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Thread: Smaller fan

  1. #1

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    Lightbulb

    I changed my monstruous power supply fan (120 VCA, 65 cubic feet/min) for a smaller, less heating CPU fan (12 VCC, 32 cubic feet/min).

    I noted the data concerning temperature and humidity fluctuation, and have an idea the difference cause by a powerful fan, a medium fan and no fan.

    What surprised me though, is that I had believed a fan would lightly descrease temperature while greatly descreading humidity.
    I was wrong, on the contrary, air circulation reduces heat by more or less 5F, in both the case of a strong one and a medium one, but the airflow is very noticably increasing humidity! (and quite fast too, a 2% increase in the first 3 minutes since the installation of the small one inside.)

    My hypothesis is that, since my terrarium is pretty much closed space, their is no cooler or warmer air being displaced from outside to inside or vice-versa, hence the small temperature drop. Also, the airflow is evaporating the water in the soil and trays (I placed a bowl of water in a corner precisely to increase humidity), but since there's little exchange between the ouside and inside, these evaporated mollecules of water have nowhere to go, and thus remain in suspension in the terrarium air, increasing ambient humidity.

    =D

    (Btw, stronger fans create more air circulation, but while they col a little more, their engine creates more heat, so it's not much more effective than small one. The only use would be any effect of a stronger wind n the plants.)

    These observations are valid for a closed, or very close to closed terrarium, I have yet to test on a more open one.
    If the dragon is bigger than his treasure, it's not worth the effort.

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  2. #2

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    Hi,

    the slight decrease in temperature in the first few minutes is due to the evaporation of the water which caused the humidity to increase. When the air is saturated with air, which will happen in a closed terrarium very shortly, the temperatures will rise, because the fan disspiates power which transforms into heat.

    Cheers Joachim

  3. #3

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    Actually, the temperature descrease has been occuring very slowly, as it dropped by about 5F over a period of 5 hours, it's the humidity increase that has been hapenning very fast at first, then more slowly and steadily as the hours went pass.
    If the dragon is bigger than his treasure, it's not worth the effort.

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  4. #4

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    Ssvzein, how big is your terrarium? Because Ive heard that a CPU fan is usually way to small to create a reasonable airflow for a big terrarium...

    Also, what do you use to power the cpu fan? (Converter?)
    [img]http://home.**********.com/users/phyrex/phyrex.gif[/img]

  5. #5

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    It's 27 gallons, but honestly, I'm thinking my small CPU fan maybe still _too much_ for my terrarium, it's shaking the leaves of all the droseras, espeacially binata .

    CPU fan vary very much in power, they range from as less as 5 cubic feet/min (the really cute, 3 cm large ones) to as much as 32 cubic feet/min. Some may go even higher than than. (Those are typically running on 9 or 12 volt CC)

    As for power supply fans, they can go from 30 cubic feet/min to over 100 cubic feet/min, that's a HUGE amount of airflow, and far too much for even the biggest terrarium. (Those run on the standard 120 volt CA, which is what a wall plus will give you.)

    I've plugged my 12v cc fan on my old game gear adaptor, which transforms 120v CA from my wall plus into 12v CC at 500 mA (The fan needs 160 mA, so it's more than ok.)

    Does that answer your question Phyrex?
    If the dragon is bigger than his treasure, it's not worth the effort.

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  6. #6
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    Jeese, that's exactly what I noticed when I put a small desk fan inside my 5' x 5' x 5' foot grow chamber. It's deffinately helpful.

  7. #7

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    Thanks Ssvein.

    What about the placement of fans?

    I have a 100 gallon (160 cm long) terrarium myself (empty atm) and was wondering about fans and their placement.
    I could have 1 or 2 CPU fans on top of the terrarium cover (through a hole in the Plexiglas), this will create a downwards flow AND will suck in air from the room (and also pushes air out back into the room).
    Think this will help cool temperatures at night? (Less humid air can absorb more ultrasonic mist so the air cools perhaps..? [img]http://www.**********.com/iB_html/non-cgi/emoticons/new/confused.gif[/img] )

    Another way would be to place 2 fans inside the terrarium on the wide end each. (And also placed diagonal) so in theory this should create some sort of small cyclone effect in the length of the terrarium.

    Oh and by the way, how long does your fan operate? All day and night long or at intervals?
    [img]http://home.**********.com/users/phyrex/phyrex.gif[/img]

  8. #8

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    Ahhh I must say I have yet to find the optimum solution when it comes to the placement of fan, but I believe that to push cooler air in from the outside would be good. I don't know about your cyclone idea, but I would like to know, try it and tell me!
    Wow, 100 gallons is a BIG terrarium....CPU fans might not be enough, I'd say go for power supply fans (though they heat a bit more), probably two 65 cubic feet/min ones, but not a 100 cubic feet/min one, that's too hard, it would blow the plants close to it too harshly while not necesarily moving air so well at the far end. And I think the 65cfm might be overkill too, it's just not so good for the plants nearby, drying the surface of their soil and sending them dirt and all...

    And another thing I can tell, there isn't much need to ventilate during the night as far as I can tell (others may correct me on this), but since your heat proucing lights are off AND the ambient temperature cools, your terrarium will gradually cool down on it's own, and humidity increases on it's own as well as there is some evaporation anyway while the lights aren't drying the inside.

    I'm only ventilating while the lighting is on, which is on a period of 15 hours during the day, in oder to counter it's troublesome drying and heating.

    The question is, do you just want to create some air circulation, or do you need to really reduce temperature?
    If the dragon is bigger than his treasure, it's not worth the effort.

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