John Deluca (jdeluca@adm.schoolofvisualarts.edu)
Tue, 23 Mar 1999 09:55:44 -0500
We have just completed an exposure table that contains 36 4 foot UV
tubes. The Ballasts used were 60 watt rapid start ballasts. Each ballast
powered 2 tubes. Most of the electrical industry has switched from
ballasts that require a starter to units that have a built in pre-heat,
or rapid start circuit. Don't panic about not being able to find
ballasts that require starters. Starters are more trouble then they are
worth.
As for the difficulty with keeping the bulbs loose to get them to work,
there are generally two reasons this happens. The first is that the
distance between the fittings is too great. Most people building their
own boxes space the two ends a little too far apart. You are better off
with a snug fit then with a loose one. ( Experience taught me that one.)
It is rarely a problem with the actual contacts. The second reason is
simple, make sure that all of the fixtures are properly grounded. A
common ground is best. If you are making up your own fixtures, i.e..
buying the end fixtures and individual ballasts, place a piece of sheet
metal behind the tubes and ground the sheet metal. This step is
relatively important. I'm not an Electrical Engineer, but I think it has
something to do with the electromagnetic field that the ballasts and
tubes give off. Also, don't plan on using the edges of the light box.
The tube ends don't give off the same frequency or amount of light that
the rest of the tube does.
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