Tuning-Up Your Swamp Cooler

For those of you not familiar with the term, it refers to an evaporative cooler. I live in the desert Southwest where the summer humidity stays between 15-19%. When you blow dry air over water, that air will turn some of the water into vapor. That process is endothermic. So the result is that the hot air is cooled considerabl​y. It also provides a side-benefit or humidification. Perhaps most importantly, for the price of running a half-horse electric motor and some water, you get cooling to rival air conditioning at a fraction of the cost. 

Anyway, at the start of the season, one must:

• Change the pads
• Lubricate the roll cage
• Inspect the drive belt
• Check out the water pump. 
• Verify the output temperature

Note that the electric motor is sealed, requiring no lubrication. 

WHENEVER YOU HAVE YOUR SWAMP COOLER OPENED, BE SURE IT IS UNPLUGGED. YOU COULD BE SERIOUSLY INJURED OTHERWISE.

I'm going to assume that everyone can handle changing the pads.

Lubrication is required for the roll cage, the big round thing that the motor drives (via the belt). On either side of the axle there is a small, spring-loaded cap the size of a nail head. You have to hold it open and squirt oil in there. You can't use household oil, you need high-performace machine oil; I recommend the "Zoom Spout" turbine oil that the home stores sell (in the ecaporative cooler area). There is often lots of crud around these ports. Be sure not to let any of it get into the lubrication port. You may have to wipe the area around the port with a rag before you open it.

Each unit has a specification about the belt, but you need to look at it for cracks and check the tension; it should deflect about 3/4 of an inch when you push on it. Belts are like a once-every-five-years sort of thing.

The water system is the thing that that gets a little tricky. Start with an inspection. Remove the three panels and run the unit on "pump only". Observe the water flow out of the water distribution ( "spider" ) lines. If you get a steady flow out of all of them, you're fine. If not, there are two possibilities: the line(s) are fouled, or the pump is bad. In some areas with hard water, you have to change the pump every season.

If your flow isn't good, buy a spider-line snake (about six bucks) at the home store. It's basically a short, thin plumbing snake. Snake each line, starting from the pad side. Then retest the flow. If the flow still isn't good, then you either need to install new lines or a new pump. Usually it's the pump. Installing a new one is literally just one slide-on connection and a plug into an electrical socket. If you have to replace the spider lines, there is a fifteen dollar kit at the box store that gives you everything you need. Consult YouTube for videos.

All of the preceding is pretty generic advice. My personal innovation was to check the flow more technically. I mean, you can eye it and say it seems to look okay, but how do you know if it's providing enough water for your cooler to achieve maximum cooling?

If you look online you can find a temperature chart for evaporative coolers that, given the temperature and humidity of the outside air, will show you the expected output temperature for your unit. My trick is to use an infrared thermometer. They used to be expensive. Cooks like to use them, especially for chocolate work because you can get instant readings from a distance. You put the red dot on the target, and it tells you the temperature. Nowadays you can get one of these thermometers for about twenty-five bucks.

Given one of those thermometers, you can check the output temperature of your swamp cooler by taking the temperature of the grating the air comes out of (make sure its been running long enough so that all the start-up transient effects have worked through). Once you have that temperature, you can compare it to the chart entry for your current weather. It should be within a degree of it. If not, then you're back to troubleshooting. If everything looks otherwise okay, it's likely that your water pump is failing. Don't be shocked. These pumps last maybe two or three years, much less if you have hard water.

The important thing here is to not look at the temperature on your wall and wonder WTF. What temperature your house achieves has a lot of confounding factors involved. Not achieving the desired interior temperature doesn't mean your swamp cooler isn't working. Judge the cooler by its output temperature, NOT room temperature.

The last thing worth noting is that some people don't balance the house air flow correctly. Swamp coolers require that you open your doors/windows to let air flow out of your house. What people often screw up is what they open and how much they open it. Champion recommends that you open a window and hold up a piece of paper to the screen. If the outflow is strong enough to hold the paper to the screen, then  your flow is nominal. You can open the window more and more until the paper drops. However, to get cooling into other parts of the house, one usually opens two or more windows and/or a screen door. Air flows towards those openings, introducing cooling. So there is some artistry to cracking a few windows in different rooms to get cooling to flow how you like it. In most cases, its maybe two or three inches per window. The paper rule still holds. Once you've cracked a few windows, you need to make sure the flow is still strong enough to hold a paper on each screen. So you're likely to walk around checking and adjusting until you've got things balanced as you like it.

This is my third season with a swamp cooler. I grew up in the Northeast where the humidity is too high for these things.  Natives of the Southwest grow up knowing swamp coolers, but I had no clue.

For those of you transplants to the Sothwest, I hope this helps.