Led Light Density In Larger Rooms

[OlgaStruthio]

Hi all, thanks for blazing the trail in LED technology. For years I've been running dozens of old-school S52 ballasts and Hortilux Super HPS bulbs. I've bought hundreds of those bulbs, and I'm getting a bit tired of heat, bulb replacement, and inconsistent light output.

I'm also designing a new grow facility, build-out starting in 2 months. I'm planning rooms about 16 x 25 feet in size, 400 ft^2 per room, 15 foot ceilings. I had initially planned for Gavita Double-Ended 1000 Watt HPS, but new LED technology looks just about ready to take over and outperform. LED cost is an issue, but less of an issue after factoring in sealed room cooling requirements.

So the question: What is an appropriate light density to plan on? I really like my current setup of 3 x 3 foot spacing of 1000W lights. Bright light makes everything easier.

I've read recommendations in the range of 35 - 45 watts / ft^2. That doesn't pay off easily if using top-shelf lights, at least way up north where cooling is cheaper. The cheap light kits using good components (CXB3590 or Vero29 COBs) are well priced, though. Suppliers like rapidled, Timber, and Pacific Light Concepts suggest similar spacings around 35 watts / ft^2. Cost seems just over double that of a Gavita setup, ignoring A/C differences.

If I space LED lights out at that density, it looks like I would light a 16x25 foot room with about 14,000 watts, about 24 600 watt fixtures.

Now I start second-guessing the whole thing -- 14000 watts of LED? That sounds like a lot, especially when compared to the 18000 watts Gavita lights would use at a 4 x 6 foot spacing.

Also, I see lots of great examples here and elsewhere of LED grows in small spaces, but what about the big rooms? The larger grows I've seen on Youtube sure appear to have even less than 35 watts / ft^2. How much advantage do larger rooms get from side lighting of large arrays of light?

 

[DemonTrich]

@sixstring

He is the go to led guru. I'm sure there a few more on here with led exp, but six Imo is the guy.


I personally would.look into CMH technology. Superior to led, mh, and hps.i swapped out all my mh.Nd hps for all.cmh.and couldn't be happier with the results.

 

[Icemud]

With LED watts really isn't an accurate way to judge light spacing and quantity, its a decent guess for home growers in tents, but for what you are doing it really isn't the best way.

LED lights are all different, you have the ones like Mars which have no dual lenses, 90 degree beam angles and a ton of chips packed onto a pcb board... or you have things like fluence which has a bunch of chips, spread evenly over a large surface area, or you have cobs with a single high wattage chip that spreads generally around 114 or 125 degrees or LED arrays with dual lenses and 60 degree angles which don't spread much but give off super intense "beams" of light....

So with all the different applications of LED, and the incorporated way they are mounted, and the beam angles, wattage tells very little of the story.

The best is to go by PPFD or Micromoles per meter squared every second.....this is a measurment of "PAR" light.

Since plants have certain requirements of light per day, not having enough light will lead to decreased metabolism, fluffy nugs, less cannabinoids...whereas too much light can also slow metabolism, cause burning of leaves or buds (with LED typically referred to as bleaching) and so on...

So best to look for a panel that outputs at least 500umol/m2/s-1 of Par light across your entire canopy or more (500 is the bare min for optimal results according to most current research).

Most growers actually look for around 800-1000umol/m2/s-1 on their canopy for the best results.

How do you find this info?

The lighting companies should provide a 4'x4' grid at multiple hanging heights that shows PAR readings every 1/2' to 1' on the grid. This "mapping" allows for you to see at "X" height, the pattern or output of light intensity across this 4x4 area. You want to look to make sure your entire canopy is getting at least 500umol/m2/s-1 of PAR light or more.

Many cheap LED companies will not provide these charts as they are generally clueless how plants actually use light. Never use a LED manufactures "recommended" coverage area as 99 times out of 100 they are wrong and usually are inflated estimates with no scientific backing or rhyme or reason to them.

Most good LED companies will provide you with this information, at least they should if they actually want buyers to make educated decisions on horticulture lights based on plants needs for light. (Its call DLI or Daily Light Integral).

This IMO is the only accurate way to judge plant lighting according to actual plant metabolism. (spectrum has little to do with metabolism, and more to do with morphological growth effects).

Also... the type of LED setup you go with has a lot to do with vertical space.... with LED its very possible to grow amazing plants without lights hung 4-6' over the canopy like the days of HPS or HID... You can literally have plants grow right up to certain LED fixtures....(less intense LEDs spread evenly over a huge surface area)

Or you can choose LEDs that have a very intense light, narrow beam angles and hang them in a similar fashion to HID/HPS lights 4' over the canopy...

