The Counter Flow Chiller or "CFC" is a standalone heat exchanger built as coil within a coil. Unlike an immersion chiller, hot wort flows by gravity or is pumped through the inner coil (usually made of copper). While the wort flows, cold tap water is fed into an outer jacket that surrounds the copper coil. This outer jacket is rubber or vinyl hose in budget CFC's but may also be made of larger diameter copper. The counterflow gets its name from the fact that the cold water enters at the end of the coil in which the wort exits (they each flow in opposite directions) presumably to maximize the heat differential. CFC's are designed so that the wort will exit the chiller at pitching temps making it capable of cooling an unlimited batch size. The potential disadvantages to using a CFC are the requirement for cleaning/sanitizing the inside of a long copper coil and also a way to get your hot wort into the coil (bulkhead or metal racking cane).
Counterflow Chillers can be easily constructed using 3/8" OD copper and 5/8" ID high temp garden hose. The end fittings are the key to keeping the cooling water and wort separated. If you can solder copper pipe/fittings, the most economical fitting is constructed of a 1/2" Tee, three short 1/2" copper pipe sections (about 2" long each), and a 1/2" to 1/4" reducing coupling. See the picture for details. In order to avoid soldering, you can build the fitting using a brass tee with compression ends. Two in 1/2" and a one using a reducing 3/8" compression nut. This is a more expensive option but it works just as well.Bobby M 23:03, 12 February 2007 (CST)
