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Bill Wichers wrote:
"Ideally you would want to have the
fan blowing on the cool end and exiting out the hot end, with the hood
acting as a duct to carry the air along the tube. In this way the
tube would see a nice, cooling thermal differential. "
This is true if your ideal is cooling efficiency rather than lighting
efficiency. The most efficient cooling is achieved if you (I am
quoting Pabst's technical manual) "locate components with minimum heat
rise closer to the air inlet and components with the highest heat rise
closer to the exhaust end of the air flow path."
However, flourescents work best within a certain range of temps
(roughly 120 degrees F for many). Above that temp and the bulbs
blacken and fail too quickly. Below the range the mercury doesn't
fully vaporize and lighting efficiency is reduced. The extent of
mercury vaporization is generally determined by the coolest part of the
tube. So it may be more efficient to have the fan blow first on the
hot end and then the cool. This will avoid overcooling the cool end.
There's a plus and minus either way. But, since you can remove the
reflector and move the lamp socket over to the other side of the hood,
you can try it one way. If you don't like it, you can try it the
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