Re: Lighting Specs

Neil Schneider wrote:
> What I have discovered though is (4) 110W VHO lamps (total 440W), daylight
> spectrum, will put out 19,800 lumens compared to 24,400 mean lumens for a 400
> W MHD. I don't know how the heat output would compare, though I suspect the
> difference would be considerable.. Personally, I'd choose VHO. It seems less
> expensive and less a problem for heat buildup. Lumen per watt are comparable
> and the fluorescent ballasts should be less expensive, providing you don't
> buy them through Aquarium suppliers.

Heat output is easy. 440 watts of FL lighting ALWAYS generates 440 watts
of heating. The units are the same. 400 watts of MH generates 400 watts
of heat which is less heat for more mean lumens. The heat build up should
be less of a problem with MH because 1) a pendant is open to air circulation
2) you really have to pack the bulbs in tight when using FL and the
FL bulbs are much more severely affected by a hot operating environment.
Another potential hood related problem is humidity which affects corrosion
on the FL bulb contacts.

We tend to think of fluorescent lighting as "cooler" than incandescent
because we can get an equivalent amount of light using much lower power.
The same is true of MH lights, just that we're not interested in low
power, just more light.

BTW. higher wattage MH bulbs are *cheaper* than lower wattage MH bulbs 
because they are used far more commonly in industrial applications such 
as green houses. They are also more efficient.