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    RedHeather's Avatar
    RedHeather Posts: 1, Reputation: 1
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    #1

    Feb 24, 2012, 05:08 PM
    Can a three lamp ballast be run with only one fluorescent bulb?
    We have a system of linear, fluorescent lights that use three bulb ballasts (we believe these are from the late 1970s). Three bulbs is way too bright for our needs, and I understand that we can't simply sub out the 15W bulbs because they must match the ballast. We have attempted to run the lights with just one bulb in a ballast; we have tried a single bulb in all three positions, but see just a dim pink at one end of the bulb in two positions, and in the third position the bulb flickers and is not as bright as normal. We unfortunately do not have any dead bulbs to fit into the other two positions while we do this.

    What we are wondering is this: is there any way to trick the ballast into lighting just one bulb (eg. Would it work to insert two dead bulbs?). Or do we need to change out the ballast for a single bulb ballast and rewire? If so, how do we choose a new ballast?

    Some details...
    Ballasts: Universal trigger series, 120V, 60 cycles No. 675-L for three 20, 15, or 14 watt preheat start lamps (they have underlined the 'three' for emphasis)
    Bulbs: Phillips F15T8 Natural sunshine 15W
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #2

    Feb 24, 2012, 05:20 PM
    No. Older magnetic ballast must run all lamps together.
    With newer electronic ballasts you can run any number of lamps the ballast will accept.
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