How many watts & lumens are recommended for a successful CFL box?

[Fingolito]

How big is the space and how many plants? Going for one big cfl or many small?

Recommended lux (lumens per square meter) is 10k for veg and 40-80k flower.

I have used 250w cfl and distance is everything. I would even opt for a cheap LED panel from amazon instead of a cfl. They are really only good for support unless you plan to put one or several light per plant. For a LED you should go for at least 80w per every 30cm2.



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[fanleaf]

You sure dont need or even want 80W for every 30cm squared. Thats 80w per square foot. The heat would be crazy. 50 watts per square foot is the standard high end amount. You can get away with 40 even.

 

[Fingolito]

You sure dont need or even want 80W for every 30cm squared. Thats 80w per square foot. The heat would be crazy. 50 watts per square foot is the standard high end amount. You can get away with 40 even.

Yes for sure you can grow with much less! Those are numbers I've read from an article and it kinda makes sense if you want to maximise the space. The more light the higher par rating you will have at a greater height therefore a bigger footprint. I'm really no expert but it kinda makes sense.
I'm growing with a 130w on a 0.8m2 space and yes it works but I believe that if I put another one it would be awesome hahaha!

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[Lost In Nugs]

Re: How many watts & lumens are recommended for a successful CFL box?

This watt per square foot thing doesnt make any sense...

The reason is that a HPS, a CFL, a cheap China 1000W LED that only pulls 100 from the wall and a modern COB LED all use watts for light, but only a part of it is light. Lets say a 1000W of HPS that was used a couple of hours only generate 300W of actual plant usable light energy, a 1000W Cheap China LED that pulls 100W maybe is in that range too, but maybe its only 10 percent efficient. so you get 10 to 30W of light from that 100W that was sold you as a 1000W light. And only for a couple of month because light output is getting lower and lower while the wattage draw stays the same. And finally a 1000W of soft driven COBs like Cree CXB3070 generate 550W of light from that 1000W at 700mA on s certain temperature. The rest is heat. Heat that sometimes needs even more watts to get rid of it.

So W per sq foot is only interesting if you know how efficient your light source is. And you only get this info for shure with high quality parts that have been tested for big money from the big companies.

The rest is guessing and when you go for a Mars or something like that you will need a lot more W/sqft then you would with a COB fixture.

I bet i have better growth with 30w per sq foot on underdriven COBs than someone with 60W per sq foot from old tech HI Diodes or more inefficient lights

You can add the new COBs to the left side. A Cree CXB3590 CB 3000K would give you that 2600 lumen at about 13 Watts so you see the difference.

A plant wants light, no watts

Edit: based on the pictures and the Homepage of gavita and their 138K lumens from 1000W i made some basic calculation.

So the 3590 CB produces ~2600Lm with ~ 13,5W and its 60% efficient. Check

If thats true a brand new gavita must be about 40 percent efficient if all the other variables while testing light energy for these charts were the the same. In theory. Ok 40 percent. possible.

A CFL based on the picture and the same formula seems to be only 14 to 26 percent efficient. So look on the box of your cfl, divide the max lumen with the wattage draw for your lumen per watt. So you can calculate the efficiency some kind with the data in here.

Lets say the COB needs 13W for 2600lumens and is 60 percent efficient. Now you have 200 lumen per watt. Now take your cfl box and lets say it has 2600 lumens at 40W. That will be 65 lumen per watt. Divide the 200 lm with 65lm. You get a factor. In this case it is 3,076. Now you take the 60 percent and divide it with the factor. Now you have your efficiency in Percent. 19,5% of your watts will be photons, 80,5 are heat. Take away another 10 percent and you will have anything to work with without any tools.

So when they say 50W per square foot is good and the person claiming this is using HPS and its a brand new gavita for example you will have to add 100W of this fictional CFL per square foot to have the same growth.

Oh man i am baked and calculated this over a cup of coffee just from this 2 pictures . I hope i am not completely off the hook.

At least thats a point thats better then guessing. lol

 

[Lost In Nugs]

You sure dont need or even want 80W for every 30cm squared. Thats 80w per square foot. The heat would be crazy. 50 watts per square foot is the standard high end amount. You can get away with 40 even.

What do you think of my twisted thoughts about this? Is it a legit way to get an quick idea of how efficient a light could be compared to the efficiency king of all lights? When you have the time take a lil for good ol nugz lol
I never read anything about calculating efficiency, so this came from my brains as it is... Be gentle )

 

[fanleaf]

Re: How many watts & lumens are recommended for a successful CFL box?

What do you think of my twisted thoughts about this? Is it a legit way to get an quick idea of how efficient a light could be compared to the efficiency king of all lights? When you have the time take a lil for good ol nugz lol
I never read anything about calculating efficiency, so this came from my brains as it is... Be gentle )

It makes perfect sense. The "standard" actual 50w/ per square foot pretty much applies to mh, hps and normal led panels like mars hydro and such. Its not a perfect scale but works well for those to get people an acceptable amount of light. Imo, normal led panels using 3w and 5w panels arent a whole lot better than hps. They truly run about the same efficiency or close enough that it doesn't really matter. Especially when you take into account for light coverage area of the three watt panels. A double ended HPS will smoke 3 watt or 5 watt panels and efficiency and they only run about 40%. So all-in-all I think if someone is using LED panels or metal halide or HPS the 50 actual watts per square foot Works fairly well because their efficiencies are about the same. If someone is using Cobb lights like me and you do then that number is probably somewhere between 33 - 38 watts per square foot to get the same result. CFL, I don't even care to take a guess LOL

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[Rider509]

Watts is simple a measure of how much energy a light source uses.
Lumens is the total output of a light source.
Lux is the measure of how much light is striking a surface.

A good reflector will put more light energy on a target than a poorly designed reflector.

 

[Rider509]