alex801
New Member
It must level out a bit though as the exaust fan has the resistance when it hits the carbon filter
Max's PC Grow Box Journal - 2013
- Thread starter Maxximilian
- Start date
Pressure inside the grow room:
You don't need any fan on your air inlet, just the outlet. The fan on the outlet sucks the air out creating a negative pressure inside the grow area, which forces air to be sucked in through the inlet to equalize the pressure. There's a few reasons behind this, but mostly the main 2:
1. Efficiency. 1 fan doing the work is better than 2, less wasted performance and electricity.
2. Environment control. Forcing air through the inlet makes it harder to control temps and humidity. Why create more problems?
This applies to most circumstances, obviously there are areas where the opposite effect would be needed.
A passive intake (just a hole/ vent or duct of some description) with a dust filter over it (no nasties get into the grow area this way) and an active outlet with carbon filter and exhaust fan to suck the air out will give the required results in most situations.
As an extra note get a good outlet fan for the size of your area. Opinion ranges, but in general you should recycle the entire capacity of air inside the tent 3-7 times per hour, so get a fan that can pull the capacity of air per hour that you need to do this.
You don't need any fan on your air inlet, just the outlet. The fan on the outlet sucks the air out creating a negative pressure inside the grow area, which forces air to be sucked in through the inlet to equalize the pressure. There's a few reasons behind this, but mostly the main 2:
1. Efficiency. 1 fan doing the work is better than 2, less wasted performance and electricity.
2. Environment control. Forcing air through the inlet makes it harder to control temps and humidity. Why create more problems?
This applies to most circumstances, obviously there are areas where the opposite effect would be needed.
A passive intake (just a hole/ vent or duct of some description) with a dust filter over it (no nasties get into the grow area this way) and an active outlet with carbon filter and exhaust fan to suck the air out will give the required results in most situations.
As an extra note get a good outlet fan for the size of your area. Opinion ranges, but in general you should recycle the entire capacity of air inside the tent 3-7 times per hour, so get a fan that can pull the capacity of air per hour that you need to do this.
- Thread starter
- #323
Maxximilian
New Member
Thanks, damn going to maybe have a think about it the bottom vents one I picked up at the homedepo and blowing the tent up like a balloon should have done the math and checked the air movement rates and then added the fact of the carbon filter. I was just too excited. Plants are in the tent thread will be done later on. Haven't had a smoke all day so nows the time. Also if anyone's got a clear way of watering their plants in relation to their pot sizes that be awesome. There's about 20L of soil in each pot. So how many liters of water for 20Lsoil. And also I'm sure that negative is worse as the plants need more co2 than o2 so a negative would mean more o2 then. anyways the fan blew on the unit taking it back tomorrow. anyways starting the new thread now 
- Thread starter
- #324
Maxximilian
New Member
rep. yo so ive got a question to follow this statement. my tent i just got has 3 slots rectangular that have a flap over them and then netting behind this. I tapped them up as i thought smell would seep out but now come to think of it if there is a negative pressure from orinitating from the top this would kinda act like a vacuum sucking from the bottom up so techincally i could un-tape them and get the cash back from the in let fan i just got. The thing im stuck with is that the temps in the tent may become too high with just with the air being pulled in. ive set up a fan in the unit. going to get a second clip fan latter on. going to test it with the flaps un-taped now. worried about summer temps once we get them
On your outlet and filter: always match your carbon filter and your fan as best you can, don't wanna pull too fast through the filter else it will 'choke' the system as the filter will be over-worked and will need to be replaced alot more often. If you really have too, get a bigger filter in relation to the fan, but make sure the fan can pull enough air through 3-7 times per hour still.
A negative pressure just draws air in. Yes the plants need the CO2, but there's plenty in the atmosphere for them. If there wasn't the correct ratios of different gases in the air, then plants wouldn't grow at all. Negative is better than positive, for the above reasons.
A good general opinion on watering your plants is water them when the top inch of soil in the pot is dry, and allow 10-20% of it to 'run-off'. This helps clear your grow medium of salt build-ups and waste products.
A negative pressure just draws air in. Yes the plants need the CO2, but there's plenty in the atmosphere for them. If there wasn't the correct ratios of different gases in the air, then plants wouldn't grow at all. Negative is better than positive, for the above reasons.
