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How to check on ballasts?

McDesign | Posted in Construction Techniques on May 12, 2006 01:16am

I’ve got (13) used 4-tube troffer fixtures to install.  All of them will light up their (4) (used) bulbs, but sometimes I’ve got to wiggle the bulbs.  Contact cleaner on the clips?

Is there a way to check the ballasts for proper voltage?  What should it be?  Is there some other thing to look at?

I’ve always wondered this – short of lots of swapping around, when is it the bulb, when the ballast?  And, is there a way to check 34/40 watt fluorescent bulbs short of installing them?  What does it mean when bulbs are dark on one end but still work?  Are they not long for this world?

Forrest

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  1. DanH | May 12, 2006 01:30pm | #1

    If the bulbs are more than a little dark at one end, replace them. (If you replace one, replace them all.) If the fixture still won't light reliably, make sure it's properly grounded. If that's not the problem, replace the ballast (or the whole fixture).

    If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
    1. User avater
      McDesign | May 12, 2006 02:09pm | #2

      Interesting about the grounding.  I bought these at a church yard sale, and once I got the BX off, I realized that the green was never hoooked up - it was just stuffed in the hole.  I'll of course hook it up in the new application, but what function does the ground do, assuming the nuetral is fine and there are no other issues (besides the obvious one of providing a safe path to ground in case of a short)?  Is there some esoteric deal with the relatively high voltage of fluorescents?

      Thanks for the reply.

      Forrest

      1. DanH | May 12, 2006 04:52pm | #3

        The fixture needs to be grounded for reliable "ignition". Has to do with capacitive coupling between tube and the metal fixture, I believe.
        If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison

        1. User avater
          McDesign | May 12, 2006 05:20pm | #4

          Sounds like a problem I had before.  (9) troffers in my finished shop; never a problem, not even any bulbs out in 6 years.  6-8 "shop" lights in my garage; ungrounded, never really worked well - always had trouble "coming on". 

          These (13) are going in that garage - (I'm doing it now & checking messages) - we'll see how they work.

          Forrest

        2. cynwyd | May 12, 2006 05:42pm | #5

          the ground hookup will usually greatly reduce the hum too. which may be related to your point about incomplete ignition

          1. User avater
            McDesign | May 12, 2006 07:00pm | #6

            Got the main (8) in, one bad ballast which I had a spare for; most of the bulbs worked . . .

            SO - I got these (11) troffer fixtures for $2 ea, with unbroken diffusion panels, one bad ballast, and four bad bulbs.

            My great idea was to space my garage attic joists with alternating centers of 24-3/4, with the balance to give me 48" OC every other joist, and screwing the fixtures directly between the joists with the 23-1/4" gap - really clean, flush look.  Probably never be drywalled, but maybe. 

            Nice and bright - my 22' square shop has (36) 4' fluorescents; my adjoining 26'x16' hot rod garage has (32).

            Forrest

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