[APD] Re: Self-ballasted PC lights?

[Bill Wichers <billw at waveform_net>]

> I was wondering if anyone had ever thought about using or tried using self-
> ballasted PC fluorescent lights (they have the ballast built into them so you
> can use a regular lamp socket). I was considering using a couple 85watt 6500K
> self-ballasted PC bulbs over my 65 gallon tank (that I will soon be 
> setting up
> as a planted tank). They only cost between $25-$30 and save you the cost of
> buying (and replacing)expensive ballasts. I can see two possible problems 
> with
> this setup...

This question comes up periodically on the list so there are a bunch of 
threads in the archives about it.
BTW, a typical ballast for regular linear PCF lights will last more than 5 
years IMHO. I wouldn't worry too much about factoring in replacement cost 
of the ballasts in your pricing calculations since you will be able to 
amortize the cost of the ballast over many years, and they aren't very 
expensive to begin with unless you're getting them from an LFS.

> 1) They are twisted bulbs instead of straight so they do not cover as much
> area (they act more like a spot light)

They are closer to point source lights, but suffer from high restrike due 
to the coiled tube. In a normal linear florescent light, light radiates 
outward roughly equally in all directions around the cylinder of the tube 
(must... resist... using vector terminology....:-). In a tightly coiled 
tube, a lot of the light is emitted on the "inside" of the coil which does 
little besides heating up other parts of the coil. This reduced "effective 
efficiency" will translate to less of the light output getting into your 
tank, so a  55 watt incandescent-replacement type fixture will *not* 
produce the same *effective* light over your tank as a 55 watt "normal" 
(linear) PCF lamp would.

> 2) You can't buy regular lamp sockets that are water tight like the aquarium
> fluorescent endcaps.

This isn't really much cause for concern. I really think the watertight 
endcaps are mostly marketing hype and have little technical value. Most of 
them aren't even truly watertight (or stop being watertight after a few 
months or years of exposure to the high-temp and high-humidity environment 
above a tank). I use "regular" bases over all my tanks since they are much 
cheaper and are easier to replace when they fail from corrosion and the 
like. And if your hot bulb goes in the tank there is a good chance it will 
break from the temperature shock and then you'll have electrical contact 
with the water despite having the watertight endcaps. My advice: use a lens 
of some sort between the water and your bulbs and don't worry about the 
endcaps, but use a GFCI on the electrical circuit feeding your tank 
equipment and *test it monthly*. Also, the breaker-type (as in 
mount-in-the-electrical-panel type of breaker) GFCI's tend to be far more 
reliable and longer-lived, IMHO, and I've seen a *lot* of both types of them.

> However, the way I look at it, people use MH lamps and (although much
> brighter) they act like spot lights too. Using a good reflector might help
> with this problem too.
MH doesn't suffer from the restrike problem since it is a "true" point 
source light (all the light comes from essentially one very small spot and 
radiates roughly equally in all directions). As a result of this, it is not 
difficult to design a good reflector to direct most of the light into the 
tank. With a coiled PCF lamp, it is impossible to realistically design a 
reflector capable of using the light emitted on the "inside" of the coil, 
which results in that light being wasted in restrike, which does little 
beyond heating up the florescent tube.

> As far as I am concerned, using a regular lamp socket MIGHT accumulate a 
> bit of rust on it, but they only cost a few dollars... if they accumulate 
> rust I can just replace them when I replace the bulbs and still save 
> money. Coralife has the same thing in a 10watt version in either

Use a commercial ceramic light socket (even Home Depot has them) with brass 
contacts if you can find them (many use aluminum for the screw contact and 
brass for only the pin in the base). You can clean corrosion off of a brass 
socket with a scouring pad or a dremel with a wire brush disc. You'll get 
*years* out of even a cheap socket though unless you have water making 
direct contact with it over a prolonged period of time (such as in the case 
of a light socket placed over an area of the tank with an air stone, which 
will create a "mist" in the air above the water surface in that area).

> 6500k or 50/50(10,000k/actinic) so obviously people have thought of doing 
> this
> for small tanks. I am interested to hear what other people think about this
> idea.
> __________________

The basic consensus is usually that it can be done, and that the cheap 
lights will work, but they're not as good as a "real" linear PCF is in 
terms of efficiency or light delivery to the tank water. If you're on a 
tight budget, the incandescent-replacement type fixtures are definitely 
worth a try, but if you're looking for the best performance or electrical 
and lighting efficiency from your system there are much better options on 
the market.

Since it sounds like you are planning to DIY your lighting, have a look at 
the linear PCF supplies available at http://www.ahsupply.com. Many on the 
list (including myself) have had very good luck with their equipment, and 
the prices are much better than the prebuilt assemblies the tank 
manufactures sell.

        -Bill


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

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