400w HPS. Week 6

Discussion in 'Growing Marijuana Indoors' started by whackyac, May 2, 2016.

  1. This is 1.5 weeks into flowering in a 4x4 tent. The temp stays at 77 and sometimes rises to around 79 so heat is not a problem. I don't understand what is going wrong. I have an 8 inch exhaust at 720 CFM. The HPS is around a foot and a half to two feet away. Im not over or under watering. What could cause the top leaves to curl like this? 197f72790b18b6a7ff150882c2acaaf6.jpg 1515f36efd78417492b60d358522d7a7.jpg 13b5b570d3c609d126f39f983da3bd09.jpg

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  2. Do you have a oscillating fan blowing air around on the inside?
  3. I do put its blowing more above the plants not really moving the plant around.
  4. #5 Bunks, May 2, 2016
    Last edited: May 3, 2016
    I looks like a lack of air flow over the leaves. What is your tents humidity? What is the temp above those curled leaves?

    I should add. When ever my plants are curling at the top but not the bottom, I've found there to be a lack of air flow in that area causing the air to heat up and the humidity drops. I leave a temp/hum gauge hanging from a piece of rope in between the plant canopy and the light. Floor temp can be 77f 45% and the air between the canopy and light can be as high as 95f 30%.

    Even with high CFM blowers/fans, there can still be dead spots.
  5. The air in my tent is replaces entirely at least 7 times per minute though. My exhaust fan is overpowered for a 4x4 space. The humidity is around 48-50%. The temp stays at around 75 most of the time.
  6. A blower may read 720CFM's but I can promise you its not. There are just SO many variables. Here is a great website, depending on your ability to accurately measure your grow conditions. You may find your 720 SCFM fan be 400 ACFM or less. SCFM vs ACFM | Standard CFM vs Actual CFM | pdblowers, Inc.
    Room pressure
    Actual pressure
    As well as the filter and tubing.

    Could be a PH problem though. Maybe someone else can chime in with some ideas :)
  7. Even with that my ACFM is 513 which is 5 times more than my sq ft

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