Common Evaporative Cooler Mistakes

Those living in hot, dry climates can attest to the fact that evaporative coolers are an extremely effective way to cool and humidify homes. As an alternative to traditional air conditioners, evaporative coolers utilize a more refined concept of evaporation to provide cooling comfort, and they can inexpensively lower the ambient temperature by several degrees.

When water evaporates, it absorbs a large amount of heat from its surroundings, and one of the most familiar examples of this can be observed when water is splashed onto skin during a hot day. This will result in an immediate cooling sensation because of the rapid evaporation of moisture on the skin that occurs in arid climates.

Although evaporative coolers have been in use for thousands of years, modern evaporative coolers are more than just a wet cloth and an open window or fan.  However, the cooling method still remains the same. Evaporative coolers use a combination of simple technology and electric power to create cold airflow. A large box contains a fan that is surrounded by wet pads, and a pump then circulates water to keep the pads wet. The fan then blows air through the pads and the cooler air is blown into the house, while the hotter inside air is exhausted out through open windows, doors, or vents. Therefore, not only does a swamp cooler cool the air, but it can make the atmosphere more pleasant by adding moisture and increasing humidity levels. Also, unlike traditional air conditioners where air is constantly recirculated, evaporative coolers constantly bring in fresh air from the outside.

However, despite these benefits, evaporative coolers can present some limitations, and choosing the wrong type of evaporative cooler for your home can leave you suffering in the heat. Here are some common mistakes consumers make when choosing evaporative coolers:

1. Purchasing the Wrong Type of Cooler for a Given Environment
Unfortunately, while evaporative coolers are cost-effective, energy efficient, and relatively easy to maintain, they only work in areas where the air is dry, particularly in temperatures above 80 degrees Fahrenheit with humidity levels below 50 percent, making them ill-suited for humid climates. As the humidity in the outside air increases, this results in a decrease in effectiveness of the evaporative cooler.

If an evaporative cooler is used in a humid environment, very little water will evaporate, and the air outside will almost be the same temperature as the air that has already been passed through the unit. In addition, humidity in the air accelerates corrosion and causes condensation.

Therefore, for humid climates, a portable air conditioner may be more suitable, as the refrigeration cycle used in these units reduces the humidity in the air and decreases the overall temperature.

2. Choosing the Wrong Sized Evaporative Cooler
Keep in mind that for an evaporative cooler to effectively cool, a room's size must be taken into consideration. However, unlike portable air conditioners, there is no harm in purchasing an evaporative cooler that is a bit bigger than a room's requirements. While a portable air conditioner's output is rated by BTU's, evaporative coolers are rated by CFM's, or the cubic feet per minute of air that the unit can blow into a home.

The simplest formula to use to calculate the correct sized evaporative cooler suitable for your room or home involves finding the cubic feet of the space being cooled and dividing that number by two. This quotient will give you the CFM rating for the proper-sized evaporative cooler. For example, if you have a 2,000 square foot home with 7 foot-high ceilings, you can calculate the CFM's like so:

With that in mind, for a room with the above dimensions, you would require an evaporative cooler with a CFM rating of 7,000 or above.

3. Insufficient Temperature Change
Evaporative coolers have been shown to be an effective alternative to standard air conditioners throughout the desert regions of the United States, but many consumers may not be aware of an evaporative cooler's limitations when it comes to temperature control.

Evaporative coolers can only reduce the air temperature throughout a room by 10 to 20 degrees Fahrenheit, and they are primarily used for personal cooling only. They are incapable of controlling a room's complete temperature. In addition, the overall effectiveness of an evaporative cooler greatly depends on two factors: the outside temperature and the humidity level. Evaporative coolers work best in the hottest time of the day and when humidity levels are below 50 percent (the lower the humidity levels, the better).

Refer to the chart below to get an approximation of temperature changes delivered by evaporative coolers:

4. Insufficient Exhaust
Although evaporative coolers do not need to be vented like portable air conditioners, the air that is forced into a room or home needs some sort of exit path in order for sufficient cooling to take place, such as an open door or window. If an evaporative cooler does not utilize exhaust ducts, there needs to be enough space for exhaust and proper airflow, and this should be taken into consideration before purchasing an evaporative cooler. As a general rule, it is recommended that a 2 square foot opening be allowed for each 1000 CFM the evaporative cooler provides.

See Evaporative Coolers

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