AC condenser cooling with water spray.

[Windy in Kansas]

Some 15-20 years ago, maybe even longer ago, I read of trials being done using water being misted onto condenser units to help improve efficiency. The efficiency of the AC system went up dramatically-----until hard water deposits/scale formed on the fins lowering the efficiency.

In science news this morning is talk again of using water mists/sprays.
http://www.sciencedaily.com/releases...1106065600.htm

There are a number of other interesting energy articles to read at that site today.

[Beeman]

The cooling from evaporation helps the condenser shed heat which makes the AC colder.

[Harry Chickpea]

I've researched this extensively, and used misting on the coil of our AC in Florida.

First, you can destroy the fins on a coil as you mentioned.

Second, it is more complicated than it seems. The cooling of an AC is a function of the expansion of the refrigerant from liquid to gas. The AC will not run appreciably cooler if the liquid refrigerant is slightly warmer. What does happen with misting is that the head pressure on the compressor is reduced, extending compressor life and limiting problems with short cycling because of the overpressure cutout.

Third, most electric motors have little energy draw variation between being loaded or unloaded. Compressor motors are the same.

So, actual improvements in efficiency are real, but much smaller than you might expect. Misting can help when a system is under stress on an extremely hot day. FWIW, the preferred method is not to mist the coil but to mist a prefilter, keeping the corrosive effects of the water away from the coil.