So will it be enough to have this fan to fully ventilate 4x4 grow tent? http://www.ebay.co.uk/itm/4-Hydropon...EM&refid=store As I understood it can push air in & out, is that correct? Or only out? Thanks
I'l be using 400w hps btw.
Need help with ventilation
- Thread starter acekard
- Start date
justugh
Well-Known Member
no it is to small
a 4x4x6.5 tent is 108 cfm .......your fan is 114 cfm......u still have to account for the heat from the 400watt system air temp from the intake air and the humity in your area
personally i will tell u to get a 6 inch active air this is a 400cfm and get this to lower it or use at full power and if u are using a 4 inch ducting for a cool tube u can get this increaser/reducer
when u get it set up u can increase the speed to lower the temp or lower the speed to increase the temp....................yes u can use it as intake and exhust .......but it would be best as exhust if u only own one.........u can open the flaps on the lower part of the tent and use a passive air intake with this higher CFM fan u should be fine
a 4x4x6.5 tent is 108 cfm .......your fan is 114 cfm......u still have to account for the heat from the 400watt system air temp from the intake air and the humity in your area
personally i will tell u to get a 6 inch active air this is a 400cfm and get this to lower it or use at full power and if u are using a 4 inch ducting for a cool tube u can get this increaser/reducer
when u get it set up u can increase the speed to lower the temp or lower the speed to increase the temp....................yes u can use it as intake and exhust .......but it would be best as exhust if u only own one.........u can open the flaps on the lower part of the tent and use a passive air intake with this higher CFM fan u should be fine
justugh
Well-Known Member
Dan's Method
Calculating By Room Volume You will find many calculations on the web for sizing a fan for ventilating indoor gardens; however, what many of these calculations fail to take into consideration is the friction loss on carbon filters and increased temperatures from HID lights. So here's my calculation method which you can use as a guide for sizing an exhaust fan for a growing area (keep in mind that this calculation will give you the lowest required CFM (Cubic feet of air per minute) required to ventilate the indoor garden.)
Step 1: Room Volume
First the volume of the room needs to be calculated. To calculate multiply length x width x height of growing area e.g. A room that is 8' x 8' x 8' will have a volume of 512 cubic feet.
Step 2: CFM Required
Your extraction fan should be able to adequately exchange the air in an indoor garden once every three minutes. Therefore, 512 cubic feet / 3 minutes = 171 CFM. This will be the absolute minimum CFM for exchanging the air in an indoor garden.
Step 3: Additional factors
Unfortunately, the minimum CFM needed to ventilate a indoor garden is never quite that simple. Once the grower has calculated the minimum CFM required for their indoor garden the following additional factors need to be considered:
Number of HID lights — add 5% per air cooled light or 10-15% per non-air cooled light.
CO2: add 5% for rooms with CO2 enrichment
Filters: if a carbon filter is to be used with the exhaust system then add 20%
Ambient temperature: for hot climates (such as Southern California) add 25%, for hot and humid climates (such as Florida) add up to 40%.
An Example
In our 8' x 8' room we have 2 x 1000w air cooled lights, and we plan to use a carbon filter. We also plan to use CO2 in this room. The ambient temperature is 90 °F (32°C), however, we will be using air from another room that is air-conditioned. Here's the minimum required CFM to ventilate room:
1) Calculate the CFM required for room (see above.)
2) Add 10% (for 2 air cooled lights.)
3) Add 5% of original CFM calculation (For CO2.)
4) Add 20% of original CFM calculation for Carbon Filter.
5) Air is coming from air-conditioned room so no need to add any other percentages.
6) CFM = (171 CFM) + (171CFM x 10%) + (171 CFM x 5%) + (171CFM x 20%) + ( 0 )= 231 CFM.
This is the absolute minimum CFM required to ventilate your room.
The next step might seem to match the closest fan to this CFM. However, for this example I'd choose a six inch fan with a CFM of around 400 or more, and a 6 inch carbon filter to match. The extra CFMs may seem a bit excessive (calculations on most indoor gardening websites would recommend a 4" fan and a 4" carbon filter) but it's always better to over-spec since we need to compensate for air resistance in ducting too.
Also, as we are using a carbon filter we will need to match the fan with the filter so that the fan that will neatly fit onto the filter.
If all the variables are kept the same and we changed the room size from 8' x 8' to a 12' x 12' then the minimum required CFM would be 519 CFM.
The All-Important Inflow!
An intake port can be anything from a gap under the door to an open window - even a hole in the wall. The best place for an intake port is diagonally opposite from your exhaust fan; that way, air has to pass across the entire room - very efficient. You can put a piece of screen over the opening to keep insects and animals out, a piece of A/C filter to keep dust out, or a louvered shutter or backdraft damper that opens when the fan turns on and closes when it turns off. You can also use a motorized damper. This gets installed in-line with your ducting and is plugged into whatever device controls your exhaust fan. When your fan turns on, it allows air to pass. When your fan shuts off, it seals completely, preventing CO2, air, etc. from passing. You can get creative with these devices and use one fan to control two rooms, etc.
One additional note about intake ports - you will see much better results from your exhaust system if you install a second fan to create an active (as opposed to passive) intake system. Normally, when your exhaust fan sucks air out of your room, air is passively going to get sucked back into the room. By installing a second fan on the intake side, you will reduce the amount of negative pressure created in the indoor garden, thereby cutting down greatly on the amount of work the exhaust fan has to do and allowing much more air to pass through. If you're not sure or you don't want to spend the money, start out with just an exhaust fan. If it's not performing as well as you thought it would, try adding an intake fan - you'll smile when you see the difference!
