Too much negative pressure?

soundman

Member

• Sep 12, 2017

• #1

Has anyone noticed a difference in plant growth under a decent negative pressure vs slight negative pressure?

I changed my tent setup for the next round and have a decent amount more negative pressure than I am used to. Tent sucks in very hard. Only one 6 inch fan extracting with two 6 inch passive intakes. The other fan strictly cools lights and adds a very slight positive pressure, from tiny leak in seals on lights. 5 x5 Tent.

Just curious how plants like growing in a slight vacuum? I can add another speed controlled fan to input to help reduce negative pressure if needed.

Anyone have experience with issues like this?

Thanks!!

 

H

HqFarms

Member

• Sep 12, 2017

• #2

How often will your exhaust kick on?

 

soundman

Member

• Sep 12, 2017

• #3

HqFarms said:

How often will your exhaust kick on?

Click to expand...

Exhaust has always ran 24/7. I like to exchange tent volume of air 1 - 3 times a minute. Right now I am about twice a minute exchange rate. DR150 tent, 150 Cubic feet, and exhaust running at about 300 - 350 CFM.

I may slow down the exhaust some but like the temps and humidity as is.

 

H

HqFarms

Member

• Sep 12, 2017

• #4

I see no reason to exchange air that much and never seen a difference between doing a exchange that often compared to every fifteen minutes. I feel like with exhausting that much you are wasting energy plus wasting what plants aren't using in that amount of time. What are your temps and humidity like?

 

soundman

Member

• Sep 13, 2017

• #5

HqFarms said:

I see no reason to exchange air that much and never seen a difference between doing a exchange that often compared to every fifteen minutes. I feel like with exhausting that much you are wasting energy plus wasting what plants aren't using in that amount of time. What are your temps and humidity like?

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I will have to see humidity when wet coco is in the tent. Temps are 76 out of direct light. Humidity upper 30s with no plants inside tent.

I can slow fan down till temps rise but I can tell now I cant slow it down much.

I only have a timer on hand that can run 30 min on / off at minimum. I can try that for giggles. This little tent is pissing me off. Im going to really have to babysit it daily. Need an AC on programmable thermostat.

 

Ringodoggie

Well-known member

Premium user

• Sep 13, 2017

• #6

http://www.just4growers.com/stream/...-deficit-the-hidden-force-on-your-plants.aspx

Pretty good real on pressure's affect on your plants.

 

OldPhart

Member

• Sep 13, 2017

• #7

What may appear as a large amount of neg. pressure, is actually a VERY neglectable amount of neg. pressure. For example, if you actually achieved 0.5 psi of vacuum on the tent, which would turn any tent into an envelope (**0.5 psi would exert 2300lbs of force on a 4'x8' surface**); would be equivalent to adding 1000 ft. of elevation. So even though the tent is sucking in quite hard, I doubt that it is equivalent to adding more than 50' of elevation. So bottom line, any air pressure that you can create with a fan will have NO effect on the plants.

 

Last edited: Sep 13, 2017