Fans most effecient??

adas · July 2008

Aloha, maybe a wee bit off topic, but what is the most effecient fans for my shop. Right now we have 3 stations using 1/2 HP 7amp Grainger 3' fans and sucking up the watts. Would squirrelcage fans give more bang for buck?
I have tried the blue carpet drying fan and although it gives a bit more flow, it sucks up the watts even more.

thanks
Frank

icarus · July 2008

Re: Fans most effecient??

Can you be a bit more specific? Fans for what? Venting the attic, venting the whole building? Exhaust vents? Intake fresh air vents? Etc.

Tony

adas · July 2008

Aloha, Fan for blowing air onto a workarea where an employee is working. Although under shelter, the workarea/welding area is open on both ends. 55' wide 85' long and 18' tall...kinda like an aircraft hanger. We use a blue carpet blower to help the welder get rid of the Galvanized fumes when in an enclosed area. Other workers like the 3'-4' grainger air circulator fans to keep a bit cool. I also have a 1/2 hp chicken house type air mover that really moves the air.
thanks
frank

BB. · July 2008

Re: Fans most effecient??

Generally, you are talking about pressure, speed, and volume...

You can move a lot of air (volume) at slow speed and pressure.

Or you can move a little air at high speed (and pressure).

Sort of depends on what you are trying to do, and not over sizing the motor/fan for the application...

Moving a lot of air, at slow speeds, and slow moving blades implies less friction--so more efficient at moving air.

But, that is useless if you are trying to move dust/welding smoke from specific area...

Perhaps, looking at application specific air movement. For a welding station, air hoods and back wall (think fireplace or range hood) with exhaust stacks and smaller squirrel cage fans that do well against back pressure, to move the smoke/fumes away from the welder. And a large, high volume, low speed to keep the workers cool... And watching that the second fan does not draw smoke/fumes from the exhaust hood.

Air really is quite massive, for example a cubic yard of air (27 cuft) weighs about 2 lbs... If you want to get that moving, it takes energy. If you want to "lift it" against back pressure--that takes energy too...

You are in a humid area (I presume), so inducing airflow with water spray/etc. is not useful. About all you can do is agument natural air flow (prevailing wind) and possibly temperature differentials (using solar to heat a column of air in a stack to induce draft???)... But anything like that is probably just going to be more work and cost vs just adding more panels.

About the only thing I can think of--can you change over to brushless DC motors and linear current boosters for use during the day (when the sun is out)... You will be saving losses of a charge controller, battery, and inverter (90%*80%*85%=62% efficient or 1/62%=1.61) or 61% more electricity for air movement with the same solar panels, and no charge controller, battery, or inverter costs.

-Bill

adas · July 2008

Re: Fans most effecient??

"About the only thing I can think of--can you change over to brushless DC motors and linear current boosters for use during the day (when the sun is out)... You will be saving losses of a charge controller, battery, and inverter (90%*80%*85%=62% efficient or 1/62%=1.61) or 61% more electricity for air movement with the same solar panels, and no charge controller, battery, or inverter costs."

Aloha, actually we are on the very dry side of the island. I checked out DC 24v fans and there seem to be no savings except as how you described above. I would take the battery out of the equation as I will be running off the panels and not drawing from the battery. Also the fans used are already correct for the particular worker and job, and I checked wattage and surprising reasonable. Around 500 to 600 watts for big blowers. I may toy around with motion detection with delay, so the fan goes off when the worker leaves his station. Should be easy to streamline this as we are open for business only while the sun is up.

mike95490 · July 2008

Re: Fans most effecient??

adas wrote: »

I may toy around with motion detection with delay, so the fan goes off when the worker leaves his station.

When ambient is close to body temps - IR motion detectors just don't detect well. Maybe get some of the 30 minute bathroom heater timers, and plug the fans into those.

May as well stay with the motors, wait till you price out the DC versions of the motors. A lot to be said for mass production. Have you looked at the big "box" fans with giant V belt drive?
http://www.grainger.com/Grainger/items/2MV56 48" blade, $230
3/4 horse, 2 speed motor Amps 10.3/7.4

ggunn · July 2011

Re: Fans most effecient??

adas wrote: »

I may toy around with motion detection with delay, so the fan goes off when the worker leaves his station.

A simpler solution might be a rubber mat on the floor that has a membrane switch in it that you can use to trigger a relay. You can get these off the shelf; I have seen them on the floor in front of fume hoods in labs.

Fans most effecient??

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