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Thread: meggering romex

  1. #1
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    meggering romex

    today i was experimenting with my megger. i was testing it using the 1000v scale. i cut the insulation across the entire cable with my razor knife so the black and white were knicked then i tested that and everything was ok. then i wet the cable with a little bit of water and tested between the black and bare. all of a sudden it started to spark where i cut it and melted a little bit and smelled of burning plastic. is this something i should worry about if i test a piece of cable (mc, old bx, old romex etc..) inside of a house. i dont want to start any fires or worry the people living there. should i test it at 500v instead because it didnt spark then?

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    Yeah, I don't normally test at more than twice the normal operating voltage. I don't think there's much fear of setting a house alight with a megger, however.

    Bravo to you for experimenting.

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    thanks for the help

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    i already learned a lot more with just a few hours of experimenting with my new toy:smile:

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    electricalperson, what megger are you using?

    I was experimenting with the megger and nm and I smashed the wire with a hammer a couple of times and still got full scale readings. Seemed odd, as I know the insulation was smashed enough to where bare conductor was showing. What other experimenting have you done with the nm cable?

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    Quote Originally Posted by GilbeSpark
    Seemed odd, as I know the insulation was smashed enough to where bare conductor was showing.
    Doesn't sound odd at all to me. If the conductor was showing, but wouldn't show even the lowest level short on a megger, then there is no hazard. Consider that the first electrical installations used bare wire, and transmission is still that way today.

  7. #7
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    i have a model mj159 megger its a hand crank. thats the first time ive actually sat down and messed around with this. im trying to get some other type of wire and mess around with it the same way.

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    Quote Originally Posted by electricalperson
    i have a model mj159 megger its a hand crank. thats the first time ive actually sat down and messed around with this. im trying to get some other type of wire and mess around with it the same way.
    Throw some old BX (with the cloth covered conductors) in a bucket of water, and take megger readings. Take it out of the water, and megger it on consecutive days. It takes a very long time for the "short" to disappear in that stuff.

    Megger almost any underground piece of UF cable that has been in the ground a number of years, and you'll often get a failure reading too. When you start troubleshooting direct buried cables and conductors in the coming years, you'll start to curse the guys who don't use conduit for u/g runs.

  9. #9
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    Quote Originally Posted by electricalperson
    i have a model mj159 megger its a hand crank. thats the first time ive actually sat down and messed around with this. im trying to get some other type of wire and mess around with it the same way.

    Beaver! You come back into the house this minute. Your dinner is getting cold or Wally will be late to his basketball game!
    "I dont have a girlfriend, but I know this girl who would get mad if she heard me say that." -Mitch Hedberg RIP

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    Quote Originally Posted by BryanMD
    Beaver! You come back into the house this minute. Your dinner is getting cold or Wally will be late to his basketball game!
    ????

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