Re: More lighting stupidity/ actual output

["Wendy Jones" <w.jones at sympatico_ca>]

Paulio wrote:

First let me thank all those that responded to my cooling question.
My next question(s) is/are how much actual gain does one get from
overdriving
and "good" reflectors?
I went with T8 bulbs (48") overdriven 2X by Workhorse 5 ballasts and
Coralife
"Aqua Mirror" reflectors.
I have the bulbs spaced about 2" apart and each is run as if it were a 55
watt PC (two outputs to each bulb) as far as the ballast wiring is
concerned.
Im trying very hard to get away with 6 tubes over my 90 and still grow
marginally high light plants. Probably chasing my tail though.
Thanks again all.

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Overdriving 4' 32 watt (265 mA) lamps in that way increases the ballast
factor to about 1.5. A good way to estimate the ballast factor is to measure
the total wattage drawn by your ballast. Subtract 4 watts for the ballast
and then divide the remaining wattage by the number of lamps. Those lamps
are designed to run at 30.5 watts at 100% ballast factor. The new ballast
factor is approximately proportional to the estimated lamp wattage divided
by 30.5 watts. There is also a small loss of efficiency as well when you
overdrive. It is probably mostly insignificant if you are only overdriving
2x. If they are 40 watt 4' T8s then the increase in light output will be
much less but you can estimate the new BF in the same manner. Not sure about
the actual operating wattage of those lamps but I believe it is quite close
to 40 watts.

The reflectors are probably a complete waste of money. Most likely a high
quality difuse white background would do just as well. You have too much
space taken up by lamps to make a functional specular reflector.

You can easily grow high light plants with 6 lamps over a 90 gallon tank. 32
watt lamps are rated for about 2800 lumens. 6 x 2800 lumens x 1.5/90 gallons
= 280 lumens/gallon. Even if your fixture efficiency is only 80% of an AH
Supply type fixture you still end up with 280 lumens/gallon x .80 = 224
lumens per gallon. This is the equivalent of 4.5 55 watt lamps with
excellent specular reflectors. It is also more light than it is possible to
provide with T12 lamps no matter how many you used.

Wayne

Wayne