Collection: Refrigerated Air Dryers

A refrigerated air dryer holds a pressure dew point of 35 to 40 degrees F. That number doesn't move much, because the refrigerant circuit can't go lower without freezing condensate inside the heat exchanger. At a 38 degree dew point the air carries about three quarters less moisture than saturated air leaving a 100 degree compressor, which is dry enough for pneumatic tools, cylinders, spray work and general plant air. That covers most shops in the country.

Here is where a refrigerated dryer stops working for you. It cannot produce a dew point below freezing. Any line that runs outdoors, through an unheated warehouse, or into a cold room will still make ice in January, and no amount of oversizing changes that. That's a desiccant dryer job, which gets you to minus 40 degrees F at several times the purchase price plus a real energy cost in purge air. If your air never leaves a heated building, you don't need desiccant and you shouldn't buy it.

The buying mistake is matching the dryer's nameplate CFM to the compressor's nameplate CFM. Dryer ratings are published at 100 degrees F inlet, 100 degrees F ambient and 100 PSIG. Push 110 degree air into one in a hot compressor room and capacity falls off 20 to 30 percent, so the 50 CFM dryer bought for a 50 CFM compressor is undersized the day it's installed and you're back to water in the lines. Size up a step, ventilate the compressor room, and keep the filters ahead of the dryer changed.