I have several four foot fluorescent light fixtures in my basement. I
recently found that some are marked that they take either T12 or T8 bulbs.
Several others are not marked and currently have T12 bulbs.
Are these bulbs interchangable, or with T8 bulbs only go into specific
I intend on opening up the fixtures to check the ballasts next time I'm up
in the ceiling, but I'd like to know.
No, they are not. Even with the electronic ballast, they will not work for
both. You will notice the ballast model number/letters on top. It'll usually
read F32T8, or something along those lines, indicating the length and type
A universal ballast can usually be used for one or two bulbs and can work
with 120volts to 277volts. But they are not universal for T12 and T8.
My apologies. We come across many types of ballast within my employment and
have yet to see one which will work for a T12 and T8, though many will work
on a voltage range and bulb quantity. Therefore, I did not think they
existed, just yet. I stand corrected.
Check out the fine print too. It's at:
If you just want the tubes to light up, fine. If you want them to operate
at manufacturer-rated values, then look further.
The ballast operates standard 4-foot F40T12 lamps at 75% of rated output,
but standard F32T8 lamps at 5% more than the rated value.
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