HLG 650R with UV bar Height no co2 Flowering

24-36 inches is sufficient since this light replaces over 1,000wattsHPS. Shes a beast for sure and definitely generates a bit of heat but with proper ventilation this what I would go with and you want that intensity at 100% for sure to get the most out of that light. You definitely wanna train your plants nice and low for this light. Trellis set-up is best for sure. Hope this helps

16 sq ft with 630watts of fairly efficient lighting... something is wrong on their spec sheet -- minor issue but the fact that the math is off is a red flag... and no indication on diode count... if not 0.25watts per diode the efficacy listed is a lie and/or still comes with reduced longevity even if oyu can hit that value with higher bin diodes. in the past the r-spec was a lower efficacy. So, i'd be curious about diode count and if that didn't change then they are justmaking up the umol/j value. anyway... let's assume 1781 umol/s is true... that's a bit over 100/sq ft. you need about 70-80% of that for ambient co2 over 12 hours. You could dim it and use at normal distances... or you can gas it a bit and raise height slightly... the latter is slightly more waste but probably have better results with lower bud sites and greater penetration +odder angles off reflective walls reaching lower areas etc. Your maximum height in grow area may dictate that choice too, if not enough room for the plants. ppfd / DLI - good to read up on a cursory google search will do you well. light applied is proportional to hours of use. ppfd and dli are proper measurements to use to compare apples to apples between different gardens. you want 35-40 DLI. a DLI table reference shows that this is 800-900 ppfd (give or take.. ballpark ideas here, regardless some trial and error in real life is necessary) PPFD is relative to 1 m^2 which has 10.764ft^2 in it... 80umol/s * 10.764 = 861 PPFD. you take that value and reference a dli table (hours x ppfd) and you get a dli in teh 35-40 range... (use 50-60 DLI for boosted co2 context). The same DLI over 12 or 18 hours is no different, within reason... certainly the eye cannot tell the difference. 1781umol/s / 16ft^2 =~110 //// 110 * 10.764 ~= 1184 PPFD. This is great for boosted co2.. you need 850 / 1184 = 72% of that... So, try 75% at suggested height from manufacturer... adjust from there... (OR, more power and greater distance... inverse square law makes even 2-4" different significant.) Regardless, these idea only get you close to what you need and reduce effort dialing it in. you'll still want to use the plant's behaviour as your primary rail. Observe resulting internode length (distance between 2 grwoth nodes) and adjust as needed... avoid stretch... avoid overly tight... and take notes of what works when you find that happy zone, beause it'll be consistent in future with even less adjustments needed per genetics or seasonal variations of environment.