This post is the tenth in a multi part series on swamp cooler repair, maintenance, and replacement. If you haven’t read parts 1 – 9, I recommend you do before continuing.
Direct (open circuit) swamp coolers (continued)
Direct evaporative coolers are the simplest and, generally speaking, cheapest type of swamp cooler. However, they do have one large disadvantage – the high humidity of their output stream. Humidity values in the 80% range are fine when it’s very dry out, but when the humidity rises they can make the interior of the structure muggy, damp, and unpleasant.
Indirect (closed circuit) evaporative coolers
Indirect evaporative coolers were designed to solve the too-much-humidity problem that sometimes plagues direct systems. Indirect coolers begin their work in the same way as direct systems – by pulling air through a moist pad or membrane. After that, however, the methods diverge. Instead of pushing the moist air into the structure, indirect systems pass it over a heat exchanger. The heat exchanger is made up of a network of tubes with air inside of them. In many systems, these tubes are also moistened on the outside to boost evaporative cooling potential. The cool, moist environment on the outside of the tubes causes the air inside the tubes to drop in temperature, and it is this interior air that is pumped into the structure. In this manner, indirect evaporative coolers take advantage of the efficiency of evaporation, but without adding a bunch of humidity to the air. The main drawback to indirect evaporative cooling is that since there is an inside and outside air loop, it needs two fans instead of one. This means it consumes more electricity than a direct system, but it’s still far more electrically efficient than a refrigerated air system.
Check back soon for How to maintain your swamp cooler, when to replace it, and what to replace it with, part 11. In the meantime, check out our page on swamp cooler repair and replacement.