Chilling the Wort

Wort Chilling

All advanced, and many intermediate home brewers employ a wort chiller to bring the hot wort down to a pitchable temperature as quickly as possible. The reason for this is that there is a range of temperatures (about 90F to about 150F) in which bacteria and other wort spoilers flourish. In order to minimize the risk of infection it is beneficial to traverse this range as quickly as possible. Thus the wort chiller.

The two types of wort chillers used by home brewers today are the immersion chiller and the counterflow (CF) chiller. It is difficult to say which design is actually better than the other, as that depends upon the individual preferences of the homebrewer. Rather than try to tell you which is best, I'll discuss the advantages and disadvantages of the two, so that you'll be able to make up your own mind as to which one better fits into your home brewery.

Immersion Chiller

The Immersion Chiller is the simpler design of the two. It is nothing more than a single coil of copper tubing (25 to 50 feet long) that gets immersed into the brewpot. Cold water is then piped through the copper coil, cooling the wort over a period of a half hour or so. The immersion chiller is easier than a CF chiller in almost all respects. Easier (and less expensive) to build, easier to use, and easier to clean.

Even more important than ease of cleaning, however, is the reliability of cleaning the chiller. The part of the immersion chiller which comes in contact with the wort (namely, the outside of the copper tube) is exposed where we can see it, and see whether or not it is clean. As explained below, this is not the case with a CF chiller. Furthermore, it can be easily sanitized by immersing the chiller into the brewpot for the final 10 or 15 minutes of the boil.

The main disadvantages of an immersion chiller are that it is not as quick in cooling the wort as a CF chiller, and that there is a slightly higher risk of infection since the chilling takes place in an open brewpot.

One really nice plus of the immersion chiller is that break material settles to the bottom of the brewpot, and can be racked-off when the wort is siphoned into the fermenter. Although CF chiller users can leave the hot break behind in the brewpot with the help of a gooseneck siphoner (or similar device), they have to rack the beer twice if they want to get rid of the cold break.

If using an immersion chiller, you should immerse it with about 15 minutes left in the boil, to sanitize it. The wort will chill a lot faster if you gently stir the contents of the pot during the chilling process. To see this in action, before you start to stir, monitor the out-flowing water from the immersion chiller. (Carefully, though, it's HOT!) It will start off really hot, then will cool off. Just as soon as you stir the contents of the pot, you will be able to feel that the out-flowing water suddenly becomes really hot again (BE CAREFUL!), which means that the efficiency of the chiller increases dramatically if you stir.

Counterflow Chiller

The Counter-Flow (CF) chiller (more properly called a Heat Exchanger) is more complex than the immersion style. It consists of a length (usually about 25 feet) of copper tubing inside of a rubber hose - usually a regular garden hose - or inside of a larger diameter piece of copper. On each end of the apparatus are fittings which allow water to be run through the outer tube in one direction, and hot wort to be siphoned through the inner tube in the other direction. The different directions of the flows are where the chiller gets its name. It is worth mention that the reason for running the liquids through in different directions is that it is more efficient this way in comparison to running them through in the same direction. This type of chiller is more expensive to build, and more difficult to use and maintain than an immersion chiller.

There are some newer 'turbo' counterflow chillers on the market which are more efficient than the standard ones at chilling the wort. The trick to these ones it that the inner copper coil is made from copper which has fins on the outside of it. Others are made from 'convoluted' copper which has channels running the length of it in a spiral fashion, so the copper coil is not rounded as is normally the case. Both designs create a larger surface area for contact between the wort and the cooling water, and also create turbulence which fluid dynamicists tell us make the whole process more efficient as well.

To sanitize the device, a sanitizing agent must be run through the inner copper tube for 10 or 15 minutes prior to use, then the agent must be thoroughly flushed with water. After being used, it should again immediately be flushed for 5 minutes with really hot water. Of course, since it is the inside of the inner copper tube which comes in contact with the wort, one never really knows if the chiller is clean. There could be all kinds of gunk inside that tube, and we'd never know about it. This is why the brewer must be absolutely meticulous when cleaning and using a CF chiller. There is absolutely no room for laziness or poor sanitation habits.

Probably the most effective way to ensure proper sanitation of a counterflow chiller is to use Powdered Brewers Wash, details of which can be found on our sanitation page. This product is designed specifically for clean-in-place applications in the brewing industry, where you cannot see the surfaces you are cleaning. It is extremely effective at removing the organic compounds left behind by beer and beer wort. Another good cleaner to use here is OxyClean. Both of them need to be extremely well rinsed, and afterwards the chiller needs to be sanitized with a sanitizing solution. If you have a pump, an effective way to sanitize a counterflow chiller is to circulate 170F+ water through it from the hot liquor tank for 5 or 10 minutes.

The major advantage of this style of chiller is that it is extremely quick at what it does. The wort enters one end of the chiller, and comes out the other end already cooled. So you can chill the entire volume of wort in the amount of time it takes to siphon it off. And since the chiller is faster, and the wort enclosed while it is being cooled, there is a slightly lower chance of infection then when using an immersion chiller. Of course, this is nullified (and then some) if the user isn't cleaning the device properly.

Another bonus of the CF chiller is that it can be used with a hop back, which is not the case for an immersion style. Also, if the out-flowing wort is allowed to cascade into the primary fermenter, the wort is automatically aerated such that this step can be eliminated from the brewing process. Users of an immersion chiller will have to aerate explicitly.

Aside from the ease-of-use issues mentioned above, another disadvantage of a CF chiller is that it doesn't leave the cold break material behind in the brewpot like an immersion chiller does, so the beer will have to be racked one extra time if the brewer wants to get rid of it. Of course, most experts currently agree that leaving the cold break in the primary fermenter for a few days isn't going to have any affect on the beer. At least as far as Ales go. But for true Lagers, many experts such as Dave Miller and Gregory Noonan recommend removing the cold break as well before fermentation. Of course, this introduces another variable into the equation : with an immersion chiller you automatically get rid of the cold break by nature of the device, but since a CF chiller cools the wort faster, you are likely to get a much better break when using it rather than an immersion chiller, even though you'll still have to rack the beer twice to get rid of it. So the decision still isn't that easy to make.

Using a CF Chiller

Before using the CF chiller, it must be properly cleaned and sanitized. You can sit the chiller on a counter top and sit a bucket of cleaning agent beside it. Siphon the whole bucket of agent through to another bucket sitting on the floor. Make another run through with warm water to rinse the insides and then a final run with iodophor to sanitize. Many brewers eliminate the cleaning step by filling the inner coil with cleaning agent (PBW or Oxyclean) right after use, and storing the chiller with the ends capped and full of agent. Then one need only drain the inner coil, rinse, then sanitize.

After using the chiller, immediately run hot water out of the faucet through the outer hose and into the bucket that is still sitting on the counter. As soon as there is enough water in the bucket start siphoning the hot water into the empty catch bucket. By running hot water through the outer hose the chiller is kept as hot as possible, ensuring it will also be as clean as possible. If you wanted to store your chiller full of cleaning agent simply mix some into the water when doing this.

After all of this is done, pick up the chiller and rotate it a few times to get the water out for storage. It will have to be rotated once for each coil in order to get all the water out. Make sure you rotate in the proper direction. To do this, just hold the chiller so the coils are parallel to the floor, and then make it rotate similar to how a plate rotates (or wobbles) when dropped on the floor.