Section 3:
To “shed some light” on the proper way to choose and setup your HID’s or LED’s (growing puns!), there are a few important factors to consider.
How many plants (at what size) do you plan on growing?
How much space do you need to cover?
Is there a limit to how much electricity you can use?
To what extent can you control your environments temperature?
Since plants grow faster in DWC, the type of light you choose should be able to cover an area that supplies your plants with adequate lighting on all sides, ensuring even growth. In addition, your lighting setup should be able to deliver intense light down to the bottom leaves of the plant in the correct frequencies! Note*: If you are running a sea of green setup, light penetration is not as important since your plants bulkiest flowers are in the top set of leaves, but sea of green (in my personal experience) is not ideal for DWC.
So, now that one has an understanding about the functions a good grow light has to serve, lets assess the products available individually and rate accordingly.
LED: These lights deliver over 95% absorbable light to your plants, compared to only 15% with High Intensity Discharge (HID) Lighting. To achieve this, LED diodes output light at specific frequencies which are beneficial to the plant. In addition, the power usage of these lights ranges from 90-350 watts (incredibly low!), and the 300-350 Watt models are able to cover what a 600W metal halide is able to do during the vegetative stage (in my personal experience). However, the intensity of the light fades very quickly over distance with these units, since the initial output is relatively low. This means that taller plants will get nice tops but anything below will suffer greatly. The light will have to sit closer to the plants too, to ensure that the full intensity is reached and since flowering plants need more light than their veg. counterparts, LED’s are sometimes inadequate sources of light. Do not worry about heat though: LED’s are great for stealth because in addition to the low electric signature, there is no thermal signature. Currently the technology is on the expensive end, so for growers with a modest budget, this is not an ideal route, but it definitely has a promising future in the market and has already delivered good results for those who use it right!
http://www.prosourceworldwide.com/pr...ies%20350w.htm
HID’s or High Intensity Discharge lights can be separated into two categories: High Pressure Sodium (HPS) or Metal Halide (MH).
p.s. - metal halide is for vegetative growth, high pressure sodium is for flowering
MH / Conversion bulbs: Combination HPS/MH lamps combine a metal halide bulb and a high pressure sodium bulb in the same reflector, either with a single integrated ballast assembly or two separate ballast assemblies. The combination of blue metal halide light and red high pressure sodium light is said by manufacturers to create an ideal spectral blend and extremely high outputs, but in reality it is a compromise on both situations. These types of lights usually cost quite a bit more than a standard light and have a shorter life span. Also because they use two smaller lights rather than one larger light the distance that the light penetrates is significantly shorter, in comparison to a regular hid bulb, due to the inverse square law of light.
However, companies like Hortilux are producing pure MH “blue” lights that replicate daylight sun and are the first true vegetative HID lights that are not combination bulbs.
http://www.hydrogardencenter.com/hor...alide400w.aspx
HPS: High pressure sodium lamps yield yellow lighting (2200K) and have a very poor color rendering index of 22. They are used for the second (or reproductive) phase of the growth. If high pressure sodium lamps are used for the vegetative phase, plants will usually grow slightly more quickly. The major drawback to growing under high pressure sodium alone is that the plants tend to be taller and leggier with a longer internodal length than plants grown under metal halide. . They are used in less color critical applications such as parking lots, street lights and for supplemental greenhouse lighting. The benefit of high pressure sodium lamps to the horticultural industry is their ability to enhance the fruiting and flowering process in plants. Orange/red spectrum HPS is the spectrum plants use in their reproductive processes, which generally produces larger harvests of higher quality herbs, vegetables, fruits or flowers. Sometimes the plants grown under these lamps do not appear very healthy (although they usually are). This is due to the poor color rendering of high pressure sodium, which makes the plants look pale, washed out or nitrogen starved. Benefits to high pressure sodium lighting are their incredibly long usable bulb life (up to two years in many cases); and unparalleled efficiency at six times more light output per watt of energy consumed than a standard incandescent grow lamp.
While HID’s use up more electricity than LED’s or CFL’s (compact fluorescent lighting), they put out more intense usable frequencies from one source than any grow light available to the average consumers. This allows for deep and wide coverage, but remember your electricity bill will be a reminder of the lighting system you are using! In addition, because DWC systems sit underneath the lights, a common problem is that your nutrient solution (and roots) get pretty hot from the heat of the HID. Its for this reason that air cooled reflectors are always recommended to take away excess heat and keep your plants happy and close to the light.
http://www.hydrogardencenter.com/day...extension.aspx
Basic chart for height above plants and coverage area with HID and LED’s
Vegetative
(400W MH) - 24” / 3‘x3’ coverage
(350W LED) - 12” - 24” /3‘x3’ coverage
Note*: Your plants requirements for light during flowering are 2-4 times your vegetative stage
(600W HPS / Combination) - 24”- 36” / 4’x4’ coverage
(1000W HPS) - 36” - 48” / 5’x5’ coverage
In the grow room seen in the pictures, we are using two MH bulbs, and two HPS bulbs in 4 daystar air cooled hoods (as seen in the link). We chose this lighting scheme for a few reasons...
The plants should produce 1-3 pounds each depending on the strain, so the density and height of the plant requires lighting that can reach to the bottom flowers.
Using a MH during flowering (in addition to your normal HPS bulb) increases potency in the plant because MH bulbs emit more UV intensity, a frequency known to increase cannabanoid contents.
In the next section, we will go over feeding regimens and what nutrients are worth your time for DWC specific growers

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