Taking your grow style into consideration will determine the best type of LED fixture to go with.... If you want to use LED's like traditional HPS, then go with something that is a small fixture, dual lenses, high wattage but small surface area...

If you want to grow more of a sea of green style, vertical grow (stacked) or have short plants then its best to get a large LED fixture with LEDs that are less intense spread evenly over a large surface area....

Its all about the light penetration and what is necessary.

Hope this helps.

 

[BioStimz]

With LED watts really isn't an accurate way to judge light spacing and quantity, its a decent guess for home growers in tents, but for what you are doing it really isn't the best way.

LED lights are all different, you have the ones like Mars which have no dual lenses, 90 degree beam angles and a ton of chips packed onto a pcb board... or you have things like fluence which has a bunch of chips, spread evenly over a large surface area, or you have cobs with a single high wattage chip that spreads generally around 114 or 125 degrees or LED arrays with dual lenses and 60 degree angles which don't spread much but give off super intense "beams" of light....

So with all the different applications of LED, and the incorporated way they are mounted, and the beam angles, wattage tells very little of the story.

The best is to go by PPFD or Micromoles per meter squared every second.....this is a measurment of "PAR" light.

Since plants have certain requirements of light per day, not having enough light will lead to decreased metabolism, fluffy nugs, less cannabinoids...whereas too much light can also slow metabolism, cause burning of leaves or buds (with LED typically referred to as bleaching) and so on...

So best to look for a panel that outputs at least 500umol/m2/s-1 of Par light across your entire canopy or more (500 is the bare min for optimal results according to most current research).

Most growers actually look for around 800-1000umol/m2/s-1 on their canopy for the best results.

How do you find this info?

The lighting companies should provide a 4'x4' grid at multiple hanging heights that shows PAR readings every 1/2' to 1' on the grid. This "mapping" allows for you to see at "X" height, the pattern or output of light intensity across this 4x4 area. You want to look to make sure your entire canopy is getting at least 500umol/m2/s-1 of PAR light or more.

Many cheap LED companies will not provide these charts as they are generally clueless how plants actually use light. Never use a LED manufactures "recommended" coverage area as 99 times out of 100 they are wrong and usually are inflated estimates with no scientific backing or rhyme or reason to them.

Most good LED companies will provide you with this information, at least they should if they actually want buyers to make educated decisions on horticulture lights based on plants needs for light. (Its call DLI or Daily Light Integral).

This IMO is the only accurate way to judge plant lighting according to actual plant metabolism. (spectrum has little to do with metabolism, and more to do with morphological growth effects).

Also... the type of LED setup you go with has a lot to do with vertical space.... with LED its very possible to grow amazing plants without lights hung 4-6' over the canopy like the days of HPS or HID... You can literally have plants grow right up to certain LED fixtures....(less intense LEDs spread evenly over a huge surface area)

Or you can choose LEDs that have a very intense light, narrow beam angles and hang them in a similar fashion to HID/HPS lights 4' over the canopy...

Taking your grow style into consideration will determine the best type of LED fixture to go with.... If you want to use LED's like traditional HPS, then go with something that is a small fixture, dual lenses, high wattage but small surface area...

If you want to grow more of a sea of green style, vertical grow (stacked) or have short plants then its best to get a large LED fixture with LEDs that are less intense spread evenly over a large surface area....

Its all about the light penetration and what is necessary.

Hope this helps.

That was an outstanding reply.

~

 

[Icemud]

That was an outstanding reply.

~

Thanks :) I kind of know a little bit about plant lighting ;)

Happy Friday all! Thanks for the compliment!

 

[AvidLerner]

For design, I would plan for 25-35w psf during veg phase over your 3x3 tables. For bloom I would plan for 50w psf. For CO2 I would increase to 100w psf bloom.
hope that helps
peace

 

[OlgaStruthio]

Thanks all. I know watts are a crappy way to measure, when PPFD PAR measurements really count. I just listed watts above, but I had worked these numbers out on the PPFD scale also. That's what got me wondering about these recommended light spacings I keep seeing. It's starting to seem like I've been growing under significantly more light than most setups I see:

• My current rooms, 1000W HPS 3x3foot spacing:
  
  • 1100 umol/m^2-s, according to my light meter, if the light, ballast, and hood are all in good repair. Down to maybe 700 umol/m^2-s when capacitor or bulb needs replacing.
    • (115 watts/ft^2)
• Gavita Pro HPS 1000 @ 4x6 foot spacing:
  
  • 922 umol/m^2-s. Using Gavita's claimed 2100 umol for the bulb, and 96% efficient reflector for half the light
    
