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Thread: T8 Lighting and GFCI ?

  1. #1
    DIY Junior Member Mike Turner's Avatar
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    Default T8 Lighting and GFCI ?

    Back 4/28/11 I replaced my old fluorescent lights with T8s and they've been working great... One section of my lights feed through an outlet and then to a switch then to the lights. Yesterday I replaced this one outlet with a GFCI .... I use this outlet a lot..The GFCI works good...The test/reset works and there is power through the switch and to the lights...This morning I went to shop and that section of lights isnt working...Everything else is working fine ..GFCI included .... I don't know how to check the ballasts but there is power to the light.

    Yesterday and I have wondered this ? before. I traced which wire was the line and which was load and am sure I hooked this up right...If I had that backwards would it still work ? Im sure it isnt but just wondering on that.....

    Any ideas on the lights? I bought them from Lowes on 4/28/11 ...Maybe the ballasts???

    I did change the bulbs...they are good ...If the line/load is reversed would anything work in the outlet ?
    Last edited by Mike Turner; 07-03-2011 at 08:49 AM.

  2. #2
    Plumber jimbo's Avatar
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    Did the gfi trip, or did the light never work after you put on the GFI?? Certainly you need to verify that the hot goes to line, and the downstream circuit is connected to "load". You also have to be careful that the load connected to the "load" terminal of the GFI does not have a multiple connection to neutrals downstream, such that not all of the current flows back to the neutral "load" terminal on the GFI. Or the corollary to that...that neutral current from a load connected to a different hot source also flows back to the GFI.
    Last edited by jimbo; 07-03-2011 at 08:09 AM.

  3. #3
    DIY Junior Member Mike Turner's Avatar
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    I did a google search in it it said the line / load connections are reversed the test/trip wouldnt work properly....Is this correct?



    I went back out an hr after I changed the bulbs and now everything is working.....Perplexed now!! Thanks everybody !
    Last edited by Mike Turner; 07-03-2011 at 11:02 AM.

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    Jack of all trades DonL's Avatar
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    Mike,

    The test button will tell you that the Line input is connected properly, but not necessarily that the load is properly connected.

    It only knows if there is a fault on the load side and will trip if all the current on the Hot is not returning to the load neutral.

    I know that a lot of the cheap fluorescent lights sold at big box stores have marginal ballasts in them. I have one that don't work very well when the humidity is high.


    Enjoy your day.


    DonL
    Theory only works perfect in a vacuum.

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  5. #5
    DIY Junior Member Mike Turner's Avatar
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    Thanks Don and everybody else too. I'm not a electrician but I do a little stuff like this and always want to be safe..Is there any way to tell without unwiring it to tell if load is properly connected ? When I test it instantly turns it off and then I reset it and it works fine...It is so hot out there right now and this one was a bugger to trace the wires..Had to remove a piece of paneling to see them.. Thanks !!

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    Jack of all trades DonL's Avatar
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    If you followed the wire color code and it is not tripping, then you should be OK.

    You can use a voltmeter and test to ground and verify that your neutral is on the correct wire and should be white.

    Or if it feeds an outlet you can use a plugin AC GO/NO GO Polarity tester, Available at your local hardware store.


    DonL
    Last edited by DonL; 07-04-2011 at 04:57 AM.
    Theory only works perfect in a vacuum.

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    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by jimbo View Post
    Did the gfi trip, or did the light never work after you put on the GFI?? Certainly you need to verify that the hot goes to line, and the downstream circuit is connected to "load". You also have to be careful that the load connected to the "load" terminal of the GFI does not have a multiple connection to neutrals downstream, such that not all of the current flows back to the neutral "load" terminal on the GFI. Or the corollary to that...that neutral current from a load connected to a different hot source also flows back to the GFI.
    Jimbo, excellent note that the load's neutral must be connected only to the GFCI Neutral load connecttion screw. If the load was connected so its neutral was not coonected that way, the GFCI would most like trip as soon as the power was turned on, and not be able to be reset.
    I am definitely not a pro plumber, but I am a pro crastinator

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    Consultant cwhyu2's Avatar
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    Your T8 fixture should not be powered by the load side of your GFCI.
    If direct connect your T8 fixture and install a switch you will not have any more problems,a ballast fixture can mess with a GFCI.

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    DIY Senior Member BobL43's Avatar
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    Actually any magnetic devices (I'm not sure if the T8 fixture being discussed here has a magnetic or electronic ballast) can cause problems with GFI devices. Household GFI's are designed to trip at about 5ma of ground fault current, and my company back in the 80's tried using them as machine control voltage protection. We had to have/use special Hi magnetic GFI's built by Sq D, and those were built to trip at 15ma, which is not as good.
    I am definitely not a pro plumber, but I am a pro crastinator

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by cwhyu2 View Post
    Your T8 fixture should not be powered by the load side of your GFCI.
    If direct connect your T8 fixture and install a switch you will not have any more problems,a ballast fixture can mess with a GFCI.
    Good point Clay.

    And there is really no benefit to having the lighting fixtures on a GFCI.

    Sometimes we try to be to safe, and make things worse.


    Have a Great Day All.


    DonL
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

  11. #11
    DIY Junior Member Mike Turner's Avatar
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    Your T8 fixture should not be powered by the load side of your GFCI.
    If direct connect your T8 fixture and install a switch you will not have any more problems,a ballast fixture can mess with a GFCI.

    I went to my local Lowes and found this out too ! And thats what it was... I had the light on the load side..Changed it and it is fine ! Thanks everybody for helping me through this !

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    The simple way to check what's on the load side is to trip the gfci and see what no longer works.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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