I would like to understand how to evaluate a ballast and determine if it is suitable for a T12 8 foot flourescent bulb. What is the process / questions to ask?

I have several known good working pulls and new ballasts that were inherited:

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2 Answers 2


The common 8' fluorescent tube is an F96T12 and has 1/4" steel nubs on both ends of the tube. They take 1 wire per tube end.

You need to look on the ballast at the list of tubes it supports. If that tube is not on it, then it won't work.

Also, if the ballast diagram calls for 2 wires per lamp end, it cannot support F96T8 which obviously has only 1 wire. So most of your stash can be immediately excluded.

Also be aware that most ballasts for 8' fluorescents are not the same "form factor" (package mounting bolt positions) as 4' tubes.


...how to evaluate a ballast and determine if it is suitable

Your ballasts are not suitable. If you find yourself in the presence of ballasts, the only suitable course of action is to dispose of them via EPA approved means. Especially if they're leaking or have PCBs. Then visit your favorite supplier of LED lighting and buy some better quality LED bulbs.

Tips from the trenches:

  1. Avoid the "ballast compatible" LED bulbs common at the orange home improvement store. I've seen dozens of them fail within a year or two. Don't know why, don't care.
  2. Prefer single ended bulbs. When doing retrofits, you'll always be able to reach one end of the fixture with the existing fixture wiring.
  3. Buy a bag of tombstones. When doing mass replacements in existing fixtures (sample size: 150 fixtures, installed over 50 years, many brands/models), about 1 in 7 of the fixtures have broken or incompatible tombstones. They're quick and easy to replace.

I've had good luck with Hyperikon bulbs, and so have thousands of verified purchasers at a certain popular online shopping store.

Pile of old ballasts

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