lights on GFI protected circuit

Discussion in 'Electrical Forum discussion & Blog' started by pmayer, Nov 1, 2009.

  1. pmayer

    pmayer New Member


    I have a circuit with about 10 fluorescent light fixtures (4' x 2 bulbs), along with a GFI outlet on the same circuit. The lights are on a 3-way switch. I keep intermittently tripping the GFI. I have replaced the outlet, and the switches, but it keeps popping. When I remove the GFI, and put a regular outlet in, there is no problem. I hear a little bit of very minor electrical crackling in the switch regardless of GFI or not. This was the original reason that I swapped switches.

    Am I not supposed to have lights on a circuit with GFI???

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    There may be a good reason to have the lights on a GFCI, but if not, wire the lights off the line side of the outlet, not the load side and it won't trip (or shouldn't!).
  3. drick

    drick In the Trades

    Fluorescent light can trip a GFCI. The problem is the ballasts have capacitors that store power. They suck it off the line side, but don't immediately send it back on the neutral. The GFCI thinks this is a ground fault and will trip.

    So why do you have lighting on a GFCI? Its not normal to.

  4. Billy_Bob

    Billy_Bob In the Trades

    GFCI's are designed to keep people from being electrocuted.

    And the problem area with being electrocuted is mainly with handheld things which plug into an outlet. This is under "consumer control". A consumer can plug ANYTHING into an outlet! They might go to a second hand store and buy an old electrical appliance with a frayed cord for example. Or they might use a 3 prong to 2 prong adapter so they can use a less expensive 2 wire extension cord - bypassing the grounded safety feature of new wiring.

    Anyway the GFCI would protect the consumer from themselves or from faulty hand-held appliances - things they would regularly touch with their hands.

    Permanently installed light fixtures however are typically under "electrician control". That being they would be installed properly and to code. And wired in a safe manner along with proper ground wires. In this case, if there was a ground fault to a metal case, the ground would be there. This would cause an overload on the breaker, and the breaker would turn off the electricity. Or at least the metal case would always be at ground "potential" and not be a shock hazard.

    So in my opinion, there is no need to have permanently installed light fixtures on a GFCI so long as they are installed properly. (Metal parts grounded and in the case of incandescent lights, the center light bulb contact wired to hot, and the hot wire switched. [When the light is switched off, there is no "hot" power present at fixture*.])

    *This is the reason for "polarized" plugs on table lamps (one prong larger than the other). This makes sure the center light bulb contact is the "hot" wire and that the switch controls the hot wire. Then if you accidentally touch the metal "ring" of the bulb socket or bulb, you will not be shocked.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    Two problems with wiring lights through a GFCI
    1. They can cause false tripping, and
    2. When the GFCI trips, for whatever reason, ALL the lights go off, which can be a hazardous situation sometimes.
  6. pmayer

    pmayer New Member

    Thank you

    Thanks guys. There was no particular reason that I wired from a GFI outlet. I didn't realize it would be a problem, so I just did it. The suggestions are good ones, and I understand this better now thanks to your responses.


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