A good general opinion on watering your plants is water them when the top inch of soil in the pot is dry, and allow 10-20% of it to 'run-off'. This helps clear your grow medium of salt build-ups and waste products.
- Thread starter
- #326
Maxximilian
New Member
Thanks a lot Smokes, you new to this community? Welcome!
- Thread starter
- #328
Maxximilian
New Member
aight man enjoy.+
jlt1202
New Member
Perfect description, i just recently added a vent that is a cold air return basicly, keeps like from coming in/ out very much, and i can control venting, had more info but you hit the nail on the head man!
alex801
New Member
I would worry that with a 600 watt hps on 18 hours a day with only an exaust fan blowing out air it has passivly sucked in through a vent hole away from the lights that max's room temps would be high 90's-100°
I agree completely with the theory. But I also think that a fan sucking air in through a ducting aimen somewere neer max's lights would be very benificial
I agree completely with the theory. But I also think that a fan sucking air in through a ducting aimen somewere neer max's lights would be very benificial
- Thread starter
- #331
Maxximilian
New Member
Thanks for the help. ive removed the tape on all the inlets on the bottom sides of the tent. Also started my new thread check it out its in my sig now too enjoy.
enjoy.- Thread starter
- #332
Maxximilian
New Member
with the window cracked open the temps read 26.4 C and humidity is sitting at 40%
alex801
New Member
I stand corrected
Im in. Although im kinda jealous you got 2 dots AND 2 sigs?? You two ^^ will be in the MOTM contest before I take my first pull of my HG
!!
!!
alex801
New Member
Iv give u some reps spinp to help u get to the 2 dots. The reps are overdue man iv been watching ur grow carefully
BudTester420
New Member
What if you can't take air from the room your tent Is in? I pull clean cool air from one room and run it into my tent, then I exhaust it to a different room.
- Thread starter
- #337
Maxximilian
New Member
the way its set up now is a vent slot on the right next to the wall but theres space as theres a radiator inbetween and right above that a bit to the right is a window, where on top of the then the felxible duct is directed to the windows edge to be messed around with there. temps were at 22.2C just be4 lights out with the window open so it seems temps are okay going to give it a run tomorrow with the window closed to see how temps are and then put the vent in ill have switched out i hope to something smaller and hopefully quieter as the other one was making quite the racket.
Sorry for the late reply, got smoked out with the missus last night 
You don't need to tape up the slots, having a dust filter over them though is beneficial. Yes some smell will escape, but with the air being drawn in through these slots it will be very negligible, you would probably stink the place more if you smoked a J. Yeah I'd take the intake fan back, or keep as a spare for an outlet maybe.
The temps with this method would only become too high if the grow area exhausted the air into the same space as it drew in from, and this space had no ventilation such as a window or vent. A fan on the inside to circulate the air around the grow area is good, it can help with temps being kept down but mostly it's beneficial as the plants develop stronger as they grow, as they have a little wind and they have to grow stronger to grow against it and healthily.
Basically, good air = good plants.
As long as the area being vented into from the exhaust was well ventilated, it should be a non-issue. If you're worried about the temp from the lights that much then you can get reflective hoods that attach to vents and your whole light rig is vented by your exhaust vent. This is plenty enough to keep your lights cool.
You don't need to tape up the slots, having a dust filter over them though is beneficial. Yes some smell will escape, but with the air being drawn in through these slots it will be very negligible, you would probably stink the place more if you smoked a J. Yeah I'd take the intake fan back, or keep as a spare for an outlet maybe.
The temps with this method would only become too high if the grow area exhausted the air into the same space as it drew in from, and this space had no ventilation such as a window or vent. A fan on the inside to circulate the air around the grow area is good, it can help with temps being kept down but mostly it's beneficial as the plants develop stronger as they grow, as they have a little wind and they have to grow stronger to grow against it and healthily.
Basically, good air = good plants.
As long as the area being vented into from the exhaust was well ventilated, it should be a non-issue. If you're worried about the temp from the lights that much then you can get reflective hoods that attach to vents and your whole light rig is vented by your exhaust vent. This is plenty enough to keep your lights cool.
Ideal situation, everyone would do this.
alex801
New Member
Weres the updates on pc journal miximmilian?? How are they looking? Don't forget this little grow dude
