Many Grow Lights vs 1 W/ same wattage - Comparison Help

Discussion in 'Growing Marijuana Indoors' started by NewbGrowTech, Feb 11, 2014.

  1. Hello all!
    I am a new grower and I have done a ton of reading and studying first, but with no surprise I am having some issues on my first grow.   
    I designed my grow area with a non typical light setup as I obtained a bunch of 175w MH ballast and fixtures for free which I designed around.   I setup a 6x4 grow area with 6x 175w MH on adjustable height pulleys for a total of 1050 watts combined.  I also figured I would add CFLs as needed, but as of yet the plants are still small and I have not seen a need to add the CFLs.  I have done a lot of reading online for my first grow, but I have not found much information about the difference in lighting with many lights vs one large one.... this is where my questions lie.
    I've seen multiple charts with info on how far away to put your lights, and I have used 1000w as my reference point, but I am wondering if it would be the same with my multiple light setup or completely different?
    Currently the lights are 8-14" away from my plants.  That sound good for my setup?
    I never found information on the light distance charts weather or not it was referring to the distance from the top of the plants leaves or to the base of the stem at the soil.  Can anyone shed some light there?
    Is my light setup adequate? Or am I hurting myself by using these free lights?
    My plants are only about 4" tall at day 21 from initial germination (white widow), and I feel like their growing slow, but again I am very new at this does that seem like a normal height at this point?
    I appreciate any suggestions, comments or helping information you guys can add.

  2. #2 zippy657, Feb 11, 2014
    Last edited by a moderator: Feb 11, 2014
    No, a point source bulb should not be treated the same as a source that is spread out.  Without seeing your setup it is difficult for me to picture how you have the lights positioned, but if you are doing something like one or two of those bulbs over each plant then you want them much closer than a single 1000W would be from the canopy.  Really though you just always want any light as close to the plants as possible without burning them.  Get yourself a thermometer with an outdoor temperature probe (they are cheap) and hang the probe just above your highest vegetation.  Keep lowering the lights until the temperatures aproach 85F or so, (fans help a LOT) and you've got your ideal distance.  Obviously ambient air temps and circulation are extremely important.  If you are growing in a room that is 60F you will be able to keep the light a lot closer than in a room with 80F ambient temps...  
    To answer you specifically though, for 175W bulb i would think youd want to be more like 4 or 5 inches or less if you can... 8 sounds a bit far.  I grow an inch away from t-5s and my closest plants are 5 - 8 inches away when i use a 400W MH.  Also, the distance of the bulb is always referring to distance from top of canopy, and not from the soil.

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