Smart Cooling for Desert Dwellers

By Pax Rasmussen

Evaporative coolers, done right, are the way to go.

Undeniably, spring has arrived. It’s time to get your swamp cooler up and running for the season. If you don’t have a swamp cooler yet, and are still cooling your house with barbaric and energy-sucking A/C (or sweltering through a Utah summer without cooling at all), check out our story in last September’s issue about the economics of evaporative cooling. It really is the better option all around in our dry desert climate.

Not all swamp coolers are equal

Don’t just rush out and buy the first one you see. They come in a variety of configurations, and install a couple of different ways, too.

The most common type of swamp cooler is the multiple-inlet padded-wall type. These are the sort of tan-colored ones you seen in windows or on rooftops around town. They are either side draft or down draft, with three pad walls in the former case, and four walls in the latter. There are also some more high-efficiency single-inlet types available now which use one very thick pad instead of multiple walls, and a much bigger blower and motor. They’re also quite a bit more expensive.

Swamp coolers can be installed either on the roof or in a window. The roof installation is probably the best, since it makes bringing the cool air to a central location easier. The downside is that it requires a hole cut in the roof with ducting down through the attic to a vent in the ceiling. Window mounting is a lot cheaper and easier (something most homeowners, even renters, can do themselves, as long as they’ve got a couple people to hold the cooler in place while it’s attached), but has the drawback of making the air inlet on one side of the house, and that door to the room in which it’s installed will need to remain open. If going the window-mount route, install the cooler on a north- or east-facing window, if possible. Keeping the cooler in the shade really helps.

If you have a forced-air heater, one of the best swamp cooler options is to interface the duct from the swamp cooler to the existing heating ducts in the house. This way, cool air is delivered to the entire house.

Maintenance and upkeep

Unlike a/c units, swamp coolers do require a little bit of maintenance. They need to be decommissioned at the end of the season and cleaned up and prepped at the beginning of hotter weather. They also need to be periodically checked on and possibly cleaned during the summer. To get your cooler running this spring:

First take the cooler cover off and remove the damper (if your model has one). Store the damper somewhere you’ll find it in the fall.

At this time, change the cooler pads (I like the aspen pads—they need replacing every year, unlike paper pads, but they are way more efficient in terms of cooling power, and they smell nicer).

Spray out the bottom pan and replace the drain plug and stem.

Reconnect the water line to the float valve and turn on the water. Wait for the pan to fill, making sure that the float valve shuts off the water before the level gets to the top of the drain stem.

Adjust or replace the valve if necessary.

Check the belt tension. You should be able to push the belt in with your finger about one inch using moderate effort. If there’s too much play, slightly loosen the bolts holding the motor to the frame and push it out so more tension is on the belt. Retighten the motor mount bolts. If you can’t move the motor out far enough to get proper tension, the belt needs replacing.

Oil the bearings. You should see little cups or holes just over where the blower connects to the frame of the cooler. Add a few drops of oil to both sides. (A special bottle of cooler oil can be purchased at most hardware stores—the bottles have special spouts that can be extended to make this easier—but any multipurpose oil, such as 3-in-1, can be used.)

Replace the walls of the cooler and you’re done! Just check the cooler every couple of weeks during the season to make sure everything is running smoothly, that the pan isn’t overflowing, etc. If you notice a funky smell coming from the cooler, you can install a bleed-off tee between the water pump and the spider lines, but this will radically increase your water use (I have one which I crimp off normally, only opening it for a day or two whenever I notice any smells). There’s also a chemical brick you can put in the water pan to inhibit bacterial growth.

Also recommended is an inline mineral remover—a canister that is installed between the water supply and the float valve inlet—that filters out much of the stuff that creates the crusty deposits in the cooler. This also helps keep bacterial growth down.

A matter of balance

Whether you’ve gone the window or roof option, once you’re up and running with a swamp cooler, it’s important to operate it correctly. Unlike a/c, evaporative coolers require windows to be open in the house. The air from the cooler is drawn in from outside and needs to pass through the house to the outside to work properly. Without open windows, the cooler can’t bring air into the house at all.

You can’t just open up all the windows, however. The air from the cooler will take either the shortest route out of the house or the easiest (biggest opening)—or some ratio of the two. If you’ve got all the windows open, you’ll actually end up creating a suction effect from the windows furthest from the air inlet, drawing hot air in from outside. Also, this makes it easier for hot air to blow in when it’s windy out.

The easiest way to get the cooler working right is to balance’ the airflow to where you want it. For example, if the cooler is on the north side of the house and you want to cool the main areas, open just one window on the south side, and maybe slightly open a window in each bedroom. Then, go around with a small piece of tissue and stick it in front of the window screens. You want enough air to be going out any open window to hold the tissue firmly against the screen. Adjust which windows are open and how wide they’re open until all windows can hold up the tissue.

Automation for efficiency

One of the best things you can do to reduce the cost of cooling, whether you’re using a swamp cooler or an a/c unit, is to let technology handle keeping the temp steady. Instead of just using the standard dial to control a swamp cooler, invest in a thermostat cooler controller. These work just like the thermostat on your heater, and some are even programmable. This way, instead of having the cooler on all the time, it turns off when the desired temperature is met. It’s important to buy a controller that’s specifically for evaporative coolers, though, since it’s necessary to run the water pump for a few minutes to get the pads wet before the blower kicks in. If the pads aren’t wet, all you’ll get is outside-temperature air coming in for several minutes. Evaporative cooler-specific controllers turn the water pump on for about five minutes before engaging the blower.

Pax Rasmussen is CATALYST’s techmeister. He also teaches creative writing at the University of Utah.



This article was originally published on May 2, 2018.