Sign In to join the community | Help
Install & Replace

Fluorescent four foot (4 bulb) home fixture

I am changing bulbs around the house. Some are flickering.Besides looking at the ballast is there an easy way to tell if I can use different (t-8  t-12?) bulbs in these fixtures, and can I use either bulbs with the same ballast?

Not what you were looking for ? Try posting a question
Posted 2012-06-30T15:40:21+0000  by fredg fredg

Hey fredg,


Thanks for your question and welcome to the community!


I work in the lighting department at my Home Depot here in Atlanta, and this is a pretty common question we get. 


To accurately tell if you have a F32 T8 or F40 T12 bulb is to do 2 things, illustrated below.

flourescent light bulb

Almost all manufacturers will give you specifications for the light bulb on the glass. To break it down even further, a F32T8 bulb means you have a 4 foot fluorescent tube that is 1 inch diameter (T8 means 8 eights on an inch), same for the T12.  If you can't see any specs on your bulb,  you can measure the diameter of the bulb to see what size tubes you currently have. Equally as important, the specs should give you the right color temperature, or type of light color on the bulb, expressed in K (Kelvins). This way, you won't have a different color bulb than what you had previously.

Bulb Color Temperature Chart


Luckily, fluorescent bulbs that are in older (2003 or earlier) fixtures are generally T12 bulbs. All of our fixtures (and the U.S. lighting industry too) after that are usually T8 bulbs, as well as electronic ballasts. Why? 


Simply put, the T8 bulb lasts longer, has little to no flickering issues and the ballast is a much more efficient one versus the older T12 magnetic ballasts. With that said, you can not mix T8 and T12 bulbs or ballasts, you'll need to either use what you have now, or do an entire replacement of the bulbs and ballast. They are literally 2 different systems, so putting a different bulb into what you have now won't work.  The wrong bulb can most certainly fit, but it won't light up. So again, check the bulbs first and then come down to your local Home Depot, and lets hope its just the bulb that needs replacing. 


Another last piece of advice, if a simple replacement of the bulb didn't solve your flickering issues, newerreplacement ballasts aren't that expensive and are no longer magnetic (if the fixture calls for F40T12 bulbs). Make sure to write down or even take the old ballast into your local store and we can get you squared away with a new ballast that was better than before. 


Hope this helps you out,


Posted 2012-06-30T19:25:49+0000  by Joseph_HD_ATL
Not what you were looking for ? Try posting a question