LED Grow Light Forum

SME,

I appreciate your input. Got a quick question. You stated you need 40 watts per square foot, so a 1000 watts would cover 5x5 space correct? When calculating LED do you use the actual draw watts or calculated watts? An example would be you have 84 /three watt LED's in a panel the calculated watts would be about 250 watts. So you would need 4 panels.... Yet the actual draw would be around 130 - 140 watts depending on the fan configuration. I honestly don't think that you can compare "apples to oranges" LED's are more spectrum specific. I have run 600 watt HPS and 520 watt LED. Running the same strains you might get a 10 % weight difference. Where LED excel is in quality of the medicine. The problem I see is the density HPS seems to produce denser nuggets. I believe this is due to the lack of penetration or the heat the HPS provides. I have been searching for a HPS / LED combo mix. Was looking to see if this can be proved out. Instead of running the HPS for the full 12 hours,run it say 3 hours off then 1 on then 3 off then back on. You actually run it 4 hours in the 12 hour period. Not sure of the affect on the bulb starting and stopping it like that. What do you think?

Welcome to the forums!
(I split your questions to a new topic since the other was dead for several months.)

I never stated that you need 40w/sqft; that's what CLW suggests for their lights to get good results. If you want exceptional/top-shelf results you'll need more than 50w/sqft. Even then you'll need to keep the plant height down to make up for penetration issues.

LED watts (what you call calculated watts) are pretty meaningless; I only go by actual draw. You can compare any light by the results, imho. Based on results so far I'd say that you need the same number of actual draw watts vs HPS watts to get similar results but that assumes that you're growing small plants with a fairly even canopy. If you veg them too long LED can't keep up at all.

That (estimated) 10% weight difference between a 600w HPS and 520w LED is almost the difference in wattage too. While most, if not all LED manufacturers claim their smaller LED lights can replace much bigger HID lights it's nothing but sales propaganda, imho, when it come to results.

Quality is harder to prove, definitively, unless you grow side-by-side tents with the same nutrients, clones, conditions, etc and THEN run them through lab tests it's only a "subjective" claim.

We have a grow journal here that backs up the fact that HPS will grow bigger/denser/more flowers than LED even at high w/sqft numbers in a one plant vs one plant test. The problem, for LED, seems to be penetration and intensity.

There is a theory that LED will yield better with higher heat in flower, supposedly due to less IR spectra but some LED lights have IR diodes too and, so far, none perform as well as HID.

We've had a few theories about HPS/LED combos; some considered using HPS to supplement LED, some considered using LED to supplement HPS. Yours is the first to consider that rotating type of schedule. You will shorten the life of the ballast and bulb by switching it on/off so often but since you're allowing it to cool down for 3 hours before turning back on at least you don't have the hot-start problem. How much you'd gain by doing that is unknowable unless you tried it and ran side-by-side tests without the HPS and with the combo running all 12 hours. Obviously, with SOME added light it should help but it's hard to say how much.