This exceptional water chiller can regulate fermentation temperature by pumping cold water through the jacket of the 3-in-1 (or 4-in-1), lower wort temperature post-boil when warm municipal water can't finish the job, AND chill beer in-line from keg to tap. A few of its many features include:
Tap water or another chilling water source should be used for removing the large heat load post boil and this chiller used for maintaining fermentation temperature. Since this is a water chiller, it is not designed to crash cool near or below freezing temperatures.
BREWinfo: Water, Beer and Wort Chiller Instruction Manual
BREWinfo: Installing a portable fermenting temp controller
Video: Overview of the Water, Beer and Wort Chiller
BREWinfo: Maintaining temperature during fermentation