Silent Bob
420 Member
[derail]
I'm not arguing here, just getting something straight.
Heat is always radiant, whether it comes from the internal ballast on CFL's, or if it comes from pushing electrons through a filament. It's not the light in HPS's which create the heat, it's the glowing metal bar inside the glass bulb. They are both above the plants. They're exactly the same kind of heat (i.e. heat), it's just generated in different places. And since the HPS does get hotter (I can touch the ballast on my cfl while it's on), it wastes more energy to heat than a cfl. That's what the whole environmental argument for CFL's over tungsten filament bulbs boils down to.
[/derail]
I know what you are saying... but you might be missing my point.
Have you ever seen the two types of plug in heaters you can buy? One is small and has a fan - and uses a heating coil to heat the air - this is like the internal ballast giving off heat to the air in a CFL.
The second type has big rods which glow red and a metal reflector to focus the radiant heat out into the room - this is like an HPS bulb which heats your plants directly with radiant heat.
If you put your hand near an HPS bulb, you will feel the radiant heat - it's coming from the high pressure sodium chamber (there is no "filiment", just a chamber of sodium which radiates light when current is passed through) just like the light. Radiant heat is simply radiation with a longer wavelength than visible light, and it's part of the spectrum an HPS emits.
If you put your hand near a CFL bulb, you will feel very little radiant heat - the emission spectrum of a CFL does not include the lower frequencies that you would feel as heat, so while it heats the air, it does not project heat on to the plants.
My point is, 200 watts of energy consumption will heat up your closet equally, whether it's HPS or CFL. However, you need more ventilation with 200 watts of HPS since it's heating up your plants more directly with the radiant heat focused right on them.