High temperature vs Long Light Distance / Air cooled or Not?

[greenops]

I need some advice...

I'm going to scrog 5 plants in a 1m x 1m // 40in x 40in area.

They been vegging for over a month now and I just switched the setting on my ballast from 400w to 600w. Even though I'm using an Air Cooled Hood, I have not yet attached the glass, as I prefer not to use it if possible because of the potential lumen loss.

Now after 2 hours into the light cycle I have the light 50cm / 20in away from the canopy and I'm getting temps of 28 C - 31 / 82.4 F - 89F.

According to the HPS lumen/distance chart, a light distance of 20in with 600w HPS will bring about 10'000 lumen.

Do you guys think these numbers are within the ideal range? The temperature worries me, because the first time I grew I had to deal with high temps (...around 30C plus because it was summer) the buds lost their smell in late flower, and the cure didnt help.

Will they get enough lumen to ensure a proper yield? When I get the light closer I'm sure that the temps will rise up quickly.

If I have to bring the temps down, I will have to mount the glass on the hood... but that also means changing the whole ventilation system. So I wanna be sure before I do any of that.

Pics in my sig...

Thanks!

 

[señorsloth]

Cooled Hood, I have not yet attached the glass, as I prefer not to use it if possible because of the potential lumen loss.

as for the glass, there is a sticky in the lighting forum where i guy tested this and it was like a 1% loss...so put that glass back in there! it is sooo not worth it to ever take it out...and here is why:

for starters...stop worrying about lumens, they mean nothing to plants, lumens are a measure of part of the spectrum the plants cant see, the yellows i believe, so whether a bulb is putting out more or less lumens is completely meaningless to plants...sure it's super relevant for describing the way a bulb lights a house or street...because we see yellows, but plants don't so don't even worry about lumens, except maybe as an arbitrary way of comparing distance...for example if you know a bulb is 146,000 lumens at the bulb and only half that 2 inches from the bulb, you can assume that the spectrums your plants CAN see have also been cut in half at that 4 inch mark...those spectrums that plants see are measured in par watts...for this explanation i'll use the word "light intensity" instead of lumens, because that terminology bugs me, and light intensity is more accurate imo because it leaves room to describe bulbs in terms of lumens, but not specifically referring to the spectrum that lumens measures, more like referencing the intensity of the spectrums that the plants do absorb while recognizing that they are likely comparative to lumens and vice versa.

now...here is the part where your lack of glass is screwing you over...without the glass, the light is super duper hot right? so hot that you have to raise the thing 20 inches above the plant, which is, imo way to high...you do this because you don't want your plants to get too hot, so in the end, you took out the glass, to save 1% of the overall light intensity that it would have obstructed, but in return the lamp is so hot you have to keep very far away from your plants...which in turn is costing like 75% of your light intensity...it's not very logical to sacrifice 75% of your light intensity to save 1% now, is it? the strength and penetrating power of a bulb diminishes exponentially from the bulb(as im sure your lumen graph reflects), so it's extremely important to keep your plants as close as possible to the lamp without burning or bleaching it...moving your plants just 2 inches closer to the bulb DOUBLES TO TRIPLES your light intensity!I can't stress enough how important the glass in your reflector is for it's efficiency...there is no possible way getting rid of the glass in an air-cooled horizontal grow will EVER help you in ANY way!

basically if you put the glass back in, that 1% of "lumens" you may lose will mean NOTHING, because you can go from that 10,000 lumens at 20inches with 85 degree temps, to like 20-30 thousand "lumens" at probably a lower temperature at 12-14 inches...do it...you will be glad you did, there is a reason people plug every leak in air cooled lights, they work most efficiently by far when air is drawing quickly over the bulb, without the glass it's not air cooled anymore, as very little of the air is doing what its supposed to, cleaning the hot air out of the hood...

i keep my 400 around 10 inches from the canopy, maybe a little less...a 600 i wouldn't want more than 14 inches away...though i prefer a very high wattage per square foot...a square meter is the perfect amount of space for a 600w light and with proper ventilation AND THE GLASS ON YOUR REFLECTOR!!!!you should have no problem getting the light between 12-14 inches of the canopy, which will give you much, much better penetration power than it will at 20 inches...

for veg it's less important to max out your light intensity, and 20 inches is probably fine, but if you put the glass back in i guarantee you will get almost exactly the same intensity as without it, but your temps will drop down to 75...which will give you tighter node spacing, meaning denser buds...assuming you keep it at that height and just put the glass back in...

