What kind of fan can suck without overheating or dying?
March 12, 2014 6:13 PM   Subscribe

I’d like to build an evaporative cooler for the coming summer, but I don’t want to start a fire. Will a box fan draw air through cooling pads (and possibly ducting) without overheating or worse, or should I look for any other type of fan? Squirrel-cage fan maybe?

I’d like to build an evaporative cooler for the coming summer: some kind of box with a fan attached to it that draws air through cooling pads. Examples to give you the idea are:
- here (can’t see the fan but I assume there’s a box fan there)
- here
- and here (I’d like more surface area than this for cooling and stronger fans)

Where I’m stuck is that some people have mentioned box fans can overheat if you restrict the air coming into them because they're working too hard and there's not enough air moving to cool them(?). I’d like to leave this thing running unattended, so that’s a problem.

What kind of fan could I use that’s reasonably priced (ideally) and will tolerate some “sucking”? I’ll save quite a few bucks by not using air conditioning, so I’m willing to pay around $100ish for a fan if I had to.

Is a squirrel-cage fan any better/safer for this? I’ve seen this and have heard they might be a better option than a box fan, plus they seem to show up in HVAC related products. Or just some kind of “industrial strength” fan?

FYI if you’re into the details: the area being cooled is about 500 sq. feet, so I don’t think I need a gigantic fan.

Yes, I could just buy a portable evaporative cooler, but I’d like to design something I can mount to the interior of a window so that fresh dry air is drawn in (can’t install a traditional window unit to the exterior). I might have to just put it near the window and use some kind of ducting to pull in fresh air (let’s say it’d be 6 feet of 6 or 10 inch ducting, which would also restrict airflow).

If the fan dies after a few years that’s fine, but I’d prefer not to start a fire.

Thank you!
posted by powpow to Home & Garden (3 answers total) 1 user marked this as a favorite
The type of fan in your second link tends to be very cheap to buy and quick to die. A box fan might work OK if it's a better quality one, but it will be easier to find a better quality squirrel cage fan. Compare the sound of the fan with no load v.s. what you want to do, if you hear the motor straining it's probably not going to last long.

There are other types of window units. I also see window units mounted on wooden stands instead of to the building itself. Another configuration if you can place the unit outside at all is for it to be on the ground or a pad with ducting entering the building.

The big problem with trying to run this unattended is that the cooler will run out of water. If you have a portable cooler sitting in the room it's not a big deal, but if it's drawing hot air in from outside you are just making the place hotter than it was before the water ran out. You'll want to figure something out for this. You'll either need a huge water reservoir or a way for the fan to shut off. Don't route a hose in like you would a cooler located outside the house, this is a bad idea, just don't.

Another factor in reducing load on the fan is that in addition to drawing air in, you need to have a place for it to leave.

(I'm assuming you live somewhere with an appropriate climate for swamp coolers, if not you should give up on this plan.)
posted by yohko at 6:37 PM on March 12, 2014

Response by poster: Thanks yohko. I can't have anything outside, even sitting on the ground unfortunately, so it'll all have to be inside.

For water, I'm planning to use a 5 gallon bucket or a storage bin with a small pump to keep the pad wet. And of course some kind of pan/drain system to catch what drips off of the pads.
posted by powpow at 7:03 PM on March 12, 2014

here is a whole lot of homemade ac's
posted by bartonlong at 7:38 PM on March 12, 2014

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