# To run an intake fan or not?



## 000StankDank000 (Apr 23, 2014)

Hello
I am running 1000watts in a 4x4x7 tent temps are high. I have a 6" exhaust pulling threw filter pushing threw light then out of my tent.

I was thinking of getting a 4" fan to dump fresh air in the bottom of the tent.

Would this help with heat?

What do you guys think ? I'm running in the high 80 like 89 lol


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## orangesunshine (Apr 24, 2014)

the air in the tent is only going to be as cool as the air u a pulling in---fresh air is good---but my guess is the exhaust is a sufficient air exchange for ur space---cooling the tent is a completely different animal and others with tents will hook u up there---green mojo

also running your lights at night will also keep the temperatures cooler than running them during the day


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## The Hemp Goddess (Apr 24, 2014)

No.  Orange is right--unless the incoming air mis cooler, it is not going to cool your space, no matter how much air you are putting through there.  Also, I don't really believe that an intake fan boosts exhaust--your exhaust fan is pulling what it can and adding more air is going to do nothing to help if you have adequate passive intakes.  I pull my air from my crawl space, which always stays cool.  I always run my lights during the night--summer and winter.  In the summer, it is cooler, so easier to keep the space cooler.  In the winter, the light warms the space up--otherwise I would need a space heater during the night.


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## 000StankDank000 (Apr 24, 2014)

I understand that the same air temp mix in will not help it has to be cooler come on I'm not that much of a noob am I?

The temp hits 90f when I wake up lights on at night window open fresh air flaps open a swell .

Wanna pull cool fresh air from outside need to drop another 10 f to reach 80f

What do you guys suggest other than the oblivious an AC system.


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## The Hemp Goddess (Apr 24, 2014)

If you want to pull air from outside, you are actually going to have to pull air from outside.  By the time it moves through the window and through your bedroom from outside, it warms up to the ambient temp in the room.

I do not know the math involved, but you may have to drop your incoming temps more than 10 degrees to actually achieve a 10 degree drop in the space.  Do you have a crawl space you can access?


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## 000StankDank000 (Apr 24, 2014)

No 
Why can't i do a VERY short run of insulated pipe from outside into the tent? 
I believe this is my best option I understand a long run threw my room will heat up but very short insulated should drop 10F ???


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## The Hemp Goddess (Apr 24, 2014)

Well, you can, but a piece of ducting sticking out a window is very suspicious.....give it a try and see what happens with your temps.


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## 000StankDank000 (Apr 25, 2014)

Why? 
It looks just like the Hot pipe from a stand up AC. Lots of people have those sticking out the window.


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## MJ20 (Apr 27, 2014)

A 6" is not enough to cool a 1000W HPS bulb.That is more suited for a 400W to 600W.Right now i'm running the same 1000W bulb with an 8" fan with passive intake in a 4x3x7 closet.I don't believe I even tried it with a 6" before even though I have one..never worth the risk.I also have a 6" home/deskfan that sits at the bottom of the cabinest and pushes air up.

My intake hole is about 4" wide and is to the right of my bulb (the bulb is simply mounted on the wall, no reflector).My exhaust fan is to the left of my bulb, with the suction side being less then 6" from the left side of the bulb.The air is then pushed through a hole , out of the cabinet.

I know from experience that if you have no intake fan, your exhaust fan will be working somewhat harder to suck whatever air it can from your grow space...worse yet if your intake hole is very small and not matched to the size of your exhaust fan.If you have an intake fan supplying fresh abundant air, your exhaust fan will not have to work as hard to "suck"..and will therefore be much more efficient...This option is obviously more expensive and LOUD.

My cabinet stays relatively warm in the day when I have my lights on, living on the equator and all..I don't think I pass 33-35 celcius on a hot day.

Also, try putting your fan after your bulb to suck air over the bulb..not the way you have it right now: pushing air onto the bulb.See what kind of result you get there before upgrading..


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## The Hemp Goddess (Apr 28, 2014)

I have a 6" that does a fine job of cooling my 1000W.  Most of it depends on the temps of the incoming air.  I draw intake air from my crawl space, which stays fairly cool year round--not too hot in the summer and not too cold in the winter. 

If you have an intake fan that is significantly smaller than the exhaust fan, it impedes the air more than a passive opening.  The exhaust fan is trying to suck air through a space that is mostly taken up by fan.  IME and IMO, there is no advantage to something like a 140 cfm intake fan with a 440 exhaust fan.  The intake fan is blowing in 110 cfm, but the exhaust fan is trying to suck in 440 cfm.....with no place to suck it from.  It is easy to size your intakes so your exhaust fan is not overworked.  On the other hand, if the intake fan is too large, you will not have negative pressure and the odors will escape from your space.  You do want your fan after your light though, sucking air past the bulb and then through the fan to be exhausted somewhere is more effective than pushing the air over the bulb for some reason.


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## Hushpuppy (Apr 28, 2014)

I have myself used a single fan and hose (both 6") and pulled through 2 600w lights and a 2', 6" filter, and I had no trouble keeping my temps in upper 70s when the incoming air was in low to mid 70s. One thing that helps, if you have your fan inside the grow space then move it to a location outside the grow space so that the heat generated by it and through it will be outside the grow space. I had my fans located next to the opening to the outside of my building and then pulled through about 12-14' of fflex hose from my lights and filter. I had only passive intakes to my tents, and I had passive intakes in the ffloor of my building.


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## 000StankDank000 (Apr 29, 2014)

I am gonna try and do a short Run of maybe 8" from the cool fresh air to the tent .

Will my 6" fan be enough to pull in fresh air? 
 I don't wanna have to spend $100 on another one plus noise to being in fresh air.
The run of pipe is 2 feet long.

Those super cheap inline fans look like they would barley move any air looks like a CPU fan in ducting junk.


I don't wanna move the exhaust outside as I have gotten all my noise problems taken care of.

It's 45F hear today so if I bring that into the tent it should cool it down.

Is there any problem with leaving the tent open when lights are on?

I will be remedying  this problem by the end of the week thinking a big short passive intake of cool fresh air will work


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## Hackerman (Apr 29, 2014)

Make sure you screen your intake of outside air so bugs don't get in.


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## Hushpuppy (Apr 30, 2014)

That should work just ffine for pulling air in efficiently. However, iff you are pulling air in ffrom outside the room into the tent and then exhausting back into the room, you will have to have another opening to the outside of the room so that the exchange of air will continue. Otherwise the room will pressurize and no more air will come in.


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## The Hemp Goddess (Apr 30, 2014)

The problem with leaving the door open is that sometimes you forget to close it or are away when it needs to be closed.  I know that you think that you will always remember to close it, but you won't.  You only have to leave the door open couple of times before you have problems.


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## 000StankDank000 (Apr 30, 2014)

The problem is solved with a 6" passive intake from fresh air. The tent hit high of 85F last night . I know it's still a little high but I got my light cranked up so if it gets hotter I will dial back


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