Oversize fan with controller = silence?

[Chrellyboy]

Hey friends

Does anyone have experience with buying an oversized fan and running it on a fan-controller? For example running a 1500 cfm fan in a room requiring 800 cfm.

Of course a fan would never be 100% silent due to the moving air, but getting an oversized fan with a 315mm exit compared to a 250mm running on full power should make a big difference, right?

Chrellyboy

 

[malufizzgig]

I know that a larger fan spinning slower will generally generate less noise than a smaller fan spinning faster when moving the same volume of air. That said, there are a lot of considerations to running a fan on a controller, variac, etc. Depending on the motor type, certain controllers may damage the fan or cause the motor to hum, create impedance that could potentially cause the motor to wear out sooner. I'd suggest looking into fan mfgs and contacting their support about using controllers or if they recommend one.

 

[RonSmooth]

It will be quieter with a speed controller but IME, the fan motor noise isnt the problem, its the "whoooosh" sound of the air that is most noticeable. Duct mufflers really help cut down on air noise and are easy to make if you're into the DIY thing.

The motor noise can be addressed by encasing it in an insulated box, hanging it from bungees and using a speed controller. Also, a quality fan will generally be quieter than a cheap one.

 

[malufizzgig]

Ron makes a good point. Compare a quality fan with the cheap value line units and the noise difference is night and day. Nicer (and more quiet) fans are definitely on my list of upgrades next go around.

 

[stoned-trout]

I always oversize fan and use controller and duct muffler......works for me

 

[Jnugg]

Larger fan on controller,using oversized insulated ducting (6"+ for a 4" fan,8"+ for a 6" fan,etc.),an acoustical fan box,duct mufflers,and a carbon filter will make it as quiet as possible,but you'll never obtain 100% silence.

 

[ogrerun]

Yes it will be quieter

 

[Nme2Me]

Larger fan on controller,using oversized insulated ducting (6"+ for a 4" fan,8"+ for a 6" fan,etc.),an acoustical fan box,duct mufflers,and a carbon filter will make it as quiet as possible,but you'll never obtain 100% silence.

What is this acoustical fan box you speak of?

 

[Jnugg]

A simple box made from MDF and lined and filled with acoustical foam around the fan.

 

[Nme2Me]

thank you

 

[xxxstr8edgexxx]

building an insulated box around fan is defrinately the most effective and also cheapest option.

 

[HUGE]

1 this ng is some fans actually get louder as you slow them down as you near the harmonic resonance point.

 

[Snook]

build boxes out of duct board, there are different thicknesses, is much easier to work with, lighter and cheaper.

http://www.homedepot.com/p/Master-Flow-48-in-x-120-in-Duct-Board-R-6-DBOARD1/202974245

A box cutter knife and a roll of duct tape. it's silver on one side, white on the other..

 

[SpiderMite]

A reostat or steady state speed control should work to slow it down with little effect on the life expectancy of the fan. I have a 6" 435CFM that I run at about 55% through insulated ducting. Very quiet, it is a CAN fan. I just set mine on a couple towels to isolate vibration on the floor and wrapped the fan and the connection of the fan to carbon filter in towels/cloth and duct taped it all up. Works great but a box built around it would obviously reduce sound more...

 

[xxxstr8edgexxx]

i hang all my big fans and air pumps from bungees rather mounting. cuts down on vibration noise in the rest of the house
a surprising amount.