Re: Aquatic Plants Digest V1 #281

> From: User645273 at aol_com
> Date: Sat, 24 Feb 1996 19:28:54 -0500
> Subject: Re: Aquatic Plants Digest V1 #271
> >Scott Corbeil asked about the heat of Metal Halide lights.
> 1) the heat thrown by X watts of MH light is the same as the heat
> from X watts of FL lights. But you can easily have more watts of MH :)<
> I would have to disagree with that statement.  I have never seen someone get
> burned on a flourecent tube or an electronic ballast, but I assume that they
> don't put fans on those MH enclosures for nothing!
>     Just my two bits.

That analogy may be too simple; you have to consider the physics of the
situation.  MH bulbs concentrate 175 or 200 watts of energy in a very
small surface area, whereas the equivalent fluorescent wattage is spread out
over a much larger area.  Of course you won't get burned by touching it. 

In one of my small tanks, I have a 13W compact flourescent ("U" tube type)
which gets hot enough that it might burn me when I touch it; compare this
to the 18W "normal" fluorescent, which I can pull out at any time.

I suspect T-8's feel hotter than T-12's for the same reason.

Though the main purpose of fans in MH hoods is to take the heat away from
the surface of the bulb, I suspect that if you had an enclosed 500 watt
fluorescent hood, you'd want a fan on that too. 

    - Dr. Erik :)

Erik D. Olson					         amazingly, at home
eriko at wrq_com