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[APD] Re: Spiral fluorescents - Walter

Walter (or anyone else with some ideas),

I have an old 48 fluorescent hood (the regular plastic kind) that is all
corroded and non functional. I was thinking about gutting it and using the
plastic casing to put 4 spiral fluorescents in because I thought it would be
a cheap source of light and I already aquired the 2-sided fixtures a few
years ago for like 5cents. Any idea how to add a fan or adequate

Easy, get a cheap muffin fan (preferably from a surplus place -- fans are *far* cheaper that way and you can *always* get new fans from surplus places. Apparently industry is very bad at ordering the correct numbers of fans so a lot alway go to surplus). Measure the diameter of the INSIDE of the fan's frame -- that is the part the blades twirl around in. Get a cheap hole saw from your local hardware store of that size (Black and Decker make some cheap hole saws that are about $5-8 that are excellent for this purpose). Make an "X", with the two lines at right angles to each other, on the hood, centered the way you want the fan to be aligned. Measure the DIAGONAL distance between the CENTERS (or the edge on the same side of each hole, which is easier to line up on) of two screw holes. Divide that distance by two and mark that distance out from the center of the "X" on each line. You now have a drilling pattern for your fan -- drill the screw holes first, then use the hole saw to *carefully* drill the large central blow-hole. If you drill smallish screw holes you can use self-tapping sheet metal screws to mount the fan which saves the hassle of dealing with nuts and washers. I've modified several all-glass hoods this way to take PC lights. I found the 60mm (if I'm remembering correctly) fans are a perfect match to the easily available 2 1/8" hole saws that Black and Decker makes. If you use a finger guard on the outside part of the fan you'll have a very professional looking installation that is easy, cheap, and only takes maybe an hour for the first try.

I mount the fans on the back of the hood at one end, and then bend the reflector in such a way that the air is blown down the length of the PCF bulb, then up above the reflector and out the two vents. If you don't bend the reflector on the end near the fan a lot of your fan's air just blows right out the near vent and doesn't remove the heat from the bulb. This is a problem for the all-glass hoods with the two top vents at either end of the hood. The idea is to blow air *through* the length of the hood, and then vent the heated air at the far end from the fan.

Any way of putting 48 inch (or 2 24") compact fluorescents in
one of those?  Any idea how much they may cost?  Would CP need to be cooled
too?  Any other ideas for putting light over a 55 gallon tank that has the
plastic hoods?


If the hoods are open you probably don't need any cooling. If they are all sealed up like the all-glass hoods then you need at least some extra vents (AH Supply includes a few snap-in vents with their kits). My hoods smelled like hot plastic and I didn't like that so I added some small fans. You don't need much in the way of fans -- even just a little air movement makes a big difference and you don't want to cool the lights off so much that their efficiency drops off. My aim was for quiet fans that were inexpensive and easy to get. I ended up with a pair of little Nidec fans that cost about $4 each. I run them on a 12v power supply (mine is way, way overkill (35 amp), but I had it available. A $2-3 wall-wart type supply is easy to get from any surplus place and will run a few fans just fine) that is on the same timer with the lights. Works great, and keeps the temperature low enough that I don't smell plastic. The plastic wasn't hot enough to be soft or in danger of bursting into flame, but it was a bit too, um, "aromatic" for my tastes :-)

BTW, a 55w PCF light will fit perfectly in the usual 24" light hood, so a pair would probably be exactly what you'd want for your 48" hood.


***************************** Waveform Technology UNIX Systems Administrator

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