The small ballasts used in shop lights are very poor quality. They are
usually a series C-L ballast that produces very high lamp current
crest factor which in turn results in short lamp life.
My bit of experience with a few of these is not only that mentioned
above, but also lower light output than with a good ballast.
A spikier lamp current give reduced efficiency because the low pressure
mercury arc is less efficient at higher instantaneous current. But in
addition to this, it appears to me that these cheap undersize "shop light"
ballasts do not even give full power to the lamp(s).
One more thing about those cheap "shop light" ballasts: At least some
of these are less tolerant of heat than good ballasts, and that is why
many cheap "shop lights" come with chains to hand them on - the ballast
may overheat if the fixture is mounted flush against a beam. (Not sure
the latter is good practice even with a good ballast, but I sure have the
impression that the cheap ballasts in cheap fixtures that mostly go into
basements, etc. tend to be fussier about heat and maybe anything else.)
What I like to do with cheap fixtures: Replace the ballast with an
electronic one for T8 lamps, trashpicked from a dumpster by a hospital
that has a new or recently renovated section being renovated (or renovated
again) - and check that the ballast takes 120V rather than 277V. Get T8
lamps.
- Don Klipstein (
[email protected])