 

[supermanlives]

the amount the glass reduces lumens is offset by the close distance you can place the aircooled lights.

 

[ItsTopShelf]

superman is correct.

 

[greenops]

Thanks people. I heard somewhere that the lumen loss was about 10%.. but if it's just 1% then hell yeah. Honestly I was just looking for a reason not going thru the hassle of changing my ventilation. But I just did it.. so I'm good now. Thanks again!

 

[señorsloth]

actually, even if it were 20% it would still be worth it to keep it in i think, because without it you would have to raise the lamp so high that you are losing literally 66% of the total(going from 12 to 20 inches)...so either way you save light intensity by keeping it low.

however, thankfully, it's not...i went back and found the post...pico tested many hoods, his thread is a sticky in the lighting forum, he made a grid of tape marks and tested with a light meter at each grid point...with and without the glass, you can go to his thread for more info, it's a great read, but here is the info where he does the testing with and without glass...turns out it was like 2.4% which is still nothing because it's offset by being able to keep the bulb twice as close to the plants...

At 18 inches. Measured in footcandles.
glass : no glass
1. 1140 : 1230
2. 1960 : 2120
3. 2140 : 2340
4. 1200 : 1310
5. 2110 : 2250
6. 4500 : 4650
7. 4930 : 4910
8. 2270 : 2230
9. 1950 : 2040
10. 3980 : 4020
11. 4310 : 4170
12. 1670 : 1880
13. 1160 : 1230
14. 2020 : 2020
15. 2080 : 1980
16. 1160 : 1140
Average with glass: 2411
Average without glass: 2470
2.4% of light is lost with glass.

 

[OldSSSCGuy]

Great stuff Senor... Would have been nice to also see a radiated heat temperature level for each.

 

[de145]

I bet different glass makes for a wide range of percentage loss as well. All glass is definitely not equal in other areas of endeavor I imagine it's the same with glass for lights as well.

 

[DrFever]

Lumens. The more the better.
Kelvin's are semi-important, only because of the wavelength of the light emitted.
Watts are totally irrelevent.

 

[señorsloth]

I bet different glass makes for a wide range of percentage loss as well. All glass is definitely not equal in other areas of endeavor I imagine it's the same with glass for lights as well.

that might be true, although since most glass doesn't cast a shadow even i wouldn't think it's much, and i think any reflector manufacturer would take that into consideration when engineering them...furthermore, i'm pretty sure there is an industry standard as far as the type of glass goes, it's all tempered high clarity safety glass and i think it's all 4m thick, so probably 99% of quality air cooled hoods follow that graph pretty closely... although even a small layer of dust can lower it by a lot so be sure to clean it often.

Lumens. The more the better.
Kelvin's are semi-important, only because of the wavelength of the light emitted.
Watts are totally irrelevent.

plants don't see lumens, it's a part of the spectrum that they don't see, and the amount of them doesn't correlate with the amount of par watts(a true measure of how well a light works for growing) for instance, a regular incandescent house bulb puts out around 1000 lumens, yet doesn't put out enough par watts to even grow a sprout...

lumens are designed to describe the brightness of a bulb as WE see them, not as plants see them, lumens describe how bulbs light houses and roads, not how well they light plants...par watts describe how much light the bulb puts out specifically in wavelengths that plants see and are the only true measure of a bulb for growing.

