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How many fixtures do I need for my crop?


When calculating the number of fixtures required to light your crop you need to take the following into consideration:


1. When we light a surface, we always light the entire cultivation area. We do not light separate tables with their own fixture, uniformity is based on the synergy of the entire lighting system. 


2. There is a minimal distance between the lamp and the crop. For 600W this is 60cm/2 ft, for 750W this is 70 cm / 2 ft 4 inch, for 1000W this is 90 cm / 3 ft. In larger rooms with many overlapping lights the optimal distance is often even a bit further away. 


3. The reflectivity of your walls is a crucial factor. The lower the reflectivity of the walls, the lower the average light levels and the lower the uniformity. Walls have a bigger influence in a smaller room. We recommend to use high reflective material such as orca film of >90%. 


4. Because of the influence of the walls the uniformity of the light near the walls is always lower. When we calculate the quality of the light as in uniformity % (min/avg) we always calculate a surface at 20-50cm from the walls (depending on the size of the room). 


5. We calculate with 1000 umol m-2 s-1 for the generative phase (flowering, 12 hours cycle) and 670 umol m-2 s-1 for the vegetative phase (18 hours veg cycle). This is because your plants get 50% more light in the vegetative phase because you light them 18 hours instead of 12. The daily light integral (DLI, total amount of light the plants get per day) stays the same this way.


The light intensity you require depends on a lot of factors. If you are an experienced grower and have CO2 systems and advanced climate control systems, 1000 umol m-2 s-1 gives you the optimal yield per square meter. If you are growing less high-tech, or do not have a long experience as a grower, we recommend to go about 20-30% lower than that, for veg and for flowering. The yield per watt invested light will actually be a little bit higher at a bit lower light levels, though the yield per square meter will be a bit lower.  


6. When combining plasma light to HPS we recommend a minimum of 1 LEP fixture per 600W HPS in veg, and minimum of 1 LEP fixture per 1200W in the flowering phase. More LEP will increase the quality of your crop. 


7. In most cases the dimensions of a room are not ideal for the footprints of the lamps. Therefor most rooms have a different "sweet spot" for the lamps. In general though you should hang your lamps in-line, with the centers of the lamps between 90 cm and 110 cm apart. The distance between the rows is between 1.8 and 2.3 meters. The distance between the rows and the walls should be less than half the distance between your rows: when the rows are 2 m apart the ideal distance from the walls is likely to be 80 cm or less. At the head and tail of the rows the lamps should be really close to the walls (30-40 cm to the center of the lamp). This is because a HPS fixture always has a wide footprint. 


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Article details
Article ID: 22
Category: Knowledgebase
Date added: 2019-10-16 09:15:08
Rating (Votes): Article rated 3.2/5.0 (37)

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