Evaporative Cooler Maintenance
Although evaporative coolers require a fair amount of maintenance, homeowners can often easily perform it inexpensively by doing it themselves. Evaporative coolers vary, so the specific instructions that are available in the owner’s manual are very important. In general, coolers should be inspected monthly and serviced as required. Ground and some eave mounted coolers are sometimes preferred because of their ease of maintenance as compared with roof mounted units.
During a monthly inspection, first unplug the unit and look for any damage or wear. Belt tension and water level in the reservoir should be checked. To insure maximum cooling, make sure that all pads are thoroughly and evenly wetted. Pad maintenance is probably the most important part of keeping your cooling system working properly, and is discussed more thoroughly below.
Fiber pads are typically the least expensive pad and require the most maintenance. The pads need to be replaced every year or two, depending on the pad. To lengthen the life of a pad, you can rotate and turn the pad upside down so that the previously downstream side becomes the upstream side. Fiber pads made with Aspen wood are recommended because they typically last the entire cooling season and are efficient air coolers. However, they can produce debris in the water reservoir, which will require further maintenance. Cellulose fiber media are also recommended for their cooling ability and durability over several seasons. Spun aluminum and plastic pads are the least expensive, but often require frequent replacement within a single season.
Rigid-sheet pad coolers are a thicker, more expensive option, but they don’t need to be replaced as often. These pads move air through a stack of corrugated sheet material.
The primary reason that pads need replacing is because many evaporative coolers operate with hard water (i.e. water with a high concentration of dissolved minerals). As the hard water evaporates, it leaves mineral deposits, or “scale” on the pads and cooler. This causes pads to be less efficient and can corrode and rust metal coolers. This can shorten a cooler’s life span by 50 percent and requires pads to be replaced frequently.
To counter this problem, many systems include bleed valves that drain some of the re-circulating water. In addition, “sump dump” systems drain water periodically from the reservoir. Sump dump systems are very useful because they also flush out much of the dirt and debris that collects in the reservoir. Both practices help to reduce the amount of scaling that occurs on the coolers. However, they also substantially increase the amount of water used by the coolers. The water that is flushed out from these systems can sometimes be used for irrigation purposes if the concentration of minerals is not too high.
In places where water conservation is important, another option to reduce scaling is to “soften” the incoming water with chemicals that will increase the solubility of calcium and other minerals. This will reduce the bleed rate and therefore water usage. However, you should consult your cooler supplier before going ahead with this option.
If you chose not to install a bleed valve or sump dump, you should do a thorough cleaning of the unit at least once during the cooling season in order to remove the build-up. Rigid pads should be washed down every fall when the scale/build-up is still soft. Aspen pad coolers should be maintained or replaced in the spring.
Other Maintenance Tips
In combined systems (systems where evaporative coolers and refrigeration units share ductwork), dampers should be checked annually.
“Evaporative cooler water use” by Martin Karpiscak of Arizona Cooperative Extension. Accessed April 11, 2003.
“Installing and Maintaining Evaporative Coolers” Home Energy Magazine Online May/June 1996. Accessed May 1, 2003.
“Swamp Cooler Maintenance” Accessed May 13, 2003.