The Truth About Evaporative Coolers

What exactly is a swamp cooler?

A Swamp Cooler is an air handling unit with a wet medium and a 100% outside air fan. The medium is wet continuously with fresh water and as the air passes over it evaporates water and lowers the sensible heat (dry bulb temp.), but increases the humidity. As opposed to an air conditioner which has a coil with chilled water or refrigerant that cools and dehumidifies the air as the fan blows it over the coil.

Swamp coolers are simple and relatively inexpensive, but are NOT very effective in humid climates, as very little water evaporates. You often see simple versions of this at football games and such with big fans on the sidelines with a water mist.

If you have an instance of an air conditioned space next to a swamp-cooled space, part of the swamp cooler supply can be derived from the AC condensate drain. Using this water which is usually sewered or drained to the ground will replace some of the water demand and is colder than most water supplies.