90 watts, 3800 lumens is very weak output for plant growth.

LED lights appear very bright to the eye because they are single point sources.

LED grow light in your situation may not be good because most of the leaves are in shadow.

Looking at the design of the fixture, I counted 45 LEDs. I think they only make 1 watt, 3 watt and 5 watt LEDs in that shape. 45 x 1 watt = 45 watts, not 90 watts. Perhaps they are counting the three cooling fans and three driver power supplies as part of the power in watts.

Try regular fluorescent lights.

dcarch

This post was edited by dcarch on Mon, Feb 24, 14 at 12:38

Thanks for your response.

I'm amazed, this light lights up my entire balcony at night; as you said, it seems very bright to the naked eye.

But what are these particular grow lights good for then? I mean, what should I do with it; how can I put it to good use? Maybe place it very close to one or two plants.

You might get more responses if you post this question on one of the gardening fora rather than the Cooking Forum :-)

"---But what are these particular grow lights good for then? I mean, what should I do with it; how can I put it to good use? Maybe place it very close to one or two plants.---"

Not much else you can use those lights for because they are of limited spectrum (red, blue) lights. You can put the light closer to the plants and surround the plants with mirrorized Mylar to reflect more light to the plant.

I use a 400 watt Metal halide light for my plants, which puts out 38,000 lumens of white light. Big difference in brightness, 38,000 lumens vs 3,800 lumens.

Because it is white light, it lights up the entire big room in the night, so I don't need other lights in the night. My herbs and vegetable seedlings are very happy, and I am happy also.

dcarch

First; Colleenoz, I apologize for being in the wrong in the wrong forum; did realize I was in cooking /-: Wish it could be moved; moderators usually do that when this happens

Finally, this thing cost a bundle; Looks like it's only good for a single plant; what a waste!!!!!! Guess I should have done more research!

I just figured you're growing herbs or other edible/useful plants. :)

I've read some poor reviews on various LED growlights and systems so I haven't tried an LED growlight yet! A good friend just bought one to try, and I'm anxious to hear how it works.

The light you cited says that it should cover a 3x3 to 5x5 growing space. Do the instructions give you tips on the proper height placement?

Most plants that require bright light will want that light on for at least 12-15 hours. What's the reasoning for your 6 hour 'on time'?

Assuming the light is new, perhaps there are other factors coming into play, like incorrect outdoor temps?

Here's a link to the forum regarding growing with lights. You can repost there or perhaps find help in previous threads.

My problem is having too much light, and so I am unable to help you! What direction is your balcony? Does it have northern exposure? Is it possible to move to the southern part of the building, or does it not have southern exposure?

Lars

I have a northern exposure but I thought the light was supposed to make that irrelevant. I cut the time because my plants weren't thriving and I thought I was harming them with too much of this light. See you on the plant forum, where I will continue this discusstion

I didn't send you to the "Lights" Forum because I didn't think you will get useful advice there.

A few more comments:

I looked further in the design of your unit. Very poor design, IMHO. The three power drivers put out 45vDC to 65VDC, but LED cannot be operating at that voltage, so they wired the LEDs with blocking resistors in seris, which waste a lot of electric power, that's why the so call 90W power only puts out 3800 lumens of light. I have a 50W LED light that is giving me 4,500 lumens.

The heat sink is also poorly designed and it may not be able to dissipate al the heat generated, which may shorten the LED's life. Over voltage and over heat kill LEDs.

In your case, the built-in LED lenses give wide spread light distribution, so 60% of the 3,800 lumens are lost.

The best thing to do is to lower the light and drape a curtain of reflective Mylar around the light and plants, and you may be able to make use of this expensive light.

Good luck.

dcarch

I don't know about LED lights, but when I grow tomatoes I keep flourescent lights just an inch or so above the seedlings. I raise the lights as the tomatoes grow. It helps that fluorescent lights are cool. How hot are LED lights?

Sally

"---It helps that fluorescent lights are cool. How hot are LED lights?"

Actually the light from LEDs are very cool, cooler than fluorescent light, but the LED itself generates heat and heat can destroy LEDs, that's why high power LEDs need heat sinks and fans to keep from overheating.

I can see LED grow lights become much better and affordable, with more states legalizing "Medical" plants.

dcarch

Whoa, the only thing I understood that you wrote was the last paragraph. LOL.

So, going back to your explanation, does that mean that with LED lights it's okay to keep them an inch or two above the plant or not? Is it necessary? Curious (and dense) minds want to know.

Sally

Yes, it is OK to put the LED light right above the plants.

However, when you do that more leaves will be in shadow.

I have a single bulb 50 watt LED light and it is just a little warm an inch away.

Typical LED grow lights use 1 or 3 watt LEDs.

dcarch

Okay.

Sally