How often should exhaust fan be running?

OldMedUser

Well-Known Member
Use something like an Infinity fan that has temp and rh controllers built in or buy such for your fan so it doesn't run 24/7 and keeps the environment in the grow space dialed in to where you want it. I like a speed controller too especially in the winter so the cooler air is coming in slower and the oscillating fan can mix it up before it even touches the plants.

:peace:
 
Use something like an Infinity fan that has temp and rh controllers built in or buy such for your fan so it doesn't run 24/7 and keeps the environment in the grow space dialed in to where you want it. I like a speed controller too especially in the winter so the cooler air is coming in slower and the oscillating fan can mix it up before it even touches the plants.

:peace:
I do have an AC infinity fan, I bought an 8" for my 5x5x7 tent, I know its a little overkill but between the filter and ducting bend losses I didnt want to have to run it at 100% anyways. If it is cycling for say only half the day, will that still be sufficient C02 for the plants? That was my initial main concern.
 

OldMedUser

Well-Known Member
I do have an AC infinity fan, I bought an 8" for my 5x5x7 tent, I know its a little overkill but between the filter and ducting bend losses I didnt want to have to run it at 100% anyways. If it is cycling for say only half the day, will that still be sufficient C02 for the plants? That was my initial main concern.
More than enough I'm sure but it depends on how many plants are stuffed into a space. If it's packed with plants then either a lot of airflow or CO2 supplementation is needed. With lots of plants the RH will quickly climb and the exhaust fan will be triggered so the airflow problem is solved for that. If only a couple of plants then they aren't going to use up the CO2 so fast so there is less need for as much airflow.

In my instance all the air going into my grow room comes from the greater area of the underground bunker the room is in and stays cool all year round. The highest it gets is maybe 65F tho the last couple summers has only hit 63. Can get down to almost freezing in the winter but usually hovers around 40F. Until recently I was using a 400W CMH light and it didn't warm up the room enough to trip the fan but I wasn't trying to get fast growth out of the two plants in there so no matter. Now there's a 600W MH and the fan kicks in every now and then but I've raised the thermostat to let it get up to about 85 in there so I can burn my alcohol lamp and feed them lots of extra CO2. I just put them in 7gal pots and set up a ScroG screen in preparation for flowering and need to stuff some more but smaller plants in there with them. Going to be a bit crowded but can use the light mover to make sure everybody gets enough light or switch up to 1000W SHPS.

:peace:
 

xtsho

Well-Known Member
My fan runs 24/7. It's the only fan I run. Just a 400 CFM on a speed controller. Passive intake from the bottom of the tent and filter-fan-light from the top. I don't use any other fans in the tent. The exhaust fan provides plenty of airflow from the bottom to the top and a constant exchange of air.
 
More than enough I'm sure but it depends on how many plants are stuffed into a space. If it's packed with plants then either a lot of airflow or CO2 supplementation is needed. With lots of plants the RH will quickly climb and the exhaust fan will be triggered so the airflow problem is solved for that. If only a couple of plants then they aren't going to use up the CO2 so fast so there is less need for as much airflow.

In my instance all the air going into my grow room comes from the greater area of the underground bunker the room is in and stays cool all year round. The highest it gets is maybe 65F tho the last couple summers has only hit 63. Can get down to almost freezing in the winter but usually hovers around 40F. Until recently I was using a 400W CMH light and it didn't warm up the room enough to trip the fan but I wasn't trying to get fast growth out of the two plants in there so no matter. Now there's a 600W MH and the fan kicks in every now and then but I've raised the thermostat to let it get up to about 85 in there so I can burn my alcohol lamp and feed them lots of extra CO2. I just put them in 7gal pots and set up a ScroG screen in preparation for flowering and need to stuff some more but smaller plants in there with them. Going to be a bit crowded but can use the light mover to make sure everybody gets enough light or switch up to 1000W SHPS.

:peace:
Didn't make the connection with the transpiration from the plants. Thank you, sounds great! Really looking forward to getting this up and running
 

conor c

Well-Known Member
For you maybe but not everybody has the same setup. I still use HIDs partly because I need the heat most are trying to get rid of.

Even with 90 degree days going on out there my heater comes on when the light is out to keep the room at 70.It's still only 58 in my basement where the air for my room is drawn from. Free A/C :)
I use hids mate lol plus where i stay aint super warm far from it
 

1212ham

Well-Known Member
24/7. Fungus (bud rot) grows better in the dark and you don't want the air to stagnate when it's dark. Air movement also protects against fungus, so don't add dark and take away air movement. That's a +2 in the column that fungus likes.
There should be air movement 24/7 but the topic is the exhaust fan and air exchange, not air movement within the tent.
 
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