# hows it supposed to go



## blondlebanese (Aug 29, 2014)

is it preferred to place the extraction fan at the beginning of the run or the end of the run.  so push or pull the air.  considering i'm using flex ducting.


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## MR1 (Aug 29, 2014)

I have mine at the beginning, I think it is better that way.


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## pcduck (Aug 30, 2014)

I pull my air. Keeps a negative pressure in my tent.


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## The Hemp Goddess (Aug 30, 2014)

I also pull my air to have negative pressure.  My fan is actually in my crawl space and being there it is totally silent.


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## orangesunshine (Aug 30, 2014)

fan will work on either end---1st choice is always to pull rather than push


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## Dr. Green Fang (Aug 30, 2014)

I always will pull. <3 negative pressure!


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## blondlebanese (Aug 31, 2014)

pcduck said:


> I pull my air. Keeps a negative pressure in my tent.



both ways produce neg. pressure in a sealed room.


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## pcduck (Sep 1, 2014)

blondlebanese said:


> both ways produce neg. pressure in a sealed room.



Having a sealed room has nothing to do with having negative pressure in your room.

Having a completely sealed ventilation system does. When pushing air the ventilation must be sealed in order for no air leaks putting air back into the room. This means taping all connections along with your reflector. Pulling your air you do not need to do this. If there are air leaks, those air leaks are still sucking air out


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## MR1 (Sep 1, 2014)

Pc, I don't think Blonde is pushing air into grow room, just wants to no where to place the exaust fan, I have mine in my tent so I like beginning, some like their's outside of tent so end, it depends on your setup.


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## pcduck (Sep 1, 2014)

That is what I am trying to explain. The difference between pushing/ fan at the beginning and pulling/ fan towards the end. With the fan pushing/at the beginning any air leaks in your duct or reflector will be pushing/ adding air to your room. If these air leaks are in your reflector or duct work you will be forcing hot air back into your room when pushing.


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## MR1 (Sep 1, 2014)

Got it.


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## blondlebanese (Sep 2, 2014)

I do get it.  for the third time I have rearranged my grow room.  relocated the exhaust fan so now the system sucks.  biggest benefit I see is the flex duct collapses .  making a tighter neater fit instead of ballooning stretching .   pulling is the best way to go.


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## JimB (Sep 17, 2014)

Fluid dynamics, same law for;

low density fluid, our atmosphere

medium density fluid, water=1

high density fluid, maybe a volcano erupting.

None will pull but a tiny bit, All will push with million+ psi.

If your set-up pulls satisfactorily, then you're good to go within small margins at your location but as a design principle/application, results are unpredictable at untried locations if plan is pulling fluid rather than pumping.


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## Sherrwood (Sep 17, 2014)

Heat rises so naturally you want fresh air coming in from the lowest point, exhausting from the highest point.
Pull the air from top.


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## JustAnotherAntMarching (Sep 17, 2014)

JimB said:


> Fluid dynamics, same law for;
> 
> low density fluid, our atmosphere
> 
> ...



 Huh??????   you sure do give some confusing answers...


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