[pontiac]

Hi IC, what CFM rating would you recommend to cool a 600w hps in an aircoolable hood? I'm thinking a 265cfm dayton or a 270cfm canfan would do the trick.

im using a 6" vortex at 449cfm, I tryed a 265cfm fan but I did not help much with heat

[pontiac]

Is the hps in an aircooled hood?

its in a Daystar AC

[UNREGISTRD]

How to size your exhaust fan



There are many calculations on the web for sizing a fan for ventilating grow rooms; however, what these calculations fail to take into consideration is the friction loss on carbon filters, increased temperatures from HID lights and CO2, etc. The following calculation can be used 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 required to ventilate the grow room):



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
The fan should be able to adequately exchange the air in a grow room once every three minutes. Therefore, 512 cubic feet/3 minutes = 171 cfm. This will be the absolute minimum cfm for exchanging the air in a grow room.


Step 3 – Additional factors
Unfortunately, the minimum cfm needed to ventilate a grow room is never quite that simple. Once the grower has calculated the minimum cfm required for their grow room the following additional factors need to be considered:

1. Number of HID lights – add 5% per air cooled light or 10-15% per non-air cooled light.

2. CO2 – add 5% for rooms with CO2 enrichment

3. Filters – if a carbon filter is to be used with the exhaust system then add 20%

4. Ambient temperature – for hot climates (such as Southern California) add 25%, for hot and humid climates (such as Florida) add up to 40%.

Example 1:

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, however, we will be using air from another room that is air-conditioned.

Minimum Required CFM to ventilate room:

(CFM required for room – step 2) + (CFM required for room – step 2 x 10% (2 air cooled lights)) + (CFM required for room – step 2 x 5% (CO2)) + (CFM required for room – step 2 x 20% (Carbon Filter)) + (Ambient Temperature 0 (Air coming from air-conditioned room)).

= (171cfm) + (171cfm x 10%) +
(171cfm x 5%) + (171cfm x 20%) + ( 0 )


= 231cfm – this is the absolute minimum cfm required to ventilate your room.


The next step would be to match the closest fan to this CFM. 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. The filter that we will use is a Dutch Breeze Carbon Filter - DFS4. The DFS4 has a 6" flange. Our options for 6" fans are as follows:

- Eco Plus 6” – 440cfm

- Fantech 6” – 252cfm

- Fantech 6” XL – 392cfm

- Elicient 150B – 309cfm



The DFS4 filter has a cfm rating of 255-309, so the fan that we will choose for our room will be the Elicient 6” fan. This will be an ideal fan for this room and carbon filter, since the extra cfm will help compensate for the small amount of ducting we may have to run.

If only step one and two was used (the calculation that is most commonly displayed on garden websites) then the grower would have chosen a 4” fan and a 4” carbon filter; the grower would have soon found out that this fan and carbon filter would have been inadequate for their grow room.

compliments of BGH.com

from what iv heard Elicient fans are no good

[UNREGISTRD]

Originally Posted by mr.blast_420

from what iv heard Elicient fans are no good

yes your right VORTEX IMO is the best..There the quietest at least!

they are quiet, well made and have the highest cfm rating for 6" next to the hurricane fans

[pontiac]

Hmm, thats some good info unregistrd, but i dont think it applies to grow cabs. Mathematically the formula is way off target for a grow cab. Thanks anyway, i might use it if i ever do a room grow.

My grow cab is 4'x4'x2' and i'm currently running a non-aircooled diy 400w hps with a 160cfm duct fan for exhaust. The temps in the cab are around 87 F and near 90 F on hotter days. I plan on getting a 600w hps and a daystar AC or a cooltube for my next grow. So i'll think i'll get a 449 cfm vortex just incase.

BTW, do you know the noise level output of a 449cfm vortex in dBA?

49 dba i think