For those of you who are not familiar with RIMS, it stands for Recirculating Infusion Mash System. Basically it is a method for regulating the temperature of your mash tun during the mashing process when the grain starches are converted to sugars. The mash temperature is critical when brewing a beer and a swing of just a few degrees can have a dramatic impact on your finished beer. For instance, a mash temperature of 146F to 150F will create very simple sugars that are easy for yeast strains to convert into alcohol, providing you with a beer that has a dry finish. While a mash temperature of 154F to 158F will create a good deal of complex sugars that the yeast can not digest which makes for a very full bodied beer that will be lower in alcohol.
If you conduct your mash in metal kettles such as the stainless steel Blichmann 20 gallon kettles that I use, you will find that your kettles will shed a good deal of heat during the mash process. In order to maintain a proper mash conversion you will need to either heat the kettle or the fluid inside of it. The problem with adding direct heat to your mash tun kettle is that you risk scorching your grain bed or wort and may also have a large temperature variance at the bottle of the mash tun and the top of it. If you are going to apply direct heat, it is important that you are recirculating your wort with a pump to help minimize those issues. Another potential problem with direct heat is that it can be difficult to monitor and control with out the use of a temperature controller and means for regulating the heat source; if you are not careful your temperature can swing by 5 degrees very quickly.
For the reasons I stated above, I recently started work on a RIMS (Recirculating Infusion Mash System) to help me properly maintain my mash temperature. I am still conducting tests with it but plan on brewing my first test batch of beer this weekend and am optimistic that it will work out well and help me brew the best beer possible. The system is rather simple. I am constantly recirculating the wort in my mash tun via a march pump. The wort flows into a stainless steel chamber where I have an electric stainless steel heating element at the point of entry. At the opposite end of the chamber is a thermowell that is connected to a Ranco digital temperature controller. If the Ranco temperature controller detects that the temperature of the wort has fallen below my target temperature, then it activates the low watt electric heating element until the target temperature is once again reached and then shuts the element off. The wort flows out of the chamber and back into my mash tun via my MoreBeer Ultimate Sparge Arm. Instead of obsessing over my mash temp and constantly fiddling with my burner and pumps, I can kick back, toss the football around with a friend and enjoy a cold beer until my timer goes off! It should make for a more controlled mash and less stressful brew day if all goes well. Once the design is fully tested I will submit another blog entry with more details on how to build one of your own. In the meantime, you can find Ranch temperature controllers and the MoreBeer Ultimate Sparge Arm here.