A watt is a watt?

[MrRobbyRob]

So I am near completion of my third smallish medical grow, last one I managed about 6oz, using an eight bulb VHO T5. I am fairly happy with the light, but when I bought my tent, I didn't buy it big enough, so the light forms almost like a blanket over the canopy, and by the time the negative pressure exhaust kicks in and sucks the sides of the tent in, the problem is multiplied.
So my question is, if I were to replace the T5 unit (uses 760 watts before factoring in anything for the ballasts) with a 600w HPS, theoretically, even with the ballast I would be at no more than 680 watts... it should be easier to cool, right? Based on the concept that energy cannot be created or destroyed? Any input is appreciated.

 

[Maer]

I have also struggled with this question.

When cooling a server room you go on total "dissipated" watts, in other words add up the actual max wattage used and base your heat load on that.

I know my T5's run at 95 degrees on the bulb and since I use Sunblaze strips with integrated ballast the part of the strip where the ballast is gets to 140.

 

[MrRobbyRob]

OK, I see... so because I would then have to run an additional fan to air cool, etc., it may actually break even... I vent into a alrge bedroom, temps are not an issue in there because cool weather is upon me, and I have central air in the summer... but if I could mount all the fans, ballast, etc. outside the tent, then even though I would probably be producing the same amount of heat overall, one would reason to beleive that my immediate growing environment would be cooler...
One of the problems I am having is that my T5 fits fairly tightly in the tent, and forms a nice thermal blanket over the canopy...

 

[MrRobbyRob]

And these VHO's run quite a bit hotter than my Badboy I use for veg!

 

[PrairiePoet]

In power consumption, a watt is a watt.......
But different light technologies put out differing amounts of light using the same wattage. How efficient is the bulb in using power to produce light? The more lumens produced per watt means it is more efficient.

But with HID bulbs run at a higher temp to create light than CFL's. So they generate more heat at the same wattage. Though with the larger HID's the ballast are separate from the fixture, allowing you to place the ballast outside the grow room. Ballast create heat, which ever form of bulb is used.

HTH

 

[Maer]

I think this is the deal:

Lamps (of any sort) convert electricity to light at varying efficiencies. Lets say Lamp A produces light at 20% electrical efficiency, Lamp A is also powered by a 90% efficient ballast (MH, Flourecent, LED all have voltage / amperage conversion). The bulb in lamp A is rated for 1000Watts (easy math) so the wall draw will be about 1111.1 Watts, 200W goes to light, 911.1 goes to heat (111.1 from ballast and 800 from lamp).

So you can see increasing the efficiency of the lamp can effect heat output. According to wiki here are some stats:

Luminous efficacy - Wikipedia, the free encyclopedia

It is worth a mention that LED's gain an additional advantage by emitting only the wavelengths (we think) plants need, in the correct ratios. By eliminating 1/3 of the light spectrum that isn't used by the plant in theory you can focus your energy from unused wavelength to used wavelengths.

 

[Maer]

I don't have VHO, the Sunblaze 24's I have are T5HO. They have an integrated ballast that probably cranks the heat a bit more than a standard fixture with the ballast not right next to the bulb (like a BB)

 

[MrRobbyRob]

I guess my question is, 600w, regardless of how efficiently its used, should in theory come out as 600w of energy, be it in the form of heat or light? I would reason to believe that it would, but I wasn't sure if overall efficiency of the particular source had anything to do with it...And knowing that light is quickly converted back into heat...

 

[Maer]

Yea the source will have an effect, light that is absorbed by plants does not get converted back to heat.

 

[MrRobbyRob]

This was along the lines of what I was thinking... once again, I appreciate the prompt response...(+rep) Now its time to sell the idea to the old lady!