Years back I grew in a closet using two 250-watt HID lights, well four actually if you count two MH and two HPS that I would switch for vegging and flowering. There with no ventilation other than opening the door and letting a small fan blow softly over the tops of my plants and I could easily keep the lights at 8 inches above the tops of my plants without any heat issues. In the winter when it was slightly cooler in my home, with the fan blowing on low speed I did at times get my lights at close as 6 inches from the tops of my plants and did not have heat issues.
You can get a 250-watt, or two 250-watt HID lights pretty close even if you only have slight air movement where the lights heat would be the highest. As long as your box, or if someone uses a closet or a tent, has at least a slight constant flow of air directed at the area of the lights themselves and the tops of the plants unless there is a general heat buildup problem that would raise temps to high you can get 250-watt HID lights pretty darn close. You just have to watch them closely, especially when in flower when inches of new growth can be gained in a day. Most important it to check as soon as the lights come on. Plants grow very efficiently during hours of darkness, that is just how they are made, it is what they do, and if you keep your lights close it is not unusual to find the safe distance that existed when the lights turned out to be more than gone by the time your lights come back on.
Often if I had one or two or three plants that were slightly taller I would allow their tops to grow higher than the light bulbs and almost be touching the hoods, sometimes they did touch for short periods of time. As long as the higher plant tops were not right by the light bulbs, as in they were towards the far end of the light hoods opposite from the light bulbs, the plant tops could easily be at an equal height or slightly higher than the light bulbs and there was not any heat issue problems and when using low wattage lighting it worked better overall to allow plant tops that high now and then rather than to raise the lights and take light from the lower portions of the plants.
Just because you had two 250-watt HID lights dont allow yourself to believe you have major lighting and that you do not need to keep your lights as close to your plant tops as you safely can. A 250-watt HID light, or two of them, is really pretty low in light production and light dissipates quickly. While lower areas of the plants will seem well lit to the human eye they can easily be in low-light conditions by plant need standards.
Figure that you have roughly 18 inches of decent light to work with, thats all, just 18 inches, and you have to measure/estimate/guesstimate from the bulb down and not from the plant tops down plus the space above them to your lights.
Without knowing your pot size, as in actual height, and what types of light hoods you use and how tightly they can be tucked up to the top of your cabinet I am estimating that you have about 3.3 feet of usable growing height.
Depending on strain to strain differences I would say you could get to around 6 to maybe 8 inches and then flower and not run out of usable growing height.
While it did not take me long to know I needed to up my wattage I do admit there was some use in running two separate 250-watt lights, even though they were using 500-watts and giving me less light/penetration while using 100-watts more at the same time than a 400-watt, but in some grows either by chance or because of mixed runs I would end up with several shorter plants and often times I could group the taller plants under one light and the shorter under the other. That seemed to help in two ways. One was I could keep all or most plant tops that close 6 to 8 inches to the lights helping more light reach the lower portions of plants. The other was a plus that was connected to at times having two HID lights at different levels. If I had half a crop of something shortish and the other half was something taller, or maybe the same strain but I only topped half or whatever, if the height difference between the two HID lights was about 5 inches or more, more helped this even more, I would see an increase in production on the middle and lower third of the taller plants besides the shorter plants. The lower light provided increased lighting from the side to the middle and lower portions of the taller plants and that increased bud production.
Learning that led to me intentionally using that capability or flexibility every couple runs or so. I would pick two strains, one a fairly quick finishing strain, though not like super short flowering time major indica since I am anything but an indica fan, but something that was quick finishing to me and then the other half of the crop was something with a rather long flowering time, like roughly 4 to 6 or more weeks longer than the other half of the crop.
Basically that meant a slightly to fairly sativa predominant strain and a very close to all sativa or all sativa strain for the other half of the crop so in both cases I knew I had to factor in my low wattage lighting limitations.
I tried starting right from 12/12 but I found using Uncle Bens topping techniques, or more accurately a fairly similar one I had come up with and then later made a couple little changes making it Uncle Bens and found it to be more reliable for getting 4 main leaders/main-stems/colas on plants, or at least three, rather than the two that I would get more times than I liked the way I had been doing it. Then at a certain point I would do a little tying down. The combination kept me within my height limitations and increased yields.
Part of the increased yields at times was in the planning of growing two strains with significantly different flowering times combined with keeping the shorter flowering time strain shorter than the other as much as possible.
