Watts per square foot?

[DRM Ranch]

In veg I'm working with 54w/sq.ft. 432w over a 4x2 SCROG.

In the future I'm considering a 600w HID over the same area, 75w/sq.ft.

I'm wanting the best return on my electric investment, so my question becomes at what point is there an obvious point of diminishing returns based mainly on the watts per square foot metric with HID lights.

A related question would be what/where might be a good place to research multiple fixtures performance in terms of PAR maps. I've found a few, and will keep looking.

Thanks in advance.

 

[neon green]

You may be sacrificing some lumens, but 2 400s I think would be better than 1 600. I doubt you would need 2 600s in a 2ft wide space. My veg tent is 3x3 with a 600 in it an I think its over kill. Unless your running trees, I think I would go with more points of light over 1 point and minimal spread. I'm in the same position and leaning toward 2 600s in my tent. W/sq ft I don't think really matters when your in a rectangle like that. You could have 100,000 lumens directly under the light, and darkness on the edges.

 

[Graytail]

I've looked into PAR values and 3000 umols is clearly the upper limit, and sunlight is about 2000 umols. Here's a chart for distance and PAR for various HID bulbs.

Also, 600W hps are significantly more efficient than smaller bulbs, and even the 1000s. That means less heat for the same wattage, too.

I just checked my notes, and a 85,000 lumen 600W bulb delivers about 600 umol average over a 4x4. If you run two 600W in a 2x4 at 14-16 inches from the canopy, you'd be getting 2000-3000 umols. Plenty.

But how you gonna dump the heat?

 

[Papageno]

Lots of great info here. By the end you will know what hood is right for you.

 

[neon green]

600w per 4 sq ft? Good god man. I don't think your taking into account things like overlap of the light foot pattern, and height of the garden. Looking at paper can be deceiving, nothing like real world experience. You would have to use gallons of calmag to protect your lady's from that. I said 2 400s because of startup cost, heat, LIGHT OVERLAP/added efficiency from the 2nd light point in a 2x4 tent, and a host of other variables. 2 600s Is solely based on a chart correct?

 

[DRM Ranch]

My SCROG carts are space limited to 2'x3' and at best I can run 3 in flower at 23 day intervals.

Some light overlap would occur as the carts are to be kept side by side forming a total area of 6'x4'.

The choice for using 600w lights is simple as they are the most efficient (thanks Greytail).

Using more than one 600w per cart, is it even possible to pull 1200 grams of finished meds from a 2'x4' area from one plant veged for 70 days? That sounds like an above exceptional yield for any strain based on that often argued 1g/w measure. By most real life measures I have researched 227g seems like a realistic first run goal per cart based on a rough average of 1lb finished from 4'x4' SCROG grows that I have seen.

Obviously there are many interrelated factors here, one of which is plant number limitations for me so SOG is out of the question for me. Of slightly less concern is total power consumption and its related heat oufans, my space is small and well insulated, however I see summer cooling being a very real high impact cost.

I don't want to chase temp issues so I'm limiting my fixture possibilities to air cooled fixtures, with temp controlled extraction fans. I suppose from there it is simply a matter of where PAR values fall, thanks for the video link VillageIdiot I'll check that out.

neon green, I'd have 600w over 2'x4'=8sq.ft. or 75w over each sq.ft. assuming an even distribution of light which isn't exactly possible or practical to the best of my understanding. If 200w lamp and fixture combos were equally efficient as a single 600w I'd go that route simply for more even coverage. However it seems the combined lack of efficiency would be a killer. At least that is my assumption.

 

[Graytail]

I just remembered another 420 grower who ran a 400W CMH and a 600W hps in a 2x4 tent, for 1000 total watts. He ran them in inline cooltubes. His username is Icemud, if you want to check him out. That grow was a year or two ago, sometime ...

As far as grams per watt, my sense is that it goes down as you increase power. There's a sweet efficient spot where the power and the dispersion and the room and the needs of the plants all sorta sync up. I did very well with a 600W hps in a closed reflective 4x4. Now I'm running 1000+ watts of LED and my yield isn't any better. But my plants have more trichs, which is what I'm after.

 

[Papageno]

I forgot to add a few things. The video eludes to them but just to be clear...

(now we are not talking cheapest we are talking most PAR per sq ft)

1) DE bulbs are much brighter than SE bulbs watt per watt. MUCH brighter I will never go back!

2) Running air cooled systems reduces the efficiency. The bulbs are hot for a reason. Running cool air over them cools them off. They are not getting the reactions at the optimal temps. Or at least at the temps they could achieve. Hotter is brighter.

3) Running air cooled systems puts glass between the bulb and the plants. That is a 10-15% loss on a well cleaned glass surface. Most of them don't stay clean very long.

So running air cooled reduces PAR per sq ft.

4) Not all ballasts are the same. There are lots of tests you can find out there. Solistek has won every test I have seen and not by a trivial amount.

As an EE I can say do not buy one with a fan

HID ballast PAR comparison

So to get the best PAR per sq ft. You use a Solistek On a DE bulb in an Open reflector. Not to mention it is best to spend the money on top of the line bulbs. That is another 10-15%. So doing it right can get you more than 30% more PAR (15 with no glass, 15 with no cooling, + another 10 maybe with top of the line ballast).

No joke my friends. I have both. Old school SE 1000W and DE 1000W on a Solistek with the best bub on the market and they are not even in the same ballpark. You MUST have eye protection to get near my tent now.

And as always it pays for itself in 1 grow. What does a pound of weed go for?


