4x4 I/O question

My 4" adjustable fan and filter should be here today / tomorrow. Just in time - I opened the office door before lights-out this morning and WHOOSH!

Currently I'm running:
Intake - passive 6" duct feeding the tent from a dark box for light leaks.
Exhaust - 4" inch inline fan taped to 6" duct - curved and blowing down into an unused felt pot for light leaks.

NEW Setup
Intake - 4" duct from dark box, 4" fan pulling from inside tent.
Exhaust - 4" Carbon filter / fan / 6" duct to exterior exhaust.

Tent pressure - The adjustable fan will be on the intake to dial in neutral / slightly negative pressure inside the tent.

Does this sound like a good plan?
Or is there a better way to configure?

What is the temperature of the intake air? This is the key to the setup cooling well. That and good duct runs. Bends kill flow, each 90 degree bend knocks off about 15% of the CFM. Accordion duct also inhibits flow compared to smooth walled duct.

Intake temps - ext of tent - 65-78f

Hadn't considered the cfm loss in accordion duct - I'm going to run the accordion as straight as poss. to mitigate loss, but I don't want to screw with it too much this round. I'll be getting some smooth wall duct for the next run...

Does having the adjustable fan on the intake make sense?

Lockedin said:

Does having the adjustable fan on the intake make sense?

Click to expand...

Well if odor control is critical then you want negative pressure. Being able to slow the intake fan so that it doesn't out run the exhaust fan would allow you to maintain the negative pressure required to ensure that odor isn't leaking out of the tent. With duct restriction on the exhaust line it would be likely that the intake fan would have more real world CFM than the exhaust fan provided they are the same model.

I also like to use a larger than required fan for my exhaust then slow it with a variac so it's just enough to do the job, this results in a very quiet setup and leaves room to turn the fan up if heat becomes a problem.

Using a two fan system isn't going to increase the overall CFM since the exhaust fan is the bottleneck. The only way I would use an intake fan is if it was required to move cooler air from another room.

You probably don't need an intake fan. I don't use one with a 6inch 400cfm exhaust.