With the one light lower as I said it added a significant amount of additional lighting to the plants next to it increasing production in the mid and lower portions of the plants. The real kicker to it was once the faster finishing plants were harvested I would position my then unused light at a height where its upper directed light rays would hit just above where the light rays of the light above the still flowering plants would be getting weak. I would rotate the hood of the then unused light so it would be directed sideways and slightly down, while keeping the bulb horizontal. That would add a large amount of light to the areas of the remaining plants that were existing in lower light conditions. It would give them good light in the areas of otherwise low light for the last 4 or 6 or more weeks of flowering. That made a real difference. With the added side lighting between rotating plants and repositioning plants I was able to get a lot more light to areas that would otherwise receive low to minimal lighting that late in flowering and the increased bud size was proof that it worked and that it was worth continuing to use the otherwise then unneeded light.
While it only took a very short bit of time of having a 400-watt light replacing my 250s for me to love it, now that I think back to running multiple lower wattage HID lights I realize that in a way I actually enjoyed it in some ways. Production was not as good but it made you think a bit more, you had to keep your eyes open and sort of think on your feet and even plan different strategies, sometimes one or more as a backup in case your primary strategy failed so you could still have a chance of maximizing yields given the limitations in lighting.
You did not have the safety net, or maybe more accurately described as the luxury of higher wattage lighting to as your backstop, as something to make up for things that would otherwise be needed to be done to achieve acceptable final results.
Yes it was a pain in some ways. I always had a stack of bricks close by and handy and many times I would have one to half of my plants on anything from one layer of bricks to maybe four or five layers of bricks so I could keep all the plant tops under one light as close to being the same as possible without working with thin strips of things besides the bricks, so I could then use the second light to the best advantage.
In an odd way as much of a pain as it was I now look back on it with fond memories. It was sort of like my very first car, a 1970 Fiat 850 Sport convertible. That is when I learned that Fiat stood for Fix It Again Tony. The car was almost as much of a hobby as it was transportation because there was always some minor repair that needed to be done, or like one that was a chronic problem, the snapping of the throttle cable that ran from the gas peddle under the car to the carb on the rear engine. One might last a month and the next a week or two but they would snap. I kept a spool of wire and tools in my car and got to the point to where I could replace it in the dark in about 15 minutes. Running two 250-watt HIDs was somewhat similar. Not as in repairs needing to be made, but I had to learn them well and figure out how to tweak things to make the most of what I had to work with. At times I would be a grow or two ahead on paper/computer planning what strain, or what strains if I was going to do the secondary light use deal. I would have general plant positions, which could change depending on growth results, and what light cycle I would use and if I was going to top some or all of them etc. Then I would come up with backup plans about what I would do if some part of my main plan let me down and I had to make alterations.
Thinking back it really was a lot of fun in some ways. It is much simpler now and the results are better but there was some real satisfaction to be found in some of the results I used to get knowing what all it took to get them. It was doubly sweet when I would read messages of the successes of others with similar or better setups got from them and I would compare them to my results. Many times I would smile and think to myself, I won.
Oh, one other thing that I initially did was my first set of lights had very basic exact duplicate batwing reflectors, that I later replaced. When using them something I would do if I was growing a lesser number of plants and did not need as large of a light footprint as possible is I would attach the two batwing reflectors together. I drilled tiny holes in the connecting coners/edges of two hoods and attach them with tiny nuts and bolts.
What that did was make the light hoods almost like an umbrella, the overall curvature was increased with more hood running lower on the sides of the plants. It also slightly lowered the light bulbs themselves and also slightly spread apart the light bulbs a bit from where they would be if not attached but placed to close that the edges of the hoods would almost be touching.
On the somewhat upper portions of plants where they would begin to rely a bit more on light reflected from the white walls they would then be receiving light reflected from the connected hoods on the sides on that level of the plants, light being reflected from a closer higher reflective material.
While at the time I did not have a light meter and can only guess while I did at times wonder if the repositioning of the light hoods had as many negatives as positives but they were just unknown to me, my observations told me increased amounts of light were striking the plants at a lower level than when the hoods were used separately rather than connected. With closer more efficient reflective material once low enough on the plants where that became important, there was an increased amount. That assumption seemed to be verified when later I upgraded hoods and again later when I totally upgraded my lighting and each time the basic same results were seen, well even more so once stepping up to the 400-watt light, but with each change the results I only received when the batwing reflectors were connected were normal with the higher grade hoods, and even more with the increase in wattage, though that would mainly be due to increased light penetration and increased reflective light due to the increased wattage.