    • (44 watts/ft^2)
• Gavita Pro HPS 1000 @ 5x7 foot spacing:
  • 645 umol/m^2-s
    • (30 watts/ft^2)
• Pacific Light Concepts, PLC 6 LED, at recommended 4x4 foot spacing:
  • 760 umol/m^2-s.
    • (37 watts/ft^2)
• RapidLED Vero29 4x4 kit, 600 Watts, 12 Vero29 COBs over 4x4 foot area:
  • 760 umol/m^2-s.
    • (37 watts/ft^2)
• Philips CMH Agro 315 @ 2.5 x2.5 foot spacing:
  • 845 umol/m^2-s
    • (54 watts/ft^2)

I guess I'm just surprised to see so many recommendations and setups down around 650-800 umol/m^2-s.

Focusing on watts and power consumption: Assuming I'm comparing light arrays of similar light intensity and plant growth, I really end up picking a system based on purchase cost, operating cost, and A/C cost. I focus on watts since it has a large influence on both operating cost and A/C cost. I haven't built the rooms yet, so each watt saved counts against both the power bill and the A/C installation bill. For larger setups A/C costs are really adding up.

One of the best discussions I've found on this has been Growmau5 and Greengenes at 1:57 into this Youtube video.

 

[OlgaStruthio]

For design, I would plan for 25-35w psf during veg phase over your 3x3 tables. For bloom I would plan for 50w psf. For CO2 I would increase to 100w psf bloom.
hope that helps
peace

Thanks! I think this is sort of like the game I've been playing for years. Flood the plants with lots of light, probably a bit in excess of what's really needed. The plants love it, and there's still plenty of light even if some lights dim a bit, bulbs need replacement, ballasts need repair, glass is dirty, etc.

I've been successful that way, but I really want to step up efficiency in the new build. I hope small farmers like me can be competitive in the rapidly changing marketplace. I think it will require high quality and low cost. Full lifecycle costs are surprisingly similar for these lights. Low cost high quality LEDs match the cost of even the cheapest HPS after several years' worth of bulb changes.

 

[sixstring]

300w of cree cob over a 4 x 4

525w of cree over a 4 x 6 area

Think i average 30w per sq ft for the room maybe 40w ,been a minute since i did the math lol.no co2.seeing awesome growth in veg with 20w per sq ft using vero 29 -3000k better than any t5 setup i have used and less then half the power.

 

[DemonTrich]

Your vegging and flowering with a 3k bulb/cree?

 

[sixstring]

Your vegging and flowering with a 3k bulb/cree?

Yeah for veg 3000k vero.i flower with a bunch of different colors but the 2700k are my favorite. I have panels with all 3500k some with all 2700k some with a mix of 3500k and 3000k and also a mix of 2700k and 3000k.but the 2700k rock it in flower.
Gotta remember these cobs are all higher cri either 80cri or 90cri.only the cmh competes with these wider spectrum colors.
I bet you could use 3100k cmh for veg and be shocked how nice the plants come out if ya kept the lamp closer than your used to .

Lots of blue in the 3000k veros :)

 

[DemonTrich]

Im on the fence (honestly, I'm lazy) about just leaving in the 4k cmh bulbs all thru harvest vs swapping them out after stretch is done. I usually just rock a 3k flower cmh bulb and not bat an eye, from flip to cut. But wanna see how the 4k does for stretch vs the 3k bulb.

One local guy I take his word, said his yield suffered when running 4k veg bulb to chop.

I've vegged with my 3k flower bulb, didn' see a huge growth like I do with the 4k cmh. All Philips bulbs in my rooms.

 

[OlgaStruthio]

Great stuff! I just found a detailed section in the middle of SixString's LED thread where there's lots of discussion about light spacing and intensity. The photos certainly are compelling, and in terms of numbers I'm getting more comfortable planning on 800 PPFD, or somewhere around 40 watts/ft^2, depending on light details.

And I already feel an impending sense of relief to move to something better than these hot, old, short-lived single-ended HPS lights.

 

[CBDfutute4]

I'm a tiny fish in a big pond here knowledge wise but I'd consider a mix of Cree/vero/cmh

I've been reading n pestering the shit out of the knowledgeable dudes here since the day I joined.

Still trying to figure out my best lighting options while dealing with heat n no ac for summers.

But when u break it down by lights, imho, u have the guys using leds, really cobs on the progressive side

Some who either just think or actually do get decent yields with eBay leds

The guys who still love the hid/hps.....no matter what new technology is out...some what old school

Than the ones who've switched to 315/630 cmh

In my 4x4, I plan 1 315 n 1 cob 200

GL