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Re: Ballast Cooling Problems

Hoa Nguyen wrote:
It's a nice web page, but I just can't help wondering:  with the added cost 
of the fans and power supply, plus additional electricity, plus all the 
work to put them in, wouldn't it be better just to replace your ballasts 
with cool-running, energy-efficient electronic ballasts?  (I'm assuming 
your current ballast are tar-ballast, since they run so hot.)

Actually, doing both would be even better.  Even with the ballast mounted
remotely, the lamps would tend to run warm in such a confined space.
Perhaps not enough to distort the plastic and reduce the usable lamp life
down to a month, but they would definitely be running warm.

From p. 209, Lighting Handbook, 8th ed., Illuminating Engineering Society of
North America, the rule of thumb given is, "There will be a 1% loss in light
for every 1.1 C (2 F) by which the ambient temperature around the lamp
exceeds 25 C (77 F)."  If you read other lighting literature (or even this
handbook), don't confuse this with the Minimum Bulb Wall Temperature, which
is the temp. of the coldest point on the lamp (usually higher than ambient).

It also mentions, "In general, the lamp color shifts toward the blue-green
with increasing temperature due to the increasing contribution from the
mercury arc visible spectrum."

Wade Shimoda