker did not react at all. Isit possible that the pipe is somehow "hot" My big problem is that I can't get an electrician to look at it until after the first of the year and I'm nervous that I may have an unsafe situation. We only use the house sparingly but we have guests joining us there for Thanksgiving...please help/advise ...If more info is needed I'll try to provide...Thanks

b · Posted: Mon Nov 01, 2004 12:43 am Post subject:

The metal gas pipe is ground. If the cord for the cage light was plugged in backward it would cause the cage to be hot and the gas pipe to be ground which would create the arc. (You are right that it made a weld - arc welding). The proper way for the light to be plugged in is so that the bottom of the light where the base of the bulb makes contact is hot and the screw shell is to be the nuetral. The nuetral is the grounded conductor... so there would not be the arc that you made. The nuetral side of the cage light will have a bigger prong than the hot side, you will only be able to plug it in correctly with a new receptacle. Everything in the system needs to be bonded to ground including the water and the gas piping. That way everything is at the same ground potential. My guess is that you had the light plugged in backward and made a direct short as older plugs have the same configuration for hot as nuetral. Have the breaker box checked as well since the breaker didn't shut off with your incident. Bet the fireworks made you bump your head down there in the crawl! Make sure the breaker size is in compliance with the wire size.
Thanksgiving at the cabin sounds like a good time!
b

amik59mg · Joined: 31 Oct 2004 Posts: 3 Location: Denver, CO

B

Thanks Although I don't have the luxury of checking the outlet right now I understand your answer/solution. I think what may have happened is that the "old" two prong outlet was replaced with a 3 pronged outlet (but the gound was not wired) and the neutral/ hot are reversed. I'll be able to test it and check it without any problem. Is it fair to assume that the circuit braked should have tripped? I can easily replace it but I've read about an "arc-fault" breaker...would this be a safer alternative? At any rate it looks like I'll be "safe" over the thansgiving holiday...Please let me know what you think about the breaker and thanks again!!

b · Posted: Mon Nov 01, 2004 3:01 am Post subject:

Your summation theoretically follows... sounds like you have a good understanding. Arc faults are currently required in the bedrooms of new constructions. I was informed at a code update class that they are pushing to eventually have them be required throughout the structure (like gfi's at all water and outdoor areas). An arc fault would have disrupted the circuit before you were welded and would be a good fix for now. They are a little pricey. A ground fault plug would have interrupted the circuit in this instance as well. A simple plug in tester with 3 lights on it to indicate if the plug is wired properly or what needs fixed is available at a minimal cost. That would help to prevent a situation like you encountered. Some arc fault circuit breakers have been recalled so check to make sure the one you get is not a recall. As with any new product they are working the bugs out yet, but it is a good safety device.
b

amik59mg · Joined: 31 Oct 2004 Posts: 3 Location: Denver, CO

b,

Thanks for your help.....I'll get to work on it once we get out there for the holiday.....Thanks again