In article , Jim Elbrecht wrote:
On Tue, 17 Nov 2009 20:42:28 -0600, "DanG" wrote:

It sounds to me as if you bought T8 bulbs to go in an old fixture
made for T 12 bulbs. The bulbs will fit, the ballast cannot drive
T8's. If you installed new fixtures, this is not the problem
assuming you have T8 ballasts for T8 bulbs.

While you're discussing the difference- What *is* the difference
between the T8 & T12 bulbs?

I just bought a dozen ballasts of ebay for the T8s and fixed the pile
of dead $10 shoplights in the corner of the garage. [worked out to
about $6 a ballast] I bought a case of T8s for them.

I just ran across a 1/2 box of T12s- will they work ok in the new T8
lights?

T8 requires less current and more voltage than T12.

If you run T8 bulbs from T12 ballasts, they may or may not start, and
they may flicker or have unstable operation if they do start. If they
run, their life is likely to be shortened.

T12 bulbs powered by T8 ballasts will be underpowered. This *may*
shorten their life. 34 watt T12 bulbs may flicker or swirl or bead with
T8 ballasts as well as run dim.

- Don Klipstein )