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DIY RV Air Conditioning (Works Wonders In Dry Climates)

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DIY RV Air Conditioning (Works Wonders In Dry Climates)

“Cool Your Camper With A Fan And A Wet Towel!”

A misting fan

A misting fan (Photo credit: Wikipedia)

What if I told you that you don’t need to use a traditional air conditioner in the desert. (Crazy right? But under certain circumstances, totally true!)

For an RVer one of the most expensive drains on your reserve battery power is running the AC. And if you live in a hot climate, it might seem ridiculous to consider living without it.

If you live in a hot and HUMID climate you may be stuck with using expensive traditional air conditioning. (At least for a little while longer, until technology catches up.)


But if you happen to live in a hot and DRY climate, you can often get away with something that may be far cheaper.

The one essential ingredient to make this type of non-AC cooling system work is something that most of us have in such ready supply that we don't even think about it: WATER.

Ironically, that's the one thing that runs in short supply in HOT and DRY climates like the popular Desert Southwest snowbird destination.

But if you happen to have a full water tank or -- much better -- are close to a ready water source, then you can have the makings of a quick and dirty evaporative cooling system.

If you're not from the American Southwest, you may not be familiar with the concept of "swamp coolers". These are what residents of hot dry climates use to cool their houses cheaply, without the use of air conditioning. Essentially a swamp cooler -- technically an "evaporative cooler" is nothing more than fan that blows hot dry air through a water soaked fabric mesh. As the hot air passes through the mesh, some of the water evaporates into water vapor, carrying some of the heat with it, up and out of the building. In a dry climate, a swamp cooler has the benefit of not only cooling the air, but adding some desirable moisture to the parched air as well.

(If you're from the humid Southeast, you might be wondering why the heck you'd want to add moisture to the air! Trust me. If you ever visit Arizona you will figure it out within the first 24 hours, when you wonder why you're so dehydrated.)

A typical home air conditioning unit.

A typical home air conditioning unit. (Photo credit: Wikipedia)

A traditional air conditioner uses so much energy because it's doing something that's very difficult. It works on a heat pump principle, that uses some laws of how liquids and gasses behave at different pressures to force little bits of heat to go from a cold place to a hot place. A heat pump is always working "up hill," and the steeper the temperature difference between the cold and hot place (think of your freezer) the more it has to work.

But an evaporative cooler only requires a simple and efficient DC fan, and sometimes not even that.

For illustration:

  • A great way to cool down your motorhome on the hottest and driest of days is to soak some towels and lay them onto the roof. If it's really hot and dry, it may take a few buckets of water, but it'll give you some quick relief from the "oven" effect.
  • To cool the inside, simply use a fan and a wet cloth. For a quick blast of cool air, lay a soaked towel over a fan.
  • For a semi-permanent "mini-installation", hang a wet washcloth over your incoming air vent (with the fan on obviously) and spray it with water when it gets dry.
  • If you're handy, you can turn this into a full swamp cooler installation by using a more efficient wicking mesh, a small water basin, and a small water pump.

A key thing is to make sure the air on the intake side is the dry outside air, so that it can absorb the water vapor. Once the inside air is saturated, you've hit your cooling limit.

Keeping the inside air dry enough to keep cooling it is where advanced air conditioning technology is required. There have been a lot of small developments in swamp coolers technology over the years, but getting past this hurdle has been a tough challenge for cooling engineers. (Check out the Coolerado system.)

But these ideas should be enough to get you started experimenting with evaporative cooling tricks. In future articles I'll be discussing different plans for more sophisticated DIY camper cooling systems.

Can I make this more permanent?

Absolutely! If you want to have a more permanently installed "swamp cooler" in your camper, you'll essentially need 1) a permanently installed fan, 2) a porous absorbent mat in front of the fan (optionally removable when you don't need the cooling), and 3) a way to keep the mat wet.

Assuming you can figure out the fan part, either by using a cheap AC fan (from the thrift if you want to save money) or a DC fan you can connect straight to the battery via a switch (which can come from a junked computer tower)...

You'll need some type of absorbent mat to place in front of the fan. It needs to be porous enough for the fan air to blow through and absorbent enough to hold water. A Shamwow works really well, but you could do better with an actual swamp cooler pad. A popular type available in home improvement stores in the Southwest is the Aspen Cooler Pad.

Then you'll need a way to keep the pad moist. While a more sophisticated operation would involve rigging up a traditional swamp cooler mechanism that continuously sprays the pads (pretty much like a drip irrigation system does), if your pad wicks well, you may be able to get away with a pan of water under the pad that you can refill after it's wicked all the water out... OR if you don't need much other than a quick blast to cool the cabin, you could just spray the pad with a water bottle a few times until it's cooled down enough.

In my own homemade camper...

I haven't bothered with a permanent installation (though I may do it in the future). Instead I use a DC clip-on fan (made for truckers that runs from the cigarette lighter outlet) that I just clip over the door, and I put a wet Shamwow over it, just like it the video. Since my camper is really well insulated, I don't need to run it all the time -- once I get the cabin back to a sane temperature, it will stay that way for a while. (It really only gets "too hot" when I've been away from the camper for awhile and left the skylight windows uncovered.)

I should add, though, that my main strategy for keeping cool in the summer goes along with my overall philosophy for having wheels on my tiny house in the first place -- When it approaches summer, I just drive away to somewhere it doesn't get too hot! (I try to save Sedona for springtime.)



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