Another plus that came with the fewer plants and connected batwing reflective hoods is one that depending on someone elses size and shape of growing area might or might not allow them to use is with the light bulbs spread slightly further apart I had more flexibility in plant positioning. The slight difference between light bulb distance, while still having the entire area under one large hood, allowed me to move plants into positions that would not have been as desirable if the hoods were separate and in their standard positions, or near to them. While certainly not a computer designed shape to maximize light ray distribution it was obvious that under the area where the two hoods were attached there was increased lighting to when the two hoods were hanging side by side unattached and at the same level and a plant or plants were placed near or under what would be the outer edges of both individual light hoods.
Using the slight additional distance between light bulbs, and the improved lighting of the dual-hood setup I could allow the tops of most plants where their tops were not right under a light bulb or very close to a light bulb to grow up into the top of the combined hoods. Even being above the bulbs with so much reflective light coming from such a close source and the natural turning/curving of leaves and even individual leaf blades those tops were receiving as much light as my lighting could offer.
At the same time with the two bulbs also being slightly lower than when the two hoods were not attached, that helped to provide slightly increased levels of light penetration. I know it was not a massive increase by any means but considering the limitations of 250-watt HID lighting, and how it is even more limiting when using even lower wattage HID lighting, If you can not provide absolute top notch light to all portions of your plants or even good light to all portions of your plants, if you can manage to get just adequate amounts of light another inch or three, when working with 250-watt lighting, and also lower, that small difference in deeper penetrating light can be what strikes the next lower level of buds that without the slight increase in light would at very best nice firm but small buds and instead they become nice firm not massive but definitely respectable sized buds.
When working with lesser numbers of plants in a somewhat limited space and using lower wattage HID lighting, doing various things like I mentioned above, and any number of others that can be done, doing them whenever possible using whatever means necessary can be what turns a small smile into a big smile come harvest day.
No offense meant to anyone who uses HID lighting that is anything from one 400-watt light to multiple 1000-watt lights, but other than discounting the occasional way off the scale on the bad side grow, for whatever not all that common but yet not unheard of reason, if you are not a Ricky Retardo you will rather consistently produce yields that are most definitely respectable and now and then some might go off the charts on the Holy Shit Thats Amazing, good side of the scale.
I am not saying that everyone who uses more than 400-watts of HID lighting is like just a few grams shy of a world record on most or any grows, but unless you are an idiot savant minus the savant part if you have GOOD to GREAT lighting, including of course anything else that might also be needed because of the lighting used, unless it is just one of those snake-bit grows that are just going to happen now and then if you use at least truly decent quality to true high quality genetics, come harvest day you might not be doing back-flips but you will not have to hang your head in shame over your yield. If you are one of those who does not believe or fear loose lips sink ships, and who would share information with real life pals about grows, the person would not feel compelled to tell a little white lie and pad their yield weight a tiny bit to keep from being made fun of. Face it, all of us in that group have a bit of an edge, a safety net of sorts built into our systems that will do anything from to a degree make up for some slight deficiency in a particular setup to maximizing what an individual has to work with. An acceptable degree of success is almost always there at the end
. almost always.
But when using lower wattage HID lighting, or CFLs for that fact (for the record I hate CFLs) you really have to know how to tickle every gram possible out of your setup if you want that big smile or a chance to do back-flips over your yields on a very regular basis.
I used to do it
I tried just about everything imaginable, and some that likely are beyond the imagination of some, and all I can say is my hat is off to any lower wattage grower that is able to crack the enciphered code hidden in their setup that tells them how to suck every last gram of productivity out of what they have to work with.
Of course the same argument could be made about individual higher wattage setups and their maximization of yields, especially when talking about a commercial grower and I am only talking about someone trying to keep themselves in a constant supply of quality herb and nothing more. That is where there is a true separation between the two actually different but yet still sounding the same points or positions or arguments.
If you are just looking out for yourself, and of course any and all immediate family you may have of an age you believe to be acceptable for them to then partake of a family tradition, right up there close to Thanksgiving Day in my book, like I said, if you are not Ricky Retardo or an idiot savant minus the savant part, and not including that now and then lightning strikes grow, we basically have it made in the shade. We will be able to keep ourselves supplied.
