T8 Lighting and GFCI ?

Discussion in 'Electrical Forum discussion & Blog' started by Mike Turner, Jul 3, 2011.

  1. Mike Turner

    Mike Turner New Member

    Messages:
    12
    Location:
    Laurinburg NC
    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: Jul 3, 2011
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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: Jul 3, 2011
  3. Mike Turner

    Mike Turner New Member

    Messages:
    12
    Location:
    Laurinburg NC
    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: Jul 3, 2011
  4. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    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
  5. Mike Turner

    Mike Turner New Member

    Messages:
    12
    Location:
    Laurinburg NC
    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 !!
  6. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    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: Jul 4, 2011
  7. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    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.
  8. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,331
    Location:
    Cincinnati OH
    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.
  9. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    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.
  10. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    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
  11. Mike Turner

    Mike Turner New Member

    Messages:
    12
    Location:
    Laurinburg NC
    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. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,806
    Location:
    New England
    The simple way to check what's on the load side is to trip the gfci and see what no longer works.
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