How to avoid a bad experience and get the most from your cooler
Evaporative coolers, or “swamp” coolers have been around in one form or another for millennia. The Egyptians used the same basic principle when they put water soaked cloth over the entrances of their buildings.1 It’s a proven system brought forward into the modern age with plenty of advantages. Still, consumers are of two minds when they purchase an evaporative cooler.
Check out the reviews on Amazon for any evaporative cooler product and you’ll find just as many one stars as five. It seems that either people love them or hate them. An example of the love side:
“…this is NOT an air conditioner. [...] It doesn’t work very well in humid areas, but it works GREAT where the air is dry.2”
And one from the hate:
“I would have loved a 2 degree drop from the normal room temperature, though I did not get this… I am very disappointed.3”
This article should either put you solidly into the very satisfied column, or keep you from buying an evaporative cooler altogether.
Types of coolers
There are two general types of evaporative coolers – wicked and fixed media. The differences may be important, depending on your situation. A wick style unit uses a fabric that is immersed in a water tank. Water “wicks” up through the cloth, moistening it. A fan then blows room air through the fabric, evaporating the water.4 What comes out is cooler, damper air.
Fixed media types have a grating made of fibrous material. The water from the reservoir is pumped up above the grating (which looks like the wavy layer between the outside surfaces of cardboard) and drains down. As it flows downward on the backside of the fixed media, a fan blows it through the grate (which may be an inch or more thick) and the water evaporates.5 What comes out is cooler, damper air.
In general, you get more cooling capacity with a fixed media type of cooler. But they are also more expensive because of the pump and because the fixed media costs more than a cloth wick. There’s also the matter of having the proper air flow for the media used. A fan speed that is set too high has the potential of throwing water out – literally blowing it off the fixed media. This is much less likely with a wick style.
The number one complaint is not getting enough cooling. For this reason, you should check a trusted guide to see if an evaporative cooler is even worthwhile in your area. Unlike a standard air conditioner, an EC will work better or worse depending on the humidity where it is operated.
You can see that if the temperature is 95 with a relative humidity of 10%, you’ll get an impressive drop in temperature down to 70 degrees6. Quite nice. On the other hand, with the same outside temperature and a relative humidity of 60%, the drop is only to 87 degrees.
What complicates this a bit is that running the cooler adds water to the air and raises the humidity. At some point, either the room has to be vented or the EC will simply stop cooling altogether.
To avoid problems, you’ll want to look at a few things in your area.
- Where do you fall on this map? Purple areas are best, while blue will still find some use. The white areas would only have a very short season (if any) and an evaporative cooler wouldn’t be a good choice.
- Are you the type of person who has trouble with dry air? If so, an evaporative cooler could be an option even with air conditioning – the EC adds moisture and increased humidity.
- What are others using in your location? Are they satisfied?
- Could you “try before you buy” with a rental or a borrowed unit?
- How much do you need to cool and how big an area? Capacity is set by square footage, but these do not consider ceiling heights above 7.5 ft, nor do they consider the number of occupants. Go larger rather than smaller.
- Is noise an issue, as when using it in a bedroom while sleeping? Fans always sound quieter with the background noise of a store.
Know what you’re getting
Just as with other appliances, features cost money. Some manufacturers add things that appeal to consumers but don’t deliver much. For example, a high capacity cooler (large square footage) might base its numbers on a very strong fan and the ability to push air around. It might be better (and cheaper) to use more than one smaller unit to accomplish the same task.
Do you need the options offered? Common options are multiple fan speeds, remote controls, timers, special filters and air purification functions. Timers can be replaced by a plug in at the electrical outlet (about $11.00 at the hardware store), remotes are a convenience, but for evaporative coolers, most people set ‘em and forget ‘em. Plus, you have to keep track of another remote. Air purification is nice, but coolers don’t do half the job a dedicated air purification unit will do – if you need air purification, consider buying one.
Some manufacturers tout the humidifier aspect of evaporative coolers. They do add water to the air, and this can be a benefit when they are used to cool in overly dry environments. However, if you really need to raise the humidity, a humidifier works best. And it will still work in the winter, when you aren’t interested in cooling.
Features come with a price. Just know what you want and what you don’t need going in.
Ice or no ice? Some users recommend adding ice to the water supply to get more cooling. This is usually not a good idea, for two reasons. The first is that raising the temperature of the ice-chilled water to the point where it will evaporate doesn’t require much energy and doesn’t remove much heat. The real payoff only comes when the water evaporates. In fixed media systems, using very cold water can actually throw off the cooling – the water drains down too fast to evaporate. In these systems, chilled water can also lead to “spitting” – water droplets expelled out of the front of the unit.
Another reason not to use ice comes from physics. Freezing the water generates heat at your refrigerator. You can’t make it up when the ice melts in the cooler. It’s a net heating for the house. Finally, ice is expensive, you might be overpaying for whatever cooling you get with the extra electricity used to make the ice.
Multiple solutions. There’s no reason to think in one dimension with an evaporative cooler. It can be used along with regular fans which increase air flow and help you feel cooler. An air conditioner can be a supplement you turn on only when the EC is overwhelmed. The combination is nice because the evaporative cooler adds moisture and a traditional air conditioner removes it – a nice balance. Also, there’s no reason not to run multiple EC’s for added effects. Having more than one gives you options about what to run and when, as opposed to a single, larger unit.
Cleanliness. Before you buy, make sure you know how to change the filter and how much replacement filters cost. The filter stops the wick (or fixed media) from getting clogged with dust. Dust not only lowers air flow and makes the unit work harder, accumulated dust is a place for mold and other nasty stuff to grow. Cleaning and sanitizing is an important part of running an evaporative cooler. A common complaint is a musty or other smell from an improperly serviced wick. You should know how to clean the unit before you purchase it.
Warranty. You should think about buying locally instead of the Internet, if only because it’s usually easier to replace a defective product or get a repair. Ask about warranties before you buy. The more complex a system (like the fixed media with pump), the more a good warranty pays off.
Water. If you have poor water at the tap (rusty or hard water), you may need to buy water to run through the cooler. Make sure you know before you buy. You also want to know how much water your evaporative cooler will hold and how long it will run before you need to refill it. Is the tank removable? For larger units, it pays to have a tank you can carry to the sink (or bathtub) to fill.