3 way switching & fluorescent lights

Discussion in 'Electrical Forum discussion & Blog' started by jjapogee, Sep 5, 2010.

  1. jjapogee

    jjapogee Light construction, remodelling

    Messages:
    9
    Location:
    So. Cal. Mountains
    First time post- take it easy on me, folks...

    I'm wiring new construction in a garage, and installing 3, 96" fluorescent controlled by 3 way switches. Power source at switch #1, 3 light fixtures, then switch #2. This is a 20A circuit, with 12 gauge wiring throughout.

    I ran 12-3 from switch #1 to the first fixture, then two 12-2 wires between the 3 fixtures, and then 12-3 from the last fixture to switch #2. It worked- I got light, controllable at both ends- but the lights soon started to pulse and flicker slightly.

    After an hour or two, one of the fixtures failed completely (not a bulb problem)- this is the fixture furthest from switch #1 (power source).

    Does this wiring scheme sound appropriate? What would cause the flickering or outright failure? Thanks for any help.
  2. drick

    drick In the Trades

    Messages:
    392
    The way you have wired the fixtures is incorrect. There is no reason to run the travelers for the 3-ways thru the fixtures. You should have connected power at the first 3-way, run 12-3 between the switches and connected the lights to the 2nd 3-way with one piece of 12-2. You could also connect the lights and power to the same 3-way if that makes more sense. Anyway this is not your problem.

    Your problem could be: 1) The fixtures are not grounded. Fluorescent lights must be grounded for proper operation. 2) Are you using the correct bulbs for the ballast? Just because they fit does not make them the right bulbs! You must cross reference the markings on the ballast with the bulbs. Using higher wattage bulbs than the fixture is rated for can cause flickering or failure to start. (This usually won't damage anything though). Using lower wattage bulbs will overload the ballast and cause it to overheat and fail. 3) The ballasts are bad.

    -rick
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    By any chance is either of the switches a LIGHTED switch, meaning there is a small locator lamp which lights when the main fixture is off??? You can't use that with fluourescents. Also, temperature ( cold ) is an issue with long bulbs, but I assume at this time that is not an issue. A good ground on the fixture IS important.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,882
    Location:
    Cave Creek, Arizona
    All switches do is turn power on or off, and it makes no difference what the power is going to, so if it is an electrical problem we would have to see HOW you wired everything together.
  5. jjapogee

    jjapogee Light construction, remodelling

    Messages:
    9
    Location:
    So. Cal. Mountains
    This is how the fixtures were wired:
    Power to first switch -- 12-2.
    First switch to first light -- 12-3 with white neutral and red/black travelers.
    First light to second light -- One 12-2 is neutral continuing onward and switched hot coming back. Other 12-2 is traveler pair.
    Second light to third light -- Same as preceding.
    Third light to second switch (end) -- 12-3 with red and white travelers, and black for switched hot coming back.

    The wiring scheme must have been correct, since it worked for at least an hour (controllable from either switch)...right?

    After an hour or so, they started to flicker, then one unit failed. The ballasts were VERY hot- the units are virtually suspended between/parallel to rafters (not flush mounted), so there's lots of air movement around them.

    The fixtures are Lithonia T8 MVOLT 120-277v, about $55/ea from the Big Orange Box...could they just be poor quality? (Wouldn't be the first time with HD.) I matched the bulbs properly (32W T8, 48"), according to the fixture's specs.
  6. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Lithonia is top quality. How about the ground on each fixture? Are the switches lighted?
  7. jjapogee

    jjapogee Light construction, remodelling

    Messages:
    9
    Location:
    So. Cal. Mountains
    No, the switches aren't lighted- they are Decora 20A switches. Each of the fixtures are grounded to the ground wires- all ground wires are connected all the way back to the source.

    Thanks for your continued persistence on this...
  8. drick

    drick In the Trades

    Messages:
    392
    >>I matched the bulbs properly (32W T8, 48"), according to the fixture's specs.

    1. Check the ballast to make sure it supports these bulbs. It probably does, but just to be sure.
    2. Go back to HD and buy four T8 32watt bulbs from a different manufacturer. GE and Phillips have slightly different manufacturing processes so switching the bulbs may help.

    What brand of bulbs are you using now? I ask because I have 4 Lithonia T-8 Tandems sitting on the floor of my garage waiting to go into a HO's basement. The ballast is different from the one in your fixtures so it my not matter much though.

    -rick
  9. jjapogee

    jjapogee Light construction, remodelling

    Messages:
    9
    Location:
    So. Cal. Mountains
    "1. Check the ballast to make sure it supports these bulbs."

    Ballast info:
    Philips 'Advanced' 120v to 277v
    Optanium 10PA-4P32-HC

    From the compatibility table:
    (4) F32T8
    (4) F25T8
    (4) F17T8

    Bulb info:
    Philips
    F32T8/TL741
    700 series, 32 watt


    "2. Go back to HD and buy four T8 32watt bulbs from a different manufacturer....What brand of bulbs are you using now? "

    Philips (see above). The units are 96" tandems. Would a variance in bulb manufacturers result in unit failure, though?
  10. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Neither philips, Advance Transformer, or Lithonia....have any kind of reptutation about ever shipping a "bad batch". This all seems unlikely, especially if all 4 bulbs in each of 3 fixtures is having problems. There may be some problem with your electric power......anything from a loose neutral connection, etc.

    I would say "call an electrician" but honestly unless you get a pretty sharp guy, and are willing to pay him a couple of hours at his rate......if you have some electrical skills, you may just need to start on paper and then get hands on with this problem. Think outside the box, and don't assume that ANYTHING is correct to start!
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