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Heating & Cooling

What in the World is a Swamp Cooler?

Also known as evaporative coolers, swamp coolers perform similar duty to air conditioners.  They take in hot outside air and output cooler air into the home. 

Swamp coolers work very differently than air conditioners though.  Using the principle of cooling air through water evaporation, these coolers are very simple and cheap to operate.  Basically a box with a large fan inside, swamp coolers have outside vents with pads or wicks saturated with water blocking these vents.  Fan operation sucks outside air through these pads, forcing evaporation of the water and cooling the air which is then blown inside the home.  Unlike air conditioned homes, those using an evaporative cooler operate with the windows open, passing large volumes of cool, humid air all throughout the house. 


As you might expect, swamp coolers would be uncomfortable to use in areas of hot, humid weather.  Indeed, you will not see them east of the Mississippi river.  Only about the western 1/3 of the United States has an arid enough climate for evaporative coolers to be useful. 

The lower the relative humidity, the more effective swamp coolers are.  If it’s 90 degrees F outside @ 50% humidity, these coolers will bring the home temperature down to about 79 degrees F.  Change the outdoor humidity to a more reasonable desert number of 10%, and the cooler can output humid air at 67 degrees F!  When you live in an arid climate, the added humidity is a real benefit as well. 


Swamp coolers do have a few more parts besides the wick and fan, but not many.  Putting so much water into the airstream requires a pump to keep the wicks saturated.  The pump draws water from a pan in the box bottom, which is kept filled by a valve and float system that works just like the ones in toilet tanks.  Compared to the innards of an air conditioner, these units are really simple! 

Earlier I mentioned the need for open windows.  It turns out that there is a process called “balancing” your airflow that optimizes the coolers operation.  To obtain the maximum cooling capacity, you should open your windows until the air inside you house is nearly balanced with the outside.  As you open your windows you decrease the pressure buildup inside the home, and the cooler is able to output increasingly more air until the capacity of the cooler is reached.

One method to determine if the air is reasonably balanced is to place a piece of tissue paper up against the screen of the window farthest from the cooler and adjust the opening of the windows in the house until the tissue paper stays lightly on the screen.  If the tissue plasters itself to the screen, open the windows more.  If it falls, close the windows more.  Each window in the home should be opened roughly the same amount.  In this way, the cooler can effectively condition the entire living area.

The example above is a roof top evaporative cooler.  Below is a window unit.

Simple, effective and long lived, swamp coolers do a great job of conditioning summer heat in arid climates.



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Posted 2016-08-23T19:42:10+0000  by Chris_HD_CHI Chris_HD_CHI
Greetings Chris,

I had no idea that cooling had any other aspects, or options, I am completely amazed, great post!

I wish that our east coast air conditioners were able to work effectively with windows open as well.....after months of above average temperatures here in Boston, the air conditioners have been running constantly, and the windows have been closed up tight. I am looking forward to the shift of season just to be able to open the windows and let some fresh air in!

Thank you for some insight into how homes across the country are managing with this crazy hot summer weather!    

Stay cool, Maureen
Posted 2016-08-25T13:13:32+0000  by Maureen_HD_BOS
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