Ventilation Help Needed

First time posting, long time reader of these informative threads. Very thankful to be a part of this great community. Lots of knowledgeable people on here for sure.

First time growing in tent Need Ventilation Advice!

I’m having negative pressure issues in my 4x8 tent. Tent pulls inwards 6 inch or more to the point it looks like it will collapse on its self. I understand slight negative pressure is beneficial but with my current set up I can’t achieve that.

Location: Basement
Exhaust: 8” 790cfm inline w/ Carbon filter (speed controller)
Intake: 6” 390 CFM w/ can intake filter drawing air from main level via floor register vent. (speed controller)

I have exhaust fan on lowest speed and intake speed controller set at max. Intake is drawing air from upstairs via floor register vent. Because I’m dumping the exhaust into the same room as tent I need a constant supply of fresh air/co2. Opening the flaps on tent is not an option as I only want filtered air entering the tent. I read somewhere that as a rule of thumb you want to have a slightly higher output exhaust fan to intake ratio? That’s not the case in my situation that’s for sure.






What are you guys running for ventilation for 4x8 tent? like to see other setups that people have tried with success.

Anybody have any advice or something I missed along the way? It would be much appreciated thanks.

By doing what your doing and bringing air from outside and venting air into the same space your increasing the air pressure outside the tent as well as reducing it inside.

You can get tent bars which stop the tent walls pulling in too much. But really you need to reduce the negative pressure.

I don't know what speed controller you have but it might be wise to pick up a proper variac so you can turn the extraction down far more.
That would allow 100%-0% speed control.

coreywebster said:

By doing what your doing and bringing air from outside and venting air into the same space your increasing the air pressure outside the tent as well as reducing it inside.

You can get tent bars which stop the tent walls pulling in too much. But really you need to reduce the negative pressure.

I don't know what speed controller you have but it might be wise to pick up a proper variac so you can turn the extraction down far more.
That would allow 100%-0% speed control.

Click to expand...

^^ This, I'd vent to the outside as well reducing your room's pressure depending on how tightly sealed the room containing your tent is.

curious2garden said:

^^ This, I'd vent to the outside as well reducing your room's pressure depending on how tightly sealed the room containing your tent is.

Click to expand...

Totally. Vent outside when ever possible!

coreywebster said:

By doing what your doing and bringing air from outside and venting air into the same space your increasing the air pressure outside the tent as well as reducing it inside.

You can get tent bars which stop the tent walls pulling in too much. But really you need to reduce the negative pressure.

I don't know what speed controller you have but it might be wise to pick up a proper variac so you can turn the extraction down far more.
That would allow 100%-0% speed control.

Click to expand...

I'm going to try a proper speed controller like you suggested. Its a vivosun controller even when it is on the lowest possible setting it still pulls hard not much difference in sound from min to max. What brand controller do you recommend?

Cangrow613 said:

I'm going to try a proper speed controller like you suggested. Its a vivosun controller even when it is on the lowest possible setting it still pulls hard not much difference in sound from min to max. What brand controller do you recommend?

Click to expand...

I have something like this


They come in various sizes , just look at the amps your fan pulls and get one rated a bit higher.

I ended up getting a variac transformer. Definitely worth the price. It’s a very heavy piece of analog equipment looks like it’s from the 1950s Cold War era. Very smooth controls no hum from fan motor even a low speeds. I was able to dial my air flow perfectly at 60 volts. The controller itself is a bit overkill rated at 1000v 10 amps but the instructions state it can be run indefinitely at 5amp draw without over heating. It’s been running for three days now and puts off zero heat. Thanks for the suggestion. Great product.