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Thread: Troffers, Emergency Ballasts

  1. #1
    Join Date
    Aug 2009
    Location
    Central NC
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    1,878

    Troffers, Emergency Ballasts

    Working on some 2x4 troffers in a classroom. These are 3 lamp, inboard/outboard, primary/secondary pairs. Some have emergency ballast to light 1 lamp.

    I am replacing batteries in some of the ballasts, where lamps are getting very dim on backup. I'm seeing that the test buttons do not work consistently. Existing EM ballasts have no diagram printed on them, so I assume they are wired correctly. I can kill the breaker and the lamp lights correctly. If I press the test button with light on, it lights correctly, kills the outboards and lights inboard lamp on 1st light. If the lights are off and I press the switch, it makes all lamps in both lights flicker. I think I should rewire the test button to break all neutrals for consistent test results and less confusion. If it were my facility, I wouldn't worry about it; as they work properly when power fails. But I see why a customer might be uneasy with it.

    I have to replace ballasts in a few others that I haven't looked at yet. I have never liked these kind of lights, as some ballasts have replaceable batteries and some do not. Replacement ballasts connect in different ways. Some have only a connection to the charging light & no switch. The light acts as the switch too. Some of the lights are missing the original PBNC switch and I guess I have to find some to make them all test out consistently.

    I have seen before that many of these lights are constant trouble. Replace EM ballast and 1 or both others go out a month later. Replace all and customer isn't happy with the cost. Prices on EM ballasts vary widely and it get complicated when supplier has a few of the cheaper ones and more of the ones 3 times the cost.

    I hate being a grump but I cringe when I have to mess with these kind of lights. Is it just me or do others hate them too?
    Yes, I'll be happy to do a first class job for less than anyone else and take a dollar a week for 10 years.

  2. #2
    Join Date
    Jul 2005
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    Quote Originally Posted by jmellc View Post
    I can kill the breaker and the lamp lights correctly. If I press the test button with light on, it lights correctly, kills the outboards and lights inboard lamp on 1st light. If the lights are off and I press the switch, it makes all lamps in both lights flicker. /../ Is it just me or do others hate them too?
    They can be a head scratcher, and thats after you get up to them around stocked shelves in a store.
    There are a few styles of them emergency "ballasts", some are "micro inverters" and use the existing ballast to fire the lamps, other is battery pack and DC ballast usually fires only one lamp and I think the test buttons are wired differently depending on the type.
    Some want the test button wired to the ballast like so:
    Name:  Em_ballast_wiring.jpg
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    Others have the button you describe that opens the always hot to em em ballast.

    So perhaps retrace with the wiring diagram that came with your replacement ballast and confirm the test button circuitry is correct.

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