Bulbs: Gavita has been doing DE's the longest. They are on like Gen 5 I think and the others are all playing catch-up. Gavita had such a good product that Philips has been contracted to make it for them. But any DE bulbs is better than and SE. They run hotter so be prepared for that. You need a bit of extra distance to the plants and a faster fan. They are more expensive but last more than twice as long and degrade MUCH slower. So cost wise they are actually cheaper.

Another test for you

These guys make the best bulbs and were the leaders in the industry. They were the ones who moved DE into the the grow room. I hear Hydro farms has a knock off that is actually better now...but the guys at the store will tell you anything. They said you can find online the results so give it a search if you care.

 

[DRM Ranch]

There is a slight bit of false information in the statement that glass blocks certain spectrums, the truth is some glass does, some do not, and some fall in-between.

I happen to own quite a bit of glass that is UVB transparent, it is used to allow UVB into reptile enclosures for those that require it.

That said I am not arguing that the glass used in most fixtures is this type of glass, just pointing out that there is more to glass than stated.

My space is such that a 24k BTU AC unit (mini split) should be able to maintain optimal temps. So I could run three Gavita pro 600 fixtures. I'm not sure however if I have the height needed, I have 8' to work with, and my SCROG net is right at 4', seems a close call. The price for entry seems about right, with top of the line bud going for $240 oz here payback is fairly quick.

 

[Papageno]

I never said I was right. All I said was I am an idiot.

 

[DRM Ranch]

I never said I was right. All I said was I am an idiot.

Ha-ha, for the record knowing there is UV transparent glass is fairly esoteric knowledge. The stuff is expensive, and it takes a real idiot to buy it to house a couple hundred pairs of 8" lizards when just moving the lamps into the enclosure would be a near zero cost option.

 

[Papageno]

yeah yeah I know...I would have posted "well you gotta retrofit just about any hood" if I wanted to be a right fighter.

You are correct! Good luck finding one for cheap! I try not to get TOO literal on basic questions like this. Most grow stores wouldn't even know what you are saying and would just be like..."buy that one...it is great"

Air cooled has its place...just not in my grow tent.

 

[ZARBU]

I download a free LUX light meter app to my samsung galaxy and run at 58000 LUX for HPS , i lower the light until i achieve that light level or increase my wattage or number of lights for coverage.

58000 LUX at plant level from HPS is the perfect lighting for best buds, veg low compact plants, with close nodes, dont grow stretchy veg trees.

any less than 58000 LUX and your yield will drop. Any more is not needed for small to medium plants.

height of light from plants is far more important than watts per square foot, LUX drops off very quickly further away you get from bulb.

even 15cm higher from the ideal height can drop a whopping 25% off your LUX reading for a 400 watt hps.

Higher watt bulbs are slightly more forgiving but only slightly.


Kiwiiwik

 

[DRM Ranch]

I download a free LUX light meter app to my samsung galaxy and run at 58000 LUX for HPS , i lower the light until i achieve that light level or increase my wattage or number of lights for coverage.

58000 LUX at plant level from HPS is the perfect lighting for best buds, veg low compact plants, with close nodes, dont grow stretchy veg trees.

any less than 58000 LUX and your yield will drop. Any more is not needed for small to medium plants.

Kiwiiwik

My t-5 lights are 22073 lux at the canopy...I'll have to play with this tool.

I know lux isn't PAR, but I'm a numbers guy, numbers give me wood....okay maybe I'm just high and need to go to bed.

 

[Papageno]

Just to be clear... Air cooled even with an awesome glass is still less efficient. He is asking best PAR per square foot. As soon as you cool the bulb you are getting less PAR.

Hence why I use a good ventilation system for my temps and a nice adjustable strap for the light and I run the bulb hot. I have a similar concern as this poster. I want my light to be as "effective" as possible. I don't care about cost so much. You can't get better than a top of the line ballast on a DE bulb in an open and small reflector. That is just science. (well in HID anyway...)

 

[ZARBU]

ok sorry just finished editing my post and adding a few things and fixing typos.

Ha ha im high as too and it usually takes me 20 edit cycles to get my post reading right lol.

Kiwiiwik

 

[DRM Ranch]

I don't care about cost so long as the return justifies it.

Within reason I can afford any light system, I just don't want to spend an inordinate sum of money on a system that doesn't fit my needs.

I'm interested in the DE fixtures enough to look a bit deeper. I'm fairly sure I don't want to go beyond three 600w fixtures but that is about all I'm sure of at the moment. The Gavita Pro 600s are looking like a front runner, the other brands seem to have stuck with 1000w versions (dimmable but less efficient when dimmed)....

 

[ZARBU]

No need to spend much on lighting.

600 watt HPS are awesome, keep low and add more for coverage if need be.

They veg perfectly fine at 58000 lux, absolutely no need for a separate veg light. They pack nodes really tight.

Kiwiiwik

 

[DRM Ranch]

No need to spend much on lighting.

600 watt HPS are awesome, keep low and add more for coverage if need be.

They veg perfectly fine at 58000 lux, absolutely no need for a separate veg light. They pack nodes really tight.

Kiwiiwik

I'm seeing the Gavita Pro 600/750 flex DE for around $400 ready to fire up. That seems reasonable to me.

 

[ZARBU]

I'm seeing the Gavita Pro 600/750 flex DE for around $400 ready to fire up. That seems reasonable to me.

Its your money. If you like go for it, would I nope.

I once ran 1200 watt HPS 2 x 600 watt in a 4" x 4" tent 1.2m x 1.2m with air con heat was definitely a issue in summer from my experience but amazing plants.. but project got crushed mid way, hoping to try it again soon in a sea of green flood and drain zero veg situation, just need my dam clones to hurry up and root something good.

Kiwiiwik.