Calculating By Room Volume You will find many calculations on the web for sizing a fan for ventilating indoor gardens; however, what many of these calculations fail to take into consideration is the friction loss on carbon filters and increased temperatures from HID lights. So here's my calculation method which you can use as a guide for sizing an exhaust fan for a growing area (keep in mind that this calculation will give you the lowest required CFM (Cubic feet of air per minute) required to ventilate the indoor garden.)
Step 1: Room Volume
First the volume of the room needs to be calculated. To calculate multiply length x width x height of growing area e.g. A room that is 8' x 8' x 8' will have a volume of 512 cubic feet.
Step 2: CFM Required
Your extraction fan should be able to adequately exchange the air in an indoor garden once every three minutes. Therefore, 512 cubic feet / 3 minutes = 171 CFM. This will be the absolute minimum CFM for exchanging the air in an indoor garden.
Step 3: Additional factors
Unfortunately, the minimum CFM needed to ventilate a indoor garden is never quite that simple. Once the grower has calculated the minimum CFM required for their indoor garden the following additional factors need to be considered:
Number of HID lights — add 5% per air cooled light or 10-15% per non-air cooled light.
CO2: add 5% for rooms with CO2 enrichment
Filters: if a carbon filter is to be used with the exhaust system then add 20%
Ambient temperature: for hot climates (such as Southern California) add 25%, for hot and humid climates (such as Florida) add up to 40%.
An Example
In our 8' x 8' room we have 2 x 1000w air cooled lights, and we plan to use a carbon filter. We also plan to use CO2 in this room. The ambient temperature is 90 °F (32°C), however, we will be using air from another room that is air-conditioned. Here's the minimum required CFM to ventilate room:
1) Calculate the CFM required for room (see above.)
2) Add 10% (for 2 air cooled lights.)
3) Add 5% of original CFM calculation (For CO2.)
4) Add 20% of original CFM calculation for Carbon Filter.
5) Air is coming from air-conditioned room so no need to add any other percentages.
6) CFM = (171 CFM) + (171CFM x 10%) + (171 CFM x 5%) + (171CFM x 20%) + ( 0 )= 231 CFM.
This is the absolute minimum CFM required to ventilate your room.
The next step might seem to match the closest fan to this CFM. However, for this example I'd choose a six inch fan with a CFM of around 400 or more, and a 6 inch carbon filter to match. The extra CFMs may seem a bit excessive (calculations on most indoor gardening websites would recommend a 4" fan and a 4" carbon filter) but it's always better to over-spec since we need to compensate for air resistance in ducting too.
Also, as we are using a carbon filter we will need to match the fan with the filter so that the fan that will neatly fit onto the filter.
If all the variables are kept the same and we changed the room size from 8' x 8' to a 12' x 12' then the minimum required CFM would be 519 CFM.
The All-Important Inflow!
An intake port can be anything from a gap under the door to an open window - even a hole in the wall. The best place for an intake port is diagonally opposite from your exhaust fan; that way, air has to pass across the entire room - very efficient. You can put a piece of screen over the opening to keep insects and animals out, a piece of A/C filter to keep dust out, or a louvered shutter or backdraft damper that opens when the fan turns on and closes when it turns off. You can also use a motorized damper. This gets installed in-line with your ducting and is plugged into whatever device controls your exhaust fan. When your fan turns on, it allows air to pass. When your fan shuts off, it seals completely, preventing CO2, air, etc. from passing. You can get creative with these devices and use one fan to control two rooms, etc.
One additional note about intake ports - you will see much better results from your exhaust system if you install a second fan to create an active (as opposed to passive) intake system. Normally, when your exhaust fan sucks air out of your room, air is passively going to get sucked back into the room. By installing a second fan on the intake side, you will reduce the amount of negative pressure created in the indoor garden, thereby cutting down greatly on the amount of work the exhaust fan has to do and allowing much more air to pass through. If you're not sure or you don't want to spend the money, start out with just an exhaust fan. If it's not performing as well as you thought it would, try adding an intake fan - you'll smile when you see the difference!
NoBarriers
Well-Known Member
I ran a 4" fan filter combo in a 400 watt grow box about that side and kept it a few degrees above the ambient room temps without a problem. If you can go bigger just in case you wanted to upgrade the light to a 600 or 1000. With the 400 mh that fan will work fine.
So this http://www.ebay.co.uk/itm/Plug-in-Hydroponics-Grow-Light-Fan-Speed-Controller-/130842299637?pt=UK_HomeGarden_Garden_PlantsSeedsBulbs_JN&hash=item1e76cf0cf5 & this http://www.ebay.co.uk/itm/In-Line-Duct-Fan-Mounted-Extractor-Fan-Hydroponics-Grow-Room-4-5-6-8-10-12-/130620450641?pt=UK_Home_Garden_Hearing_Cooling_Air&var=&hash=item1e6995e751 is all I need for proper ventilation in grow tent/closet, that's right?
NoBarriers
Well-Known Member
Yes that fan and controler would work just fine.
Do you guys think this 12 inch 50watt fan will be any good for vertical 400w grow? thanks 
http://pigu.lt/ventiliatoriai/ventiliatorius_kyt_30bwh_equation?id=4146983
http://pigu.lt/ventiliatoriai/ventiliatorius_kyt_30bwh_equation?id=4146983