2x50watt hps

djh420

Active Member
I have a small grow box I am working on. It is 16in.x 23in which i think is about 2.5sq ft. Anyway I will be using (2) 50 watt hps lights, the ones you buy at Home Depot. They are security lights that cost around $30US each. I will be keeping them in the housing they come with except without the plastic light covers. They are both mounted to a board with enough space in between the two lights (about 8 in.) for the exhaust fan mounted on the side of the box at the top. The lights will hang by chain and the only reason I didn't get a third 50 watt hps is because it wouldn't fit on the board with the other two because of the fan. I have a limited height available so the lights had to be able to go as high as possible when the plants grow......So with the exhaust fan at the top only two lights would fit.
My questions are: how can I make a good homemade reflector for the lights? Should I make one big reflector for the two lights even though they have a space between them, or should i make two smaller ones? what is the best material to use?
Also do you think it would be a good idea to add a warm white 42 watt cfl mounted between the two 50hps? Each 50 watt hps puts out 4050 lumens, so 8100 lumens total with just the two so adding a 42watt cfl would add another 2500 lumens or so.... I will be using the hps for flowering and a homemade cfl setup with 6 23 watt cfl for vegging. Is this enough light? Check out the pics: one pic is of the exhaust fan and how it is mounted in the box. the other is a plant's eye view of how the lights will be hanging (at their highest point) in relation to the fan. As you can see I have very little room to play with which is why I can't fit another 50watt hps. That's why I'm thinking about adding a 42watt cfl.....Or is the 100 watts enough? Should I add a 42 watt cool white to help even out the spectrum (remember, this will be for flowering) or 42 watt warm? Or just go with the 2 50watters? anyway help is appreciated. thanks for reading!
 

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pacman123

Well-Known Member
I'll be subscribing as this is similar to my sel up adn I'm trying to figure out how to go with HPS for flowering. Ism't 10,000 lumens/sq.ft. the general rule? So for a 2 sq.ft. you def. would want well over 10,000, as close to 20 as possible. That's why the more powerful HPS are used more, the lumen increase to wattage is not static, i.e. bigger lights means lots more lumens.
 

Bongulator

Well-Known Member
5000 lumens per square foot is the goal. That's roughly equivalent to bright sunlight at the equator at noon. More is better, but you reach the point of diminishing returns well before 10k lumens per square foot. The exception would be if you're feeding your plants a steady diet of CO2, in which case they can absorb more light and handle higher temps too. 10k/sqft might be pretty nice with a CO2 setup. Otherwise, wasted electricity, double your grow space and go back down to 5k/sqft and you'd get waaaay more yield than half the space with 10k/sqft.
 

bfq

Well-Known Member
i think you need to recheck your lumens of the Sun, Bongulator... the Sun is so powerful its output is measured in horsepower, not lumens in the data i have read.

those boxes are reflectors and to use a different reflector you have to remove them.

here is a good one: GROWFAQ

i would probably make one and put a bulb at each end under it.
 

greenhorn08

Well-Known Member
Those lights stink and are close to a joke. You could at least take off the plastic covers those suck.

You really need to get a 250w hps 0r 400w. Anything less than that is just half ass and childish. I dont even think thoses lights are even worth messin with. Unless you just want to yeld a weak 8th.
Just keep buying weed until you are in position to get real lights. (thats what I did)
 

techhead420

Well-Known Member
Bongulator is essentially right.

10,000 Lumens per square foot is closer what full sunlight at the equator is, not 5,000. (100,000 lux / 10.764 = 9290 lumens/foot^2...the equator can be up to 130,000 lux).

The photosynthesis net saturation point for a C3 plant like pot is 1000-1200 umol/sec/meter^2 WITHOUT carbon dioxide enhancement. This works out to roughly 6000-6500 lumens per square foot for HPS.

Plants actually can not take advantage of full sunlight intensities. Some plants will actually shut down for awhile at full sunlight intensities:
Photorespiration - Wikipedia, the free encyclopedia
 

pacman123

Well-Known Member
Bongulator is essentially right.

10,000 Lumens per square foot is closer what full sunlight at the equator is, not 5,000. (100,000 lux / 10.764 = 9290 lumens/foot^2...the equator can be up to 130,000 lux).

The photosynthesis net saturation point for a C3 plant like pot is 1000-1200 umol/sec/meter^2 WITHOUT carbon dioxide enhancement. This works out to roughly 6000-6500 lumens per square foot for HPS.

Plants actually can not take advantage of full sunlight intensities. Some plants will actually shut down for awhile at full sunlight intensities:
Photorespiration - Wikipedia, the free encyclopedia
Dont you mean pacman123 is right?:mrgreen:
 

Bongulator

Well-Known Member
No, he meant I am right. Why, if 5000 < 6500? Because sunlight is comprised of many spectra, and plants use only a small chunk of the spectra of the light that the sun emits. So while the sun may in fact look (to human eyes) as if it's brighter, the plants only use a portion of those lumens. Horticultural bulbs are optimized for plants though, with much of their light intensity right smack in the middle of the spectrum that plants need. Sunlight is not optimized for plants, it is what it is, lots of spectra. So 5k/square foot from a decent bulb will give you more plant-usable light than the sun will at the equator (which is already more than the plants could use anyway). I was just trying to keep it simple, and not start dredging up lumens/lux and spectra and metric conversions and whatnot.

But seriously, if you hit 5k/sqft with a decent bulb, your plants will be entirely and totally happy. The only reasons to overload any plants with 10k/sqft is if you're using one bulb and the distant plants won't get 5k/sqft unless you overload the closer ones, or if you're enhancing with CO2 (or both).

The fact that plants can only process a certain amount of light is something I sort of accidentally discovered before I read it. I had a 1k bulb in a 12 sqft area (4' x 3'). I took that light out and replaced it with a 600-watt light, and it barely affected yield, if at all. That led me to conclude that the 1k light was simply too much light for the plants to use, at least in that small of an area. I get the same yield I was before, but I do it with 400 watts less power usage, and less heat too.
 

techhead420

Well-Known Member
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