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Re: replacing CF bulbs
A lux meter, if it is weighted for PAR rather then human sensitivies,
will certainly tell you just how much useful light is coming from a
bulb. If you know just what your tankful of plants need you can tell
just when a bulb is ready for use and when to replace it to maintain
precisely x amount of light for your plants. You'll need a very
special lux meter for you the bulbs in your UV lamp ;-). But if you
use a PC for a year, you won't have much of a problem.
You do not require a PAR meter to test lamps. The amount of lumens that
lamp emits is proportional to the amount of PAR for a given lamp
spectrum. So as long as the spectrum of the lamp does not shift then a
LUX meter will do the job. If you want to compare lamps of different
spectra you just have to use a lumen/PAR conversion factor like the ones
found in Ivo Busko's article.
Most folks going for a Boothian or Barroque high-light tank will have
to base total wattage on how many bulbs they can fit on their tank.
PCs give a few more options in many cases. People using the slow and
Walstady method might have even more options.
AFAIK George Booth never used any more light than he had to. A concept
that I really agree with. I wonder if he is wondering when he should
replace his lamps? Not sure what Tom's light levels are but I am pretty
sure it not simply the maximum possible.
> All flouresecents lose about 10-20% of their acdtual lumen output
> their intitial burn-in period of several hundred to about a 1,000
> I write:
> This is too sweeping a statement. Some do some don't.
If they don't it's only because 1) they have already been burned-in or
2) they are rated for lower lumens. Maybe a T8 has an even shallower
The burn in period is only a 100 hours. Nobody rates lumen loss from
before the burn in period it would just be misleading. The lumen
maintenance curves really are very different depending on what you have.
Some PCs are way different than other PCs. Some T8s are quite different
than other T8s. Some T8s are just like PCs and so on.
As for vendors, I was thinking more of AH Supply as a trustworthy
vendor that many experts recommend. If you don't want to fuss too
much, you can call Kim Bryant and get very good advice. There are
others that are trustworthy and helpful.
I agree. The only thing that I ever had against AH Supply is they supply
a very high quality system for a reasonable price ;-) It is nearly
impossible to make a system of equal performance in your garage. It's
kind of frustrating. They sort of put the damper on DIY lighting
projects and that is one of the things I like the most.
I still think 32 watt T8 lamps are almost as good for less money if you
have a 4' tank but it is still difficult to find nice lamps. I have some
865s that I like a lot and they are pretty much the equivilent of any
Tri-phosphor lamp but you cannot buy full spectrum in 32 watt lamps
unless you go to a lower efficiency lamp. If you live in Europe you are
golden as there are really great 5' 950 and 965 lamps readily available
there. Lately I have been paying attention to people who are seriously
overdriving T8 lamps and think that they might really be onto something.
This could reduce the number of lamps required for a tank and make
specular reflectors a viable option with T8 lamps. I just do not know
how badly efficiency and lumen maintainance are affected. I did some
tests with some crude equipment on old and new lamps and the efficiency
drop did not seem to be so bad. In fact, when driven at a 1.5 B.F. they
appeared to still be more efficient than PCs. However, the lumen
maintainance thing is the big question mark. I couldn't recommend that
anybody do this without knowing what the lumen maintainance curve will
look like and as such wouldn't have much of an idea of how often the
lamps should be changed. I am completely certain that a 1.2 B.F. does
not do any significant harm to T8 lamps but who knows when you go beyond
that. The only way I am going to find out is to test them for a year or
so and check them with a lux meter every month. I think I am going to
add an extra ballast to one of my tanks and overdrive a couple of lamps
and then compare them with the non-overdriven lamps.