Polarity for wiring ceiling light

Discussion in 'Electrical and Wiring' started by Frank0, Apr 13, 2013.

  1. Apr 13, 2013 #1

    Frank0

    Frank0

    Frank0

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    Hi!
    I have new light fixture for ceiling and instructions say attach smooth wire to power and wire with "longitudinal ridges" to neutral. Well I see and feel no difference in the two wires, which look like speaker wire. What happens if I wire it backwards?

    Thanks!
     
  2. Apr 13, 2013 #2

    JoeD

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    When you unscrew a bulb there is exposed metal on the threaded part of the bulb as it unscrews. The ribbed wire (neutral) is connected that part of the socket so that if the power is on when unscrewing the bulb you will not get shocked. The power will be the button down in the bottom of the socket which is not exposed while removing the bulb.
     
  3. Apr 13, 2013 #3

    Frank0

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    So if I have the power going to the ribbed section of the bulb it would not light and I'd know it was backwards? I can't believe this pos light fixture does not use colored wire or colored shielding.
     
  4. Apr 13, 2013 #4

    JoeD

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    It will function either way. It is only a safety issue.
     
  5. Apr 13, 2013 #5

    Frank0

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    Thanks Joe! :beer:
     
  6. Apr 13, 2013 #6

    kok328

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    Visually trace a wire to it's destination on the fixture or use a volt/ohm meter to identify a wire and hook it up correctly.
     
  7. Apr 13, 2013 #7

    CallMeVilla

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    It is more than a safety issue. I installed a multi-bulb bathroom light fixture which was manufactured backwards. When I lit the fixture, it worked for a while but then ... wait for it ... the light bulb glass fell out.

    YES WAY. A crack developed around the bas of the bulb and it fell out! "HUH?" I said. So, I noticed the bulb was from China and replaced it with an American bulb. It stayed lit but the one next to it fell out. Replaced it. Then the American bulb fell out!

    Sense the polarity problem, I reversed the wiring. Tossed the Chinese bulb. Re-lit the fixture. It worked fine.

    True story! :D

    LIGHT.jpg
     
  8. Apr 14, 2013 #8

    Frank0

    Frank0

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    Thanks kok, after joe's reply I came to my senses and remembered I had a meter in the garage and and checked the wires for continuity to the wrap on the inside of the light socket and the power post at the top of the socket and then wired it up.
     
  9. Apr 14, 2013 #9

    Frank0

    Frank0

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    I could see that happening to me.....
     
  10. Apr 15, 2013 #10

    Blue Jay

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    Never heard of such a thing, unless you are off grid and using battery power there is NO polarity. Alternating current is what comes from the power company, yes it changes from positive to negitive at the rate of 60 times a second (here in the US) that is where we get the term AC. We have a hot side and a neutral side and a light bulb could care less which side is which, so the safety aspect is the only thing to be concerned with.
     
  11. Apr 15, 2013 #11

    kok328

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    Technically you are correct but, with that being said, can you explain to us polarized AC outlets and plugs?
     
  12. Apr 15, 2013 #12

    bud16415

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    Plugs are polarized for the same reason if it’s a light with a socket it keeps the safety aspect of it correct. If it’s a device that is controlled by a switch you want the power leg to kill the power with the switch, not to open the circuit with the neutral and leave everything inside the device hot. Devices that have no access to the power and no switch I see still come without a polarized plug things like little transformers (wall warts) etc.

    That doesn’t explain why a light bulb would come apart though assuming one wired one way and the other wired correctly in a parallel circuit. My only guess is that there had to be some sort of shorting going on between the top of the screw in connection and the frame of the light that was connected to the safety ground that produced heat and thus the crack. With the light lit there was voltage to ground no matter how it was wired. With it off the side that had the threads hot could remain shorting maybe. But Villa said they both failed at one point.

    Could be a freak random thing where he just happened to have 3 bad bulbs from two different makers from opposite sides of the world or the bulbs were made in the same place and just labeled differently to fool you into thinking they were American made. He just happened to run out of bad bulbs at the same time he fixed the problem.
     
  13. Apr 16, 2013 #13

    Blue Jay

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    The polarized outlets and plugs came about several years ago when some appliances (mainly radios) had one side of the cord tied directly to the chassis so if it was plugged in backwards ie. the hot side to the frame or chassis it would be VERY dangerous.
     

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