View Full Version : Fan Size ?

02-17-2007, 03:13 PM

I'm putting together a grow cab in a 2.5x3x6 metal office cabinet .
I have a 400W coolbreeze / Goblin and plan on using 1 fan to cool the light and exhaust the cabinet.
Thinikng that bigger is always better, I purchased a 6" vortex, but ..... 2 words can decribe it... Big and loud. Even with a speed controller, it's still way to loud even on the lowest speed.

Therefore, I'm going to buy a smaller dayton blower to do the job. My question is :
what size blower ? as I only have 45CF to exhaust, the rule of thumb calc posted here, would mean 45/5 = 9 CFM . Of course that's way to small, but I'm unsure how to add the bulb cooling required into the equation.

Would a 140 CFM blower be sufficient ? or should I get a 265 blower and a speed controller for it ? I'm not sure what kind of speed controller can be used with blower motors ? ( I didn't think that regular diac/triac types were suitable ) I've read folks recommending speed controllers for blowers, but I'm not sure they realize that use different motors than inline fans ?

Any suggestions ?



David G.
02-25-2007, 12:18 PM
The fan may seem too loud because you are using it in a small metal cabinet, and if it's not mounted properly it can make a lot of noise, especially if the metal doors start rattling. Yes, a 4" Vortex would have been more than enough, but reducing the speed on the 6" should do the trick. You should also use some rubber or foam between the fan and the metal cabinet during installation to help reduce the noise.

Ironically, the Dayton blower will most probably produce more noise than the Vortex, since it is a squirrel cage blower as opposed to a centrifugal blower, so I would try to work with the Vortex. Also, you cannot use a speed controller with squirrel cage blowers. And, the 140 cfm model would be too small to use with the Goblin.

Although the formula for choosing a fan is to exchange the air at least once every 5 minutes, most growers try to acheive this in 1-2 minutes; even quicker when using small chambers like yours.

03-10-2007, 11:19 AM
Thanks for the info.

I found the only way to slow the fan down enough to limit the noise and still maintain the right air flow for exchange and heat elimination was to use a variac to controll the fan speed. Works wonderfully and it's far better than the triac based controllers that are really the cheap and nasty way of controlling fans.
Now I'm glad I picked up a 6" vortex, it's big enough that I can run it quite slowly and it still flows a tremendous volume of air.



01-18-2008, 11:11 AM
What do you mean by a variac and where do you get it ? I got a speed controller here at BGH and have a 4 inch eco plus, and at a little over 1/2 speed it whines like a jet and at full speed it is way way loud. I just couldn't imagine it in any kind of a cab. Here I was thinking of going to a dayton cuz that is with comes with the most of the cabs out there, so I thought they would be quieter. So if inline is quieter than I'm at a total loss what to do to get a more SILENT system for my air and smell exchange. My closet is 3x6x7 tall and running a 400 watt ducted reflector. Quiet is the MAJOR ISSUE.... Any thoughts on a quieter fan setup?

David G.
02-17-2008, 04:08 PM
The only other suggestions I can make are to use a Suncourt Duct Muffler with your Eco Plus and/or to switch to insulated ducting (the Muffler will have a much bigger impact on the noise, though).

Another thing that would help would be to switch from the Eco Plus to the Vortex. It won't make a huge difference, but the Vortex is the quietest of all the centrifugals (whereas the Eco Plus is the cheapest).