 

[DrFever]

and why do i say this ok i will use this example senorsloth grows 400 watt i believe he is doing 100 watts per Sq foot and getting i think i read .5 to .7 grams dried per bud correct me if i am wrong
a 400 watts HPS = Although the total light output of a high pressure sodium (HPS) bulb varies, you can expect a 400 watt to produce between 40,000 and 45,000 lumens over its lifetime, depending on the brand of the bulb and how you mount it.

now other example 1000 watt light produces 145,000 - 150,000 lumens 40 watts per Sq foot imprint results averaging 7 to 16 grams per bud dry

So to break it all down watts per Sq foot means nothing really

 

[señorsloth]

? huh? it does mean something to me but means nothing to this thread...because at 100 watts per square foot i can get 800 grams per square meter, you can't do that with this plant at 65w per square foot...space is more of an issue than wattage for me so this is the best way for me to max my yield, and it has nothing to do with his question...im getting really annoyed at you making everything personal, these are forums, if you post wrong info people correct you, that's how it works, you don't form a grudge, follow my grow, and misquote/misrepresent the facts of it in your little "examples".

either way this is irrelevant, i don't know why you think it's so fun to contradict me constantly to boost your ego but my info IS correct and comes from science, not your backwards reasoning, not only that it's common frickin knowledge and i can cite a million frickin sources if i have too...in fact i check my work whenever i am contradicted, something you obviously didn't do, and i apologize and correct myself, because it's important to me to know the true facts, whether i am initially right or wrong...ive been doing this for a long, long time though and i like to think i am right a lot more than i am wrong.

but it is, as i said, common knowledge...so i really shouldn't have too, you should do some reading before you go out of your way to try and discredit me for no reason...id prefer to not get into a pointless argument over stuff everybody already knows...if you don't believe me do some reading but im done arguing with you about every single subject on this site because you need to feel superior...

 

[masshole61]

Any one with any experience with the gavita 1000de? They are all about par output with a double ended bulb that is supposed to last for years. I contacted gavita and they recommend 4000 btu of cooling per 1000w. Any input?

 

[DrFever]

? huh? it does mean something...because at 100 watts per square foot im getting 800 grams per square meter, you can't do that with this plant at 65w per square foot...and it has nothing to do with his question...im getting really annoyed at you making everything personal, these are forums, if you post wrong info people correct you, that's how it works, you don't form a grudge, follow my grow, and misquote/misrepresent the facts of it in your little "examples".

either way this is irrelevant, i don't know why you think it's so fun to contradict me constantly but my info IS correct and comes from science, not your backwards reasoning, not only that it's common frickin knowledge and i can cite a million frickin sources if i have too...in fact i check my work whenever i am contradicted, something you obviously didn't do, and i apologize and correct myself, because it's important to me to know the true facts, whether i am initially right or wrong...ive been doing this for a long, long time though and i like to think i am right a lot more than i am wrong.

but it is, as i said, common knowledge...so i really shouldn't have too, you should do some reading before you go out of your way to try and discredit me for no reason...id prefer to not get into a pointless argument over stuff everybody already knows...if you don't believe me do some reading but im done arguing with you about every single subject on this site because you need to feel superior...

so in essence your saying your 400 watt @ 100 watts per Sq foot will out perform a 1000 watt ??? i am not making it personal and have no grudge lmao but lets be serious here
i just harvested 1000 plants 800 pounds wet gave me 200 pounds dry Out door i can guarntee you your not pulling them numbers so you claim that is total BS 800 grams dry ????
from 430 watts let say you did hahahaha your telling us your chopping 3200 grams wet BS being all serious now hey just for you i placed 72 clones in more or less same set up but under 1000 watts on its own as well c02 from what your saying i should pull 8000 grams wet from this ??? 1.5 foot by 3 feet = 222.2 watts per and specially from a clone ??? We will see

here is 3700 grams wet covering 36 x 72 door screen 2 lbs dry and your saying your pulling 800 grams from 36 clones to 12 /12
i will also mark the scrog table presently in flower and when i chop i will cut all buds in same area as you have and we will also see the weight comparison today is first day 12 /12 on all

 

[Rolldaddy]

Question

If you are running several lights in a room and the hoods are only a few inches from each other, should the lights be kept further from the plants to keep them from frying?