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Tuk U 4:20/24/7/365

Registered: 06/04/17
Posts: 95
Loc: 3rd Rock from the Sun Flag
Cooling and Exhaust Fan Run Time
    #827573 - 07/22/17 03:03 PM (11 months, 22 days ago)

I will be running 400W MH and HPS bulbs in a 3 x 3 x 5.25 tent.  I have a 4" 165cfm duct fan for exhausting the tent and bring in cool air through a 4" filtered passive intake.  My primary concern is cooling while the light is on but I am also worried about the secondary role, which is air exchange in the tent.  Reflector is wing type with no cooling (cheap).

In an effort to keep noise and operating costs down, I am considering putting the fan on the same timer as the lights and have them run parallel to each other.  My rationale is that I don't need to cool things down that I'm not heating up.  My concern then becomes whether the fan down time will cause a problem air quality wise for the plants?

Tent volume without hardware in it is ~47 cu. ft.  In an effort to play along with our government's proposed guidelines on personal grows in the upcoming legislation, it will be confined to accommodating four plants at any one time.

This needs to be thought of in the context of both veg and flower light cycles, which would have fan off periods of 6 and 12 hours respectively.  Thanks for looking.

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Registered: 10/06/16
Posts: 333
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Re: Cooling and Exhaust Fan Run Time [Re: KenInVic]
    #827575 - 07/22/17 03:31 PM (11 months, 22 days ago)

Will be fine esp if still has some passive exchange and have fans running inside. Putting it on 1 or 2 times a night couldnt hurt as its not just humidity but co2 but prob wont make much of a dif since not tottaly air tight and not pushing alot of plants

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Registered: 02/17/11
Posts: 1,935
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Re: Cooling and Exhaust Fan Run Time [Re: KenInVic]
    #827579 - 07/22/17 09:27 PM (11 months, 21 days ago)

Humidity tends to go up at night and is a good source of powdery mildew. I like to always have an exhaust fan on at night to avoid any of those problems.

I liked my last setup, where I had a booster fan blowing from the veg tent to the flower tent 24/7, then the exhaust fan tied to temperature/humidity device. That way it had a constant flow of fresh air without having to run the larger exhaust fan at night.

You can reduce noise by using a larger size fan and running it on low. An 8" fan on low is quieter than a 4" on full blast.

Hanging the fan with bungee cords from the ceiling helps a lot.

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