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PC vs standard flourescents


>Then I realized that by the time I
spend $150 or more on a canopy, then
>another 60 bucks for fixtures, and then
another C-note on wiring, bulbs and
>such, I could probably cover the cost
of a Power compact.

>So, if these things are more efficient
than standard flourescents, how much
>PC do I need to get the equivelent of
160 watts of standards?  Are they
>available in different color temps?
Any advice?

PCs especially the more powerful ones
are not significantly more efficient
than standard fluorescents we are only
talking about  efficacies of around 90
lumens per watt with the 55 watt type.
The big problem with 4 standard
fluorescents on a 55 gallon is that
although they will produce 11000 lumens
on a typical ballast they block too much
reflected light and also make it
impossible to design an effective
reflector.  Three T-8 lamps on a high
light output ballast produces 10000
lumens and with a decent reflector is
likely more effective than 4 T12s, not
because the lamps are all that much more
efficient but because they are smaller
diameter which blocks less light.
Reflector design is still a problem but
three lamps can go inside one
reflector.This is also a low cost system
because you only need one ballast and
the lamps are inexpensive. For some
plants though this may not be quite
enough light and in that case two 55
watt PCs or two 55 watt HO linear
fluorescents producing 10,000 lumens on
good reflectors should deliver more
light to the tank. Again, not because
the lamps themselves are putting out
more light but because their compact
size allows for a better reflector
design and the small lamp diameters
block less reflected light. It is too
bad these lamps are so expensive because
they really are a good system. I do not
think the PCs will light the tank evenly
though and this may or may not be
desirable. The area directly under the
lamp will be brighter than other parts
of the tank.

Note that to make these comparisons I
used the lamps with 741 phosphors. I
couldn't find  the lumen output of a 741
phosphor in a PC so I used a pentron 54
watt T5 HO lamp. For the ballasts
factors I used .875 for the T12 system,
1.2 for the T8 and 1.0 for the T5.

Wayne Jones

Wayne's DIY Aquarium Setup at
 http://www.mnsi.net/~waj