> Ok, I have some questions. T5, T8 , T12, HO, magnetic
> ballasts, electronic
> ballasts, different color temperature. It is enough to make your head
> explode.
I don't know of a FAQ, Bill, but those terms are easy enough to define :
T5, T8, T12 all refer to different bulb diameters. The number is (roughly)
the bulb diameter in 1/8 inch increments, so a T5 bulb is about 5/8" in
diameter, a T8 is 1" and a T12 is 1.5".
HO stands for "High Output". These are bulbs (with matching ballasts) that
have been made to output more light per bulb than "standard" for that
configuration.
The ballast is that black box inside the fixture with all the wires running
through it. It's main purpose is to limit the current through the bulb (and
usually to provide extra voltage for starting). "Magnetic" ballasts limit
the current using a magnetic thingy known as a saturable core transformer,
which wastes the excess power as heat. "Electronic" ballasts use a DC to DC
conversion process that is usually more efficient.
"White" is always a mix of colors, so "color temperature" refers to the mix
as approximated by how hot something would have to be to glow that mix of
colors. There's a lengthy discussion at
http://en.wikipedia.org/wiki/Color_temperature
but basically "warm white" is in the 3-4000K range, "cool white" is 4-5000K,
and "daylight" is in the 6-7000K range. Basically the lower numbers have
more red phosphors, while the higher numbers have more blue and green, with
somewhere around 5500 being a relatively even balance. Fluorescent light
still isn't "white", since each phosphor used emits a relatively narrow band
of colors, but our eyes see it as white if the colors are pretty evenly
matched.
My garage is full of 8' standard T12 2-bulb fixtures, with an extra 4' T12
over the bench and a couple of smaller lamps in dark corners. All magnetic
ballasts and cool white. Cheap (at least initially) and effective. Used to
be the 8' bulbs were actually cheaper than 4', although I haven't checked in
awhile, as they also seem to last a lot longer.
Randall
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