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Re: [APD] Re: Fluorescent lights close to the water surface -- or - Driving Lights

Nice pics, Giancarlo.

The relatively inexpensive electronic ballasts -- cheap in
part because they are mass marketed for all those
fluorescently lit office buidlings around the world -- can
be very versatile.

Wayne Jones left behind some good posts re electronic
ballasts primariliy designed for 4x32 T8 bulbs and using
those ballasts to drive, or overdrive other bulbs. For good




It was after he started measuring the voltages and the
actual current draw of diff combinations and wirings that
things got interesting. Putting two bulbs on a ballast
designed for 4 bulbs won't necessarily drive the bulbs at
twice their rated power. In fact it could be less or more.
And it made a big diff if the bulbs were wired in series or
not. And in every case, *when* they are overdriven, the
energy effciency decreases as you increase the input
energy. Basically, the bulbs are usually designed for
optimum energy efficiency at the rated power -- you run
them hotter and they put out more light but there's a
declining marginal return on the added input energy.  

But who says energy efficiency is our goal? More often,
we're trying to get more light out of a hood without being
able to put a whole lot more bulbs into the hood. [And, no,
George, I'm not trying to make a case for more than 2 wpg.
;-) ]  Besides a decline in energy efficiency, the hotter
you drive the bulbs, generally the shorter their life. But
with 4 foot T8s, which can be gotten very cheaply, that's
not a big deal,

Energy efficiency notwithstanding, you can get a pair of 4
foot T8s (32 watt rated bulbs) to shine about as brightly,
in lumens, as a 55watt PC by putting a pair on a ballast
meant for four, but you probalby won't be driving them at
double power. This comparison, of course, assumes the 55
watt PC is run on a ballast intended for a 55 watt PC. 

Diff models of ballast will behave diff than the one Wayne
experimented with. But the general point holds, that
ballast and bulb performance are a result of the
interaction between ballast and bulb. The manufacture's
printed ratings on a ballast or bulb are based on
particular combinations.

And now that one can get good electronic ballasts for about
$20-$50, there's no reason not to enjoy the alternatives
that fit your circumstances.

Scott H.

--- Giancarlo Podio <gp at isaconsulting_com> wrote:
> If you're out of space for more tubes you might want to
> consider overdriving
> your existing tubes. Good convectional venting or a fan
> is a good idea
> however when overdriving the bulbs. The ballast stays
> cool but the bulbs run
> quite hot, about the same as CFs at 2x.
> Here's a link to the retrofit I did:
> http://www.gpodio.com/overdrive_twin_strip.htm
> Hope that helps
> Giancarlo Podio
> --- Original Message ---
> Hi,
> Thanks for pointing out the heat issue.
> However my question was more focused on how to increase
> the intensity of
> light provided that I use normal T8 fluorescent and that
> the aquarium cover
> is closed. There's certainly a limit to the number of
> T8's that I can put
> side by side if there's a reflector. I would say that for
> my 20 inch wide
> tank I can stuff up to 6 such reflectors. Now the
> question is whether
> lowering them would increase or decrease... Incresase
> because of the 1/R law
> and decrease because light shall escape through the glass
> because of the
> angle...
> And yet another idea is to just put those FLs without
> reflectors and rely on
> the fact that the hood is a white reflective formica.
> VRK.
> _______________________________________________
> Aquatic-Plants mailing list
> Aquatic-Plants at actwin_com
> http://www.actwin.com/mailman/listinfo.cgi/aquatic-plants

S. Hieber

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