The lower wattage grower is not always able to do that. It is not unusual to have gaps, periods of time where you go without or purchase from others, you can easily experience dry-spells. Unless someone has a well-tuned lower wattage perpetual grow system, which most do not because if they had the cash and know how to do that almost all of them would have switched to an overall more advanced higher wattage system by then, Keeping a steady supply of herb can be challenging when you go low wattage.
That is why I tip my hat to the very best of the best of them. I know what it takes to pull it off and I also know how little it takes to cause it to go from looking like you have it made in the shade to being disappointed.
Oh
one little tip about the hood-less CFLs for vegging. Adding some sort of reflection would be wise. I really did not look close enough, or retain what I read well enough to know right now if you are using Y sockets to double the number of your CFLs.
First reflection. Any bulb will send off light in most every direction so when using CFLs, or just low wattage HIDs, maximizing every bit or every light ray is important. A quality professionally made hood that you can adapt your lighting to fit into would of course be best but just about anything would be a good improvement to make over no upper light reflection at all. An inexpensive batwing hood would be a big jump up and they are so simple they are easily adaptable. If ghetto-fabulous is good enough for you just hit a local building supply store and head for the roofing department and find flashing. Look for the widest you can find, unless it is ridiculously wide, something I have never seen but can imagine might exist, and then shape a hood from it, and be sure to give good sound considering to how your lights and it will fit and connect as well as possible.
It is not a great option, but it is a viable option. The flashing is not high quality dimpled aluminum but it is aluminum so there is a decent amount of light reflection to be found and that decent amount is way more than the zero amount of upper light reflection that I seem to remember not seeing.
Next would be the Y sockets. If you are using them ignore the rest.
If you are not using Y sockets now, use them in the future unless you switch to HID lighting for vegging. You will double the number of lights, and light, your plants will have to rely on. Depending on things like the exact size of the Y sockets you would get and the size/dimensions of the pots you grow in, at times the size and shape of a Y socket will work out so one light will be positioned directly over the top of each plant, both side by side or in two rows.
As I stated I hate CFLs but I am not one that did not try them before defaming them. Without measuring it I could not give you the length but I have an OLD light-bar from an OLD home movie camera. It has four sockets and could hold four high-wattage bulbs, very similar to yard floodlights in size but of a somewhat different design. I put one Y socket in each single socket and the way it worked out in spacing I could have 8 plants, in two rows of 4, with one light directly over the top of each plant. I do not recall the actual wattage but they were 125-watt equivalent. I want to say they were something like 28 or maybe 32 watts each but I cannot remember. They were 6500K so they were vegging bulbs.
I dug out the old batwing reflectors and overlapped them length-wise (they were the same size and shape so they fit almost like pieces of a puzzle) and again drilled tiny holes and used two tiny nuts and bolts and attached my light bar to them. The hoods were wide enough to still reflect well at the end of vegging and the plants did grow well with that lighting, the nodal spacing was tight, I can see why some people do use them.
But the results/vegging growth was slower than with my 400-watt HID and while the nodal spacing was close to being as tight it was not as tight so where I see CFLs only having a place for vegging, or keeping moms happy, Other maybe than the keeping moms happy part I see no use for them. Well ok, maybe in a tiny box/cabinet grow
maybe
just maybe because I would rather go CoolTube and lower wattage HID if it were me, so to me they are next to worthless.
But if you continue to use them come up with some sort of upper reflection and Y sockets, that is unless you already use either or both and Nevilles Haze caused me to miss them. The Y sockets will double your lighting, and you can even mix and match various Kelvin range bulbs if you want to experiment sometime or alter their position and change Kelvin range and use them for supplemental lighting from the back or side or at some angle and level like I did with my 250-watt HID. But get something reflective attached to them. Depending on your setup possibly the inexpensive standard work-light with clamp might work, you can always just use the hood
and they do come in various sizes. The ghetto-fabulous flashing would be a positive step up too, and depending on how handy you are and what you might have to work with to shape it, as malleable as it is you can really do a lot with it. I have seen the work of a few very creative people who went that route when using CFLs. In their case budgetary constraints kept them from having better options but they really thought it out well and were lucky enough to be fairly handy and have a few handy things available to help them form/shape their ghetto-fabulous hoods, but in the end they did darn well and they saw definite improved results once they begin using them.
So if ya aint a doin both now
.. git ta doin both as quick as ya kin.
Sorry for the "War and Peace' length message but there is just something about Neville's Haze that puts a whole heap-a' words in my fingertips.
