how much loss on aircooled hoods?

[Military]

... Just finished reading.. If you guys are so worried about losing light from the Aircooled hoods.. why dont you just take out the glass... ANd get a stronger exhaust fan so then no heat will escape the hood at all, since heat rises a nice strong blower to suck out the heat before it builds up in the hood and start to "fold" over the edges and go above the hood would 100% solve any problems..

I myself have build a Cooltube... I got 2 bake-a-rounds, and i am kind of regreting getting them because I think Im going to only use them for one run, then build myself or buy a cheap-o hood and just remove the glass, and have a nice strong blower pulling out my hot air.

Simple

 

[BonsaiBud]

Its the angle!

Its the angle!

knna's numbers are almost exactly what I learned in Physics class. Everyone must remember that it has EVERYTHING to do with the angle at which the light strikes the glass. Perpendicular is ideal. That is why I am making sure the quartz tube of my HPS bulbs is perfectly centered in my "cool tubes". I don't like the hoods where there is a bulb with a nicely formed reflector and a flat plate of glass. There are all sorts of reflective losses when the angle falls below 45%. From what I've read so far, UV is pretty much stopped by most any glass or plastic lens except some kind of special quartz. They use it in the sleeves of UV sterilizers and transmit 99.?% of UV. I'm just adding a pink T5 once my plants start putting on the resin.

 

[clowntown]

Military, it doesn't work that way. Especially for more than one light. Especially inline.

I would suggest that you spend time gaining some practical experience than cooking up half-baked theories based on zero experience, and wasting your time with fancy solutions that have no chance of success. Things that work in a 150w grow don't scale as easily when the wattages go up. And I mean this in the nicest way possible, after participating in a few of your threads.

 

[clowntown]

knna, I'm still unsure where you're pulling those numbers from... Are those just "feel" numbers from guesstimation, or are those numbers obtained through actual testing? I'm leaning towards the former.

I have a gut feeling (based on absolutely no science or facts) that with many air-cooled reflector designs, that the total amount of light lost by the time it's delivered to the leaf surface (or meter) is about what you quote... but I'm just curious if those are indeed measured facts?

In particular, I'm curious how much light is lost through the dual vents (especially in the case of 8" and larger); not only is (most of) light directly from the bulb not reflected at the vents, but also loss from lack of compounded reflection (no reflecting reflected light), compounded by the light loss through glass and compromises made in physical design: low turbulence vs high reflectivity and favorable footprint.

 

[BQ2]

Hi Pico!
You said, "I think the big attraction to the PL design is for greenhouse lighting. In greenhouses most of the time the lights are used for supplemental lighting so you want a small reflector that doesn't block out light from the sun."

Actually the PLs were scientifically designed to reflect way more light. It is a law of physics:the shorter the distance the light has to travel to the reflector, the greater amount of light reflected. That is the whole idea of the PLs-small bowl, close to the light=great reflectivity. They have several different "bowl" sizes and shapes for particular needs. These lights were demonstrated to me by the hydro store guy, using a light meter. The PLs put 40% to 50% more light on the canopy than a "standard" reflector design. I saw it with my own eyes. No other reflector even comes close. This design is also used in street light reflectors with HPS bulbs. I'm sure you've seen them on street lights. The small reflector size and shape concentrates the reflected light onto a particular area more efficiently. You may have seen the new bulbs that have aluminum reflectors built right into the bulb. These are super efficient. If you test a PL, you will see how powerful they are.

 

[pico]

BQ2, thanks for the input. I agree that the less distance the light has to travel the better, that is one of the reasons why the super sun 2 does better than the larger reflectors. However just putting a light meter under 2 different reflectors in the hydro shop doesn't really shed a lot of light on the situation. Was it the same exact bulb(not just same model, the same bulb)? Same ballast? Did you warm up the bulbs for 30+ minutes each? Did you test the exact same spot at the exact same distance? I am guessing you tested right in the middle and it is possible that the PL does produce more light in the middle but less light around the outer edges. I don't know any of this for sure but I am just guessing.

I do know from talking to reflector manufacturers and greenhouse industry guys that the small design of the PL is nice because it blocks less light from the sun. Directly from their website it says "These innovative, Dutch-engineered lights are streamlined for minimum light blockage, strong and durable for long-term wear, and yet lightweight for ease of installation and cleaning." Minimum light blockage......they are talking about the sun there.

Also from the website when it mentions the 1000w reflector they say "Best performances at a mounting height at 8’ or higher depending on light level required" So once again they are designed for supplemental greenhouse lighting, not really the indoor stuff we do.

I will look in to testing a PL. They should get high marks just for the fact that they don't have any aircooling ports. For my projects I need aircooling and I want a reflector that will give me a good even distribution of light at low heights. 8 feet isn't going to cut the mustard.

What is a standard reflector anyways? Super Sun 2 probably does 40-50% more than the "standard" reflector too.

 

[pico]

Oh, and I still don't understand how my light meter would lie to me about the glass. I tested 16 points with and without glass and came up with 3% loss. Anyone have any thoughts on this? At this point I am not convinced on the 10%+ loss.

 

[Military]

Meh.. Ok, We all do our different things, mine work for me atleast :-S

 

[BQ2]

Hey Pico, interesting about the "light blocking".
What we did in the hydro store was just a demo, not scientific. However this particular "hydro guy" is very experienced and he knows his stuff. He recommends PLs over anything. However, the 1000 PL, as you stated, has a footprint that is best suited to placing the lights 3 feet over the canopy, so you would pretty much need 8 Ft. ceilings. Hmmmmm....I have 8 Ft. ceilings.....
Anyway, the 600 PL is designed to be placed 2 Ft. over the canopy. It has a deep dish reflector that penetrates the canopy to the ground. It supposedly puts as much light on the canopy as a 1000 Watt light in another reflector. Again, not scientific-just anecdotal.
Also, FYI, there is a cooling kit for the PLs. The entire reflector goes in a larger hood with 6 inch openings on the sides, for air cooling.
We really need a test of the PLs to get the real numbers on them, and how they compare to other makes.
I am quite certain they are significantly brighter. I saw them in use when in the Dam.

 

[pico]

Where do you see 3 feet above the canopy on the PL website? I see 8 feet minimum.

I really can't believe anything the 'hydro guy' says. I am not blindly saying you are all wrong, I am just pointing out my numbers and stuff mentioned on the PL website. Hydro guys are in it for the money....he might make more money off PL than other systems. I don't make shit either way so when I test I will give the real numbers without any bias.

I did see the cooling kit...not totally impressed.

Again...you can't be quite certain they are brighter because the eye isn't that good. You can feel they are brighter but until we have some actual testing it is all just feelings. I feel like they aren't as good as they are cracked up to be. I won't be quite certain until I test them out. I really doubt the Dam had a PL and a Super Sun 2 side by side.

I hope you don't feel I am attacking you. I like a good discussion.

 

[clowntown]

Very good points, knna.