I have some 3-lamp recessed fluorescent fixtures that are too bright. Can I remove one of the tubes and run them just with two lamps? Will that hurt the ballast or the remaining tubes? These are T8 electronic ballasts, not the old magnetic ones, if that matters.

  • What is the make and model?
    – wallyk
    Commented Jul 7, 2014 at 3:41

2 Answers 2


Newer electronic ballasts run fine with lamps removed. Many replacement ballasts can be wired for several combinations of lamps, such that a 4-lamp ballast can be wired to a 3 or 2 lamp fixture. This will be shown right on the label and wiring diagram.

  • In my experience it is totally "hit and miss" whether an electronic ballast will work correctly with bulbs missing. You have to read the data sheet ... twice! It's more likely with 3-lamp ballasts because often, they're setup to run 2 or 3 bulbs (so you need to stock fewer kinds of ballast). Commented Mar 7, 2016 at 1:34

There is no shortcut, you must look at the specific ballast and see whether the ballast is listed for that use. Pop the maintenance cover off, take a cellphone snap of the label on the ballast, and search the web for the data sheet, which will list every combination of lamps it can support.

I often see ballasts that work on 2-3 lights or 1-2 lights, the motivating factor is reducing the number of ballasts the distributor must stock.

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