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Re: Light bulb advice
Wright Huntley wrote:
>
> I have been switching to compacts for my small tanks and buying electronic
> ballasts in preparation for converting my larger tanks to the far more
> efficient T-8 tubes.
> Wayne wrote:
>
> This is one of the problem with T8s. It is hard to buy or make reflectors
> that can compete with AH Supply reflectors. You need more reflectors
because
> the T8s even with the right ballast are still less intense than the PC
> lamps.
Wright wrote:
I have trouble understanding this statement. CFs are T-5 and T-8s will
*always* be a bit less efficient, AFAIK. Their absolute brightness is *way*
lower than most PCs. The reflector design can get you part way back, but
only if it is clever and terribly efficient.
I reply:
What I mean is that T8s take up more space because each lamp produces less
light so you need more T8 lamps than PCs which means more reflectors. For
example, over a 90 gallon tank I could use 4 55 watt PCs with 4 2'
reflectors but to get the same amount of light using T8's I would have to
use 5 lamps and five 4' reflectors. This means basically covering the top of
the tank with reflectors. You just need so much reflector material it is
quite cumbersome.
Wayne wrote:
> I have the equipment to make reflectors and they work very well but I
> don't get enough light in a deep tank if I make single lamp reflectors
more
> than 4" wide.
Wright wrote:
Width is no more significant than depth. The more you can afford (tolerate)
of both, the closer your reflector can approach ideal (steeper angle of
entry for more light). Tank depth has very little to do with it. It's how
much of the light enters at how steep an angle to the water. Once *in* the
water, light-piping will get it to all unshadowed areas with only a little
attenuation. [Of course, I refuse to have, or work in, a tank that is deeper
than my arm will reach. ;-)]
If scuba gear is required, then my statement, above, is obviously wrong.
I reply:
I am familiar with this idea but in practice the bottom of my tanks are
obviously not lit as brightly as the tops of my tanks. I am pretty sure that
the presence of so many plants pretty much screws up the light tube effect.
Both my tanks are 2' deep and now I am getting more into aquascaping I am
strarting to wish that they weren't. I am a tall guy but I still have to
practically take my shirt off to work.
Wayne:
> I have tried to make two lamp versions but two T8 lamps in a
> single reflector just doesn't seem to work. The ultimate in aquarium
> fixtures would be linear T5 HO lamps with one specular reflector per lamp
> made from a highly reflective material.
Wright wrote:
It would sure beat anything *I* can afford, right now. (^_^) BTW, how do you
bend the parabola?
I reply:
I use a heavy guage aluminized mylar and aluminum flat stock. I find it
very hard to describe but I will give it a shot. The aluminum shell is made
from a piece of aluminum sheet metal 10" wide and 4' long. I leave an 1 1/2"
flat section at the top of the shell and then I put two more bends in each
side. The bottom edges of the shell have safety edges bent toward the inside
of the shell. I then line the inside of the shell with aluminized by
tucking the mylar into the safety edges of the aluminum shell. If you cut
the mylar exactly the right width the mylar will form a parabola-like shape
inside the shell. I am not sure if I have the shape exactly right, I try to
avoid a shape that is concentric with the lamp at the top to avoid restrike.
The rest of the shape is pretty much a parabola segment on each side. If
you cut some 1/4" by 1" notches in the end of the aluminum shell then you
can mount your lamps in the shell and voila you have
a pretty darn good fixture. They really work well too but as I said they are
quite bulky.
If I look straight at the lamp all I see is the lamp reflected in the mylar
and if I shine the light on an wall I get a distinct band of light. I also
cannot see the lamp if I view it at a 45 degree angle. Quite a bit of light
escapes out the ends of the fixture but there is nothing to be done about
that. I am pretty sure there is quite a bit of restrike going on at the top
of the fixture too and I might be overheating the lamps but overall I think
it is quite effective.
Wayne wrote:
> The other problem with T8s when compared to PCs is that they are designed
to
> work at 25 degrees C. while T5 lamps are designed to work at 35 degrees C.
> Most aquarium hoods are going to be closer to 35 rather than 25 degrees C.
> On the other hand T8s are somewhat more efficient than PCs to begin with
and
> last longer as well so the T8s should be cheaper to operate.
Wright wrote:
Most fluorescents have the same negative response to heat. The T-5s just
*have* to put up with more. They aren't exactly "designed" to.
I reply:
I don't know about that. I have seen graphs of ambient temperature versus
lumen output and lamp life. For PCs the lines all meet at 35 degrees C. If
it is cooler then the lumen output is lower. If it is warmer then the lumen
output increses a little bit but then drops but the lamp life drops. I can't
seem to get into the Philips website right now to check it out.
Wright wrote:
My 40W PC is rated at 20,000 hours. I haven't seen many T-8s rated for that
lifetime.
I reply:
T8s are 20,000 hours or more you can get them up to 24,00 hours. The 40 watt
PCs are basically an NO lamp so the lamp life is really good but 55 watt PCs
are HO lamps and the lamp life drops accordingly. In general though the PC
lamp life is somewhat less.
Wright wrote:
When I outlined where I'm headed, it should be understood that I don't have
unlimited resources, so I'm looking for practical, easy-to-home-build hoods
that won't embarrass me too much if I have friends over for a drink.
The closer I get to what *I* want, the more impressed I am with the sound
compromises that led to the AH design.
I reply:
Me too. I think they are as about as good as it is going to get. It sort of
pisses me off because it has taken a lot of fun out of DIYing your own
system. I put in quite a bit of effort to build a custum light fixture and
it is still not as good as those kits. The more I learn about fixture design
the more I like the AH Supply stuff. Too bad the lamps cost so much money.
Wayne