Intake/Exhaust Fan When on 12/12..

Hi guys, just a quick n00b question..!

When my girls are in their 12 hours of darkness I currently have the intake fan on the whole time (24hrs a day) and the exhaust coming on for an hour then off for an hour and so on until their 12 hours of light where its on all the time..

My question is, do I need to have my exhaust fan on at all during the 12 hours of darkness so its just the intake on or possibly the opposite and have it running the whole time instead of on 1 hour/off 1 hour?

are you using a filter?

The exhaust fan has a large charcoal filter on it yes and the intake fan is blowing air from the top down onto them..

Anyone able to help?

i always leave mine running 24/7, but i would say that as long as temps would be ok you could just leave an oscillating fan going and shut the intake exhaust down when lights are off.

I have a box from B.C Northern lights and it runs and does everything by itself. The exhaust fan runs 24/7 but thats the only thing running 24/7 other then the airpump and airstones for the plants to breath. So i would keep that exhaust fan going it will still provide some air circulation for the plants. But if temps are fine you probly dont even need it

luckymeh said:

Hi guys, just a quick n00b question..!

When my girls are in their 12 hours of darkness I currently have the intake fan on the whole time (24hrs a day) and the exhaust coming on for an hour then off for an hour and so on until their 12 hours of light where its on all the time..

My question is, do I need to have my exhaust fan on at all during the 12 hours of darkness so its just the intake on or possibly the opposite and have it running the whole time instead of on 1 hour/off 1 hour?

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I am also sorta new at growing. I have been using the practice of turning off the exaust fan. I notice a major increase in humidity when fan is off even if the lights are off. Make sure you have a high low humidity meter if it gos above 45% or so you need to make the fan run more. I have an 8x8 grow space with 2 oscillating fans and 2 600 wat MH lamps. An intake of 135 cfm and an exaust of 425 cfm. Otherwise your tactic is sound in electricity saving and in general noise level.

In my flower room, EVERYTHING is turned off by the timer. The intake fans, the exhause fan and the lights ALL turn off when it's bed time for my little ladies.

HookdOnChronics said:

In my flower room, EVERYTHING is turned off by the timer. The intake fans, the exhause fan and the lights ALL turn off when it's bed time for my little ladies.

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you should have a door open or intake fan on they need some sort of fresh air. their roots need oxygen at night. just like you brain needs more oxygen at night.

i just run my intake and fans on but my exhaust fan is on a temp gage and the only time it turns on is if it gets to hot but in never needs to do so..

MistaKris said:

i just run my intake and fans on but my exhaust fan is on a temp gage and the only time it turns on is if it gets to hot but in never needs to do so..

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I want to do that but everyone is out of stock on it in my area.

ok you should be fine tell you can get one and just keep it running tell then

Intake should be at the bottom to be the most efficient... I keep my exhaust running 24/7 since i have it hooked to a carbon scrubber, (plants still stink at night.and i dont need any neighbors getting a whiff) Intake also runs 24/7
i do turn my circulation fans on low when lights are out, but rarely ever off

MistaKris can you post a link to the temp guage you have?

Ok so after some experimenting I am going to use both the intake and exhaust 24/7. With just the intake on the grow tent would a) expand with pressure (this can't be good for plant or set up?) if no exit holes were open and, b) when the exit holes were open and intake fan pushing air in/out of the tent the smell was far too much to feel comfortable!

With the intake and exhaust both on 24/7 I am getting a perfect temp / humidity through their dark period whilst keeping fresh air circulating and not having any odour in my room.

I also found having the small intake fan at the top of the tent was better for keeping temperatures perfect. Being higher up it is closer to where the cooler, fresh air enters the room and can blow cooling air over the tops of the plants where they will need it most. The cool air also blows around the HPS bulb which must be doing it good by limiting the bulb temp too.

hot air rises, so the air at the top of the room would be the warmest, but if it is working for you i would keep it... Glad to hear things are working out. the fans draw so little energy so running 24hrs really wont show to much month to month on energy , you could also hook up a variable speed control to your fans and just turn the fans on a lower setting at night.. also helps with quieting the air flow rush noise that is heard

exhaust fan only needs to be on when the lights are on to reduce heat and it also helps to draw in fresh air to the plants although in saying that when u hit flowering you'll find that the smell is that bad your gonna want it on almost constantly but if this is gonna reduce your temps too much set it up on a timer to , for instance , come on 15 mins every hour. when ur lights are off i'd strongly suggest having a small fan blowing all the time, it help reduces bug,mold and mildew problems by increasing air movement and reducing humidity or at least drying moisture off the plants