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lighting question

Posted by tabbycat123 maine (My Page) on
Mon, Mar 24, 08 at 0:00

this message probably could be posted in another forum, but i have had quicker feedback here.

i want to light a 3' x 4' area. growing a variety of vegetables, tomatoes, peppers, lettuce, and herbs. starting seedlings as well as growing the plants until fruiting. i want to do it rather cheaply and have found that fluorecents seem to be the cheapest. what are some reccomendations for a setup that will provide sufficent light without spending 300+ dollars on a HPS system.

thank you!


Follow-Up Postings:

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RE: lighting question

The highest long-term cost for indoor growing is the cost of electricity and MH and HPS hid systems have the lowest electric cost.

You can use fluorescents, the cost is just higher.

You are going to need 500 watts of HID or fluorescent to bring the plants to fruit.

Use the search function at the bottom of the page and type in lighting.


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RE: lighting question

I have doubts about their usefulness for tomatoes and peppers, but for making seedlings, herbs and lettuce, you can't go wrong with a standard 4 bulb system. The link is just for reference. You might be able to find one cheaper somewhere else.

They're not cheap though :(. I abhor HPS too. I dislike both the painfully ugly color of the light, and the fact that it makes things grow to tall and spindly (aka leggy). But metal halide is different. Have you considered it?

It will run you the same ~$160 as a good fluorescent system, but has different pros and cons. It will be much better for your tomatoes and peppers, since it's putting out significantly more light. On the other hand, my experience is that cole crop seedlings grow leggy and weak under it. I have no idea why, but all of my repeated attempts yielded the same result. So if the bulk of the seedlings you are trying to sprout are cole (i.e. broccoli, cabbage, brussels sprouts, mustard, cauliflower, kale, napa, chinese cabbage, pak choi,... the list is very long) HID is probably not for you.

You've got a tough, and somewhat expensive decision to make! Good luck, and I hope you make the choice that makes you happy!


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RE: lighting question

I may have offered incorrect info. Here is a guy on this forum who is seeing some interesting results with tomatoes under fluorescent lights.

Add that to your choice of lighting. Hehe, I don't envy you having to decide on a light source :). Still, it's a lot of fun once you choose one.


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RE: lighting question

Hey Willard, why are flourescents more expensive? I agree they may not work as well as HID or HPS, but as far as cost goes -- bulbs are cheaper, last longer, use less electricity, and cost much less to replace and get replaced much less often. What do you know that I don't? You just can't go over 18 - 24" high with T5 HO flourescents is all.

Thanks in advance.


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RE: lighting question

I know how many lumens/watt for fluorescent (80 lumens/watt) and hid is 100 lumens/watt.

Electricity costs about $0.15/kwh and lamps run 16 hrs/day. 16 hrs/365 days/year $0.03 difference in electric cost adds up very quickly.

If fluorescent is so much better than HID, why don't we light highways with them?


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RE: lighting question

Good observations, thanks.

This is the "grow" bulb I use (I mix them with the other bloom kind also):
http://www.sunshinehydro.com/cart/customer/product.php?productid=16978&cat=442&page=1

The link has a reference for how many lumens per watt T5 HO gives vs. older flourescent technologies:
5000 lumens per lamp 54 watts=92.59 lumens/watt.
*Reference Point: an F40 cool white lamp: 1260 lumens per lamp 440 watts =31.5 lumens/watt

I would imagine that we don't light streets with flourescents because of the lack of light intensity (my comment about not being able to raise the light higher than 18 - 24 inches on many crops.). ... but you give a good point.


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RE: lighting question

Few more things I thought of that I'd like anyone to chew on and give me their thoughts:

I am told that T5 HO flourescent lights don't need replaced nearly as often-about every four years. The MH/HPS lights need replaced every six months to a year if I understand correctly, and they cost a LOT more.

That said, I do think that MH/HPS may have better intensity and color spectrum for plants - but so far my flourescents have done very well.

Also, I am told that MH/HPS lose lighting intensity a lot earlier in their lifetimes.

Also, heat was a factor in my small closet space, and I believe the flourescents do generate heat, but, less heat than MH/HPS. Also, because of the narrow dimension of my closet, it was easier for me to fit a four foot long flourescent system in there than it would be for me to grow a 4' X 4' garden.

So I think a lot of different things can come into play when selecting lighting.

The couple pages throughout this lighting FAQ helped me a great deal:
http://www.specialty-lights.com/plant-grow-faq.html


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RE: lighting question

It is a failure to understand thermodynamics that leads you to believe that fluorescents generate less heat than HID and physics is not debatable .

The higher the lumens/watt of the source, the less heat generated as a byproduct.


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RE: lighting question

Fluorescent lights need to be changed every 6-7 months f you're concerned about peak efficiency (I'm not). Either HID or fluorescent lights will burn for years though, with ever decreasing output. At least that's what I'm told. These little screwy fluorescent lights we use in incandescent fixtures have yet to last a year without burning out. The long T5's are of course much more stable.

Regardless, I was under the impression that HID (MH) and fluorescent grow lights were fairly similar in their lumen/watt efficiency. Further, I thought it was agreed that fluorescent was better for seedling growth since the light was not as concentrated, and HID was better for plants since you can hit any square foot with many more lumens.

Plantboy's tomato plants seem to contradict that last part. They are thriving under fluorescent lighting. I'm still sticking with HID since I already own it, but those tomato photos make me wonder if I made the wrong choice.

Lastly, since you are a fan of thermo, willard3, you should remember that any light that does not ultimately impact a plant leaf will be 100% converted into heat. So even if you have a very efficient light source, if you are not taking care to make sure all of it's output hits the plants, you are creating more heat than need be.

I mean, if you put a 400W HID in a box, and 400W of fluorescent lights, or a 400w heater, or 4x100W lightbulbs in other boxes, their heat output would be absolutely identical. That makes a pretty good case for lining your growing area with that reflective wallpaper stuff I'm too cheap to buy, huh? :)


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RE: lighting question

The T5's would not be acceptable if the plants have any height to them. Plantboy is growing dwarf tomatoes which kind of limits his options. Nothing wrong with that but it is a limitation. Honestly, I'm surprised they're growing so well as big as they are, but then tomatoes are almost weeds with tastey fruits.
With MH a tall plant still gets enough light at the base. This is because the light intensity dimenishes much more quickly from a fluorescent than from MH, which also happens to be why you don't see fluorescent street lights.


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RE: lighting question

Flourescent T5's are comparable for lumens (92 vs. 100 lumens / watt), but like was said, you are limited to lower growing plants. Most websites and folks at the hydro store tell me not to go over 18 - 24" in height.

My research before buying this lamp told me I'd need to replace the tubes about every three or four years. The T5 lamps have a special coating on the inside that keeps more of the mercury in the tube from leaching into the glass, thereby keeping a higher concentration of light / longer life of the bulb.

I'd love to post more pictures now but my camera needs batteries - I have lots of tomatoes growing now - about 35 very good looking, sizeable fruits considering their age. I'll get pictures out there soon in the other thread.


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